Global warming comes with a big price tag for every country in the world. The 80 percent reduction in U.S. emissions needed to stop climate change may not come cheaply, but the cost of failing to act will be much greater. New research shows that if present trends continue, the total cost of global warming will be as high as 3.6 percent of gross domestic product (GDP). Four global warming impacts alone -- hurricane damage, real estate losses, energy costs, and water costs -- will come with a price tag of 1.8 percent of U.S. GDP, or almost $1.9 trillion annually (in today's dollars) by 2100. We know how to avert most of these damages through strong action to reduce the emissions that cause global warming. But the longer we wait, the more painful -- and expensive -- the consequences will be.