More than a million homes and businesses along the nation’s coasts could flood repeatedly before ultimately being destroyed. Entire states in the Southeast and the Corn Belt may lose much of their agriculture as farming shifts northward in a warming world. Heat and humidity will probably grow so intense that spending time outside will become physically dangerous, throwing industries like construction and tourism into turmoil.

That is a picture of what may happen to the United States economy in a world of unchecked global warming, according to a major new report released Tuesday by a coalition of senior political and economic figures from the left, right and center, including three Treasury secretaries stretching back to the Nixon administration.

At a time when the issue of climate change has divided the American political landscape, pitting Republicans against Democrats and even fellow party members against one another, the unusual bipartisan alliance of political veterans said that the country — and business leaders in particular — must wake up to the enormous scale of the economic risk.

“The big ice sheets are melting; something’s happening,” George P. Shultz, who was Treasury secretary under President Richard M. Nixon and secretary of state under President Ronald Reagan, said in an interview. He noted that he had grown concerned enough about global warming to put solar panels on his own California roof and to buy an electric car. “I say we should take out an insurance policy.”