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processes responsible for polar amplification of climate change

processes responsible for polar amplification of climate change. Peter L. Langen Centre for Ice and Climate Niels Bohr Institute University of Copenhagen. Polar amplification of model-projected climate change. 15 model intercomparison :. Holland and Bitz (2003).

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processes responsible for polar amplification of climate change

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  1. processes responsible for polar amplification of climate change Peter L. Langen Centre for Ice and Climate Niels Bohr Institute University of Copenhagen

  2. Polar amplification of model-projected climate change 15 model intercomparison: Holland and Bitz (2003) Peter L. Langen, COGCI School, Jan 27 2009

  3. Spatial distribution of warming Models with “high” PA Holland and Bitz (2003) Peter L. Langen, COGCI School, Jan 27 2009

  4. Seasonal distribution of warming … but when is the albedo feedback active? Holland and Bitz (2003) Peter L. Langen, COGCI School, Jan 27 2009

  5. Latitude of maximum warming vs. sea iceextent R = -0.80 Holland and Bitz (2003) Peter L. Langen, COGCI School, Jan 27 2009

  6. Degree of PA vs. amount of sea ice R = -0.66 R = 0.65 PA seems weakly related to amount of sea ice in weak-to-medium-strength-PA models Holland and Bitz (2003) Peter L. Langen, COGCI School, Jan 27 2009

  7. Snow on land? R = 0.67 … but snow extent correlates also with sea ice extent and not with change in snow Holland and Bitz (2003) Peter L. Langen, COGCI School, Jan 27 2009

  8. Clear-sky and cloud shielding of SAF The surface albedo feedback is given by, where Qu and Hall (2006) Peter L. Langen, COGCI School, Jan 27 2009

  9. In Fourth Assessment Report simulations Qu and Hall (2006) Peter L. Langen, COGCI School, Jan 27 2009

  10. The surface albedo sensitivity Inter-model differences in SAF strength derive from parameterizations of surface processes rather than from clouds! Qu and Hall (2006) Peter L. Langen, COGCI School, Jan 27 2009

  11. Fixed-albedo experiment Hall (2004) Peter L. Langen, COGCI School, Jan 27 2009

  12. Fixed cloud experiment (I) Vavrus (2004) Peter L. Langen, COGCI School, Jan 27 2009

  13. Fixed cloud experiment (II) Vavrus (2004) Peter L. Langen, COGCI School, Jan 27 2009

  14. Effect of fixing low or highlatitude clouds only The warming due to low-latitude cloud feedback contributes to high-latitude warming! Vavrus (2004) Peter L. Langen, COGCI School, Jan 27 2009

  15. Exp 3 Exp 2 Exp 2 + Exp 3 Exp 1 Ghost forcing experiments Response Forcing Exp 1 Exp 2 Exp 3 Alexeev, Langen and Bates (2005) Peter L. Langen, COGCI School, Jan 27 2009

  16. Fixed temperature perturbation (I) Tropical-only SST change gives positive high-latitude tendency: Radiative -2 Wm Turbulent Alexeev, Langen and Bates (2005) Peter L. Langen, COGCI School, Jan 27 2009

  17. Fixed temperature perturbation (II) Uniform Increased heat transport warms and moistens high-latitude troposphere Temperature change (K) Ex-trop Tropical Vertical Profiles at 80N Tropical Uniform Abs. humidity change (g/kg) Ex-trop Ex-trop Uniform Tropical Alexeev, Langen and Bates (2005) Peter L. Langen, COGCI School, Jan 27 2009

  18. Vertical structure of recent Arctic warming 1979-2001 Graversen et al. (2007) Peter L. Langen, COGCI School, Jan 27 2009

  19. Polar amplification as an excitation ofa preferred mode of response Manabe and Wetherald (1980): Early GCM experiments Two different forcings … and very similar responses Manabe and Wetherald (1980) Peter L. Langen, COGCI School, Jan 27 2009

  20. Surface budget and mixed-layer model Vector containing all surface temperatures Heat capacity of water column Collection of “external” parameters: CO2, solar constant, etc. Vector containing surface fluxes. Langen and Alexeev (2007) Peter L. Langen, COGCI School, Jan 27 2009

  21. Linearization Langen and Alexeev (2007) Peter L. Langen, COGCI School, Jan 27 2009

  22. External forcing 0 in new equilibrium “forcing” Climate change Langen and Alexeev (2007) Peter L. Langen, COGCI School, Jan 27 2009

  23. Forcing excites least stable mode Forcing expanded in basis of eigenvectors If k’th term dominates Least stable mode Actual run Linear estimate Langen and Alexeev (2005) Peter L. Langen, COGCI School, Jan 27 2009

  24. Perturbation decay in linear system Time (years) Langen and Alexeev (2007) Peter L. Langen, COGCI School, Jan 27 2009

  25. Two-box energy balance model Langen and Alexeev (2007) Peter L. Langen, COGCI School, Jan 27 2009

  26. EBM (II) Alexeev et al. (2005): Tropical perturbation Global Extra-tropical Langen and Alexeev (2007) Peter L. Langen, COGCI School, Jan 27 2009

  27. Eigenanalysis Fast mode Slow mode Langen and Alexeev (2007) Peter L. Langen, COGCI School, Jan 27 2009

  28. Response to steady forcing Langen and Alexeev (2007) Peter L. Langen, COGCI School, Jan 27 2009

  29. Decay in GCM ensemble High lats Global Low lats Tot-clear LW High lats Total Global Low lats SW Langen and Alexeev (2007) Peter L. Langen, COGCI School, Jan 27 2009

  30. Extraction of cloud fields Cloud radiative forcing: Total LW SW positive is warming Langen and Alexeev (2007) Peter L. Langen, COGCI School, Jan 27 2009

  31. So when iso-lines are vertical ( ) there is no polar amplification. Regimes of heat transport sensitivity Climate change experiments are often found to give nearly unchanged heat transports. These experiments follow approximately iso-lines of transport. Caballero and Langen (2005) Peter L. Langen, COGCI School, Jan 27 2009

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