Attribution of Evolving North American Climate Conditions · Attribution of Evolving North American...
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1970-2007 Trend 2008 Anomalies Appraisal of 2008 Climate Conditions Attribution of Evolving North American Climate Conditions Judith Perlwitz 1,2 , Martin Hoerling 1 , Jon Eischeid 1,2 , Taiyi Xu 1,2 and Arun Kumar 3 1 NOAA/ESRL/PSD, 2 CIRES/CU and 3 NOAA/NCEP/NWS Observations CMIP (Anthropogenic Forcings) AMIP (observed (SST/Sea Ice) Observations CMIP (Anthropogenic Forcings) AMIP (observed (SST/Sea Ice) Q: What caused North American warming since 1970? A: Model simulations indicate that most of the observed warming was due to anthropogenic forcing. The physical process of continental warming was via the inNluence of SST and sea ice changes. Q: Why did the warming not continue in 2008? A: Model simulations indicate that 2008 coolness was caused by a strong bout of naturally-induced cooling. This resulted from the continents sensitivity to unusually cold SSTs in the tropical PaciNic. Q: What was the natural versus anthropogenic impact on 2008 North American temperatures? A: AGCMs forced by estimates of the natural and anthropogenic components of 2008 SST conditions indicate that the warmth induced by the latter was overwhelmed by the coolness induced by the natural state of SSTs. 2008 NA temperatures would have been considerably cooler in the absence of anthropogenic forcing. Observed SST CMIP SST Obs – CMIP SST
Transcript of Attribution of Evolving North American Climate Conditions · Attribution of Evolving North American...
19702007Trend 2008Anomalies Appraisalof2008ClimateConditions
AttributionofEvolvingNorthAmericanClimateConditionsJudithPerlwitz1,2,MartinHoerling1,JonEischeid1,2,TaiyiXu1,2andArunKumar3
1NOAA/ESRL/PSD,2CIRES/CUand3NOAA/NCEP/NWS
Observations
CMIP (Anthropogenic Forcings)
AMIP (observed (SST/Sea Ice)
Observations
CMIP (Anthropogenic Forcings)
AMIP (observed (SST/Sea Ice)
Q: What caused North Americanwarmingsince1970?
A:Modelsimulationsindicatethatmostof the observed warming was due toanthropogenic forcing. The physicalprocessofcontinentalwarmingwasviatheinNluenceofSSTandseaicechanges.
Q:Whydid thewarmingnot continuein2008?
A: Model simulations indicate that2008coolnesswascausedbyastrongbout of naturallyinduced cooling.This resulted from the continentssensitivity to unusually cold SSTs inthetropicalPaciNic.
Q:What was the natural versus anthropogenic impact on 2008 NorthAmericantemperatures?
A: AGCMs forced by estimates of the natural and anthropogeniccomponentsof2008SSTconditions indicatethatthewarmthinducedbythelatterwasoverwhelmedbythecoolnessinducedbythenaturalstate of SSTs. 2008 NA temperatures would have been considerablycoolerintheabsenceofanthropogenicforcing.
Observed SST
CMIP SST
Obs – CMIP SST
