Mandatory reductions in CO2 emissions, pursued to prevent dangerous global warming, would have little or no discernible impact on global temperatures, but would greatly increase the price of energy and therefore of everything else. Such policies would put more people at greater risk than the warming they are intended to prevent, because they would slow, stop, or even reverse the economic growth that enables people to adapt to all climates. They would also harm the poor more than the wealthy, and would harm them more than the small amount of warming they might prevent.