Over the past four years during the Biden administration, the United States started spending ever-greater sums on efforts to blunt global warming and help communities adapt to a hotter world. Many analysts expected the total tab for this work to exceed $1 trillion over the next decade.

But in a matter of days, President Trump has thrown much of that spending into question, though how much money is affected is unclear. Some funds are frozen. Some projects are paused. And while a portion of that money is already out the door, there is an acute sense of uncertainty among people doing climate-related work that relies on government funding and approvals.

To take just one example of the chaos, consider the aid that the United States sends to foreign countries to deal with climate change. The United States Agency for International Development alone manages appropriations of roughly $40 billion annually, a fraction of which goes to climate-related projects.

Raj Kumar, the chief executive officer of Devex, a media company that tracks foreign aid closely, said he had spent the past week on the phone with the leaders of organizations working on development projects around the world, and even he can’t make sense of this moment.

“There’s no precedent to this,” he told me. “As the recipient of U.S. aid right now, you really don’t know what the state of your program is.”

Even among people who track federal spending closely, there is widespread uncertainty about what the U.S. government is going to fund. The White House and State Department did not respond to requests for comment.