In the interim, a notice said “this page is being updated” and added that the site would be changed to reflect the agency’s priorities under the Trump administration. When material was restored with changes in late July, the report said, the site had been cut to 175 pages from about 380.

“I think it’s very alarming” said Adam Parris, who leads the Science and Resilience Institute at Jamaica Bay in New York. “These are not the kind of resources that are just basic climate science. These are the kind of resources it has taken years to develop across the federal family.”

The report comes on the heels of a four-year blueprint of priorities the E.P.A. issued that does not include climate change. The 38-page draft strategic plan, issued for public comment this month, does not use the phrase.

Under the Obama administration’s four-year strategic plan issued in 2014, “Addressing Climate Change and Improving Air Quality” was the E.P.A.’s first of five goals. Climate change was cited 43 times.

Gina McCarthy, administrator of the E.P.A. under Mr. Obama, said in a statement that one of the agency’s most important jobs was to provide scientific and technical expertise so local officials could write appropriate policies. She said the now-discarded data was collected and shared over a number of years to help states, cities and towns build resilience to fiercer storms, floods, droughts and wildfires.

“There is no more significant threat than climate change and it isn’t just happening to people in far-off countries — it’s happening to us,” Ms. McCarthy said. “It is beyond comprehension that E.P.A. would ever purposely limit and remove access to information that communities need to save lives and property. Clearly, this was not a technical glitch, it was a planned shutdown.”

Toly Rinberg of the Environmental Data and Governance Initiative said that there was no evidence the E.P.A. had destroyed any records. The original pages are available from several sources, including the Internet Archive, which maintains a mirror of the E.P.A. website as it appeared near the end of the Obama administration.

A number of resources, like emissions inventories, remain intact on the E.P.A. site.