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This was intended as a handbook of science updates to supplement the IPCC AR4 in time for the meeting in Copenhagen in December 2009. I've copied the executive summary onto the Azimuth Project and everyone here should read it, e.g.:
The turning point must come soon: If global warming is to be limited to a maximum of 2 °C above preindustrial values, global emissions need to peak between 2015 and 2020 and then decline rapidly. To stabilize climate, a decarbonized global society – with near-zero emissions of CO2 and other long-lived greenhouse gases – need to be reached well within this century. More specifically, the average annual per-capita emissions will have to shrink to well under 1 metric ton CO2 by 2050. This is 80-95% below the per-capita emissions in developed nations in 2000.