1. Anthropogenic Climatic Attentuation
2. A. The evidence of past climates
3. Paleo-environmental reconstruction
• Step #1 – find your evidence
• Step #2 – date your evidence
• Step #3 – examine you evidence
• All spread over a bed of nice…..
4. What is Paleoclimatology?
• Scientists take samples from the centre of the coral. Clipperton Atoll,
• Paleoclimatology is the study of past climates. Since it is not possible
to go back in time to see what climates were like, scientists use
imprints created during past climate, known as proxies, to interpret
paleoclimate. Microbial life, such as diatoms, forams, and coral serve
as useful climate proxies. Other proxies include ice cores, tree rings,
and sediment cores (which include diatoms, foraminifera, microbiota,
pollen, and charcoal within the sediment and the sediment itself).
• Past climate can be reconstructed using a combination of different
types of proxy records. These records can then be integrated with
observations of Earth's modern climate and placed into a computer
model to infer past as well as predict future climate.
5. Step #1 – find your evidence
How Are Microbes Used As Proxies?
Foraminifera, such as this Globigerinoides species, can be used as a climate proxy (copyright O. R.
Anderson, accessed from the Micro Scope website).
Foraminifera, also known as forams, and diatoms are commonly used microbial climate proxies. Forams and
diatoms are shelled microorganisms found in aquatic and marine environments. There are both planktonic, or
floating in the water column, and benthic, or bottom dwelling, forms. Foram shells are made up of calcium
carbonate (CaCO3) while diatom shells are composed of silicon dioxide (SiO2). These organisms record
evidence for past environmental conditions in their shells. Remains of foram and diatom shells can be found
by taking sediment cores from lakes and oceans, since their shells get buried and preserved in sediment as
they die. The chemical make up of these shells reflect water chemistry at the time of shell formation. Stable
oxygen isotope ratios contained in the shell can be used to infer past water temperatures. These oxygen
isotopes are found naturally in both the atmosphere and dissolved in water. Warmer water tends to evaporate
off more of the lighter isotopes, so shells grown in warmer waters will be enriched in the heavier isotope.
Measurements of stable isotopes of planktonic and benthic foram and diatom shells have been taken from
hundreds of deep-sea cores around the world to map past surface and bottom water temperatures.
Researchers may also use foram and diatom population dynamics to infer past climate. Relative abundance as
well as species composition in particular areas may indicate environmental conditions. Typically, warmer
weather will cause organisms to proliferate. In addition, since each species has a particular set of ideal
growing conditions, species composition at a particular site at a particular time may indicate past
6. Step #1 – find your evidence
How Are Other Proxies Used?
Combinations of proxy data are generally used to reconstruct records for past
climate. In addition to forams and diatoms, common proxies and their
respective analytical methods include:
Ice core records- deep ice cores, such as those from Lake Vostok, Antarctica, the
Greenland Ice Sheet Project, and North Greenland Ice Sheet Project can be
analyzed for trapped gas, stable isotope ratios, and pollen trapped within the
layers to infer past climate.
Tree rings- can be counted to determine age. The thickness of each ring can be used
to infer fluctuations in temperature and precipitation, since optimal conditions
for the particular species will result in more growth, and thus thicker rings for a
given year. Scars and burn marks can indicate past natural events such as fire.
Sediment cores- can be analyzed in many ways. Sediment laminations, or layers, can
indicate sedimentation rate through time. Charcoal trapped in sediments can
indicate past fire events. Remains of microorganisms such as diatoms,
foraminifera, microbiota, and pollen within sediment can indicate changes in
past climate, since each species has a limited range of habitable conditions.
When these organisms and pollen sink to the bottom of a lake or ocean, they
can become buried within the sediment. Thus, climate change can be inferred
by species composition within the sediment
7. B. What are the causes of climate
8. The Greenhouse Effect
9. Match the letters to the numbered boxes on your diagram
Human activity increases
concentration of GH gases, resulting
in global warming
10. The Greenhouse Effect & Global Warming
11. The Greenhouse Effect & Global Warming
12. The Greenhouse Effect & Global Warming
13. The Greenhouse Effect & Global Warming
14. The Greenhouse Effect & Global Warming
15. The Greenhouse Effect & Global Warming
16. The Greenhouse Effect & Global Warming
17. The Greenhouse Effect & Global Warming
18. The Greenhouse Effect & Global Warming
Human activity increases
concentration of GH gases,
resulting in global warming
19. The Causes
1. Earth-Sun Geometry is best
• The Serbian astrophysicist Milutin Milankovitch
known for developing one of the most significant theories
relating Earth motions and long-term climate change.
Milankovitch dedicated his career to developing a
mathematical theory of climate based on the seasonal and
latitudinal variations of solar radiation received by the
Now known as the Milankovitch Theory, it states that as the
Earth travels through space around the sun, cyclical
variations in three elements of Earth-sun geometry combine
to produce variations in the amount of solar energy that
Variations in the Earth's orbital eccentricity—the shape of the orbit
around the sun.
Changes in obliquity—changes in the angle that Earth's axis makes
with the plane of Earth's orbit.
Precession—the change in the direction of the Earth's axis of
rotation, i.e., the axis of rotation behaves like the spin axis of a top
that is winding down; hence it traces a circle on the celestial
sphere over a period of time.
Together, the periods of these orbital motions have become
known as Milankovitch cycles.
20. The Causes
1. Earth-Sun Geometry
21. The Causes
1. Earth-Sun Geometry
22. 2. Volcanic eruptions
Scientists are quite certain that over a
period of several million years, increased
volcanism can create enough dust and soot
to block out sunlight and produce climatic
512,000 cubic km = the 1980
eruption of Mount St. Helens
produced 1 cubic km of volcanic
material. 60-65 Myr BP
For instance at the end of the Cretaceous
period and beginning of the Tertiary
(known as the KT boundary) there was
increased volcanic activity, with huge
volcanic eruptions spewing forth floods of
lava. The Deccan traps in India are an
example of K-T boundary ruptures in the
Earth's surface, which may have lead to
the extinction of dinosaurs.
23. 2. Volcanic eruptions
• Mt Pinatubo June 15, 1991, 20 million tons
of SO2 and ash particles 12 miles (20 km)
high into the atmosphere.
• In the stratosphere circled the globe for
24. 2. Volcanic eruptions
• Large-scale volcanic activity may last only a few days, but the massive
outpouring of gases and ash can influence climate patterns for years. Sulfuric
gases convert to sulfate aerosols, sub-micron droplets containing about 75
percent sulfuric acid. Following eruptions, these aerosol particles can linger as
long as three to four years in the stratosphere.
Major eruptions alter the Earth's radiative balance because volcanic aerosol
clouds absorb terrestrial radiation, and scatter a significant amount of the
incoming solar radiation, an effect known as "radiative forcing" that can last
from two to three years following a volcanic eruption.
"Volcanic eruptions cause short-term climate changes and contribute to natural
climate variability," says Georgiy Stenchikov, a research professor with the
Department of Environmental Sciences at Rutgers University. "Exploring effects
of volcanic eruption allows us to better understand important physical
mechanisms in the climate system that are initiated by volcanic forcing."
25. Do they warm or cool?
COOLING - Scientists are quite certain increased
volcanism can create enough dust and soot to block out
sunlight and reduce global temperatures in the short
term (several weeks). Further more, for several years
volcanic sulphuric acid aerosol clouds can help reduce
temperature through ‘radiation forcing’ by scattering the
sun’s radiation. The eruption of Mt Pinatubo in 1991
(20 million tons of sulphur dioxide and ash particles
blasted more than 20km high into the atmosphere) is
believed to have reduced global temperature by 0.20.5C.
26. What about warming?
WARMING - In the very distant past, there have been
volcanic eruptions so massive that they covered vast
areas in lava more than a kilometre thick and appear to
have released enough CO2 to warm the planet after the
initial cooling caused by the dust. But even with such
gigantic eruptions, most of subsequent warming may
have been due to methane released when lava heated
coal deposits, rather than from CO2 from the volcanoes.
27. What about the past 50 years?
• Measurements of CO2 levels over the past 50
years do not show any significant rises after
eruptions. Total emissions from volcanoes on
land are estimated to average just 0.3 Gt of
CO2 each year (a hundredth of human
28. 3. Solar output
29. Relative to 1961-1990 average
Relative to 1961-1990 average
30. Some interesting links
Ecologists’ own goal: ozone saver
is global warmer
of the case against
31. Who is to
32. Emissions v Population (% )
% of global CO2
% of global
33. Wealth v Pop:Gas ratio
Pop : CO2 ratio