Is 450 ppm politically possible? Part 8

A U.S. climate bill should set a target of reducing U.S. greenhouse gas emissions 20 percent to 30 percent below 1990 levels by 2020. That conclusion is based on the latest science from the Intergovernmental Panel on Climate Change and NASA, among others, but it also involves matters of timing and U.S. cap-and-trade design. To achieve its goals, domestic climate legislation should limit the use of both international and domestic offsets.

That is the executive summary of a new report I have written for the Center for American Progress (Full report here [PDF]). I have changed my thinking on the 2020 target a bit in the past year for three reasons:

Scientific observations and analysis in 2007 and 2008 make clear the pace and threat of climate change has accelerated (see Nos. 8, 7, and 3 here).

Grist