Want climate news in your inbox? Sign up here for Climate Fwd:, our email newsletter.

WASHINGTON — President Trump had a clear message Monday when asked about the core conclusion of a scientific report issued by his own administration: that climate change will batter the nation’s economy. “I don’t believe it,” he said.

Mr. Trump then laid responsibility for cleaning the atmosphere on other countries like China and Japan: “Right now we’re at the cleanest we’ve ever been, and that’s very important to me. But if we’re clean but every other place on Earth is dirty, that’s not so good. So I want clean air. I want clean water. Very important.”

The remarks fit a pattern, and not just for their bluntness. In almost two years since taking office, Mr. Trump has denied the scientific reality of climate change and taken aggressive steps that will increase emissions of heat-trapping greenhouse gases — despite unequivocal scientific evidence that those pollutants are warming the planet to dangerous levels.

“Since virtually the first day the administration came into office they have systematically worked to reverse policies in place to reduce greenhouse gas emissions,” said Robert N. Stavins, a professor of environmental economics at Harvard. “But this report, which is mandated by law, shows that greenhouse gas emissions are going to have profound effects on the United States in this century.”