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Climate Change and the SECART Region

Climate Change and the SECART Region. Greg Carbone Carolinas Regional Integrated Sciences and Assessments University of South Carolina Southeast and Caribbean Regional Team (SECART) Workshop Jacksonville, FL, 24 May 2010. IPCC, 2007; Working Group 1, Figure 3.9.

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Climate Change and the SECART Region

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  1. Climate Change and the SECART Region Greg Carbone Carolinas Regional Integrated Sciences and Assessments University of South Carolina Southeast and Caribbean Regional Team (SECART) Workshop Jacksonville, FL, 24 May 2010

  2. IPCC, 2007; Working Group 1, Figure 3.9

  3. IPCC, 2007; Working Group 1, Figure 3.10

  4. For the globe…. models do well when we know the forcings For regions…. models do well if we know the oceans Observations Coupled Ocean-Atmosphere GCMs (external forcing: GHGs, solar, aerosols) Atmospheric GCMs (using observed SSTs) Hoerling et al., GRL 2008

  5. Post-1975 warming: external forcing • oceans warm, atmosphere responds Hoerling et al., GRL 2008

  6. Observed June-July-August daily mean temperature changes (°C), 1976–2000 Pan et al., GRL, 2004; adapted from Folland et al., IPCC 2001

  7. Why the observed cooling in the southeastern US? Interdecadal variability? Indirect response to global warming? Aerosols?

  8. When forced with Pacific observed sea-surface temperatures, GCMs reproduce cooling. • robust (all model runs) • must use observed SSTs Robinson et al., 2002. Journal of Geophysical Research

  9. unique response in SE (strong Pacific SST/SE cloud cover & temperature decrease) Robinson et al., 2002. Journal of Geophysical Research

  10. Observed Temperature, 1950-2000 Modeled Temperature winter spring summer fall Wang et al., Journal of Climate 2009

  11. Why the observed cooling in the southeastern US? Interdecadal variability? some evidence Indirect response to global warming? Aerosols?

  12. 4°C 3°C 1°C 2°C Projected Temperature Changes, 2071-2100

  13. +0-10% +10-20% > 20% -10-20% - 0-10% Projected Annual Precipitation Changes, 2071-2100

  14. Projected Temperature Changes, 2071-2100 • 11 GCMs • NC/SC grid cells • 2071-2100 • A1B emissions scenario

  15. 11 GCMs • NC/SC grid cells • 2071-2100 • A1B emissions scenario

  16. •2.2°C warmer • 15% wetter

  17. GW signal Total SST trend Pacific Decadal signal Figure 8 Wang et al., Journal of Climate 2009

  18. Why the observed cooling in the southeastern US? Interdecadal variability? some evidence Indirect response to global warming? no evidence Aerosols?

  19. Aerosol Cooling Watts per square meter Penner et al., 1998. Climate Dynamics

  20. May, June temperature trends, 1950–2006 Portmann R W et al. PNAS 2009;106:7324-7329

  21. 1950–2006 precipitation trends NOT correlated with decreasing Tmax in the Southeast US Portmann R W et al. PNAS 2009;106:7324-7329

  22. Plausible causes: increasing biogenic aerosols USGCRP USDA Forest Service

  23. Why the observed cooling in the southeastern US? Interdecadal variability? some evidence Indirect response to global warming? no evidence Aerosols? some evidence

  24. Challenges to predicting future temperature change….. Dealing with uncertainties Source: IPCC, 2007

  25. Probability curves for mid- and late-21st century Sokolov, et al., 2009. Journal of Climate

  26. Tropical cyclones and climate change • Conflicting results in the literature • Natural variability and data limitations obscure detection of historical trends • Future (Knutson et al., 2010 Nature Geoscience3, 157-163) • Theory & high-resolution dynamical models: • greenhouse warming will cause greater average intensity (2-11% by 2100) • increases in the frequency of the most intense cyclones; increases (~20%) in precipitation rate within 100 km of the storm centre. • 6-34% decreases in the globally averaged frequency of tropical cyclones • large variations between models

  27. Tropical cyclones and climate change • Why not knowing the climate future might not matter so much…. • Less frequent?, more intense? We probably won’t know until it happens. • The societal future will trump the physical future in terms of losses. • The markets have already assumed things will be worse. • (Warren Buffet and Pascal’s wager)

  28. Pascal’s wager Truth God exists God doesn’t exist God exists Belief God doesn’t exist

  29. Truth Warren Buffet’s wager More frequent and/or intense hurricanes No change More frequent and/or intense hurricanes Belief No change

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