Global Warming Projections for the IPCC SAR and

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) Funded by DETR IPCC SAR version IS 92 emissions 6 scenarios Gas-cycle models Radiative forcing Climate model Temperature change Sea level rise IPCC TAR version SRES emissions 35 scenarios Gas-cycle models Radiative forcing Climate model Temperature change 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 Sea level rise

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

Schematic treatment of well mixed gases Anthropogenic emissions Well-mixed ATMOSPHERE concentration Natural emissions 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 At 2 x. CO 2 The climate sensitivity, = zero

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

Results of CMIP 2 analysis

Shows changes in the THC in the CMIP 2 data at the time of CO 2 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 IS 92 a scenario (IPCC 2001)

Projections of total sea-level rise 1990 -2100 (IPCC 2001) SRES scenarios

Co 2 Forcing Effect Relationship between CO 2 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 2 X is the equilibrium CO 2 doubling temperature change S is the sensitivity If is reduced but T 2 X is not, then the radiative forcing due to CO 2 is reduced, while the true climate sensitivity is increased