Climate Change Climate Change Science since 2007Science since 2007

Update since release of Fourth Assessment Update since release of Fourth Assessment Report (FAR) of Intergovernmental Panel on Report (FAR) of Intergovernmental Panel on

Climate Change (IPCC) in 2007Climate Change (IPCC) in 2007

Paul H. BeckwithPaul H. BeckwithSierra Club CanadaSierra Club CanadaNovember 26, 2009November 26, 2009

Executive SummaryExecutive Summary

• Bottom line: Climate change is acceleratingBottom line: Climate change is accelerating

• Fourth Assessment Report by IPPC published in 2007 summarized Fourth Assessment Report by IPPC published in 2007 summarized state of the science of climate change as of mid-2006state of the science of climate change as of mid-2006

• Recent research since then shows that many aspects of planets Recent research since then shows that many aspects of planets climate are changing at the upper boundary of the IPCC projection climate are changing at the upper boundary of the IPCC projection range (or above it, like sea level rise)range (or above it, like sea level rise)

• Topics of accelerated change include Arctic sea ice area, Topics of accelerated change include Arctic sea ice area, Greenland and Antarctic ice melt, sea level rise and ocean Greenland and Antarctic ice melt, sea level rise and ocean acidification, global average atmospheric temperature and ocean acidification, global average atmospheric temperature and ocean temperature, solar activity, and climate change impactstemperature, solar activity, and climate change impacts

• Climate change effects are not linear; concern is that thresholds Climate change effects are not linear; concern is that thresholds will be crossed whereby large nonlinear feedback effects will be crossed whereby large nonlinear feedback effects accelerate the change and dwarf the present effects of human accelerate the change and dwarf the present effects of human emissionsemissions

IntroductionIntroduction• Post 2007: Numerous scientific studies give us a Post 2007: Numerous scientific studies give us a

greater understanding of the science behind climate greater understanding of the science behind climate change change

• This presentation summarizes this work and This presentation summarizes this work and compares it to the IPCC report projections and compares it to the IPCC report projections and conclusions conclusions

• Main supporting documents:Main supporting documents: “ “Synthesis Report from Climate Change: Global Synthesis Report from Climate Change: Global

Risks, Challenges & Decisions” , March 2009 Risks, Challenges & Decisions” , March 2009 http://www.pik-potsdam.de/news/press-releases/files/http://www.pik-potsdam.de/news/press-releases/files/synthesis-report-web.pdfsynthesis-report-web.pdf

“ “Copenhagen Diagnosis, 2009: Updating the World on Copenhagen Diagnosis, 2009: Updating the World on the Latest Climate Science”, November 25, 2009 the Latest Climate Science”, November 25, 2009 www.copenhagendiagnosis.comwww.copenhagendiagnosis.com

Arctic Sea Ice CoverArctic Sea Ice Cover• IPPC 2007 Working Group 1 Technical Summary (pg. IPPC 2007 Working Group 1 Technical Summary (pg.

44); average annual arctic sea ice area has reduced 44); average annual arctic sea ice area has reduced by 2.7% per decade since 1978 (average summer by 2.7% per decade since 1978 (average summer minimum area reduction was 7.4% per decade)minimum area reduction was 7.4% per decade)

• Most recent melting rates show significant Most recent melting rates show significant accelerationacceleration

• National Snow and Ice Data Center data shows arctic National Snow and Ice Data Center data shows arctic sea ice coverage area over last few years compared sea ice coverage area over last few years compared to longer term average from 1979-2000 to longer term average from 1979-2000 http://nsidc.org/arcticseaicenews/http://nsidc.org/arcticseaicenews/

• Ice melt in 2007 was most extensive in recorded Ice melt in 2007 was most extensive in recorded history (smallest area of ice coverage at the end of history (smallest area of ice coverage at the end of the Northern summer in mid-September). the Northern summer in mid-September).

Arctic Sea Ice Cover (2)Arctic Sea Ice Cover (2)

• Area is reducing AND ice is substantially thinningArea is reducing AND ice is substantially thinning • Summer melts in 2008 and 2009 are second and Summer melts in 2008 and 2009 are second and

third place in ranking of maximum melt (last three third place in ranking of maximum melt (last three years had much more melt than IPCC 2007 years had much more melt than IPCC 2007 projections projections

• After winter freeze-up frozen seas typically cover After winter freeze-up frozen seas typically cover 15.7 million square km (1.5x area of U. S.)15.7 million square km (1.5x area of U. S.)

• At summer end (mid-September) ice coverage At summer end (mid-September) ice coverage usually 7 million square kmusually 7 million square km

• 2007 – 2009: area reduced to about 4.3 million 2007 – 2009: area reduced to about 4.3 million square km square km

Arctic Sea Ice Cover (3)Arctic Sea Ice Cover (3)

• New projections: all floating Arctic sea-ice New projections: all floating Arctic sea-ice will vanish by late summers sometime will vanish by late summers sometime between 2013-2040between 2013-2040

• Warning: Melting Arctic ice has a strong Warning: Melting Arctic ice has a strong positive feedback effect on warming (melt positive feedback effect on warming (melt less ice less ice less reflectance of incoming less reflectance of incoming light light more dark open water more dark open water more more absorption of incoming light absorption of incoming light more more heating heating more melting) more melting)

• Tipping point: With ice gone, warming will Tipping point: With ice gone, warming will

rapidly accelerate in the Arctic, followed rapidly accelerate in the Arctic, followed by rapid warming over rest of planetby rapid warming over rest of planet

Greenland Ice CoverGreenland Ice Cover• Mechanics of ice melt not completely understoodMechanics of ice melt not completely understood

• Since IPCC 2007, discovery made that surface melt-water Since IPCC 2007, discovery made that surface melt-water of glaciers cuts pathways downward through ice until of glaciers cuts pathways downward through ice until meeting bedrock; runs underneath ice to sub-glacial meeting bedrock; runs underneath ice to sub-glacial lakes and then oceanslakes and then oceans

• Lubricates ice/rock interface increasing flow rates of Lubricates ice/rock interface increasing flow rates of glaciers and therefore calving rates at ice/ocean bordersglaciers and therefore calving rates at ice/ocean borders

• Record setting level of ice mass loss in 2007 summer Record setting level of ice mass loss in 2007 summer (same year as maximum sea ice loss)(same year as maximum sea ice loss)

• Graphs following from: Graphs following from: http://www.pik-potsdam.de/news/press-releases/files/synthttp://www.pik-potsdam.de/news/press-releases/files/synthesis-report-web.pdfhesis-report-web.pdf

Antarctica Ice CoverAntarctica Ice Cover• Record minimum snowmelt for Antarctica during Record minimum snowmelt for Antarctica during

southern summer in 2008-2009; lower than normal southern summer in 2008-2009; lower than normal melt for last several years melt for last several years http://www.agu.org/pubs/crossref/2009/2009GL0391http://www.agu.org/pubs/crossref/2009/2009GL039186.shtml86.shtml

• Warming has occurred in Antarctica but is mostly in Warming has occurred in Antarctica but is mostly in winter and spring where it does not result in ice loss winter and spring where it does not result in ice loss (temperature still less than 0 degrees Celsius) (temperature still less than 0 degrees Celsius)

• Melting only occurs in summerMelting only occurs in summer • Low melt years related to stronger than average Low melt years related to stronger than average

westerly wind strength encircling Antarctica westerly wind strength encircling Antarctica (technically: Southern Hemisphere Annular Mode (technically: Southern Hemisphere Annular Mode (SAM) is in positive phase) (SAM) is in positive phase)

Antarctica Ice Cover (2)Antarctica Ice Cover (2)• Wind strengthening likely due to human-caused Wind strengthening likely due to human-caused

stratospheric ozone depletionstratospheric ozone depletion

• As warming from greenhouse gases increase it As warming from greenhouse gases increase it will eventually dominate dynamic cooling impact will eventually dominate dynamic cooling impact of the SAM (also ozone depletion is likely to of the SAM (also ozone depletion is likely to reduce in the future and reduce SAM dynamic reduce in the future and reduce SAM dynamic cooling effects)cooling effects)

• Positive SAM Positive SAM cooling; cooling; Negative SAM Negative SAM warming warming

• Color maps of Antarctica show mColor maps of Antarctica show monthly average onthly average December-January surface temperature anomalies December-January surface temperature anomalies (degrees K): First map, 1998 strong negative SAM (degrees K): First map, 1998 strong negative SAM and Southern Oscillation Index (SOI): Second map, and Southern Oscillation Index (SOI): Second map, 1999 strong positive SAM and SOI 1999 strong positive SAM and SOI

Antarctica Ice Cover (3)Antarctica Ice Cover (3)• West Antarctic Ice Sheet (WAIS) rests on bedrock West Antarctic Ice Sheet (WAIS) rests on bedrock

base primarily below sea level (“achilles heel” of base primarily below sea level (“achilles heel” of continent) continent) http://upload.wikimedia.org/wikipedia/commons/b/bhttp://upload.wikimedia.org/wikipedia/commons/b/b7/AntarcticBedrock.jpg7/AntarcticBedrock.jpg

• Pine Island Glacier (PIG) and Thwaites Glacier (far Pine Island Glacier (PIG) and Thwaites Glacier (far west Antarctica) reach sea; drain 20% of WAIS west Antarctica) reach sea; drain 20% of WAIS

• Considered weak points; do not terminate at large Considered weak points; do not terminate at large ice shelves (like most WAIS glaciers) ice shelves (like most WAIS glaciers)

• 1970’s to early 1990’s steady stable PIG movement 1970’s to early 1990’s steady stable PIG movement (some acceleration in latter 1990’s) (some acceleration in latter 1990’s) http://www.the-cryosphere.net/3/125/2009/tc-3-125-http://www.the-cryosphere.net/3/125/2009/tc-3-125-2009.pdf2009.pdf

• Recently this has changed dramatically; glacier Recently this has changed dramatically; glacier velocities at 4 sites (55 to 171 km inland) increased velocities at 4 sites (55 to 171 km inland) increased 2-3% annually between 1996 and 2007 2-3% annually between 1996 and 2007

• 2006 to 2007 increased 6.4% 55 km from the 2006 to 2007 increased 6.4% 55 km from the terminus; 4.1% 171 km from the terminusterminus; 4.1% 171 km from the terminus

Antarctica Ice Cover (4)Antarctica Ice Cover (4)• Different study: ice loss through central cross Different study: ice loss through central cross

section of the glacier increased from 2.5 kmsection of the glacier increased from 2.5 km33/year /year in 1995 to 10.1 kmin 1995 to 10.1 km33/year in 2006 /year in 2006

• Increased ocean temperature caused melting Increased ocean temperature caused melting (since there is not significant surface melting) (since there is not significant surface melting) http://www.agu.org/pubs/crossref/2009/2009GL039http://www.agu.org/pubs/crossref/2009/2009GL039126.shtml126.shtml

• Hidden Antarctic water network much larger; more Hidden Antarctic water network much larger; more dynamic than originally thought dynamic than originally thought

• Water accelerates glacial movement due to Water accelerates glacial movement due to lubrication, could indicate melting from below lubrication, could indicate melting from below (perhaps geothermal)(perhaps geothermal)

• Useful to compare lake locations with Antarctic Useful to compare lake locations with Antarctic bedrock topography (in map on previous link) bedrock topography (in map on previous link) http://www.newscientist.com/article/mg20327253.9http://www.newscientist.com/article/mg20327253.900-antarcticas-hidden-plumbing-revealed.html 00-antarcticas-hidden-plumbing-revealed.html

Sea Level Rise: IPPC Sea Level Rise: IPPC 20072007

Sea Level Rise - metersSea Level Rise - meters(by 2090-2099 relative to1980-1999)(by 2090-2099 relative to1980-1999)

CaseCase Model-based range excluding future rapid Model-based range excluding future rapid dynamical changes in ice flow dynamical changes in ice flow

B1 scenario B1 scenario 0.18 – 0.38 0.18 – 0.38

A1T scenario A1T scenario 0.20 – 0.45 0.20 – 0.45

B2 scenario B2 scenario 0.20 – 0.43 0.20 – 0.43

A1B scenario A1B scenario 0.21 – 0.48 0.21 – 0.48

A2 scenario A2 scenario 0.23 – 0.51 0.23 – 0.51

A1FI scenario A1FI scenario 0.26 – 0.59 0.26 – 0.59

Sea Level Rise (2)Sea Level Rise (2)• IPCC 2007 sea level rise ranges from 0.18 to IPCC 2007 sea level rise ranges from 0.18 to

0.59 meters by 21000.59 meters by 2100

• Copenhagen Synthesis Report discussed at Copenhagen Synthesis Report discussed at Real Climate concludes Real Climate concludes “The updated “The updated estimates of the future global mean sea level estimates of the future global mean sea level rise are about double the IPCC projections rise are about double the IPCC projections from 2007″ from 2007″ http://www.realclimate.org/index.php/archives/http://www.realclimate.org/index.php/archives/2009/08/ups-and-downs-of-sea-level-2009/08/ups-and-downs-of-sea-level-projections/projections/

• Other recent estimates project sea-level rise of Other recent estimates project sea-level rise of 1 meter or more by 2100 1 meter or more by 2100 http://www.iop.org/EJ/volume/1755-1315/6http://www.iop.org/EJ/volume/1755-1315/6

Sea Level Rise (3)Sea Level Rise (3)

• Following is a plot of sea level change relative Following is a plot of sea level change relative to 1990 to 1990 http://www.pik-potsdam.de/news/press-http://www.pik-potsdam.de/news/press-releases/files/synthesis-report-web.pdf releases/files/synthesis-report-web.pdf

• Actual measured rise exceeds range of the Actual measured rise exceeds range of the IPCC 2007 predictionsIPCC 2007 predictions

• Up to now about 50% of sea level rise is due Up to now about 50% of sea level rise is due to expansion of water with warmingto expansion of water with warming

• Increased rate of increase recently likely due Increased rate of increase recently likely due to higher melting rates of ground-based to higher melting rates of ground-based glaciers from Greenland and Antarctica (Arctic glaciers from Greenland and Antarctica (Arctic sea-ice melting does not significantly affect sea-ice melting does not significantly affect sea levels) sea levels)

Ocean AcidificationOcean Acidification • Scientific studies (at Scripps Institute of Scientific studies (at Scripps Institute of

Oceanography and others) show ocean Oceanography and others) show ocean chemistry changing 100 times faster than chemistry changing 100 times faster than the change in the 650,000 years preceding the change in the 650,000 years preceding the modern industrial erathe modern industrial era

• Measurements indicate average ocean pH Measurements indicate average ocean pH has dropped 0.11 units since mid 1980’s has dropped 0.11 units since mid 1980’s from 8.16 to 8.05 (lower pH is more acidic)from 8.16 to 8.05 (lower pH is more acidic)

• pH is logarithmic; this means ocean acidity pH is logarithmic; this means ocean acidity has increased 41% over last 30 years due has increased 41% over last 30 years due to absorption of carbon dioxide from the to absorption of carbon dioxide from the atmosphereatmosphere

• Carbon dioxide in atmosphere is Carbon dioxide in atmosphere is chemically inert; in water it changes the chemically inert; in water it changes the chemistry chemistry

Ocean Acidification (2)Ocean Acidification (2)

• pH of ocean projected to fall 0.4 units before 2100 pH of ocean projected to fall 0.4 units before 2100 http://www.sciencedaily.com/releases/2009/09/090915http://www.sciencedaily.com/releases/2009/09/090915101359.htm 101359.htm

• This would correspond to 3-fold increase in mean This would correspond to 3-fold increase in mean acidity of the oceans (unprecedented over past 20 acidity of the oceans (unprecedented over past 20 million years) million years)

• Would severely disrupt food chain since hard shelled Would severely disrupt food chain since hard shelled animals and corals would not develop as fast (or at all)animals and corals would not develop as fast (or at all)

• 2007 IPPC Working Group 1 (Chap. 5; pg 405) indicated 2007 IPPC Working Group 1 (Chap. 5; pg 405) indicated 0.1 pH drop in ocean between 1750 and 1994 0.1 pH drop in ocean between 1750 and 1994 (calculation based on uptake of anthropogenic carbon)(calculation based on uptake of anthropogenic carbon)

• Graph following shows long term pH change of oceans Graph following shows long term pH change of oceans as well as future projections: as well as future projections: http://www.pik-potsdam.de/news/press-releases/files/syhttp://www.pik-potsdam.de/news/press-releases/files/synthesis-report-web.pdfnthesis-report-web.pdf

Ocean Oxygen LevelsOcean Oxygen Levels

• Recent thoughts: some “ocean dead zones” which Recent thoughts: some “ocean dead zones” which have very low levels of oxygen (< 2 mg dissolved have very low levels of oxygen (< 2 mg dissolved OO22 per liter of seawater) which are responsible for per liter of seawater) which are responsible for deaths of many marine organisms may be related deaths of many marine organisms may be related to ocean acidificationto ocean acidification

• Other dead zones (Gulf of Mexico) seasonal and Other dead zones (Gulf of Mexico) seasonal and due to fertilizer run-off mostly via Mississippi Riverdue to fertilizer run-off mostly via Mississippi River

• Others due to climate change ocean warmingOthers due to climate change ocean warming

• 407 dead zones globally (doubled in last decade)407 dead zones globally (doubled in last decade)

• Reference: Alanna Mitchell book “Sea Sick: The Reference: Alanna Mitchell book “Sea Sick: The Global Ocean in Crisis” published in 2009Global Ocean in Crisis” published in 2009

Global Average TemperatureGlobal Average Temperature• Table shows 10 warmest years on record back to Table shows 10 warmest years on record back to

1850 1850 http://www.sciencedaily.com/releases/2007/12/07121http://www.sciencedaily.com/releases/2007/12/071213101419.htm3101419.htm

10 Warmest Years: Mean Global temperature (°C) 10 Warmest Years: Mean Global temperature (°C) (anomaly relative to average of 1961-1990)(anomaly relative to average of 1961-1990)

1998 0.52 1998 0.52 2005 0.48 2005 0.48 2003 0.46 2003 0.46 2002 0.46 2002 0.46 2004 0.43 2004 0.43 2006 0.42 2006 0.42 2007 (Jan-Nov) 0.41 , also 20082007 (Jan-Nov) 0.41 , also 2008 2001 0.40 2001 0.40 1997 0.36 1997 0.36 1995 0.28 1995 0.28

Global Average Temperature Global Average Temperature (2)(2)

• 1998 warmest year on record with 1998 warmest year on record with temperature 0.52 temperature 0.52 °C°C above 1961-1990 above 1961-1990 averageaverage

• 2008 temperature tied with 20012008 temperature tied with 2001• Large source of fluctuation over any decadal Large source of fluctuation over any decadal

time scale are El Nino (warming) and La Nina time scale are El Nino (warming) and La Nina (cooling) events(cooling) events

• 1998 was hottest year due to combination of 1998 was hottest year due to combination of climate change and massive El Nino conditionclimate change and massive El Nino condition

• 2008 was strong La Nina year (still made top 2008 was strong La Nina year (still made top ten) ten)

• Most significantly last decade has seen Most significantly last decade has seen highest average temperature compared to highest average temperature compared to any previous decadeany previous decade

• Next plot shows surface atmospheric Next plot shows surface atmospheric temperature change from 1970 to the presenttemperature change from 1970 to the present

Global Ocean TemperatureGlobal Ocean Temperature• Updated trends since IPCC 2007 for ocean Updated trends since IPCC 2007 for ocean

energy content and water temperature energy content and water temperature have been studied have been studied

• Largest amount of heat stored at earth’s Largest amount of heat stored at earth’s surface is stored in oceans (due to large surface is stored in oceans (due to large water volume and high density and heat water volume and high density and heat capacity of water versus soil and air) capacity of water versus soil and air)

• 71% of area on planet is ocean; ocean 71% of area on planet is ocean; ocean volume 500x that of atmospherevolume 500x that of atmosphere

• Plots following from Plots following from http://www.pik-potsdam.de/news/press-relhttp://www.pik-potsdam.de/news/press-releases/files/synthesis-report-web.pdfeases/files/synthesis-report-web.pdf

Global Ocean Temperature (2)Global Ocean Temperature (2)

• Energy content of ocean dwarfs that Energy content of ocean dwarfs that of atmosphere and land masses of atmosphere and land masses (represents 14.2/15.9 = 89% of total (represents 14.2/15.9 = 89% of total storage) storage)

• Ocean heat content has significantly Ocean heat content has significantly increased since early 1950’sincreased since early 1950’s

• Ocean warming roughly 50% higher Ocean warming roughly 50% higher than reported in IPCC 2007than reported in IPCC 2007

• Especially significant because of large Especially significant because of large time lag between greenhouse gas time lag between greenhouse gas increase and ocean warmingincrease and ocean warming

Atmospheric Atmospheric COCO22 Concentrations Concentrations

• IPCC 2007 states global mean concentration of IPCC 2007 states global mean concentration of COCO22 in 2005 was 379 ppm; 1995-2005 decade in 2005 was 379 ppm; 1995-2005 decade had concentration growth rate of 1.9 ppm/yr had concentration growth rate of 1.9 ppm/yr (largest change observed/inferred for any (largest change observed/inferred for any decade in >200 years) decade in >200 years) http://www.ipcc.ch/pdf/assessment-report/ar4/wghttp://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter2.pdf 1/ar4-wg1-chapter2.pdf

• Annual concentration in 2004-2008 follows Annual concentration in 2004-2008 follows (latter 3 columns indicate yearly change, yearly (latter 3 columns indicate yearly change, yearly month to month range, and variation of yearly month to month range, and variation of yearly range) http://co2now.org/index.php?range) http://co2now.org/index.php?option=com_content&task=view&id=22&Itemidoption=com_content&task=view&id=22&Itemid=1 =1

YearYear Yearly average Yearly average carbon dioxidecarbon dioxide

concentration concentration (ppm)(ppm)

Change in Change in concentration concentration from previous from previous

year (ppm)year (ppm)

Yearly Yearly range range (ppm)(ppm)

Yearly Yearly change change (ppm)(ppm)

20042004 377.52377.52 1.741.74 374.10 – 374.10 – 380.62380.62

6.526.52

20052005 379.76379.76 2.242.24 376.72 – 376.72 – 382.45382.45

5.735.73

20062006 381.85381.85 2.052.05 378.81 – 378.81 – 384.94384.94

6.136.13

20072007 383.71383.71 1.861.86 380.81 – 380.81 – 386.53386.53

5.725.72

20082008 385.57385.57 1.861.86 383.07 – 383.07 – 388.50388.50

5.435.43

Atmospheric Atmospheric COCO22 Concentrations Concentrations (2)(2)• Concentration varies on monthly basis with Concentration varies on monthly basis with

yearly minimum each September (low value yearly minimum each September (low value in range) and yearly maximum each May in range) and yearly maximum each May (high value in range)(high value in range)

• Variation caused by vegetation growth and Variation caused by vegetation growth and vegetation hibernation with Northern vegetation hibernation with Northern hemisphere seasons hemisphere seasons

• 2009: May concentration 390.18 ppm; 2009: May concentration 390.18 ppm; September value 384.78 ppm; range 5.40 September value 384.78 ppm; range 5.40 ppmppm

• Conclusion: carbon dioxide concentration in Conclusion: carbon dioxide concentration in atmosphere is continuing upward trend at atmosphere is continuing upward trend at rapid rate in spite of worldwide emissions rapid rate in spite of worldwide emissions from fossil fuel combustion that have been from fossil fuel combustion that have been somewhat tempered by a global economic somewhat tempered by a global economic recessionrecession

Nitrous oxide concentrationsNitrous oxide concentrations

• Nitrous oxide (NNitrous oxide (N22O) arises from both natural O) arises from both natural and human sourcesand human sources

• Natural sources: biological processes in soil Natural sources: biological processes in soil and water such as microbial activity in wet and water such as microbial activity in wet tropical foreststropical forests

• Primary human based sources: agricultural Primary human based sources: agricultural soil practices, animal manure practices, soil practices, animal manure practices, sewage treatment, fossil fuel combustion, sewage treatment, fossil fuel combustion, industrial acid productionindustrial acid production

• Agricultural use of synthetic nitrogen Agricultural use of synthetic nitrogen fertilizers to increase crop yields typically fertilizers to increase crop yields typically results in significantly more Nresults in significantly more N22O emissions O emissions from soils than that occurring from less from soils than that occurring from less intensive techniquesintensive techniques

Nitrous oxide concentrations Nitrous oxide concentrations (2)(2)

• Roughly 2/3 of $100 billion of nitrogen Roughly 2/3 of $100 billion of nitrogen fertilizer used on fields every year does not fertilizer used on fields every year does not end up in plantsend up in plants

• Washed out of soil into bodies of water Washed out of soil into bodies of water causing algal blooms and “dead zones” (no causing algal blooms and “dead zones” (no oxygen) or is converted to atmospheric oxygen) or is converted to atmospheric nitrous oxide by soilnitrous oxide by soil

• Main sink for atmospheric nMain sink for atmospheric nitrous oxide is itrous oxide is destruction by photolytic chemical reactions destruction by photolytic chemical reactions (involving photons or light) in stratosphere (involving photons or light) in stratosphere (some of which produce ozone) (some of which produce ozone)

• Global warming effect for nitrous oxide is Global warming effect for nitrous oxide is about 300x that of COabout 300x that of CO22

Methane ConcentrationsMethane Concentrations• Seem to have stabilized somewhat over last Seem to have stabilized somewhat over last

decade, however there has been an uptick in decade, however there has been an uptick in concentration levels over last few yearsconcentration levels over last few years

• Large uncertainty exists over potential emissions Large uncertainty exists over potential emissions of methane from sources such as peat bogs, of methane from sources such as peat bogs, Arctic tundra and permafrost and ocean bottom Arctic tundra and permafrost and ocean bottom clathratesclathrates

• Examining regional and latitudinal dependencies Examining regional and latitudinal dependencies of concentrations should reduce some of of concentrations should reduce some of uncertainties soonuncertainties soon

• Originally, methane effect on warming was Originally, methane effect on warming was believed to be 21x greater than that of CObelieved to be 21x greater than that of CO22

• IPCC 2007 revised 100 year Global Warming IPCC 2007 revised 100 year Global Warming Potential (GWP) of methane upward to 25x due to Potential (GWP) of methane upward to 25x due to its effect on increasing tropospheric ozone via its effect on increasing tropospheric ozone via atmospheric chemistry effectsatmospheric chemistry effects

Solar ActivitySolar Activity• For 2009 and last few years solar sunspot For 2009 and last few years solar sunspot

activity has been extremely low (solar activity has been extremely low (solar minimum)minimum)

• Although sunspots are cooler than normal sun Although sunspots are cooler than normal sun surface (and thus darker) there are always surface (and thus darker) there are always warmer areas (faculae) surrounding themwarmer areas (faculae) surrounding them

• Result: higher solar radiation emitted from sun Result: higher solar radiation emitted from sun and reaching earth during sunspot activity and reaching earth during sunspot activity (counter-intuitive)(counter-intuitive)

• Normally this effect follows 11 year cycle which Normally this effect follows 11 year cycle which tracks strength of suns magnetic field (not a tracks strength of suns magnetic field (not a hard and fast rule)hard and fast rule)

• Impacts of this cycle on earth surface Impacts of this cycle on earth surface temperature record in dispute (may be as great temperature record in dispute (may be as great as 0.1 degrees Celsius from solar minimum to as 0.1 degrees Celsius from solar minimum to solar maximum with time lag of year or two)solar maximum with time lag of year or two)

Solar Activity (2)Solar Activity (2)

• Now at minimum of cycle; has cooling effect on Now at minimum of cycle; has cooling effect on climate, offsetting some of warming from increased climate, offsetting some of warming from increased COCO22

• Influence of solar variability is still an open question; Influence of solar variability is still an open question; according to IPCC 2007 contribution since 1750 is according to IPCC 2007 contribution since 1750 is about 10% of that due to anthropogenic forcingabout 10% of that due to anthropogenic forcing

• Some measurements indicate magnetic strength of Some measurements indicate magnetic strength of sunspots has been reducing over past several sunspots has been reducing over past several decadesdecades

• If trend continues sunspots could disappear for If trend continues sunspots could disappear for decades as occurred between 1645 and 1715 during decades as occurred between 1645 and 1715 during period called Maunder minimum (resulting in period called Maunder minimum (resulting in extremely cold winters in Europe and North America)extremely cold winters in Europe and North America)

• Tug-of-war could arise between global warming and Tug-of-war could arise between global warming and solar cooling.solar cooling.

Climate Change ImpactsClimate Change Impacts• Climate change: appears to cause increase Climate change: appears to cause increase

in frequency and magnitude of extreme in frequency and magnitude of extreme weather eventsweather events

• Example: number of category 5 hurricanes Example: number of category 5 hurricanes in Northern hemisphere reported to have in Northern hemisphere reported to have increased by 3-4 times in last decade increased by 3-4 times in last decade relative to previous decades relative to previous decades http://www.pik-potsdam.de/news/press-relehttp://www.pik-potsdam.de/news/press-releases/files/synthesis-report-web.pdfases/files/synthesis-report-web.pdf

• Believed to be due to increase in surface Believed to be due to increase in surface sea temperatures (SSTs) which fuel sea temperatures (SSTs) which fuel hurricaneshurricanes

• Following is a “burning embers chart” Following is a “burning embers chart” comparing impacts of climate change (2009 comparing impacts of climate change (2009 IPPC viewpoint versus 2001 IPPC viewpoint)IPPC viewpoint versus 2001 IPPC viewpoint)