Mammals have dominated Earth for approximately 55 Myr thanks to their
adaptations and resilience to warming and cooling during the Cenozoic. All
life will eventually perish in a runaway greenhouse once absorbed solar
radiation exceeds the emission of thermal radiation in several billions of
years. However, conditions rendering the Earth naturally inhospitable to
mammals may develop sooner because of long-term processes linked to
plate tectonics (short-term perturbations are not considered here). In
~250 Myr, all continents will converge to form Earth’s next supercontinent,
Pangea Ultima. A natural consequence of the creation and decay of Pangea
Ultima will be extremes in pCO2 due to changes in volcanic rifting and
outgassing. Here we show that increased pCO2, solar energy (F⨀;
approximately +2.5% W m−2 greater than today) and continentality (larger
range in temperatures away from the ocean) lead to increasing warming
hostile to mammalian life. We assess their impact on mammalian
physiological limits (dry bulb, wet bulb and Humidex heat stress indicators)
as well as a planetary habitability index. Given mammals’ continued survival,
predicted background pCO2 levels of 410–816 ppm combined with increased
F⨀ will probably lead to a climate tipping point and their mass extinction.
The results also highlight how global landmass configuration, pCO2 and F⨀
play a critical role in planetary habitability.
Site of asteroid impact changed the history of life on Earth: the low probabi...Sérgio Sacani
Sixty-six million years ago, an asteroid approximately 9km in diameter hit the hydrocarbon- and
sulfur-rich sedimentary rocks in what is now Mexico. Recent studies have shown that this impact at
the Yucatan Peninsula heated the hydrocarbon and sulfur in these rocks, forming stratospheric soot
and sulfate aerosols and causing extreme global cooling and drought. These events triggered a mass
extinction, including dinosaurs, and led to the subsequent macroevolution of mammals. The amount
of hydrocarbon and sulfur in rocks varies widely, depending on location, which suggests that cooling
and extinction levels were dependent on impact site. Here we show that the probability of signifcant
global cooling, mass extinction, and the subsequent appearance of mammals was quite low after an
asteroid impact on the Earth’s surface. This signifcant event could have occurred if the asteroid hit the
hydrocarbon-rich areas occupying approximately 13% of the Earth’s surface. The site of asteroid impact,
therefore, changed the history of life on Earth.
Climate change is already causing impacts such as rising global temperatures, sea level rise, and more extreme weather events. Many models predict these changes will intensify in the coming decades and severely impact natural systems and human communities through increased wildfires, shifting agricultural patterns, and displacement from rising seas. Understanding past climate shifts and carefully planning adaptation and mitigation can help minimize harm from the ongoing and inevitable impacts of climate change.
This document summarizes the key findings about climate change from scientific research. It finds that climate change poses a serious threat to humanity if left unaddressed. Global temperatures are projected to rise 4°C by 2100 under business-as-usual emissions, causing devastating impacts including more extreme weather, sea level rise, and parts of the world becoming uninhabitable by 2300. While climate change mitigation efforts are underway, more urgent action is needed to transition away from fossil fuels and reduce emissions 70% by 2050 to limit warming to 2°C. Failure to act risks potentially catastrophic consequences, but with cooperation and innovation in technology, the climate challenge can be addressed.
The Toba super-eruption: micro-scale traces of a global-scale climate event?Kim Cobb
Who doesn't love a super-eruption? In this presentation, I review the facts surrounding the Toba super-eruption that occurred 74,000 years ago, and present preliminary data about its impacts on a cave system in the rain forests of Borneo.
Adaptation of an Antarctic lichen to Martian niche conditions can occur withi...Carlos Bella
The study exposed the Antarctic lichen Pleopsidium chlorophanum to simulated Martian conditions in a Mars simulation chamber for 34 days to test its ability to adapt. Under conditions simulating the unprotected Martian surface, the fungal symbiont decreased metabolic activity and it was unclear if the algal symbiont was still photosynthesizing. However, under conditions simulating a protected niche environment, the entire lichen survived, remained photosynthetically active, and even increased its photosynthetic activity over the 34 days, demonstrating its ability to adapt to Martian conditions within a protected environment.
The document discusses climate monitoring and prediction in the Philippines. It provides definitions of weather, climate, and the global climate system. It then discusses how human activities such as fossil fuel combustion and deforestation contribute to climate change by increasing greenhouse gases in the atmosphere. The document notes that the Philippines is vulnerable to impacts of climate change such as rising temperatures, changing rainfall patterns, and more intense tropical cyclones. It concludes by outlining international responses to address climate change through agreements like the UNFCCC.
This document summarizes several research papers on how weather and climate affect animals. It discusses how temperature changes can impact cold-blooded animals and endangered species. Many animals experience discomfort during extreme heat or cold. The document also reviews how weather influences animal reproduction, metabolism, and corticosterone levels. One study found that weather had little impact on coyote health but more research is needed. Overall, the document analyzes how climate change and environmental conditions significantly impact animal populations and survival.
The International Journal of Engineering and Science (The IJES)theijes
The document presents a mathematical model developed to predict the vertical temperature profile in waste stabilization ponds (WSPs). The model is based on the balance of thermal energy within volume elements of the pond. It takes into account factors like solar radiation, local advection, vertical advection, energy due to mixing, and temperature. The partial differential equation representing the model is solved using a fourth-order Runge-Kutta numerical method. Results from the model are verified against temperature profile data from previous studies on WSPs in Brazil, Nigeria, and Spain, with differences between calculated and predicted values ranging from 0.6774 to 0.9990.
Site of asteroid impact changed the history of life on Earth: the low probabi...Sérgio Sacani
Sixty-six million years ago, an asteroid approximately 9km in diameter hit the hydrocarbon- and
sulfur-rich sedimentary rocks in what is now Mexico. Recent studies have shown that this impact at
the Yucatan Peninsula heated the hydrocarbon and sulfur in these rocks, forming stratospheric soot
and sulfate aerosols and causing extreme global cooling and drought. These events triggered a mass
extinction, including dinosaurs, and led to the subsequent macroevolution of mammals. The amount
of hydrocarbon and sulfur in rocks varies widely, depending on location, which suggests that cooling
and extinction levels were dependent on impact site. Here we show that the probability of signifcant
global cooling, mass extinction, and the subsequent appearance of mammals was quite low after an
asteroid impact on the Earth’s surface. This signifcant event could have occurred if the asteroid hit the
hydrocarbon-rich areas occupying approximately 13% of the Earth’s surface. The site of asteroid impact,
therefore, changed the history of life on Earth.
Climate change is already causing impacts such as rising global temperatures, sea level rise, and more extreme weather events. Many models predict these changes will intensify in the coming decades and severely impact natural systems and human communities through increased wildfires, shifting agricultural patterns, and displacement from rising seas. Understanding past climate shifts and carefully planning adaptation and mitigation can help minimize harm from the ongoing and inevitable impacts of climate change.
This document summarizes the key findings about climate change from scientific research. It finds that climate change poses a serious threat to humanity if left unaddressed. Global temperatures are projected to rise 4°C by 2100 under business-as-usual emissions, causing devastating impacts including more extreme weather, sea level rise, and parts of the world becoming uninhabitable by 2300. While climate change mitigation efforts are underway, more urgent action is needed to transition away from fossil fuels and reduce emissions 70% by 2050 to limit warming to 2°C. Failure to act risks potentially catastrophic consequences, but with cooperation and innovation in technology, the climate challenge can be addressed.
The Toba super-eruption: micro-scale traces of a global-scale climate event?Kim Cobb
Who doesn't love a super-eruption? In this presentation, I review the facts surrounding the Toba super-eruption that occurred 74,000 years ago, and present preliminary data about its impacts on a cave system in the rain forests of Borneo.
Adaptation of an Antarctic lichen to Martian niche conditions can occur withi...Carlos Bella
The study exposed the Antarctic lichen Pleopsidium chlorophanum to simulated Martian conditions in a Mars simulation chamber for 34 days to test its ability to adapt. Under conditions simulating the unprotected Martian surface, the fungal symbiont decreased metabolic activity and it was unclear if the algal symbiont was still photosynthesizing. However, under conditions simulating a protected niche environment, the entire lichen survived, remained photosynthetically active, and even increased its photosynthetic activity over the 34 days, demonstrating its ability to adapt to Martian conditions within a protected environment.
The document discusses climate monitoring and prediction in the Philippines. It provides definitions of weather, climate, and the global climate system. It then discusses how human activities such as fossil fuel combustion and deforestation contribute to climate change by increasing greenhouse gases in the atmosphere. The document notes that the Philippines is vulnerable to impacts of climate change such as rising temperatures, changing rainfall patterns, and more intense tropical cyclones. It concludes by outlining international responses to address climate change through agreements like the UNFCCC.
This document summarizes several research papers on how weather and climate affect animals. It discusses how temperature changes can impact cold-blooded animals and endangered species. Many animals experience discomfort during extreme heat or cold. The document also reviews how weather influences animal reproduction, metabolism, and corticosterone levels. One study found that weather had little impact on coyote health but more research is needed. Overall, the document analyzes how climate change and environmental conditions significantly impact animal populations and survival.
The International Journal of Engineering and Science (The IJES)theijes
The document presents a mathematical model developed to predict the vertical temperature profile in waste stabilization ponds (WSPs). The model is based on the balance of thermal energy within volume elements of the pond. It takes into account factors like solar radiation, local advection, vertical advection, energy due to mixing, and temperature. The partial differential equation representing the model is solved using a fourth-order Runge-Kutta numerical method. Results from the model are verified against temperature profile data from previous studies on WSPs in Brazil, Nigeria, and Spain, with differences between calculated and predicted values ranging from 0.6774 to 0.9990.
Kim Cobb's Borneo stalagmite talk - AGU 2015Kim Cobb
This talk presents the latest results from the Borneo stalagmite project that seeks to reconstruct Western tropical Pacific hydrology over the last half million years. We discuss our results in the context of climate forcing, the El Nino-Southern Oscillation, and climate modeling studies.
1. The document discusses the gap between scientific understanding of climate change and public/policymaker knowledge, and notes that positive climate feedbacks now predominate, risking tipping points that could lead to a dramatically different planet.
2. Paleoclimate proxy records show historical temperature and ice volume fluctuations over millions of years, and ice core data indicates rising CO2, methane, and temperatures since 1880. Climate models project continued warming this century unless additional emissions reductions occur.
3. Several "danger zones" are identified, including ice sheet disintegration raising sea levels, mass species extinctions, and severe regional climate disruptions, underscoring the need for urgent emissions reductions to remain within safer warming limits.
Climate change has caused mass extinctions in the past. The document discusses 5 major extinction events throughout history that were linked to changes in climate, including temperature rise and carbon/methane levels. These extinctions eliminated 60-96% of species. Today, human activity like CO2 emissions may be driving a 6th mass extinction as amphibian, fish, and forest populations decline rapidly due to warming temperatures, pollution, and habitat loss. If trends continue, we could face a new extinction on par with past mass extinction events.
The document summarizes five major mass extinction events in Earth's history:
1) The Ordovician-Silurian extinction 440 million years ago wiped out 60% of marine genera. Possible causes included global cooling and asteroid impacts.
2) The Late Devonian extinction 365 million years ago eliminated 70-80% of species. Changes in sea level and climate change may have been factors.
3) The Permian-Triassic extinction 251 million years ago was the most devastating, killing 83% of genera. Meteor impacts and massive volcanic eruptions likely contributed.
4) The End-Triassic extinction 205 million years ago impacted 35% of families including marine life. Asteroid impacts and volcanic activity coincided
- An extinction event is a widespread decrease in biodiversity where the rate of extinction increases compared to the rate of evolution of new species. The "Big Five" mass extinction events are the five largest extinction events in Earth's history.
- The document then describes each of the "Big Five" extinction events by time period, percentage of families/genera/species that went extinct, and possible causes. The largest was the Permian-Triassic extinction about 252 million years ago where up to 96% of marine species went extinct.
- Possible causes of mass extinction events discussed are large igneous provinces (flood basalts), sea level falls, asteroid/comet impacts, and global cooling, with flood basalts
Climate Change an hazard zonation on the circum-arctic permafrost regionSimoneBoccuccia
This document discusses the impacts of climate change on permafrost regions and the associated hazards. It finds that warming is expected to be amplified in polar regions, causing thawing of permafrost and northward shift in its boundaries. As permafrost thaws, it can cause severe subsidence in ice-rich areas, damaging infrastructure. The document presents maps showing potential changes to permafrost distribution and increased thawing depth under climate change scenarios. Areas with extensive infrastructure development in ice-rich coastal regions and parts of Alaska, Canada, and Siberia are identified as facing the greatest hazards from thawing permafrost.
Climate Change and Wilderness - A Scottish PerspectiveforestryCommission
The document discusses the impacts of climate change from a Scottish perspective. It notes that the effects of releasing fossil fuel CO2 into the atmosphere will persist for hundreds of thousands of years. Comparison of modern temperatures with paleoclimate data suggests the planet is currently at its warmest in the past one million years, constituting dangerous climate change. The impacts of climate change are already being observed globally through rising temperatures and sea levels as well as decreasing snowfall.
The document discusses the topic of climate change, past, present, and future. It provides an overview of the factors that control climate, including land surface properties, oceans, greenhouse gases, and solar radiation. It describes how the climate has varied in the past due to natural factors like variations in Earth's orbit and composition of the atmosphere. It then discusses evidence that warming trends over the last few decades are likely due to human activities like fossil fuel burning. Models predict that future climate change may have significant impacts.
- The document discusses two potential causes of the mass extinction event that wiped out the dinosaurs - massive volcanic activity from the Deccan Traps (in present-day India), and a large asteroid impact in what is now the Gulf of Mexico.
- Through climate and habitat modeling, the researchers found that scenarios involving prolonged global cooling from the asteroid impact led to a substantial reduction in suitable habitats for dinosaurs worldwide.
- In contrast, simulations of Deccan volcanism, even those with major global warming effects from carbon dioxide release, did not produce conditions severe enough to cause a dinosaur extinction.
- The asteroid impact may have been the primary driver of the non-avian dinosaur extinction, though volcanic warming likely reduced
Large-scale Volcanism and the Heat Death of Terrestrial WorldsSérgio Sacani
This document discusses the potential for large igneous provinces (LIPs) to cause the "heat death" of terrestrial planets through massive volcanic eruptions that overwhelm the climate system. It examines the timing of LIP events on Earth to estimate the likelihood of nearly simultaneous eruptions. Statistical analysis of Earth's LIP record finds that eruptions within 0.1-1 million years of each other are likely. Simultaneous LIPs could have driven Venus into a runaway greenhouse effect like its current state. The timing of LIP events on Earth provides insight into potential past LIP activity on Venus that may have ended its hypothesized earlier temperate climate.
This document summarizes the science of climate change and global warming. It discusses how human activities have increased greenhouse gas concentrations in the atmosphere through fossil fuel combustion and land use changes. It explains how increased greenhouse gases trap more heat in the lower atmosphere and warm the planet through the greenhouse effect. Observations show global temperatures have risen over 1°F in the last century, glaciers are retreating, and other indicators match projections of human-caused climate change rather than natural fluctuations alone. The document establishes the scientific consensus that human emissions are the dominant cause of recent global warming.
Paleoclimatology is the study of past climates through the use of proxies such as microbial life found in sediment cores, ice cores, and tree rings. Researchers use various analytical methods to extract information from these proxies about past climate conditions. For example, oxygen isotope ratios in foraminifera and diatom shells can provide information about past water temperatures, and the abundance and composition of microbial populations may indicate environmental conditions like temperature. Volcanic eruptions can influence climate in both the short and long term. Large eruptions that eject ash and sulfur dioxide into the stratosphere can block sunlight and cool the planet for several years through radiation scattering. However, massive eruptions that release large amounts of carbon dioxide may
The document discusses several factors related to climate change:
1. It discusses three primary factors that influence Earth's orbit and axial tilt - eccentricity, axial tilt, and precession - and how these Milankovitch cycles impact climate over long time periods.
2. It explains the Ruddiman hypothesis, which suggests that human agricultural activities beginning around 8,000 years ago prevented the onset of a natural ice age, and industrialization in the 19th century further disrupted the climate cycle.
3. It provides examples of how human activities like fossil fuel use, deforestation, and agriculture have increased greenhouse gases in the atmosphere like carbon dioxide and methane, driving unprecedented modern climate change.
The document summarizes research by Hansen et al. (2008) regarding appropriate targets for atmospheric CO2 levels. It finds that:
1) Analysis of past climate changes, such as those between ice ages and interglacial periods (Pleistocene epoch) and between warm and cold periods in the Cenozoic era, indicate the climate sensitivity including slow feedbacks is around 6°C for doubled CO2, higher than the current IPCC estimate of 3°C.
2) CO2 levels were likely around 450 ppm at the warmest point of the Cenozoic era 35 million years ago, and levels above 350-400 ppm risk severe impacts such as sea level rise
This document summarizes a study that investigated how global cooling influenced speciation rates in terrestrial orchids. The researchers reconstructed the evolutionary history of over 1,400 orchid species and found that speciation rates increased as global temperatures cooled, particularly between the Miocene and present day. They found this relationship held across the three main orchid subclades as well as in genera with diverse pollination strategies. Modeling supported temperature-driven speciation over 700 times more than a model of increasing speciation rates over time. The study provides strong evidence that global cooling was a major driver of speciation in terrestrial orchids worldwide.
1) The document discusses various causes of global climate change including changes in Earth's orbit and solar radiation, albedo effects, and greenhouse gases like carbon dioxide and methane.
2) Evidence of past climate changes is seen in temperature and carbon dioxide variations from ice cores, glacial activity, sea levels, and vegetation changes.
3) The author argues that climate change is a natural phenomenon and that the role of human-caused carbon dioxide emissions in current warming is limited and uncertain.
Past Climate as the key to understand the future: example from the Mediterran...CAESCG.org
By Vincenzo Pascucci
Dipartimento di Scienze Botaniche, Ecologiche é Geologiche.
Universitá di Sassari
pascucci@uniss.it
Conferencia impartida en el marco de los viernes científicos de la Universidad de Almería
Paleoclimate: past-climate as the key to understand the future. Example from ...Fernando Reche
Conferencia impartida por Vincenzo Pascucci el 1 de abril de 2011 en el marco de los Viernes Científicos, actividad organizada por la Facultad de Ciencias Experimentales de la Universidad de Almería
This summary provides the key information from the document in 3 sentences:
The document summarizes the 1992 United Nations Framework Convention on Climate Change, noting that it recognizes climate change as a problem, sets the objective of stabilizing greenhouse gas concentrations to prevent dangerous interference with the climate system, and directs that this be achieved within a timeframe that allows ecosystems and food production to adapt while allowing sustainable economic development.
The document discusses human-caused global warming and how it can be slowed and stopped through practical actions. While some predictions of global warming effects are exaggerated, the evidence is clear that warming is occurring due to increased greenhouse gases from human activities. Studying factors like glacial melting and climate forcing agents shows that global warming can be addressed by reducing emissions to achieve a healthier atmosphere.
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
More Related Content
Similar to Climate extremes likely to drive land mammal extinction during next supercontinent assembly
Kim Cobb's Borneo stalagmite talk - AGU 2015Kim Cobb
This talk presents the latest results from the Borneo stalagmite project that seeks to reconstruct Western tropical Pacific hydrology over the last half million years. We discuss our results in the context of climate forcing, the El Nino-Southern Oscillation, and climate modeling studies.
1. The document discusses the gap between scientific understanding of climate change and public/policymaker knowledge, and notes that positive climate feedbacks now predominate, risking tipping points that could lead to a dramatically different planet.
2. Paleoclimate proxy records show historical temperature and ice volume fluctuations over millions of years, and ice core data indicates rising CO2, methane, and temperatures since 1880. Climate models project continued warming this century unless additional emissions reductions occur.
3. Several "danger zones" are identified, including ice sheet disintegration raising sea levels, mass species extinctions, and severe regional climate disruptions, underscoring the need for urgent emissions reductions to remain within safer warming limits.
Climate change has caused mass extinctions in the past. The document discusses 5 major extinction events throughout history that were linked to changes in climate, including temperature rise and carbon/methane levels. These extinctions eliminated 60-96% of species. Today, human activity like CO2 emissions may be driving a 6th mass extinction as amphibian, fish, and forest populations decline rapidly due to warming temperatures, pollution, and habitat loss. If trends continue, we could face a new extinction on par with past mass extinction events.
The document summarizes five major mass extinction events in Earth's history:
1) The Ordovician-Silurian extinction 440 million years ago wiped out 60% of marine genera. Possible causes included global cooling and asteroid impacts.
2) The Late Devonian extinction 365 million years ago eliminated 70-80% of species. Changes in sea level and climate change may have been factors.
3) The Permian-Triassic extinction 251 million years ago was the most devastating, killing 83% of genera. Meteor impacts and massive volcanic eruptions likely contributed.
4) The End-Triassic extinction 205 million years ago impacted 35% of families including marine life. Asteroid impacts and volcanic activity coincided
- An extinction event is a widespread decrease in biodiversity where the rate of extinction increases compared to the rate of evolution of new species. The "Big Five" mass extinction events are the five largest extinction events in Earth's history.
- The document then describes each of the "Big Five" extinction events by time period, percentage of families/genera/species that went extinct, and possible causes. The largest was the Permian-Triassic extinction about 252 million years ago where up to 96% of marine species went extinct.
- Possible causes of mass extinction events discussed are large igneous provinces (flood basalts), sea level falls, asteroid/comet impacts, and global cooling, with flood basalts
Climate Change an hazard zonation on the circum-arctic permafrost regionSimoneBoccuccia
This document discusses the impacts of climate change on permafrost regions and the associated hazards. It finds that warming is expected to be amplified in polar regions, causing thawing of permafrost and northward shift in its boundaries. As permafrost thaws, it can cause severe subsidence in ice-rich areas, damaging infrastructure. The document presents maps showing potential changes to permafrost distribution and increased thawing depth under climate change scenarios. Areas with extensive infrastructure development in ice-rich coastal regions and parts of Alaska, Canada, and Siberia are identified as facing the greatest hazards from thawing permafrost.
Climate Change and Wilderness - A Scottish PerspectiveforestryCommission
The document discusses the impacts of climate change from a Scottish perspective. It notes that the effects of releasing fossil fuel CO2 into the atmosphere will persist for hundreds of thousands of years. Comparison of modern temperatures with paleoclimate data suggests the planet is currently at its warmest in the past one million years, constituting dangerous climate change. The impacts of climate change are already being observed globally through rising temperatures and sea levels as well as decreasing snowfall.
The document discusses the topic of climate change, past, present, and future. It provides an overview of the factors that control climate, including land surface properties, oceans, greenhouse gases, and solar radiation. It describes how the climate has varied in the past due to natural factors like variations in Earth's orbit and composition of the atmosphere. It then discusses evidence that warming trends over the last few decades are likely due to human activities like fossil fuel burning. Models predict that future climate change may have significant impacts.
- The document discusses two potential causes of the mass extinction event that wiped out the dinosaurs - massive volcanic activity from the Deccan Traps (in present-day India), and a large asteroid impact in what is now the Gulf of Mexico.
- Through climate and habitat modeling, the researchers found that scenarios involving prolonged global cooling from the asteroid impact led to a substantial reduction in suitable habitats for dinosaurs worldwide.
- In contrast, simulations of Deccan volcanism, even those with major global warming effects from carbon dioxide release, did not produce conditions severe enough to cause a dinosaur extinction.
- The asteroid impact may have been the primary driver of the non-avian dinosaur extinction, though volcanic warming likely reduced
Large-scale Volcanism and the Heat Death of Terrestrial WorldsSérgio Sacani
This document discusses the potential for large igneous provinces (LIPs) to cause the "heat death" of terrestrial planets through massive volcanic eruptions that overwhelm the climate system. It examines the timing of LIP events on Earth to estimate the likelihood of nearly simultaneous eruptions. Statistical analysis of Earth's LIP record finds that eruptions within 0.1-1 million years of each other are likely. Simultaneous LIPs could have driven Venus into a runaway greenhouse effect like its current state. The timing of LIP events on Earth provides insight into potential past LIP activity on Venus that may have ended its hypothesized earlier temperate climate.
This document summarizes the science of climate change and global warming. It discusses how human activities have increased greenhouse gas concentrations in the atmosphere through fossil fuel combustion and land use changes. It explains how increased greenhouse gases trap more heat in the lower atmosphere and warm the planet through the greenhouse effect. Observations show global temperatures have risen over 1°F in the last century, glaciers are retreating, and other indicators match projections of human-caused climate change rather than natural fluctuations alone. The document establishes the scientific consensus that human emissions are the dominant cause of recent global warming.
Paleoclimatology is the study of past climates through the use of proxies such as microbial life found in sediment cores, ice cores, and tree rings. Researchers use various analytical methods to extract information from these proxies about past climate conditions. For example, oxygen isotope ratios in foraminifera and diatom shells can provide information about past water temperatures, and the abundance and composition of microbial populations may indicate environmental conditions like temperature. Volcanic eruptions can influence climate in both the short and long term. Large eruptions that eject ash and sulfur dioxide into the stratosphere can block sunlight and cool the planet for several years through radiation scattering. However, massive eruptions that release large amounts of carbon dioxide may
The document discusses several factors related to climate change:
1. It discusses three primary factors that influence Earth's orbit and axial tilt - eccentricity, axial tilt, and precession - and how these Milankovitch cycles impact climate over long time periods.
2. It explains the Ruddiman hypothesis, which suggests that human agricultural activities beginning around 8,000 years ago prevented the onset of a natural ice age, and industrialization in the 19th century further disrupted the climate cycle.
3. It provides examples of how human activities like fossil fuel use, deforestation, and agriculture have increased greenhouse gases in the atmosphere like carbon dioxide and methane, driving unprecedented modern climate change.
The document summarizes research by Hansen et al. (2008) regarding appropriate targets for atmospheric CO2 levels. It finds that:
1) Analysis of past climate changes, such as those between ice ages and interglacial periods (Pleistocene epoch) and between warm and cold periods in the Cenozoic era, indicate the climate sensitivity including slow feedbacks is around 6°C for doubled CO2, higher than the current IPCC estimate of 3°C.
2) CO2 levels were likely around 450 ppm at the warmest point of the Cenozoic era 35 million years ago, and levels above 350-400 ppm risk severe impacts such as sea level rise
This document summarizes a study that investigated how global cooling influenced speciation rates in terrestrial orchids. The researchers reconstructed the evolutionary history of over 1,400 orchid species and found that speciation rates increased as global temperatures cooled, particularly between the Miocene and present day. They found this relationship held across the three main orchid subclades as well as in genera with diverse pollination strategies. Modeling supported temperature-driven speciation over 700 times more than a model of increasing speciation rates over time. The study provides strong evidence that global cooling was a major driver of speciation in terrestrial orchids worldwide.
1) The document discusses various causes of global climate change including changes in Earth's orbit and solar radiation, albedo effects, and greenhouse gases like carbon dioxide and methane.
2) Evidence of past climate changes is seen in temperature and carbon dioxide variations from ice cores, glacial activity, sea levels, and vegetation changes.
3) The author argues that climate change is a natural phenomenon and that the role of human-caused carbon dioxide emissions in current warming is limited and uncertain.
Past Climate as the key to understand the future: example from the Mediterran...CAESCG.org
By Vincenzo Pascucci
Dipartimento di Scienze Botaniche, Ecologiche é Geologiche.
Universitá di Sassari
pascucci@uniss.it
Conferencia impartida en el marco de los viernes científicos de la Universidad de Almería
Paleoclimate: past-climate as the key to understand the future. Example from ...Fernando Reche
Conferencia impartida por Vincenzo Pascucci el 1 de abril de 2011 en el marco de los Viernes Científicos, actividad organizada por la Facultad de Ciencias Experimentales de la Universidad de Almería
This summary provides the key information from the document in 3 sentences:
The document summarizes the 1992 United Nations Framework Convention on Climate Change, noting that it recognizes climate change as a problem, sets the objective of stabilizing greenhouse gas concentrations to prevent dangerous interference with the climate system, and directs that this be achieved within a timeframe that allows ecosystems and food production to adapt while allowing sustainable economic development.
The document discusses human-caused global warming and how it can be slowed and stopped through practical actions. While some predictions of global warming effects are exaggerated, the evidence is clear that warming is occurring due to increased greenhouse gases from human activities. Studying factors like glacial melting and climate forcing agents shows that global warming can be addressed by reducing emissions to achieve a healthier atmosphere.
Similar to Climate extremes likely to drive land mammal extinction during next supercontinent assembly (20)
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
The debris of the ‘last major merger’ is dynamically youngSérgio Sacani
The Milky Way’s (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the
‘last major merger.’ Hypotheses for the origin of this component include Gaia-Sausage/Enceladus (GSE), where the progenitor
collided with the MW proto-disc 8–11 Gyr ago, and the Virgo Radial Merger (VRM), where the progenitor collided with the
MW disc within the last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space,
because the morphology of debris depends on how long it has had to phase mix. The recently identified phase-space folds in Gaia
DR3 have positive caustic velocities, making them fundamentally different than the phase-mixed chevrons found in simulations
at late times. Roughly 20 per cent of the stars in the prograde local stellar halo are associated with the observed caustics. Based
on a simple phase-mixing model, the observed number of caustics are consistent with a merger that occurred 1–2 Gyr ago.
We also compare the observed phase-space distribution to FIRE-2 Latte simulations of GSE-like mergers, using a quantitative
measurement of phase mixing (2D causticality). The observed local phase-space distribution best matches the simulated data
1–2 Gyr after collision, and certainly not later than 3 Gyr. This is further evidence that the progenitor of the ‘last major merger’
did not collide with the MW proto-disc at early times, as is thought for the GSE, but instead collided with the MW disc within
the last few Gyr, consistent with the body of work surrounding the VRM.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
Gliese 12 b: A Temperate Earth-sized Planet at 12 pc Ideal for Atmospheric Tr...Sérgio Sacani
Recent discoveries of Earth-sized planets transiting nearby M dwarfs have made it possible to characterize the
atmospheres of terrestrial planets via follow-up spectroscopic observations. However, the number of such planets
receiving low insolation is still small, limiting our ability to understand the diversity of the atmospheric
composition and climates of temperate terrestrial planets. We report the discovery of an Earth-sized planet
transiting the nearby (12 pc) inactive M3.0 dwarf Gliese 12 (TOI-6251) with an orbital period (Porb) of 12.76 days.
The planet, Gliese 12 b, was initially identified as a candidate with an ambiguous Porb from TESS data. We
confirmed the transit signal and Porb using ground-based photometry with MuSCAT2 and MuSCAT3, and
validated the planetary nature of the signal using high-resolution images from Gemini/NIRI and Keck/NIRC2 as
well as radial velocity (RV) measurements from the InfraRed Doppler instrument on the Subaru 8.2 m telescope
and from CARMENES on the CAHA 3.5 m telescope. X-ray observations with XMM-Newton showed the host
star is inactive, with an X-ray-to-bolometric luminosity ratio of log 5.7 L L X bol » - . Joint analysis of the light
curves and RV measurements revealed that Gliese 12 b has a radius of 0.96 ± 0.05 R⊕,a3σ mass upper limit of
3.9 M⊕, and an equilibrium temperature of 315 ± 6 K assuming zero albedo. The transmission spectroscopy metric
(TSM) value of Gliese 12 b is close to the TSM values of the TRAPPIST-1 planets, adding Gliese 12 b to the small
list of potentially terrestrial, temperate planets amenable to atmospheric characterization with JWST.
Gliese 12 b, a temperate Earth-sized planet at 12 parsecs discovered with TES...Sérgio Sacani
We report on the discovery of Gliese 12 b, the nearest transiting temperate, Earth-sized planet found to date. Gliese 12 is a
bright (V = 12.6 mag, K = 7.8 mag) metal-poor M4V star only 12.162 ± 0.005 pc away from the Solar system with one of the
lowest stellar activity levels known for M-dwarfs. A planet candidate was detected by TESS based on only 3 transits in sectors
42, 43, and 57, with an ambiguity in the orbital period due to observational gaps. We performed follow-up transit observations
with CHEOPS and ground-based photometry with MINERVA-Australis, SPECULOOS, and Purple Mountain Observatory,
as well as further TESS observations in sector 70. We statistically validate Gliese 12 b as a planet with an orbital period of
12.76144 ± 0.00006 d and a radius of 1.0 ± 0.1 R⊕, resulting in an equilibrium temperature of ∼315 K. Gliese 12 b has excellent
future prospects for precise mass measurement, which may inform how planetary internal structure is affected by the stellar
compositional environment. Gliese 12 b also represents one of the best targets to study whether Earth-like planets orbiting cool
stars can retain their atmospheres, a crucial step to advance our understanding of habitability on Earth and across the galaxy.
The importance of continents, oceans and plate tectonics for the evolution of...Sérgio Sacani
Within the uncertainties of involved astronomical and biological parameters, the Drake Equation
typically predicts that there should be many exoplanets in our galaxy hosting active, communicative
civilizations (ACCs). These optimistic calculations are however not supported by evidence, which is
often referred to as the Fermi Paradox. Here, we elaborate on this long-standing enigma by showing
the importance of planetary tectonic style for biological evolution. We summarize growing evidence
that a prolonged transition from Mesoproterozoic active single lid tectonics (1.6 to 1.0 Ga) to modern
plate tectonics occurred in the Neoproterozoic Era (1.0 to 0.541 Ga), which dramatically accelerated
emergence and evolution of complex species. We further suggest that both continents and oceans
are required for ACCs because early evolution of simple life must happen in water but late evolution
of advanced life capable of creating technology must happen on land. We resolve the Fermi Paradox
(1) by adding two additional terms to the Drake Equation: foc
(the fraction of habitable exoplanets
with significant continents and oceans) and fpt
(the fraction of habitable exoplanets with significant
continents and oceans that have had plate tectonics operating for at least 0.5 Ga); and (2) by
demonstrating that the product of foc
and fpt
is very small (< 0.00003–0.002). We propose that the lack
of evidence for ACCs reflects the scarcity of long-lived plate tectonics and/or continents and oceans on
exoplanets with primitive life.
A Giant Impact Origin for the First Subduction on EarthSérgio Sacani
Hadean zircons provide a potential record of Earth's earliest subduction 4.3 billion years ago. Itremains enigmatic how subduction could be initiated so soon after the presumably Moon‐forming giant impact(MGI). Earlier studies found an increase in Earth's core‐mantle boundary (CMB) temperature due to theaccumulation of the impactor's core, and our recent work shows Earth's lower mantle remains largely solid, withsome of the impactor's mantle potentially surviving as the large low‐shear velocity provinces (LLSVPs). Here,we show that a hot post‐impact CMB drives the initiation of strong mantle plumes that can induce subductioninitiation ∼200 Myr after the MGI. 2D and 3D thermomechanical computations show that a high CMBtemperature is the primary factor triggering early subduction, with enrichment of heat‐producing elements inLLSVPs as another potential factor. The models link the earliest subduction to the MGI with implications forunderstanding the diverse tectonic regimes of rocky planets.
Constraints on Neutrino Natal Kicks from Black-Hole Binary VFTS 243Sérgio Sacani
The recently reported observation of VFTS 243 is the first example of a massive black-hole binary
system with negligible binary interaction following black-hole formation. The black-hole mass (≈10M⊙)
and near-circular orbit (e ≈ 0.02) of VFTS 243 suggest that the progenitor star experienced complete
collapse, with energy-momentum being lost predominantly through neutrinos. VFTS 243 enables us to
constrain the natal kick and neutrino-emission asymmetry during black-hole formation. At 68% confidence
level, the natal kick velocity (mass decrement) is ≲10 km=s (≲1.0M⊙), with a full probability distribution
that peaks when ≈0.3M⊙ were ejected, presumably in neutrinos, and the black hole experienced a natal
kick of 4 km=s. The neutrino-emission asymmetry is ≲4%, with best fit values of ∼0–0.2%. Such a small
neutrino natal kick accompanying black-hole formation is in agreement with theoretical predictions.
Detectability of Solar Panels as a TechnosignatureSérgio Sacani
In this work, we assess the potential detectability of solar panels made of silicon on an Earth-like
exoplanet as a potential technosignature. Silicon-based photovoltaic cells have high reflectance in the
UV-VIS and in the near-IR, within the wavelength range of a space-based flagship mission concept
like the Habitable Worlds Observatory (HWO). Assuming that only solar energy is used to provide
the 2022 human energy needs with a land cover of ∼ 2.4%, and projecting the future energy demand
assuming various growth-rate scenarios, we assess the detectability with an 8 m HWO-like telescope.
Assuming the most favorable viewing orientation, and focusing on the strong absorption edge in the
ultraviolet-to-visible (0.34 − 0.52 µm), we find that several 100s of hours of observation time is needed
to reach a SNR of 5 for an Earth-like planet around a Sun-like star at 10pc, even with a solar panel
coverage of ∼ 23% land coverage of a future Earth. We discuss the necessity of concepts like Kardeshev
Type I/II civilizations and Dyson spheres, which would aim to harness vast amounts of energy. Even
with much larger populations than today, the total energy use of human civilization would be orders of
magnitude below the threshold for causing direct thermal heating or reaching the scale of a Kardashev
Type I civilization. Any extraterrrestrial civilization that likewise achieves sustainable population
levels may also find a limit on its need to expand, which suggests that a galaxy-spanning civilization
as imagined in the Fermi paradox may not exist.
Jet reorientation in central galaxies of clusters and groups: insights from V...Sérgio Sacani
Recent observations of galaxy clusters and groups with misalignments between their central AGN jets
and X-ray cavities, or with multiple misaligned cavities, have raised concerns about the jet – bubble
connection in cooling cores, and the processes responsible for jet realignment. To investigate the
frequency and causes of such misalignments, we construct a sample of 16 cool core galaxy clusters and
groups. Using VLBA radio data we measure the parsec-scale position angle of the jets, and compare
it with the position angle of the X-ray cavities detected in Chandra data. Using the overall sample
and selected subsets, we consistently find that there is a 30% – 38% chance to find a misalignment
larger than ∆Ψ = 45◦ when observing a cluster/group with a detected jet and at least one cavity. We
determine that projection may account for an apparently large ∆Ψ only in a fraction of objects (∼35%),
and given that gas dynamical disturbances (as sloshing) are found in both aligned and misaligned
systems, we exclude environmental perturbation as the main driver of cavity – jet misalignment.
Moreover, we find that large misalignments (up to ∼ 90◦
) are favored over smaller ones (45◦ ≤ ∆Ψ ≤
70◦
), and that the change in jet direction can occur on timescales between one and a few tens of Myr.
We conclude that misalignments are more likely related to actual reorientation of the jet axis, and we
discuss several engine-based mechanisms that may cause these dramatic changes.
The solar dynamo begins near the surfaceSérgio Sacani
The magnetic dynamo cycle of the Sun features a distinct pattern: a propagating
region of sunspot emergence appears around 30° latitude and vanishes near the
equator every 11 years (ref. 1). Moreover, longitudinal flows called torsional oscillations
closely shadow sunspot migration, undoubtedly sharing a common cause2. Contrary
to theories suggesting deep origins of these phenomena, helioseismology pinpoints
low-latitude torsional oscillations to the outer 5–10% of the Sun, the near-surface
shear layer3,4. Within this zone, inwardly increasing differential rotation coupled with
a poloidal magnetic field strongly implicates the magneto-rotational instability5,6,
prominent in accretion-disk theory and observed in laboratory experiments7.
Together, these two facts prompt the general question: whether the solar dynamo is
possibly a near-surface instability. Here we report strong affirmative evidence in stark
contrast to traditional models8 focusing on the deeper tachocline. Simple analytic
estimates show that the near-surface magneto-rotational instability better explains
the spatiotemporal scales of the torsional oscillations and inferred subsurface
magnetic field amplitudes9. State-of-the-art numerical simulations corroborate these
estimates and reproduce hemispherical magnetic current helicity laws10. The dynamo
resulting from a well-understood near-surface phenomenon improves prospects
for accurate predictions of full magnetic cycles and space weather, affecting the
electromagnetic infrastructure of Earth.
Extensive Pollution of Uranus and Neptune’s Atmospheres by Upsweep of Icy Mat...Sérgio Sacani
In the Nice model of solar system formation, Uranus and Neptune undergo an orbital upheaval,
sweeping through a planetesimal disk. The region of the disk from which material is accreted by
the ice giants during this phase of their evolution has not previously been identified. We perform
direct N-body orbital simulations of the four giant planets to determine the amount and origin of solid
accretion during this orbital upheaval. We find that the ice giants undergo an extreme bombardment
event, with collision rates as much as ∼3 per hour assuming km-sized planetesimals, increasing the
total planet mass by up to ∼0.35%. In all cases, the initially outermost ice giant experiences the
largest total enhancement. We determine that for some plausible planetesimal properties, the resulting
atmospheric enrichment could potentially produce sufficient latent heat to alter the planetary cooling
timescale according to existing models. Our findings suggest that substantial accretion during this
phase of planetary evolution may have been sufficient to impact the atmospheric composition and
thermal evolution of the ice giants, motivating future work on the fate of deposited solid material.
Exomoons & Exorings with the Habitable Worlds Observatory I: On the Detection...Sérgio Sacani
The highest priority recommendation of the Astro2020 Decadal Survey for space-based astronomy
was the construction of an observatory capable of characterizing habitable worlds. In this paper series
we explore the detectability of and interference from exomoons and exorings serendipitously observed
with the proposed Habitable Worlds Observatory (HWO) as it seeks to characterize exoplanets, starting
in this manuscript with Earth-Moon analog mutual events. Unlike transits, which only occur in systems
viewed near edge-on, shadow (i.e., solar eclipse) and lunar eclipse mutual events occur in almost every
star-planet-moon system. The cadence of these events can vary widely from ∼yearly to multiple events
per day, as was the case in our younger Earth-Moon system. Leveraging previous space-based (EPOXI)
lightcurves of a Moon transit and performance predictions from the LUVOIR-B concept, we derive
the detectability of Moon analogs with HWO. We determine that Earth-Moon analogs are detectable
with observation of ∼2-20 mutual events for systems within 10 pc, and larger moons should remain
detectable out to 20 pc. We explore the extent to which exomoon mutual events can mimic planet
features and weather. We find that HWO wavelength coverage in the near-IR, specifically in the 1.4 µm
water band where large moons can outshine their host planet, will aid in differentiating exomoon signals
from exoplanet variability. Finally, we predict that exomoons formed through collision processes akin
to our Moon are more likely to be detected in younger systems, where shorter orbital periods and
favorable geometry enhance the probability and frequency of mutual events.
Emergent ribozyme behaviors in oxychlorine brines indicate a unique niche for...Sérgio Sacani
Mars is a particularly attractive candidate among known astronomical objects
to potentially host life. Results from space exploration missions have provided
insights into Martian geochemistry that indicate oxychlorine species, particularly perchlorate, are ubiquitous features of the Martian geochemical landscape. Perchlorate presents potential obstacles for known forms of life due to
its toxicity. However, it can also provide potential benefits, such as producing
brines by deliquescence, like those thought to exist on present-day Mars. Here
we show perchlorate brines support folding and catalysis of functional RNAs,
while inactivating representative protein enzymes. Additionally, we show
perchlorate and other oxychlorine species enable ribozyme functions,
including homeostasis-like regulatory behavior and ribozyme-catalyzed
chlorination of organic molecules. We suggest nucleic acids are uniquely wellsuited to hypersaline Martian environments. Furthermore, Martian near- or
subsurface oxychlorine brines, and brines found in potential lifeforms, could
provide a unique niche for biomolecular evolution.
Continuum emission from within the plunging region of black hole discsSérgio Sacani
The thermal continuum emission observed from accreting black holes across X-ray bands has the potential to be leveraged as a
powerful probe of the mass and spin of the central black hole. The vast majority of existing ‘continuum fitting’ models neglect
emission sourced at and within the innermost stable circular orbit (ISCO) of the black hole. Numerical simulations, however,
find non-zero emission sourced from these regions. In this work, we extend existing techniques by including the emission
sourced from within the plunging region, utilizing new analytical models that reproduce the properties of numerical accretion
simulations. We show that in general the neglected intra-ISCO emission produces a hot-and-small quasi-blackbody component,
but can also produce a weak power-law tail for more extreme parameter regions. A similar hot-and-small blackbody component
has been added in by hand in an ad hoc manner to previous analyses of X-ray binary spectra. We show that the X-ray spectrum
of MAXI J1820+070 in a soft-state outburst is extremely well described by a full Kerr black hole disc, while conventional
models that neglect intra-ISCO emission are unable to reproduce the data. We believe this represents the first robust detection of
intra-ISCO emission in the literature, and allows additional constraints to be placed on the MAXI J1820 + 070 black hole spin
which must be low a• < 0.5 to allow a detectable intra-ISCO region. Emission from within the ISCO is the dominant emission
component in the MAXI J1820 + 070 spectrum between 6 and 10 keV, highlighting the necessity of including this region. Our
continuum fitting model is made publicly available.
WASP-69b’s Escaping Envelope Is Confined to a Tail Extending at Least 7 RpSérgio Sacani
Studying the escaping atmospheres of highly irradiated exoplanets is critical for understanding the physical
mechanisms that shape the demographics of close-in planets. A number of planetary outflows have been observed
as excess H/He absorption during/after transit. Such an outflow has been observed for WASP-69b by multiple
groups that disagree on the geometry and velocity structure of the outflow. Here, we report the detection of this
planet’s outflow using Keck/NIRSPEC for the first time. We observed the outflow 1.28 hr after egress until the
target set, demonstrating the outflow extends at least 5.8 × 105 km or 7.5 Rp This detection is significantly longer
than previous observations, which report an outflow extending ∼2.2 planet radii just 1 yr prior. The outflow is
blueshifted by −23 km s−1 in the planetary rest frame. We estimate a current mass-loss rate of 1 M⊕ Gyr−1
. Our
observations are most consistent with an outflow that is strongly sculpted by ram pressure from the stellar wind.
However, potential variability in the outflow could be due to time-varying interactions with the stellar wind or
differences in instrumental precision.
Current Ms word generated power point presentation covers major details about the micronuclei test. It's significance and assays to conduct it. It is used to detect the micronuclei formation inside the cells of nearly every multicellular organism. It's formation takes place during chromosomal sepration at metaphase.
When I was asked to give a companion lecture in support of ‘The Philosophy of Science’ (https://shorturl.at/4pUXz) I decided not to walk through the detail of the many methodologies in order of use. Instead, I chose to employ a long standing, and ongoing, scientific development as an exemplar. And so, I chose the ever evolving story of Thermodynamics as a scientific investigation at its best.
Conducted over a period of >200 years, Thermodynamics R&D, and application, benefitted from the highest levels of professionalism, collaboration, and technical thoroughness. New layers of application, methodology, and practice were made possible by the progressive advance of technology. In turn, this has seen measurement and modelling accuracy continually improved at a micro and macro level.
Perhaps most importantly, Thermodynamics rapidly became a primary tool in the advance of applied science/engineering/technology, spanning micro-tech, to aerospace and cosmology. I can think of no better a story to illustrate the breadth of scientific methodologies and applications at their best.
The cost of acquiring information by natural selectionCarl Bergstrom
This is a short talk that I gave at the Banff International Research Station workshop on Modeling and Theory in Population Biology. The idea is to try to understand how the burden of natural selection relates to the amount of information that selection puts into the genome.
It's based on the first part of this research paper:
The cost of information acquisition by natural selection
Ryan Seamus McGee, Olivia Kosterlitz, Artem Kaznatcheev, Benjamin Kerr, Carl T. Bergstrom
bioRxiv 2022.07.02.498577; doi: https://doi.org/10.1101/2022.07.02.498577
Authoring a personal GPT for your research and practice: How we created the Q...Leonel Morgado
Thematic analysis in qualitative research is a time-consuming and systematic task, typically done using teams. Team members must ground their activities on common understandings of the major concepts underlying the thematic analysis, and define criteria for its development. However, conceptual misunderstandings, equivocations, and lack of adherence to criteria are challenges to the quality and speed of this process. Given the distributed and uncertain nature of this process, we wondered if the tasks in thematic analysis could be supported by readily available artificial intelligence chatbots. Our early efforts point to potential benefits: not just saving time in the coding process but better adherence to criteria and grounding, by increasing triangulation between humans and artificial intelligence. This tutorial will provide a description and demonstration of the process we followed, as two academic researchers, to develop a custom ChatGPT to assist with qualitative coding in the thematic data analysis process of immersive learning accounts in a survey of the academic literature: QUAL-E Immersive Learning Thematic Analysis Helper. In the hands-on time, participants will try out QUAL-E and develop their ideas for their own qualitative coding ChatGPT. Participants that have the paid ChatGPT Plus subscription can create a draft of their assistants. The organizers will provide course materials and slide deck that participants will be able to utilize to continue development of their custom GPT. The paid subscription to ChatGPT Plus is not required to participate in this workshop, just for trying out personal GPTs during it.
ESR spectroscopy in liquid food and beverages.pptxPRIYANKA PATEL
With increasing population, people need to rely on packaged food stuffs. Packaging of food materials requires the preservation of food. There are various methods for the treatment of food to preserve them and irradiation treatment of food is one of them. It is the most common and the most harmless method for the food preservation as it does not alter the necessary micronutrients of food materials. Although irradiated food doesn’t cause any harm to the human health but still the quality assessment of food is required to provide consumers with necessary information about the food. ESR spectroscopy is the most sophisticated way to investigate the quality of the food and the free radicals induced during the processing of the food. ESR spin trapping technique is useful for the detection of highly unstable radicals in the food. The antioxidant capability of liquid food and beverages in mainly performed by spin trapping technique.
Or: Beyond linear.
Abstract: Equivariant neural networks are neural networks that incorporate symmetries. The nonlinear activation functions in these networks result in interesting nonlinear equivariant maps between simple representations, and motivate the key player of this talk: piecewise linear representation theory.
Disclaimer: No one is perfect, so please mind that there might be mistakes and typos.
dtubbenhauer@gmail.com
Corrected slides: dtubbenhauer.com/talks.html
PPT on Direct Seeded Rice presented at the three-day 'Training and Validation Workshop on Modules of Climate Smart Agriculture (CSA) Technologies in South Asia' workshop on April 22, 2024.
Immersive Learning That Works: Research Grounding and Paths ForwardLeonel Morgado
We will metaverse into the essence of immersive learning, into its three dimensions and conceptual models. This approach encompasses elements from teaching methodologies to social involvement, through organizational concerns and technologies. Challenging the perception of learning as knowledge transfer, we introduce a 'Uses, Practices & Strategies' model operationalized by the 'Immersive Learning Brain' and ‘Immersion Cube’ frameworks. This approach offers a comprehensive guide through the intricacies of immersive educational experiences and spotlighting research frontiers, along the immersion dimensions of system, narrative, and agency. Our discourse extends to stakeholders beyond the academic sphere, addressing the interests of technologists, instructional designers, and policymakers. We span various contexts, from formal education to organizational transformation to the new horizon of an AI-pervasive society. This keynote aims to unite the iLRN community in a collaborative journey towards a future where immersive learning research and practice coalesce, paving the way for innovative educational research and practice landscapes.
The technology uses reclaimed CO₂ as the dyeing medium in a closed loop process. When pressurized, CO₂ becomes supercritical (SC-CO₂). In this state CO₂ has a very high solvent power, allowing the dye to dissolve easily.
Climate extremes likely to drive land mammal extinction during next supercontinent assembly
1. Nature Geoscience | Volume 16 | October 2023 | 901–908 901
naturegeoscience
https://doi.org/10.1038/s41561-023-01259-3
Article
Climateextremeslikelytodriveland
mammalextinctionduringnext
supercontinentassembly
Alexander Farnsworth 1,2
, Y. T. Eunice Lo 1
, Paul J. Valdes 1
,
Jonathan R. Buzan3,4
, Benjamin J. W. Mills5
, Andrew S. Merdith 5
,
Christopher R. Scotese6
& Hannah R. Wakeford 7
MammalshavedominatedEarthforapproximately55 Myrthankstotheir
adaptationsandresiliencetowarmingandcoolingduringtheCenozoic.All
lifewilleventuallyperishinarunawaygreenhouseonceabsorbedsolar
radiationexceedstheemissionofthermalradiationinseveralbillionsof
years.However,conditionsrenderingtheEarthnaturallyinhospitableto
mammalsmaydevelopsoonerbecauseoflong-termprocesseslinkedto
platetectonics(short-termperturbationsarenotconsideredhere).In
~250 Myr,allcontinentswillconvergetoformEarth’snextsupercontinent,
PangeaUltima.AnaturalconsequenceofthecreationanddecayofPangea
Ultimawillbeextremesin pCO2
duetochangesinvolcanicriftingand
outgassing.Hereweshowthatincreased pCO2
,solarenergy(F⨀;
approximately+2.5% W m−2
greaterthantoday)andcontinentality(larger
rangeintemperaturesawayfromtheocean)leadtoincreasingwarming
hostiletomammalianlife.Weassesstheirimpactonmammalian
physiologicallimits(drybulb,wetbulbandHumidexheatstressindicators)
aswellasaplanetaryhabitabilityindex.Givenmammals’continuedsurvival,
predictedbackground pCO2
levelsof410–816 ppmcombinedwithincreased
F⨀ willprobablyleadtoaclimatetippingpointandtheirmassextinction.
Theresultsalsohighlighthowgloballandmassconfiguration, pCO2
andF⨀
playacriticalroleinplanetaryhabitability.
Anthropogenic emissions of greenhouse gasses are pushing Earth’s
climate towards a warmer state not seen for millions of years1
, with
repercussionsforecosystemresilience.Yet,itisunknownwhetheror
whenEarth’sdominantterrestrialanimalspecies,mammals,willever
reachaclimatictippingpointwherebytheirascendancyisthreatened.
SherwoodandHuber2
havesuggestedthatcurrentglobalwarmingwill
raisetemperaturesaboveterrestrialmammalianphysiologicallimits,
renderingsomepartsoftheworlduninhabitable.Mid-to-latecentury
International Panel on Climate Change Sixth Assessment Report3,4
high-emission scenarios suggest that some physiological thermal
thresholdswillbeexceededinsmall,mainlycoastal,regionsofAfrica,
Australia, Europe and South Asia5,6
. Even with the combustion of all
Received: 3 March 2022
Accepted: 25 July 2023
Published online: 25 September 2023
Check for updates
1
School of Geographical Sciences and Cabot Institute for the Environment, University of Bristol, Bristol, UK. 2
State Key Laboratory of Tibetan Plateau
Earth System, Environment and Resources (TPESER), Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, China. 3
Climate and
Environmental Physics, University of Bern, Bern, Switzerland. 4
Oeschger Centre Climate Change Researcher, University of Bern, Bern, Switzerland.
5
School of Earth and Environment, University of Leeds, Leeds, UK. 6
Department of Earth and Planetary Science, Northwestern University, Evanston, IL,
USA. 7
School of Physics, HH Wills Physics Laboratory, University of Bristol, Bristol, UK. e-mail: alex.farnsworth@bristol.ac.uk
2. Nature Geoscience | Volume 16 | October 2023 | 901–908 902
Article https://doi.org/10.1038/s41561-023-01259-3
periodsoftectonicconvergentcyclesthathaveresultedincontinental
assembly30
coinciding with large variations in global temperature31
.
Relativelylittleisknownaboutthe pCO2
andclimateconditionsofthe
firstfoursupercontinents(Vaalbaraapproximately3,600–2,800 Ma,
Kenorland approximately 2500 Ma, Nuna approximately
1,800–1,300 MaandRodiniaapproximately1,100—600 Ma),although
during the Snowball Earth events (approximately 720–650 Ma), pCO2
isbelievedtohavebuilt-uptotwoorthreeordersofmagnitudegreater
than present-day values32,33
. More is known about the most recent
supercontinent,Gondwana,approximately550—170 Ma(alsoincluding
Pangea330—170 Ma).DuringthetimeoftheGondwananSuperconti-
nent, atmospheric pCO2
varied from ~200 ppm (reconstructions vary
between96–435 ppm)at~334 Mato~2,100 ppm(1,127–2,909 ppm)at
~255 Ma(ref.34).Thisledtoperiodsofextremesintemperaturefrom
panglacial climates during the Carboniferous (−5 °C compared with
the present-day global mean35,36
) to greenhouse climates of the
Devonian (+10 °C compared with the present-day global mean37
), all
periods where F⨀ was weaker (<~3%; ref. 38) than today. It has been
suggested that, once a supercontinent has assembled, the rate of
Large Igneous Province (LIP) emplacement increases, raising pCO2
.
This process can initiate continental break-up39
, leading to increased
continentalriftingandafurtherinjectionof pCO2
(ref.40).
Will the formation and decay of the PU Supercontinent lead to
Earthbecominguninhabitableformammalsbysurpassingtheirther-
malphysiologicallimitationslongbeforeF⨀ becomeshighenoughto
cause a runaway greenhouse? In this Article, we assess the impact of
mammalianthermaltolerancesresultingfromnumericalsimulations
at 0, 70, 140, 280, 560 and 1,120 ppm pCO2
, under both modern and
future F⨀ (1,364.95 and 1,399.07 W m−2
). We employ a version of the
UnitedKingdomMetOfficeHadleyCentreCoupledModel(HadCM3L)
a dynamic fully coupled atmosphere-land-ocean general circulation
model(GCM)withaninteractiveozoneschemeunderaPUgeography
(see Methods for details). Further, we utilize the spatial-continuous
integration(SCION)biogeochemistrymodelinconjunctionwiththese
simulations to quantitatively estimate background atmospheric car-
bon dioxide concentrations to predict how much of the land surface
remainshabitableby250 Myr.
Results
PUmammalianthermaltolerance
PU grid-weighted global mean annual temperature (GMAT) ranges
from 19.9 to 27.3 °C (land-only GMAT ranges from 24.5 to 35.1 °C)
(0–1,120 ppm CO2; +2.5% Modern F⨀) (Fig. 1 and Table 1). The GMAT
anomaly relative to the Pre-industrial control simulation (280 ppm
pCO2
; modern F⨀) for PU varies between +8.2 and +16.1 °C (land-only
GMAT anomalies range between +12.2 and +29.8 °C). When changing
onlytheglobalgeography(280 ppm;ModernF⨀)fromitsPre-industrial
configuration to PU, GMAT warms by +3.5 °C, while land-only tem-
peratures increase by +13.9 °C as a result of the continentality effect.
When the mammalian physiological metrics Td (Extended Data
Fig. 1), Tw (Extended Data Fig. 2), Humidex (Extended Data Fig. 3),
T0 andTfrost areappliedtoallscenarios,theypresentvaryingamounts
ofmammalianhabitation(ExtendedDataFig.4).Here,wedefinehab-
itability (Table 1) by exceeding conditions where: (1) cold monthly
mean temperature >0 °C (T0) for at least three consecutive months,
(2)Tw < 34.5 °Cand(3)THumidex < 45.
Hibernation is encoded in these metrics. Hibernation is an effec-
tive strategy for mammals in times of cold stress once sufficient fat
stores have been built up. This is required as plants (food) enter dor-
mancyoncetemperaturesare<5 °C(ref.19).Usingamoreconservative
estimate of <0 °C also removes freshwater availability. Aestivation,
thatis,warmweatherdormancy,cannotoccurinregionswhereplants
cannot grow, usually in hot, arid regions. Subsequently, we also rule
outdesertregionsashabitable(lowspeciesdiversity;Fig.1a)owingto
low water and food availability. To ensure that the model shows skill,
available fossil fuels (+12 °C by 2300), most of the land surface would
still be habitable2
. What is certain is that the Earth will leave the Sun’s
habitablezoneinseveralbillionyears7
whensolarluminosity(F⨀;W m−2
)
reachesapointwhereradiativeheatingandmoistprocessesinitiatea
runawaygreenhouse.However,conditionsthatthreatenmammalian
predominance on Earth may naturally arise sooner.
Mammalian lineage (including endothermic vertebrates
belonging to the class Mammalia of the phylum Chordata) first
emerged ~310 million years ago (Ma)8
but only became the dominant
speciesaftertheCretaceous–Palaeogene(K–Pg)extinction9
.Mammals’
success has seen habitation of nearly every terrestrial biome, encom-
passing periods of large climatic fluctuations and mass extinctions,
showing resilience to climate change10,11
. Mammalian physiology has
evolvedtoremoveexcessheatthroughthermoregulatorymechanisms
(sweatglands,locomotionandcirculatorysystem)owingtoanances-
tral legacy having evolved under warmer, non-glaciated climates12
.
Althoughmammalsareresilienttotemperaturefluctuations,thermal
tolerances are invariant across latitudes, elevation and phylogeny12
,
showing that physiological constraints exist where survivability is
limited. Sustained dry-bulb temperatures (Td) of >40 °C can lead to
mortality12,13
. Hyperthermia, a further upper limit, occurs when the
ambient wet-bulb temperature (Tw) exceeds approximately 35 °C,
because the transfer of metabolic heat through sweat-based latent
cooling is insufficient2,13–16
. Exposure above this threshold for >6 h
leads to death13,17
, but this threshold is rarely reached in our current
climate14
. Humidex, another heat stress measure, is a unitless indica-
tor based on dry-bulb temperature and vapour pressure that is used
bytheMeteorologicalServiceofCanadatorepresenthumanthermal
comfortinhot,drycontinentalinteriors18
.Valuesof≥30indicate‘some
discomfort’,≥45is‘dangerous’andprolongedexposurewillleadtoheat
stroke,while≥54indicatesheatstrokeandimminentmortality.There
isadivergencebetweenheatstressmetricswherehyperthermiacanbe
induced.Tw heatstresshasagreaterimpactontropicalhotandhumid
regimes2,17
, whereas Humidex better represents dry, hot climates like
deserts18
,suchasthosefoundinthecontinentalinteriors.Habitabilityis
constrainednotjustbyawarmingclimatebutalsobyacoolingclimate.
Hypothermiacanariseasadirectconsequenceofcoldtemperatures.
Prolonged exposure to wind chill temperatures below −10 °C (Tfrost)
causesischaemicnecrosisonexposedskin.However,amorerelevant
measure of habitability for mammals is temperatures below freezing
(T0),whichaffectsfreshwateravailabilityandinducesplantdormancy
(<5 °C; ref. 19). The planetary habitability index (PHI)20
also offers
another measure to assess mammalian survivability on the basis of
constructing indices from a star–planet distance, star temperature
and the wavelengths of light absorbed by a planetary body21
to assess
thermaltolerances.
The next supercontinent, Pangea Ultima (PU)22
(Fig. 1 and
Supplementary Fig. 1), is predicted to form in the next ~250 Myr
(ref. 23). By ~250 Myr our Sun will emit ~2.5% more energy compared
with today (~1% per 110 Myr (ref. 24) in F⨀), a radiative forcing
+5.55 W m−2
(morethandoublepresent-day pCO2
(3.7 W m−2
)).Coupled
withtectonic–geographicvariationsinatmospheric pCO2
andenhanced
continentalityeffectforsupercontinents25
,Earthcouldreachatipping
pointrenderingituninhabitabletomammalianlife.
Predicting future pCO2
in ~250 Myr is challenging. The geologic
recordhasshownlargeswingsin pCO2
(ref.26)overthepast3.5billion
years.However,thereisanapparentcool–warmin-phaserelationship
(for example, the Rodinia and Gondwana supercontinents) as part of
thenaturalcycle(~400–600 Myr)ofassembly,tenureandbreak-upof
supercontinentswith pCO2
.However,thisiscomplicatedanddepends
onmechanicalandinsulatingeffectsofcontinentsonmantleconvec-
tion27
(forexample,theNunaSupercontinentstayedwarmthroughout
theassembly–decay).Thisisaresultofcompetingfactorsthatmodu-
lateCO2 sourcesandsinks(volcanicoutgassingversussilicateweather-
ing) of the long-term carbon cycle27–29
. There have been at least five
3. Nature Geoscience | Volume 16 | October 2023 | 901–908 903
Article https://doi.org/10.1038/s41561-023-01259-3
Annual mean GLST 35.1 °C
Annual mean GLST 5.3°C
1
8
0
°
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5
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c
d
e
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8
0
°
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f
g
h
Habitable region (8%)
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b
Habitable region (25%)
Habitable
region
(66%)
Annual mean GLST 24.5 °C
No. of species
Longitude
160
120
80
40
Latitude
Longitude
Latitude
Longitude
Latitude
Longitude
°C
60
55
50
45
40
35
30
25
20
15
10
5
0
°C
60
55
50
45
40
35
30
25
20
15
10
5
0
Longitude
Latitude
Latitude
Latitude
Longitude
Latitude
Longitude
Latitude
Longitude
60° S
30° S
0
30° N
60° N
a
0
0
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0 0
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5
5
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10
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15
1
5
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20 20
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35
CMM GLST 13.4 °C
0
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4
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45
CMM GLST 23.0 °C
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5
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WMM GLST 34.7 °C
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5
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5
WMM GLST 46.5 °C
50
50
Fig.1|PUtemperatureandhabitability. a,Mammalianspeciesdiversity
withouttheinfluenceofhumans(reproducedfromref.41). b,Habitableregions
(greenarea)inthePre-industrialsimulation.c–h,Coldmonthmeantemperature
(CMMT;°C)(c,f),warmmonthmeantemperature(WMMT;°C)(d,g)and
habitableregions(greenarea)(e,h)undertwoendmembersofoursensitivity
analysis:low- pCO2
conditions(280 ppm)PUplanetaryconfiguration(+250 Ma)
(c–e)andhigh-pCO2
conditions(1,120 ppm)PUconfiguration(+250 Ma)(f–h),
withgloballandsurfacetemperature(GLST)(grid-weighted)indicated.
4. Nature Geoscience | Volume 16 | October 2023 | 901–908 904
Article https://doi.org/10.1038/s41561-023-01259-3
we evaluated our Pre-industrial control simulation against Modern
observedmammalianspeciesdistributionwheretheimpactofhumans
hasbeenremoved41
,showinggoodagreement(Fig.1).
Only one scenario (280 ppm pCO2
; Table 1) has comparable
amountsofhabitableland(54%)tothePre-IndustrialEarth(66%)under
increased future F⨀. Under 560 or 1,120 ppm, habitability decreases
to 16% and 8%, respectively. In all cases, increasing pCO2
pushes the
majorityofthelandsurfacebeyondthermalphysiologicaltolerances
forTd,Tw andHumidex(Fig.1),andat1,120 ppmtheplanetispractically
uninhabitable(8%habitability).Evenifthelandsurfaceheightisdou-
bled,habitabilityincreasesonlymarginallyfrom16%to19%at560 ppm
(Table 1). Although silicate weathering feedbacks have the potential
to draw down pCO2
to extremely low levels, leading to climates where
cold thermal tolerances are exceeded and extinction occurs, such a
scenario is less plausible under future F⨀ (ref. 42), As such, scenarios
(Table 1) and analysis where pCO2
is low (140, 70 and 0 ppm) are only
discussed in ‘Cold Stress Environments’ in Supplementary
Information.
PUenergybalanceanalysis
Energybalanceanalysis43
(ExtendedDataFigs.5and6d)indicatesthat,
changingfromPre-industrialgeographytoaPUgeography(280 ppm
CO2, Modern F⨀ kept constant to remove its influence) leads to an
increaseinGMATof+3.7 °C(ExtendedDataFig.5a)drivenbychanges
in surface albedo (+2.2 °C) and emissivity (+1.4 °C) at high latitudes
owing to there being no polar ice (mainly though ice and cloud feed-
backs).TheadditionoffutureF⨀ (+2.5%F⨀)increasesGMATby+8.2 °C
(ExtendedDataFig.5d).Afraction(+1.8 °C)ofthisincreaseisdirectly
attributabletoincreasedF⨀ andindirectlythroughchangesinalbedo
(+2.7 °C), emissivity (+3.7 °C) and heat transport (+0.1 °C) as a result
Table 1 | Pre-industrial and PU climate simulations for a range of CO2 (ppm) and solar luminosities (Sol), both Modern and in
250Myr (Sol+2.5%); see Table 2 in Methods for details
Habitability metrics
Scenario Carbon dioxide
concentration (ppm)
Habitable land
(million km²)
Habitable land
(million km²)
Percentage of total
habitable land
Desert
percentage of
planet
Land and
ocean (°C)
Land only
(°C)
ΔTeq
(°C)
Pre-industrial 280 147.9 97.5 66% 30% 11.73 5.32 3.7a
PU, 280ppm, Sol 280 145.5 78.8 54% 42% 15.28 19.22 2.4
PU, 560ppm, Sol 560 145.5 39.8 27% 40% 19.28 23.97 4.0
PU, 1,120ppm, Sol 1,120 145.5 24.9 17% 40% 22.59 28.64 3.3
PU, 280ppm,
Sol+2.5%
280 145.5 36.0 25% 44% 19.89 24.53 2.3
PU, 560ppm,
Sol+2.5%
560 145.5 23.8 16% 47% 23.36 29.28 3.5
PU, 1,120ppm,
Sol+2.5%
1,120 145.5 12.0 8% 49% 27.30 35.12 3.9
PU, 560ppm,
Sol+2.5%, 2×Orog
560 145.5 27.3 19% 43% 21.75 24.78 1.9
Total land area (km2
) and habitable land area (km2
and %; see Methods for details) for each experiment are shown for habitability metrics. The percentage of land area that is desertified is also
indicated. Grid-weighted global mean annual and land-only mean annual temperatures along with global equilibrium climate sensitivity (ΔTeq) are highlighted. ‘Orog’ signifies orography. a
From
ref. 62.
Table 2 | Description of sensitivity studies and model boundary conditions for a Pre-industrial climate (Modern geography)
and PU geography
Scenario Experiment name Time (Myr) pCO2 (ppm) F⨀ (Wm−2
) Geography Modification to geography
Pre-industrial xmxxc 0 280 1,364.95 Modern No
PU, 0ppm, Sol teurk ~250 0 1,364.95 PU No
PU, 70ppm, Sol teurl ~250 70 1,364.95 PU No
PU, 140ppm, Sol teurm ~250 140 1,364.95 PU No
PU, 280ppm, Sol teurc ~250 280 1,364.95 PU No
PU, 560ppm, Sol teurd ~250 560 1,364.95 PU No
PU, 1,120ppm, Sol teure ~250 1,120 1,364.95 PU No
PU, 0ppm, Sol+2.5% teurr ~250 0 1,399.07 PU No
PU, 70ppm, Sol+2.5% teurs ~250 70 1,399.07 PU No
PU, 140ppm, Sol+2.5% teurt ~250 140 1,399.07 PU No
PU, 280ppm, Sol+2.5% teurg ~250 280 1,399.07 PU No
PU, 560ppm, Sol+2.5% teurh ~250 560 1,399.07 PU No
PU, 1,120ppm, Sol+2.5% teuri ~250 1,120 1,399.07 PU No
PU, 560ppm, Sol+2.5%,
2×Orog
teurp ~250 560 1.399.07 PU Topographic height
doubled
CO2, solar constant and any modifications made are detailed for each experiment.
5. Nature Geoscience | Volume 16 | October 2023 | 901–908 905
Article https://doi.org/10.1038/s41561-023-01259-3
ofnon-linearfeedbacksthatarisefromincreasingF⨀.Thisisdrivenby
a reduction in seasonal sea ice at high latitudes (compare Extended
Data Fig. 5a,d), whereas just increasing pCO2
impacts GMAT predomi-
nantlythroughemissivity-drivenfeedbacks(ExtendedDataFig.5a–c).
Terrestrialalbedochangesareprimarilydrivenbyvegetationfeedbacks
due to desertification under warming conditions (Table 1) that are
already enhanced because of supercontinent formation with no pCO2
orF⨀ change(30–42%).WhenF⨀ iskeptatPre-industriallevels,deserts
showasmalldecreasewithincreasing pCO2
owingtoincreasedevapo-
ration and moisture enrichment of the atmosphere, leading to an
invigorated hydrological cycle in some regions (Table 1).
A stepwise doubling of pCO2
under F⨀ (+2.5%) from 280 to
1,120 ppm(ExtendedDataFig.6d–f)showsageneralincreaseinequi-
librium climate sensitivity (ΔTeq of 2.3–3.9 °C; Table 1). Interestingly,
ΔTeq analysisofthesamesuiteof pCO2
concentrationsbutwithamodern
F⨀ (Table1)indicatesmorevariableΔTeq with pCO2
(ΔTeq of2.4–4.8 °C),
demonstratingnon-linearclimatefeedbackswithchangesinF⨀.
Finally, we consider an astrophysical classification of PHI in con-
junctionwithanEarthSimilarityIndex(ESI)basedonplanetarymass,
radius, temperature, stable substrate, available energy, chemistry
andabilitytohostliquidwater20
.Thesearedefinedrelativetotheonly
known habitable planet, Earth, and habitability is defined as greater
than0.8(seeonlinemethodsforfurtherdetails).Hence,bydefinition,
the only parameter that changes in the future is GMAT, since all other
factors remain constant. According to the ESI, no future scenario is
predictedtoremainhabitable(Fig.2).
PU pCO2
modelling
Continent–continent collision during supercontinent formation, on
average,ispredictedtoreduce,notincrease, pCO2
drawdownbecause
hightopography(andmorereadilyerodiblematerial)isconcentrated
inthedrycontinentalinteriors,awayfrommoisturesources27
.Moisture
pathwaysmaybejustasimportantastopographyininfluencingchem-
icalweathering.Thisiscorroboratedinourmodel,whichseesareduc-
tion both in precipitation (Extended Data Fig. 7) and in runoff when
only changing the continental configuration from a Pre-industrial
worldtoaPUworld.Increasing pCO2
reducesprecipitationandrunoff
into the continental interior, theoretically further reducing chemical
weathering and increasing pCO2
.
To better constrain the likely pCO2
and understand the silicate
weathering feedback in our PU reconstruction, we use the global
climate–biogeochemical model SCION (see Methods for more infor-
mation), which computes the long-term carbon cycle and uses a
two-dimensional (2D) terrestrial weathering module informed by
climate model simulations. Here, a data structure of climate model
outputs at different CO2 levels is used to simulate spatial continental
processes through variations in atmospheric CO2, and we update
this with the climate model runs from this study both for the
Pre-industrial (which determines the initial steady state) and for PU.
To run the model, we must also prescribe the tectonic rate of CO2
degassing,whichweestimatefromaconservativesetofplatebound-
aries (mid-ocean ridges and subduction zones) that might describe
the gross tectonic fabric of the PU world (see Supplementary Infor-
mationformoredetails).WefindthatPUislikelytohave1.3–1.9times
the degassing rate of the present-day Earth, which is roughly equiva-
lent to the rates proposed for Pangea44
. SCION ensemble simulations
for PU predict a mean long-term background pCO2
of 621 ppm (range
410–816 ppm) when considering the range of uncertainty in the
degassing rate as well as the potential for changing reactivity of
global silicate rocks.
Discussion
The formation and decay of PU will limit and, given a much greater
source-to-sink ratio of pCO2
, ultimately end terrestrial mammalian
habitability on Earth by exceeding their warm thermal tolerances,
billions of years earlier than previously hypothesized. Inevitable
changesinbothplatetectonicsandF⨀ createfeedbacksintheclimate,
even in lieu of variable pCO2
, that will raise GMAT.
Further, tectonic evolution of PU will lead to large variations in
pCO2
(over102
years(forexample,hyperthermalevents45
)and105
years
(forexample,volcanism46
)),asobservedthroughthegeologicrecord
and seen as a natural consequence of supercontinent assembly and
decay27
,enhancingGMAT(20.9–24.8 °Cat410–816 ppm pCO2
).Further,
the tenure of PU possibly increases the likelihood of massive hyper-
thermaleventsakintothePermian–Triassiceventthatsawupto10 °C
warmingon104
yeartimescales45
.
Today, critical heat stress measures are rarely exceeded on land
and,ifso,onlyforshorttimescales14
(hoursordays).Ifonlythegeog-
raphywastochange,criticalheatstressisnotexceededbutdoesdrive
the climate towards critical thresholds (Fig. 1 and Extended Data
Figs. 1–3). Combined with a future increase in F⨀, large regions of the
supercontinentbreachthesecriticalthresholdsforperiodsof>30 days
(Table 1, Fig. 1 and Extended Data Fig. 4). At 280 ppm, most of the
Tropicsbecomeuninhabitable,andby1,120 ppmthisextendsthrough
the mid to high latitudes. Although the high latitudes (>50°) at
1,120 ppm offer limited refugia from critical heat stress, cold stress
metricsfurtherreducehabitability(ExtendedDataFig.4).Onlyhighly
specializedmigratorymammalswouldbeabletocompete.However,
even a migratory strategy may be perilous for mammals owing to
continent-wide deserts and aridity (Table 1) throughout PU acting as
abiogeographicbarrier(ExtendedDataFig.7).HighTd andTw asafunc-
tionofincreasing pCO2
requireplentifulwateravailabilityformammals
to balance losses through evaporative cooling to stop hyperthermia.
Ratesofevaporativewaterlosswillincreasewithhyperthermiaasthe
rateofrespiratorywaterlossincreasesindirectproportiontoincreases
in the rate of gas exchange47
, making traversing these near 50° N to
50° Scontinent-widearidanddesertregionsimpractical.Asecondary
impactoflowmoistureavailabilitywouldbeanincreaseinthevapour
pressuredeficit(VPD)andplantstress(notshown)andareductionin
theproductivityandfoodavailabilityofvegetatedlandformammals.
Under 1,120 ppm pCO2
, the VPD between 50° N and 50° S is a factor of
three or four greater than in the Gobi Desert today (with our
Venus
Mars
Ceres
Jupiter
Io
Europa
Saturn
Titan
Enceladus
Uranus
Titania Neptune
Triton
Pluto
PU, 1 × CO2
, Sol
PU, 2 × CO2
, Sol
PU, 4 × CO2
, Sol
PU, 1 × CO2
, Sol + 2.5%
PU, 2 × CO2
, Sol + 2.5%
PU, 4 × CO2
, Sol + 2.5%
PU, 2 × CO2
, Sol + 2.5%, 2 × Orog
Runaway greenhouse
Pre-industrial
0 0.2 0.4 0.6 0.8 1.0
PHI
0
0.2
0.4
0.6
0.8
1.0
ESI
Fig.2|Astrophysicalhabitabilityindex.ESIandPHIofallSolarSystembodies
andeachPU pCO2
andsolarluminosity(Modern(Sol)andsolarluminosityin
250 Myr(Sol + 2.5%))sensitivitystudy(orangesymbols).Valueswithinthegreen
zoneindicatehabitability(seeMethodsfordetails).Valuesintheredzone
indicatepoorhabitabilityduetohavingarockyinterior(highPHI)butnota
temperatesurface(lowESI)andviceversa.Seeref.20 forESIandPHIfor
definitionsandplanetarybodyvaluesfortheSolarSystem.
6. Nature Geoscience | Volume 16 | October 2023 | 901–908 906
Article https://doi.org/10.1038/s41561-023-01259-3
Pre-industrialmodelshowingsimilarvaluesofapproximately10–12 hPa
comparedwithobservations48
).
Hibernation(aseasonaladaptationtoprolongedperiodsoffood
shortage and cold) and its hot weather equivalent, aestivation, have
beeneffectivestrategiesformammalsformillionsofyearstocombat
relative extremes in temperatures. Today, ~50% of mammals hiber-
nate49
,andofthose,onlyasmallfractionformorethan1 month50
.With
pCO2
predictedtobe410–816 ppm,coldstresswillbelessofaconstraint
on mammalian habitability (Extended Data Fig. 4). Burrows and cave
systems,whicharebufferedfromexternalairtemperature,mayallow
somerefugiaforsomemammalspeciesiffoodandwaterareplentiful.
Small burrowing rodents may show greater survivorship in regions
abovethermalthresholdsifstayingactiveatnightratherthanduring
the day. However, even if increasing the aestivation period is allowed
from1–3 monthsduringthewarmestmonthsoftheyear,habitability
isonlymarginallyincreased(SupplementaryTable2)at280,560and
1,120 ppmfrom25%16%and8%to32%,21%and13%,respectively,asa
resultofadjoiningmonthsbeingabovephysiologicalthresholds.
Althoughwecannotdiscountevolutionaryadaptationtoheatand
cold stress, recent studies have shown that mammalian thermotoler-
ance upper limits are conserved through geologic time12,51
and have
not increased during past rapid (for example, Palaeocene–Eocene
ThermalMaximum)orslowerwarmingevents(Early-EoceneClimatic
Optimum).Mammalianphysiologicallimitationsshowthatincreasing
their upper thermal tolerance is a slow process (0.6 °C per Myr) with
anupperTd boundaryofapproximately40 °Cthatisrarelycrossed.At
40–60 °C,plantlifeandthebasisoftheterrestrialfoodchainbeginsto
criticallyfailowingtodamagetophotosystemII,leadingtodecreased
electrontransportratesandphotosyntheticfailure12,52
.At≥560 ppm,
daily Td > 40 °C are consistent throughout the supercontinent (at
1,120 ppm, this can often reach >50–60 °C). Although mammals are
better at adapting to cold tolerance12,51
, a more conservative ≤0 °C
threshold whereby freshwater sources are rendered biologically
unavailable offers a finite lower thermal tolerance limit. To adapt to
more humid and warmer environments, endotherms would need to
increase body temperature (Tb) above both the dry- and/or wet-bulb
temperature(Ta)tomaintainanegativeTb – Ta gradient.However,since
mostendothermsregulateTb nearlethalorphysiologicallimits,there
is probably only limited scope for thermal adaptation16
. This is likely
conservativegiventhatjuvenilemammalswillbemoresusceptibleto
lowerranges53
.
Overlong-timescales(106
years),weatheringfeedbackswillregu-
late pCO2
owing to higher F⨀ increasing surface temperatures and
enhancing the long-term hydrological cycle, thereby reducing pCO2
.
However,weatheringfeedbackswillhavealaggedresponse28
,operat-
ingonlongertimescalesthanareimportantformammalianhabitabil-
ity, meaning that any substantial pCO2
outgassing would lead to
short-term (103
–104
year) warming that would reduce habitability
through heat stress, such as during supercontinent assembly
that has consistently been shown to result in high pCO2
emissions
(1,000–3,000 ppm)54
(seeMethodsformoredetails).
Reducedmoistureadvection(ExtendedDataFig.1)intocontinen-
talinteriorsleadstolargearidregionswheresurfacerunoffisreduced
or non-existent (not shown). This reduces the carbon sink (via both
chemicalweatheringandbioticfactors),raising pCO2
throughareduc-
tioninterrestrial pCO2
sequestration,erosionandtransportofcarbon
foroceanicsequestration55
.
InPU,aTropicaleast–westtrendingmountainrange(Supplemen-
tary Fig. 1) is modelled, from which an invigorated hydrologic cycle is
derived, driven from the mountain range proximity to oceanic mois-
ture.Consequently,wespeculateamoistenedatmospherefromgreen-
houseconditions,andastrongland–seacontrastwouldprogressively
increasesilicateweathering,drawingdown pCO2
.Whenthetopography
of PU is doubled in height, the hydrological cycle decreases over the
higher mountains (Extended Data Fig. 7), suggesting that silicate
weathering and pCO2
drawdown may slow. On the other hand, if the
erodiblematerialofthesemountainrangeswasmadeofsedimentary
materialwithlowsilicacontent,itwouldinsteadreleaselargeamounts
of pCO2
throughtheoxidationofrock-richinorganiccarbonandsulfide
minerals56
,increasing pCO2
furtherandexpandingregionswheremam-
malswouldexperiencecriticalheatstress.
Todaycriticalcoldstress(Tfrost orT0)environmentsarelimitedto
the high to mid latitudes (>30°). Changing geography and increased
F⨀ bothshiftthiszoneatleast10°towardsthepoles.Coldstressisstill
a factor limiting habitability regardless of changing geography and
increased F⨀, which both act to warm the planet. Elevated pCO2
(>1,120 ppm) effectively removes all cold stress environments.
Cool-adapted mammals that have lower thermal physiological limits
willbeparticularlyimpactedbyrisingtemperaturesaswellasincreased
competitionfromotherspeciesmovingpolewardastheymigrateaway
fromtheTropics.
Otherfuturesupercontinentconfigurationshavebeenproposed
(Novopangea, Aurica and Amasia23,57
). All formations except Amasia
suggest a supercontinent landmass centred in the Tropics and would
likelyleadtoclimatessimilartoPU.Amasia,however,wouldbecentred
over the North Pole (except for Antarctica, which remains in its
present-dayposition).Insuchascenario,underarangeof pCO2
regimes,
largeregionswouldprobablybelessaffectedbycriticalheatstressand
remainhabitable.However,strongweatheringfeedbacksundersuch
a scenario may present greater challenges from cold stress on mam-
malianphysiology.Ice–albedofeedbacksmayalsopresentasituation
where Amasia57
would glaciate more readily, even under higher pCO2
regimesandmassextinction.
Ultimately, it is supercontinent geography and increased F⨀ that
drive the increased sensitivity to variable pCO2
. Continued mammalian
habitabilitywillbecontingentonnolarge,sustained,pulsesof pCO2
,either
throughprocessesinsupercontinentassemblyanddecayorcoincident
outgassingevents(forexample,LIPssuchastheSiberianorDeccantraps),
bothofwhichhaveprecedentthroughoutthegeologicrecord.Elevated
pCO2
levels(>840ppm),oftenassociatedwithgreenhouseclimates,have
been common over most of the Phanerozoic26,58
. If pCO2
was to spike
≥560 ppm, even for a short period (102
–103
years), Earth will become
inhospitable for mammalian life, resulting in a mass extinction compa-
rable to the ‘Big 5’ extinction events59
. This may even be conservative.
Song et al.60
suggest that warming of >5.2 °C from Pre-industrial levels
led to previous mass extinctions in marine animals60
, and their defined
thresholdispassedunderscenariosbelow280 ppm pCO2
.
Thisanalysispinpointstheimportanceoftectonics,atmospheric
constituentsandsolarenergyforcontinuedmammaliansurvivability.
Under all scenarios of an ‘Earth-like’ planet, regions of habitability do
exist (even for 1,120 ppm pCO2
, F⨀ +2.5%, albeit small (Extended Data
Fig. 4)). However, no future realization of PU where pCO2
is ≥280 ppm
passes a well-used astrophysical assessment of habitability (Fig. 2),
meaningthatEarthwillleaveitsastrophysicaldefinedhabitablezone
(at least temporarily) well before a runaway greenhouse occurs. This
suggeststhatthepotentialforhumanhabitabilityofmanyexoplanets
might be mistakenly discounted. This is illustrated by the recent dis-
covery of KOI-456.04 (ref. 61), which has an Earth–Sun system similar
to our own and an estimated GMAT of 5 °C. The habitability of KOI-
456.04 may be more dependent on the position of its continental
landmass and concentration of atmospheric constituents than an
arbitraryhabitablezonedefinedbyplanet–stardistance.
Onlinecontent
Any methods, additional references, Nature Portfolio reporting
summaries, source data, extended data, supplementary infor-
mation, acknowledgements, peer review information; details of
author contributions and competing interests; and statements of
data and code availability are available at https://doi.org/10.1038/
s41561-023-01259-3.
7. Nature Geoscience | Volume 16 | October 2023 | 901–908 907
Article https://doi.org/10.1038/s41561-023-01259-3
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Article https://doi.org/10.1038/s41561-023-01259-3
Methods
Numerical modelling framework
An overview of the model setup, boundary conditions, sensitivity
studiesandcarbondioxidemodellingisgivenbelow.
Model. Here, we utilize the HadCM3LB-M2.1aD63
GCM, a member of
the UK Meteorological Office HadCM3 family of climate models64
.
The grid resolution is 3.75° × 2.5° in longitude × latitude in both the
atmosphere(19verticallevels)andocean(20verticallevels),employ-
ingtheArakawaB-gridscheme.
Ocean salinity is adjusted to an ice-free world global mean refer-
encevalueof34.23practicalsalinityunitsandallowedtofreelyevolve
globally.Topreventmillennial-scalesalinitydriftduringmodelspin-up,
thetotaloceanvolumeintegraliscalculatedandisre-adjustedtoback
toice-freeworldglobalmeanaftereachoceantimestep.Sea-icecover-
ageiscalculatedfromazero-layermodeloverlayingthetop-mostlayer
oftheoceangrid.Seaiceformsusingathresholdvalueof−1.8 °C,with
albedo set at 0.8 for temperatures below −10 °C and 0.5 for tempera-
turesabove0 °C,withalinearvariationbetween.
Parameterizations include the radiation scheme of Edwards and
Slingo65
, the convection scheme of Gregory et al.66
and the Met Office
Surface Exchange Scheme (MOSES)-2.1 land-surface scheme, whose
representation of evaporation includes the dependence of stomatal
resistanceontemperature,vapourpressureandCO2 concentration67
.
There are nine sub-grid-scale land surface types, four non-vegetated
types(urban,lakes,baresoil,iceandinlandwater),andfiveplantfunc-
tionaltypes(broadleaftrees,needleleaftrees,shrubs,C3(temperate)
grassesandC4(tropical)grasses),updatedevery10modeldays.
The Top-Down Representation of Interactive Foliage and
Flora Including Dynamics (TRIFFID) dynamic vegetation model67
is
employed, allowing two-way coupled interactions between the land
surface and atmosphere. The MOSES 2.1 land surface scheme was
employed, as opposed to MOSES 2.2, owing to the former producing
abetterrepresentationofPre-industrialclimatesincombinationwith
theTRIFFIDmodel68
aswellasbecausethefuturedistributionofvegeta-
tion needs to be predicted based on the simulated climate. Crucially,
TRIFFIDallowsfullinteractionbetweenclimateandfeedbacksassoci-
ated with vegetation cover and complex land surface–atmosphere
interactions.
Desert soil albedo is interactively updated on the basis of the
soil carbon content, where low soil carbon concentrations result in a
modifiedsoilalbedoof0.32(averagemodern-daySaharanalbedo).
Typically,theozonedistributionisprescribedasastaticlatitude–
pressure–timedistributioninmanyclimatemodels.However,inwarmer
climatesofthepastorfuture,thetropopauserises,meaningthatstrato-
sphericozonepenetratesintothetroposphere69
,whichisunphysicalif
aPre-industrialtropopauseheightisprescribedforwarmtimeperiods.
Instead,theozonedistributionisprescribedusingadynamicapproach70
inwhichozoneisdynamicallycoupledtothemodeltropopauseheight
with constant values for the troposphere (0.02 ppm), tropopause
(0.2 ppm)andstratosphere(5.5 ppm).Thischangemakesanegligible
differencetotheglobalmeansurfacetemperaturebutdoeshaveasmall
impactonthestratospherictemperatureandwinds.
HadCM3LB-M2.1aD,partoftheUnitedKingdomMetOfficeHadCM3
family of climate models, has been extensively evaluated against
modern-dayobservationsaspartoftheInternationalPanelonClimate
ChangeClimateModelIntercomparisonProjectphase5,showinggood
skillinreproducingaclimatethatiscomparabletoobservationsaswell
as other higher-fidelity climate models63
. A full description of the indi-
vidualsub-componentmodelsinHadCM3LB-M2.1aDisgiveninref.63.
Boundary conditions and initialization. The reconstruction of tec-
tonics, structures and plate motion that underpin this study is based
ona+250 MyrreconstructionofPU22
.Thisreconstructionusesmeth-
ods similar to those of Valdes and Markwick71
, where land–sea mask,
bathymetric,topographicandthesub-grid-scaleorographicvariables
arerequiredbythemodelandareinterpolatedontotheGCMresolution
(Supplementary Fig. 1). There are no assumed terrestrial ice sheets in
this reconstruction. Shorelines in this reconstruction represent the
maximum transgression in sea level assuming that no terrestrial ice
sheets are present. PU is only one of four potential configurations
(threeofwhicharesimilarincontinentaldistributionwithasuperconti-
nentcentredintheTropics23
)ofsupercontinentformationby250 Myr.
AllsimulationsareinitializedfromanequilibratedPre-industrial
state(atmosphereandocean).
ModernF⨀ issetat1,364.95 W m−2
.F⨀ increasesby~1%per110 Myr
(ref. 38). We forecast an F⨀ of 1,399.07 W m−2
(+2.5% increase from
Modern) by 250 Myr. Although modern solar luminosity has recently
been revised to 1,361 W m−2
, the model has been calibrated for the
previousvalueof1,364.95 W m−2
.Forallsimulationsconducted,weusea
Modernorbitalconfiguration.Asetofsensitivitystudiestoconstrain
the impact of atmospheric carbon dioxide are conducted at 70, 140,
280, 560 and 1,120 ppm. Table 1 gives an overview of the sensitivity
studiesconductedinthisstudy.
Simulations are run for 5,000 model years and reached equilib-
rium at both the surface (not strongly trending, less than 0.1 °C per
century in the global mean) and deep ocean, with less than 0.3 W m−2
imbalanceinthetop-of-atmospherenetradiation.Longmodelintegra-
tions are required when running new configurations to ensure that
ocean circulation is fully representative of the new model boundary
conditions applied to the model. The exception was the 0 ppm pCO2
simulationsatboth1,364.95and1,399.07 W m−2
solarluminosity.Each
simulationranfor550and700modelyears,respectively.Thisiscom-
monwhereclimatemodelsusinglow pCO2
valuesbecomefullyglaciated
(completesea-icecoverage).
Heatandcoldstressindicators
Two heat stress indicators are used within this study: (1) the wet-bulb
temperatureand(2)Humidex,calculatedasfollows:
Wet-bulb temperature. Wet-bulb temperature (Tw) is derived from
a more accurate computation from ref. 72 (their equation (3.8)) with
equivalent potential temperature (θE) calculated from ref. 73 (their
equation(38)).Wet-bulbapproximationssuchasthatofStull74
arenot
desirable for use as it is calibrated for the modern day and does not
apply to warmer time periods. The complete derivation can be found
inappendixAofref.75.Tw valuesof≥35 °Careassessedtobecritically
lethalandleadtomortality2,13,17
.
Humidex index.Humidexisameasureofthecombinedeffectofboth
temperature and humidity on human physiology. Although a more
subjective metric and often equated to a simplified feels-like metric,
it does have an upper limit of 54. Above this limit for 6 h, mortality
will ensue through heat stroke as the body is unable to regulate its
core body temperature (Tb) through evaporation at the skin surface.
Humidexiscalculatedas
Humidex = T + 0.5555 × (6.11 × e
5417.7530×(
1
273.15
−
1
273.15−Tdew
)
− 10) , (2)
where T is air temperature (°C) and Tdew is the dew-point temperature
(K)76
.Here,wedefinearegionasuninhabitablewherethemonthlymean
Humidex value of ≥45 for acclimatized species, which is defined as
dangerousbytheMeteorologicalServiceofCanada,whereallactivity
should be stopped. Using mean monthly values is conservative given
thatdailymaximumHumidexvalueswillexceedthisvalueconsistently.
Warm stress: aestivation. Of mammals that hibernate, only a small
proportion do so owing to warm weather conditions, and of those,
only a small proportion aestivate (warm weather hibernation) for
10. Nature Geoscience
Article https://doi.org/10.1038/s41561-023-01259-3
several hours to days15
, of which an even smaller proportion do so on
seasonal time scales. Hibernation helps cold climate survivorship
more than warm weather. From an ecological point of view, aestiva-
tion results in different challenges and requirements compared with
hibernationinwinter;whileheatcanreduceaccesstofoodandwater
availabilityaswell,itwillalsoreduceaccesstorefugiaforlowambient
temperature(Ta)forasubstantialreductionofbodytemperature(Tb)50
.
High Ta prevents Tb from falling to low levels and will therefore limit
the energy-conserving potential of aestivation as a viable solution50
.
This is compounded by mammals’ high metabolic rates that require
an intake of large amounts of food, and when food supply is low or
fluctuating, energy requirements may exceed energy availability. In
response, here we take regions that are desert (as predicted by the
dynamic interactive vegetation scheme TRIFFID) in the model and
deem them uninhabitable owing to a lack of food (bare soil fraction
>0.5correspondstouninhabitable).
Cold stress: hibernation. Today, approximately 50% of mammals
hibernate49
, and mainly for days or weeks50
. Only a fraction can do so
on seasonal time scales, with only one known mammal able to do so
for 11 months of the year. Here, we take a very unlikely conservative
approach with our simulations and allow all mammals to develop
hibernation as a trait and to hibernate for 9 months to survive cold
weatherconditions.Wedefinecoldstressregionsthatinhibitmammal
habitationwherenineormoreconsecutivemonthsfallbelow0 °C.This
thresholdlimitsfreshwateravailabilityaswellasplacingplantsintoa
stateofdormancy(<5 °C;ref.19).
Exoplanetsimilarityindex
Exoplanet habitability assessments are commonly used quantita-
tive measures of planetary habitability. Here, we use a weighted ESI20
that measures habitability in relation to present-day Earth. A value of
between1(identicalsimilarity)and0(nosimilarity)signifiesthelikeli-
hoodthataplanetwouldhavethesamephysicalpropertiesasEarth(for
example, radius, mass and surface temperature). In this instance, the
onlychangingparameterwillbetheglobalmeanannualtemperature,
as the physical properties of Earth will not have changed in +250 Myr.
Valuesof≥0.8indicatethepotentialtoharbourlife.
ESI (S, R) = 1 −
√
√
√
√
1
2
[(
S − S⊕
S + S⊕
)
2
+ (
R − R⊕
R + R⊕
)
2
],
where S is stellar flux, R is the radius, S⨁ is Earth’s solar flux and R⨁ is
Earth’sradius.
ESIprovidesthephysicalpropertiesofanexoplanet’shabitability
but cannot explicitly measure the possibility of life. Here, we couple
ESI with the PHI in a geometric mean of separate values that would
constituteconditionsapplicabletolife:
PHI = (S × E × C × L)
1/4
,
where S is the presence of a stable substrate (influenced by solid sub-
surface,atmosphereandmagnetosphere),Eistheavailabilityofenergy
(influencedbylight,heat,redoxchemistryandtidalflexing),Cisappro-
priatechemistry(influencedbypolymetricchemistry)tosupportlife
and Lisaliquidsolvent(ineithertheatmosphereorthesub-surface).
While values for S, E, C and L are difficult to exactly determine on exo-
planets,forourpurposesheretheseareknownvalueswithrespectto
Earth.Seeref.20forfurtherdetails.
PHIrel = (PHI/PHImax) .
Eachparameter(S,E,C,L)issummedanddividedbythemaximum
attainable value to normalize the score (PHIrel) to between 0 and 1.
Here, we define values of ≥0.8 as giving a reasonable approximation of
conditions that allow life. A value of 1.0 would constitute ‘maximum’
habitability.Today,Earthhasavalueof0.96.Seeref.20forfurtherdetails.
Future pCO2
modelling
To quantitatively estimate the long-term stable atmospheric CO2
concentration during PU, we use the SCION earth evolution model77
.
SCION is a linked climate–biogeochemical model that estimates a
self-consistent evolution of the major composition of Earth’s atmos-
phereandoceansovergeologicaltime.Itisanextensionofthepopular
GeologicCarbon-Cycle78,79
andCarbon,Oxygen,Phosphorus,Sulphur
and Evolution80,81
box models that use a 2D continental surface and
look-up tables of steady-state climate model outputs to approximate
surface processes such as weathering. The model calculates atmos-
pheric CO2 based on tectonic and weathering-related CO2 inputs, as
wellascarbonsequestrationasorganiccarbonorcarbonates.SCION
has been tested over the Phanerozoic Eon and produces a reasonable
fittoCO2 proxydata,particularlyoverthelast250 Myr(ref.77).
Using HadCM3B runs for the present day and for PU, we update
theclimateandpalaeogeographicdatastructurewithinSCIONsothat
it can run from the Pre-industrial to 250 Myr in the future. SCION also
requires an estimate of global tectonic CO2 degassing. This is derived
from global tectonic fluxes (that is, the amount of new seafloor cre-
ated at mid-ocean ridges and consumed at subduction zones) and
the amount of carbon that is typically degassed from such environ-
ments.Estimatesofboththefluxandamountofcarbondegassedare
availableforpresentday82,83
,andweusetherecentestimatesofref.82
as our present-day benchmark for carbon degassing (13 and 18 Mt C
peryearatridgesandsubductionzones,respectively).
ToestimatethecarbondegassingforPU,wefirstconstructahypo-
thetical plate boundary network (that is, an interconnected set of
subductionzonesandmid-oceanridges84
;SupplementaryFig.1).The
configuration is based on that which is inferred to have existed while
Pangeawasactive(andwhatismostlystillvisibletoday):a‘ringoffire’
actingasan(almost)completegirdleofsubductioncircumnavigating
PU85–87
.Formid-oceanridges,weinferthesimplestandmostconserva-
tive of all configurations, a stable triple junction that can account for
convergence at all subduction zones. (A similar approach is taken for
platetectonicmodelsindeeptime86,88
.)
To determine the rate of crust being formed and consumed at
ridges and subduction zones, we extracted the spreading rates of all
oceanic tectonic plates that compose the Pacific Ocean since 154 Ma
(the time at which we have preserved isochrons in the Pacific Ocean).
We limit our analysis to just the Pacific Ocean, as it is most analogous
toourPUworld(thatis,platesconsistingjustofoceaniccrustthatare
beingsubducted;seethediscussioninref.89).Wefindameanspread-
ing rate of 10.42 cm per year with a standard deviation of 1.76 cm per
year(SupplementaryFig.2).Thisrangeof8.67–12.18 cmperyearpro-
vides us with a possible estimate of mid-ocean ridge and subduction
flux. We multiply and sum the fluxes by the expected carbon degas-
sing for both present-day and PU and use the ratio of the two as the
relative change in degassing. Our results suggest that PU is likely to
have 1.3–1.9 times the degassing rate of present-day Earth (roughly
equivalent to and in line with estimates for Pangea degassing relative
topresentday44
).
NowthatwehavedefinedanassumedCO2 degassingrateandhave
built a data structure of climate model runs at different CO2 levels for
250 Myr+, we can run the SCION model forwards in time to simulate
atmosphericCO2 evolutionovergeologicaltime.Westartthemodelrun
at 50 Myr with all forcings fixed at present-day values. Between 0 and
250 Myr+, we increase the degassing rate linearly between 1 (present
day) and the 250 Myr+ value calculated above. To account for model
uncertainty,werunthesystem1,000timessubjecttoarandomchoice
fromtherangeoffuturedegassingrates,aswellastheparameterspace
testedinthestandardPhanerozoicmodelensembles77
.Supplementary
11. Nature Geoscience
Article https://doi.org/10.1038/s41561-023-01259-3
Fig.3showsthemodelspatialfieldsatPre-industrialand250 Myr+,and
SupplementaryFig.1showsthepredictedatmosphericCO2 concentra-
tionforeachofthesetimes,withthecentralmarkershowingthemodel
ensemblemeanandthebarsshowingtheminimumandmaximum.Like
Pangaea,PUhasalargearidinteriorzoneinwhichsilicateweatheringis
inhibitedbutalsoalargewarmandwetclimatezoneinwhichweather-
ingisenhanced.TheoverallcombinationofhigherCO2 degassingand
altered continental weatherability results in a prediction of 621 ppm
(range 410–816 ppm) CO2, or a range of approximately 1.5–3 times
Pre-industrial(Table2).
Dataavailability
All data needed to evaluate the conclusions in the paper are present
in the paper and/or Supplementary Information. Model data can be
accessed from the repository at www.bridge.bris.ac.uk/resources/
simulations.
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Acknowledgements
A.F. and P.J.V. acknowledge the Natural Environment Research
Council of the UK (grant nos. NE/X015505/1, NE/V011405/1 and NE/
X018253/1) and Leverhulme Research Project Grant RPG-2019-
365. A.F. acknowledges the Chinese Academy of Sciences Visiting
Professorship for Senior International Scientists (2021FSE0001). A.S.M.
was supported by MSCA project 893615, NEOEARTH.
Authorcontributions
A.F. and P.J.V. designed the project. A.F. carried out the simulations
and initial analysis, and wrote the first draft. Y.T.E.L. produced further
heat stress analysis. C.S. produced the PU digital elevation model.
B.J.W.M. and A.S.M. provided the SCION model data and analysis. All
authors contributed to the discussion, interpretation and writing of the
manuscript.
Competinginterests
The authors declare no competing interests.
Additionalinformation
Extended data is available for this paper at
https://doi.org/10.1038/s41561-023-01259-3.
Supplementary information The online version
contains supplementary material available at
https://doi.org/10.1038/s41561-023-01259-3.
Correspondence and requests for materialsshould be addressed to
Alexander Farnsworth.
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