Uncertainty in Regional Climate Sensitivity

updated 11 November 2003

PI: Ken Caldeira

Climate and Carbon Cycle Modeling Group
Energy and Environment Directorate
Lawrence Livermore National Laboratory
7000 East Ave., L-103
Livermore CA 94550 USA

Phone: (925) 423-4191

Fax: (925) 422-6388

Email: kenc@LLNL.gov

Web page: http://en-env.llnl.gov/cccm/caldeiracv.html (now with pdf's of papers!)

I would like to improve our understanding of the uncertainty in regional climate sensitivity using CMIP monthly-mean surface air-temperature output. Traditionally, the uncertainty in global mean warming to a CO2-doubling has been characterized as 1.5 to 4.5 °C. What is the uncertainty in regional mean warming? I propose to address this question using CMIP monthly mean surface air temperature results. To separate global uncertainties in climate sensitivity from regional, at each time period I will divide the regional change in surface air temperature by the global mean change, thus expressing regional climate sensitivity as a fraction of the global climate sensitivity. I intend to

compare the spatial and seasonal pattern of warming at such time as each model reaches the same amount of global mean warming
compare the spatial and seasonal pattern of warming at such time as each model reaches the same amount of radiative forcing
look at the temporal evolution of the spatial pattern within each model
look at averaging and weighting strategies to improve the signal-to-noise ratio

I expect to produce maps indicating the inter-model range of the ratio of regional to global mean climate change. This value can be appropriately multiplied by the global uncertainty to estimate regional uncertainty. I also plan to look at other statistics in addition to inter-model range. I think I can do this relatively quickly using CDMS and CDAT. I plan to work in coordination with Curt Covey (PCMDI). Furthermore, I plan to distribute preliminary results to Curt Covey, Karl Taylor, Ben Santer, Krishna AchutaRao, Starley Thompson, and Phil Duffy (all of LLNL) for feedback and critical suggestions. I would be delighted if others would be willing to offer guidance or assistance. This project will be conducted on a "hobby" basis, as I have no funding to pursue this. I hope it leads to a short paper in a high visibility journal.

I will also estimate from top of atmosphere fluxes the partial derivatives dF_longwave / dT, dF_longwave / dln(pCO₂) and dF_shortwave / dT, where T is surface temperature, and from these try to estimate climate sensitivity. For this purpose I will need only annual and global mean longwave and shortwave fluxes, pCO₂, and surface temperatures.