Authored by 26 climate scientists, released in November 2009
Written to update the physical science basis for our understanding of climate change, in a manner accessible to policy makers:
"to synthesize the most policy-relevant climate science published since the close-off of material for the last IPCC report [AR4]."
to serve "as a handbook of science updates that supplements the IPCC AR4 in time for Copenhagen in December 2009, and any national or international climate change policy negotiations that follow."