2. Feb, 2007

3. JTH 17-07-2001 3 COP6bis/SBSTA Climate Change 2001: The Scientific Basis WGI contribution to IPCC Third Assessment Report Summary for Policymakers (SPM) Drafted by a team of 59 Approved ‘sentence by sentence’ by WGI plenary (99 Governments and 45 scientists) 14 chapters 881 pages 120 Lead Authors 515 Contributing Authors 4621 References quoted

4. JTH 17-07-2001 4 COP6bis/SBSTA SPM 3

5. 2007 2001 (TAR) Anthropogenic contributions to aerosols (primarily sulphate,organic and black carbon, nitrate and dust) together produce a cooling effect, with a total direct radiative forcing of -0.5 [-0.9 to -0.1] W m -2 and an indirect cloud albedo forcing of -0.7 [-1.8 to -0.3] W m -2. These forcings are now better understood than at the time of the TAR due to improved in situ, satellite and ground-based measurements and more comprehensive modeling, but remain the dominant uncertainty in radiative forcing. Aerosols also influence cloud lifetime and precipitation. The understanding of anthropogenic warming and cooling influences on climate has improved since TAR, leading to very high confidence 1 that the globally averaged net effect of human activities since 1750 has been one of warming, with a radiative forcing of + 1.6 [+0.6 to +2.4] W m -2 1 9 out of 10 chance of being correct

6. Soluble aerosol deliquesce