Looking at the NCA's own numbers, it's not at all clear that pursuing aggressive government action to mitigate climate change would produce benefits in excess of costs.
Popular Analysis of the National Climate Assessment Misleads the Public on the Economics of Climate Change
The Executive Branch's recently released Volume II of the National Climate Assessment (NCA) is a massive document that is being cited as yet further evidence that the U.S. government should act quickly and boldly in the fight against climate change. The coverage in the New York Times was typical: "All told, the report says, climate change could slash up to a tenth of gross domestic product by 2100, more than double the losses of the Great Recession a decade ago."