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MIT OpenCourseWare http://ocw.mit.edu15.023J / 12.848J / ESD.128J Global Climate Change: Economics, Science, and PolicySpring 2008For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms.1. Predicting Regional Climate: Local Effects?2. Impacts of Climate Change: Biosphere?3. Severe Storms: Damages Increase with Warming? 4. Cooling Effects of Aerosols: Unveiling of True Warming?5. Critical Thresholds:Stability of Ice Sheets,Tundra, Carbon Sinks and Oceanic Overturn?6. Stabilization of GHGs: What Levels Will Avoid Danger?7. Energy Solutions: Effects at Large Scale?8. Geo-engineering: Viable option or dangerous diversion?9. Possible Defining Climate Events: The next 20 years?15.023 - 12.848 - 12.308 - ESD.128GLOBAL CLIMATE CHANGE : ECONOMICS, SCIENCE, AND POLICYTHE CLIMATE MACHINE V:Unresolved Problems inClimate AnalysisR. PRINN, May 5, 2008MESSAGE: CURRENT REGIONAL FORECASTS ARE VERY UNCERTAIN! REF: US GCRP: CLIMATE CHANGE IMPACTS ON THE UNITED STATES 1. PREDICTING REGIONAL CLIMATESome Results for soil moisture-very important for agricultureMultimodal average percentage changes in precipitation for 2090-2099 relative to 1980-1999 (A1B SRES emission scenario). White areas: <66% of models agree in sign of change. Stippled Areas: >90% of models agree in sign of change. Ref: IPCC 4th Assessment, Summary for Policymakers, Feb. 2, 2007 Courtesy of the Intergovernmental Panel on Climate Change. Used with permission. From: Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Figure SPM.7, Cambridge University Press.Figure SPM-1. Locations of significant changes in observations of physical systems (snow, ice and frozen ground; hydrology; and coastal processes) and biological systems (terrestrial, marine, and freshwater biological systems), are shown together with surface air temperature changes over the period 1970-2004. Summary for Policymakers IPCC WGII Fourth Assessment Report, April 2007 2. IMPACTS OF CLIMATE CHANGEPhysical and Biological SystemsCourtesy of the Intergovernmental Panel on Climate Change. Used with permission. From: Climate Change 2007: Impacts, Adaptation and Vulnerability. Working Group II Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Figure SPM.1, Cambridge University Press.Key impacts as a function of increasing global average temperature change (Impacts will vary by extent of adaptation, rate of temperature change, and socio-economic pathway) BUT, HOW RELIABLE ARE THESE PROJECTIONS? Table SPM-1. Illustrative examples of global impacts projected for climate changes (and sea-level and atmospheric carbon dioxide where relevant) associated with different amounts of increase in global average surface temperature in the 21st century [T20.7]. The black lines link impacts, dotted arrows indicate impacts continuing with increasing temperature. Entries are placed so that the left hand side of text indicates approximate onset of a given impact. Confidence levels for all statements are high. Summary for Policymakers IPCC WGII Fourth Assessment Report, April 2007 Courtesy of the Intergovernmental Panel on Climate Change. Used with permission. From: Climate Change 2007: Impacts, Adaptation and Vulnerability. Working Group II Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Figure SPM.2, Cambridge University Press.Figure by MIT OpenCourseWare.3. SEVERE STORMSDamages Increase with Warming?YearAnnual total number of tornadoes1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 201001002003004005006007008009001000110012001300140015001600United States Tornadoes 1950-2006But the capability for tornadodetection has improved over this timeSOURCE: Emanuel, K., Nature, vol. 436, 4 August 2005 IS THE POWER DISSIPATION APPROXIMATION VALID? ARE THE DATA (V, T) ACCURATE? Power Dissipation Index (PDI) =T∫0 Vmax3 dt (a measure of storm destruction) Courtesy of Kerry Emanuel. Used with permission.HURRICANES:INCREASING DESTRUCTIVENESS OVER THE PAST 30 YEARS?WHAT ARE THE EFFECTS OF AEROSOLS ON CLIMATE? (A) Direct Effect: Aerosols reflect (sulfates) or absorb (black carbon) sunlight (B) Indirect Effects: activated aerosols create more and smaller cloud droplets which: (1) increases reflection, and (2) suppresses rainfall (C) Semi-direct effect: absorbing aerosols heat air and cool surface suppressing convection and condensation 4. COOLING EFFECTS OF AEROSOLSUnveiling of true warming?Ref: IPCC 4th Assessment, Summary for Policymakers, Feb. 2, 2007 Courtesy of the Intergovernmental Panel on Climate Change. Used with permission. From: Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Figure SPM.2, Cambridge University Press.Are “moulins” lubricating ice streams and is warm water undermining ice shelves? LOSS WOULD CAUSE 5 METERS SEA LEVEL RISE ⇑ STABILITY OF WEST ANTARCTIC ICE SHEET Reference: Bindschadler et al. Bindschadler, R. A., R. B. Alley, J. Anderson, S. Shipp, H. Borns, J. Fastook, S. Jacobs, C. F. Raymond, What is happening to the west antarctic ice sheet?, Eos Trans. AGU, 79(22), 257-257, 1998. Copyright [1998] American Geophysical Union. Reproduced/modified by permission of American Geophysical Union.5. CRITICAL THRESHOLDSStability of ice sheets, tundra, carbon sinks and oceanic overturnSource: ACIA, Impacts of a Warming Arctic, Climate Impact Assessment Report, Cambridge University Press, 2004Changes in summer sea-ice extent and tree-line are projected to occur by the end of thiscentury. The change in the permafrost boundary assumes that present areas ofdiscontinuous permafrost will be free of anypermafrost in the future and this is likely to occur beyond the 21stcentury.⇑⇑About 546 Pg (Gt) carbon stored in Arctic tundra andfrozen soils ! (SCOPE2004)STABILITY OF ARCTIC TUNDRA & PERMAFROSTCourtesy of the Arctic Climate Impact Assessment, 2004. Used with permission.OCEAN BOTTOM DEPTHS (meters)INCREASED RAINFALL,SNOWFALL & RIVERFLOWS, & DECREASEDSEA ICE, EXPECTED WITH GLOBAL WARMINGDRIVEN BY SINKING WATER IN THE POLARSEAS (Norwegian, Greenland, Labrador,Weddell, Ross)SLOWED BY DECREASEDSEA ICE & INCREASEDFRESH WATER INPUTSINTO THESE SEAS(MIT 3D OCEAN


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