Climate Change Science Since 2007
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Climate Change Science Since 2007

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An update of the science on climate change by Paul Beckwith.

An update of the science on climate change by Paul Beckwith.

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  • 1. Climate Change Science since 2007 Update since release of Fourth Assessment Report (FAR) of Intergovernmental Panel on Climate Change (IPCC) in 2007 Paul H. Beckwith Sierra Club Canada November 26, 2009
  • 2. Executive Summary
    • Bottom line: Climate change is accelerating
    • Fourth Assessment Report by IPPC published in 2007 summarized state of the science of climate change as of mid-2006
    • Recent research since then shows that many aspects of planets climate are changing at the upper boundary of the IPCC projection range (or above it, like sea level rise)
    • Topics of accelerated change include Arctic sea ice area, Greenland and Antarctic ice melt, sea level rise and ocean acidification, global average atmospheric temperature and ocean temperature, solar activity, and climate change impacts
    • Climate change effects are not linear; concern is that thresholds will be crossed whereby large nonlinear feedback effects accelerate the change and dwarf the present effects of human emissions
  • 3. Introduction
    • Post 2007: Numerous scientific studies give us a greater understanding of the science behind climate change
    • This presentation summarizes this work and compares it to the IPCC report projections and conclusions
    • Main supporting documents:
    • “ Synthesis Report from Climate Change: Global Risks, Challenges & Decisions” , March 2009 http://www.pik-potsdam.de/news/press-releases/files/synthesis-report-web.pdf
    • “ Copenhagen Diagnosis, 2009: Updating the World on the Latest Climate Science”, November 25, 2009 www.copenhagendiagnosis.com
  • 4. Arctic Sea Ice Cover
    • IPPC 2007 Working Group 1 Technical Summary (pg. 44); average annual arctic sea ice area has reduced by 2.7% per decade since 1978 (average summer minimum area reduction was 7.4% per decade)
    • Most recent melting rates show significant acceleration
    • National Snow and Ice Data Center data shows arctic sea ice coverage area over last few years compared to longer term average from 1979-2000 http://nsidc.org/arcticseaicenews/
    • Ice melt in 2007 was most extensive in recorded history (smallest area of ice coverage at the end of the Northern summer in mid-September).
  • 5. Arctic Sea Ice Cover (2)
    • Area is reducing AND ice is substantially thinning
    • Summer melts in 2008 and 2009 are second and third place in ranking of maximum melt (last three years had much more melt than IPCC 2007 projections
    • After winter freeze-up frozen seas typically cover 15.7 million square km (1.5x area of U. S.)
    • At summer end (mid-September) ice coverage usually 7 million square km
    • 2007 – 2009: area reduced to about 4.3 million square km
  • 6. Arctic Sea Ice Cover (3)
    • New projections: all floating Arctic sea-ice will vanish by late summers sometime between 2013-2040
    • Warning: Melting Arctic ice has a strong positive feedback effect on warming (melt  less ice  less reflectance of incoming light  more dark open water  more absorption of incoming light  more heating  more melting)
    • Tipping point: With ice gone, warming will rapidly accelerate in the Arctic, followed by rapid warming over rest of planet
  • 7.  
  • 8. Greenland Ice Cover
    • Mechanics of ice melt not completely understood
    • Since IPCC 2007, discovery made that surface melt-water of glaciers cuts pathways downward through ice until meeting bedrock; runs underneath ice to sub-glacial lakes and then oceans
    • Lubricates ice/rock interface increasing flow rates of glaciers and therefore calving rates at ice/ocean borders
    • Record setting level of ice mass loss in 2007 summer (same year as maximum sea ice loss)
    • Graphs following from: http://www.pik-potsdam.de/news/press-releases/files/synthesis-report-web.pdf
  • 9.  
  • 10.  
  • 11. Antarctica Ice Cover
    • Record minimum snowmelt for Antarctica during southern summer in 2008-2009; lower than normal melt for last several years http://www.agu.org/pubs/crossref/2009/2009GL039186.shtml
    • Warming has occurred in Antarctica but is mostly in winter and spring where it does not result in ice loss (temperature still less than 0 degrees Celsius)
    • Melting only occurs in summer
    • Low melt years related to stronger than average westerly wind strength encircling Antarctica (technically: Southern Hemisphere Annular Mode (SAM) is in positive phase)
  • 12. Antarctica Ice Cover (2)
    • Wind strengthening likely due to human-caused stratospheric ozone depletion
    • As warming from greenhouse gases increase it will eventually dominate dynamic cooling impact of the SAM (also ozone depletion is likely to reduce in the future and reduce SAM dynamic cooling effects)
    • Positive SAM  cooling;
    • Negative SAM  warming
    • Color maps of Antarctica show m onthly average December-January surface temperature anomalies (degrees K): First map, 1998 strong negative SAM and Southern Oscillation Index (SOI): Second map, 1999 strong positive SAM and SOI
  • 13.  
  • 14.  
  • 15. Antarctica Ice Cover (3)
    • West Antarctic Ice Sheet (WAIS) rests on bedrock base primarily below sea level (“achilles heel” of continent) http://upload.wikimedia.org/wikipedia/commons/b/b7/AntarcticBedrock.jpg
    • Pine Island Glacier (PIG) and Thwaites Glacier (far west Antarctica) reach sea; drain 20% of WAIS
    • Considered weak points; do not terminate at large ice shelves (like most WAIS glaciers)
    • 1970’s to early 1990’s steady stable PIG movement (some acceleration in latter 1990’s) http://www.the-cryosphere.net/3/125/2009/tc-3-125-2009.pdf
    • Recently this has changed dramatically; glacier velocities at 4 sites (55 to 171 km inland) increased 2-3% annually between 1996 and 2007
    • 2006 to 2007 increased 6.4% 55 km from the terminus; 4.1% 171 km from the terminus
  • 16. Antarctica Ice Cover (4)
    • Different study: ice loss through central cross section of the glacier increased from 2.5 km 3 /year in 1995 to 10.1 km 3 /year in 2006
    • Increased ocean temperature caused melting (since there is not significant surface melting) http://www.agu.org/pubs/crossref/2009/2009GL039126.shtml
    • Hidden Antarctic water network much larger; more dynamic than originally thought
    • Water accelerates glacial movement due to lubrication, could indicate melting from below (perhaps geothermal)
    • Useful to compare lake locations with Antarctic bedrock topography (in map on previous link) http://www.newscientist.com/article/mg20327253.900-antarcticas-hidden-plumbing-revealed.html
  • 17.  
  • 18.  
  • 19. Sea Level Rise: IPPC 2007 0.26 – 0.59 A1FI scenario 0.23 – 0.51 A2 scenario 0.21 – 0.48 A1B scenario 0.20 – 0.43 B2 scenario 0.20 – 0.45 A1T scenario 0.18 – 0.38 B1 scenario Model-based range excluding future rapid dynamical changes in ice flow Case Sea Level Rise - meters (by 2090-2099 relative to1980-1999)
  • 20. Sea Level Rise (2)
    • IPCC 2007 sea level rise ranges from 0.18 to 0.59 meters by 2100
    • Copenhagen Synthesis Report discussed at Real Climate concludes “The updated estimates of the future global mean sea level rise are about double the IPCC projections from 2007″ http://www.realclimate.org/index.php/archives/2009/08/ups-and-downs-of-sea-level-projections/
    • Other recent estimates project sea-level rise of 1 meter or more by 2100 http://www.iop.org/EJ/volume/1755-1315/6
  • 21. Sea Level Rise (3)
    • Following is a plot of sea level change relative to 1990 http://www.pik-potsdam.de/news/press-releases/files/synthesis-report-web.pdf
    • Actual measured rise exceeds range of the IPCC 2007 predictions
    • Up to now about 50% of sea level rise is due to expansion of water with warming
    • Increased rate of increase recently likely due to higher melting rates of ground-based glaciers from Greenland and Antarctica (Arctic sea-ice melting does not significantly affect sea levels)
  • 22.  
  • 23. Ocean Acidification
    • Scientific studies (at Scripps Institute of Oceanography and others) show ocean chemistry changing 100 times faster than the change in the 650,000 years preceding the modern industrial era
    • Measurements indicate average ocean pH has dropped 0.11 units since mid 1980’s from 8.16 to 8.05 (lower pH is more acidic)
    • pH is logarithmic; this means ocean acidity has increased 41% over last 30 years due to absorption of carbon dioxide from the atmosphere
    • Carbon dioxide in atmosphere is chemically inert; in water it changes the chemistry
  • 24. Ocean Acidification (2)
    • pH of ocean projected to fall 0.4 units before 2100 http://www.sciencedaily.com/releases/2009/09/090915101359.htm
    • This would correspond to 3-fold increase in mean acidity of the oceans (unprecedented over past 20 million years)
    • Would severely disrupt food chain since hard shelled animals and corals would not develop as fast (or at all)
    • 2007 IPPC Working Group 1 (Chap. 5; pg 405) indicated 0.1 pH drop in ocean between 1750 and 1994 (calculation based on uptake of anthropogenic carbon)
    • Graph following shows long term pH change of oceans as well as future projections: http://www.pik-potsdam.de/news/press-releases/files/synthesis-report-web.pdf
  • 25.  
  • 26. Ocean Oxygen Levels
    • Recent thoughts: some “ocean dead zones” which have very low levels of oxygen (< 2 mg dissolved O 2 per liter of seawater) which are responsible for deaths of many marine organisms may be related to ocean acidification
    • Other dead zones (Gulf of Mexico) seasonal and due to fertilizer run-off mostly via Mississippi River
    • Others due to climate change ocean warming
    • 407 dead zones globally (doubled in last decade)
    • Reference: Alanna Mitchell book “Sea Sick: The Global Ocean in Crisis” published in 2009
  • 27. Global Average Temperature
    • Table shows 10 warmest years on record back to 1850 http://www.sciencedaily.com/releases/2007/12/071213101419.htm
    • 10 Warmest Years: Mean Global temperature (°C) (anomaly relative to average of 1961-1990)
    • 1998 0.52
    • 2005 0.48
    • 2003 0.46
    • 2002 0.46
    • 2004 0.43
    • 2006 0.42
    • 2007 (Jan-Nov) 0.41 , also 2008
    • 2001 0.40
    • 1997 0.36
    • 1995 0.28
  • 28. Global Average Temperature (2)
    • 1998 warmest year on record with temperature 0.52 °C above 1961-1990 average
    • 2008 temperature tied with 2001
    • Large source of fluctuation over any decadal time scale are El Nino (warming) and La Nina (cooling) events
    • 1998 was hottest year due to combination of climate change and massive El Nino condition
    • 2008 was strong La Nina year (still made top ten)
    • Most significantly last decade has seen highest average temperature compared to any previous decade
    • Next plot shows surface atmospheric temperature change from 1970 to the present
  • 29.  
  • 30. Global Ocean Temperature
    • Updated trends since IPCC 2007 for ocean energy content and water temperature have been studied
    • Largest amount of heat stored at earth’s surface is stored in oceans (due to large water volume and high density and heat capacity of water versus soil and air)
    • 71% of area on planet is ocean; ocean volume 500x that of atmosphere
    • Plots following from http://www.pik-potsdam.de/news/press-releases/files/synthesis-report-web.pdf
  • 31.  
  • 32.  
  • 33. Global Ocean Temperature (2)
    • Energy content of ocean dwarfs that of atmosphere and land masses (represents 14.2/15.9 = 89% of total storage)
    • Ocean heat content has significantly increased since early 1950’s
    • Ocean warming roughly 50% higher than reported in IPCC 2007
    • Especially significant because of large time lag between greenhouse gas increase and ocean warming
  • 34. Atmospheric CO 2 Concentrations
    • IPCC 2007 states global mean concentration of CO 2 in 2005 was 379 ppm; 1995-2005 decade had concentration growth rate of 1.9 ppm/yr (largest change observed/inferred for any decade in >200 years) http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter2.pdf
    • Annual concentration in 2004-2008 follows (latter 3 columns indicate yearly change, yearly month to month range, and variation of yearly range) http://co2now.org/index.php?option= com_content&task = view&id =22&Itemid=1
  • 35. 5.43 383.07 – 388.50 1.86 385.57 2008 5.72 380.81 – 386.53 1.86 383.71 2007 6.13 378.81 – 384.94 2.05 381.85 2006 5.73 376.72 – 382.45 2.24 379.76 2005 6.52 374.10 – 380.62 1.74 377.52 2004 Yearly change (ppm) Yearly range (ppm) Change in concentration from previous year (ppm) Yearly average carbon dioxide concentration (ppm) Year
  • 36. Atmospheric CO 2 Concentrations (2)
    • Concentration varies on monthly basis with yearly minimum each September (low value in range) and yearly maximum each May (high value in range)
    • Variation caused by vegetation growth and vegetation hibernation with Northern hemisphere seasons
    • 2009: May concentration 390.18 ppm; September value 384.78 ppm; range 5.40 ppm
    • Conclusion: carbon dioxide concentration in atmosphere is continuing upward trend at rapid rate in spite of worldwide emissions from fossil fuel combustion that have been somewhat tempered by a global economic recession
  • 37.  
  • 38. Nitrous oxide concentrations
    • Nitrous oxide (N 2 O) arises from both natural and human sources
    • Natural sources: biological processes in soil and water such as microbial activity in wet tropical forests
    • Primary human based sources: agricultural soil practices, animal manure practices, sewage treatment, fossil fuel combustion, industrial acid production
    • Agricultural use of synthetic nitrogen fertilizers to increase crop yields typically results in significantly more N 2 O emissions from soils than that occurring from less intensive techniques
  • 39. Nitrous oxide concentrations (2)
    • Roughly 2/3 of $100 billion of nitrogen fertilizer used on fields every year does not end up in plants
    • Washed out of soil into bodies of water causing algal blooms and “dead zones” (no oxygen) or is converted to atmospheric nitrous oxide by soil
    • Main sink for atmospheric n itrous oxide is destruction by photolytic chemical reactions (involving photons or light) in stratosphere (some of which produce ozone)
    • Global warming effect for nitrous oxide is about 300x that of CO 2
  • 40. Methane Concentrations
    • Seem to have stabilized somewhat over last decade, however there has been an uptick in concentration levels over last few years
    • Large uncertainty exists over potential emissions of methane from sources such as peat bogs, Arctic tundra and permafrost and ocean bottom clathrates
    • Examining regional and latitudinal dependencies of concentrations should reduce some of uncertainties soon
    • Originally, methane effect on warming was believed to be 21x greater than that of CO 2
    • IPCC 2007 revised 100 year Global Warming Potential (GWP) of methane upward to 25x due to its effect on increasing tropospheric ozone via atmospheric chemistry effects
  • 41. Solar Activity
    • For 2009 and last few years solar sunspot activity has been extremely low (solar minimum)
    • Although sunspots are cooler than normal sun surface (and thus darker) there are always warmer areas (faculae) surrounding them
    • Result: higher solar radiation emitted from sun and reaching earth during sunspot activity (counter-intuitive)
    • Normally this effect follows 11 year cycle which tracks strength of suns magnetic field (not a hard and fast rule)
    • Impacts of this cycle on earth surface temperature record in dispute (may be as great as 0.1 degrees Celsius from solar minimum to solar maximum with time lag of year or two)
  • 42. Solar Activity (2)
    • Now at minimum of cycle; has cooling effect on climate, offsetting some of warming from increased CO 2
    • Influence of solar variability is still an open question; according to IPCC 2007 contribution since 1750 is about 10% of that due to anthropogenic forcing
    • Some measurements indicate magnetic strength of sunspots has been reducing over past several decades
    • If trend continues sunspots could disappear for decades as occurred between 1645 and 1715 during period called Maunder minimum (resulting in extremely cold winters in Europe and North America)
    • Tug-of-war could arise between global warming and solar cooling.
  • 43. Climate Change Impacts
    • Climate change: appears to cause increase in frequency and magnitude of extreme weather events
    • Example: number of category 5 hurricanes in Northern hemisphere reported to have increased by 3-4 times in last decade relative to previous decades http://www.pik-potsdam.de/news/press-releases/files/synthesis-report-web.pdf
    • Believed to be due to increase in surface sea temperatures (SSTs) which fuel hurricanes
    • Following is a “burning embers chart” comparing impacts of climate change (2009 IPPC viewpoint versus 2001 IPPC viewpoint)
  • 44.