Amid Biden Climate Push, a Question Looms: Is America’s Word Good?

Mr. Blinken said the United States would “lead by example” by investing heavily in clean energy. And he added a few warnings to nations he needs as climate partners. He did not name Brazil, but he warned that rainforest destruction would not be tolerated. And in an apparent message to China, he said cooperation on climate was not a “chip” countries could use to avoid scrutiny of “bad behavior” on human rights and other issues.

“Climate is not a trading card, it’s out future” Mr. Blinken said.

Many diplomats said this time around they are more cleareyed about the ability of the United States to commit on climate change. But they were nevertheless inclined to give the Biden administration the benefit of the doubt.

“I think on climate change the U.S. policy is viewed like a pendulum,” Malik Amin Aslam, adviser to the Pakistani prime minister on climate change, said in an interview. Vulnerable countries are just “happy that the Biden administration has put the pendulum in the right direction,” he added.

Rondald J. Jumeau, a former ambassador of the Seychelles to the United Nations and a longtime climate change negotiator, said he was looking with “qualified excitement” to the Biden administration’s announcements and hoped the United States could follow through, not only on emissions cuts but also finance to small island nations and other vulnerable countries.

In addition to rolling back climate regulations, Mr. Trump stopped payments to the Green Climate Fund to help poorer countries transition to clean energy and adapt to the consequences of climate change. Mr. Biden has vowed to restore funding, starting with $1.2 billion this year, subject to Congressional approval.

“I think all of us know the American political system by now,” Mr. Jumeau said. “If we haven’t learned during the Trump years, we’ll never learn how dysfunctional it is.”

Adam S. Posen, president of the Peterson Institute for International Economics, said America’s inconstancy on the world stage started long before Mr. Trump. From climate change to international development to trade laws, he said, allies have learned to live with the shifting priorities of Republicans and Democratic administrations as Congress remains largely unable to pass major policy into law.