Global Warming Projections for the IPCC SAR and TAR using simple models Sarah Raper

Model for the Assessment of Greenhouse-gas Induced Climate Change (MAGICC) IPCC SAR version IPCC TAR version New features include:  Carbon-cycle feedbacks  Forcing updated to be consistent with TAR chapters  Climate model tuning to reproduce specific AOGCM results  AOGCM consistent sea level Gas-cycle models Climate model Temperature change Sea level rise IS92 emissions 6 scenarios Funded by DETR Radiative forcing Gas-cycle models Climate model Temperature change SRES emissions 35 scenarios Radiative forcing Sea level rise

B - balanced FI - fossil intensive T - non-fossil

Well-mixed ATMOSPHERE concentration Anthropogenic emissions Natural emissions Schematic treatment of well mixed gases Removal processes proportional to concentration

UD model

Energy balance climate model External forcing (Wm -2 ) Feedback term (Wm -2 ) Heat flux from bottom of the atmosphere (Wm -2 ) At equilibrium = zero At 2xCO 2 The climate sensitivity,

The CMIP2 data set Climate Model Intercomparison project Model forcing is a 1% compound increase in CO 2

Results of CMIP2 analysis

Shows changes in the THC in the CMIP2 data at the time of CO2 doubling.

Comparison of effects on temperature Projections of SAR and TAR high and low emissions scenarios and science methods Differences can be divided into the emissions scenarios and the science The main source of emissions-related differences is aerosol forcing The TAR science leads to slightly lower total forcing and slightly larger warming For the low scenarios the effects are roughly equal, both leading to higher warming For the high scenarios the main effect is due to the new emissions scenario

Radiative forcing for low and high estimates of global-mean Warming given in the IPCC SAR and TAR From Wigley and Raper J of Climate (in press)

Low and high estimates of global-mean warming given in the IPCC SAR and TAR From Wigley and Raper J of Climate (in press)

Sea level rise Parameters to be considered Thermal expansion Land based ice - Greenland Antarctica Glaciers and icecaps Changes in permafrost Effect of sediment depositon Long-term adjustment of icesheets

Projected global-average sea-level rise for the IS92a scenario (IPCC 2001)

Projections of total sea-level rise (IPCC 2001) SRES scenarios

Co2 Forcing Effect Relationship between CO2 concentration (C) and forcing is  Q is the forcing change due to concentration change from C 0 to C  SAR = 6.3,  TAR = about 5.31  T 2X is the equilibrium CO 2 doubling temperature change S is the sensitivity If  is reduced but  T 2X is not, then the radiative forcing due to CO 2 is reduced, while the true climate sensitivity is increased