Ever since 1965, when President Lyndon B. Johnson’s science advisory committee warned of the dangers of unchecked global warming, the United States has taken steps to protect people from these risks.

Now, however, the Trump administration appears to be essentially abandoning this principle, claiming that the costs of addressing climate change outweigh the benefits. The effect is to shift more of the risk and responsibility onto states and, ultimately, individual Americans, even as rising temperatures fuel more extreme and costly weather disasters nationwide, experts say.

“It’s a radical transformation of government’s role, in terms of its intervention into the economy to try to promote the health and safety of citizens,” said Donald Kettl, a professor emeritus at the University of Maryland’s School of Public Policy.

Lee Zeldin, the administrator of the Environmental Protection Agency, this week proposed to repeal the landmark scientific finding that enables the federal government to regulate the greenhouse gases that are warming the planet. In effect, the E.P.A. will eliminate its own authority to combat climate change.

Speaking at a truck dealership in Indianapolis, Mr. Zeldin said the E.P.A. would reverse a 2009 scientific conclusion, known as the endangerment finding, that greenhouse gas emissions pose a threat to public health. He said the agency would also rescind Biden-era regulations designed to reduce planet-warming emissions from automobile tailpipes.

While few people have heard of the endangerment finding, it has had a profound effect on society. Its establishment cleared the way for the Obama administration to set the country’s first limits on greenhouse gases from cars and power plants, with the goal of putting more electric vehicles on the roads and adding more renewable energy to the electric grid.