Nicholas Stern, the British economist who warned five years ago that global warming could cost the world's GDP as much as 20 percent a year by 2050, hasn’t given up on the United States  taking action on climate even though he’s down on Washington for not passing a bill that would do just that.

“If you look around the world, of all places to sit and wonder where (climate policy is) going, this is probably the most pessimistic place -- this city,” he told a small gathering of reporters at the World Bank’s headquarters in Washington, D.C. late this week.

But all one has to do is travel out of the U.S. capital to see enormous potential for taking action, he said. Stern is optimistic about U.S. companies in Silicon Valley and Boston and other places developing low-carbon technologies such as batteries for electric cars, or new biofuels that aren’t made out of food crops.

“There are so many technological ideas on the table that you don’t need all of them to work, just some,” he said.

 He also takes heart in state level mandates for renewable energy and the reelection of Jerry Brown, the pro-solar governor of California, who wants to set the bar even higher for renewable energy.