Scientists fear the online deletions will extend far beyond changes to introductory websites and into the realm of government data. Climate change data gathered and stored by the United States government is considered among the most authoritative in the world. But scientists worry the data will be deleted during the Trump administration.

Since Mr. Trump’s election, about 50 scientists at universities around the country have volunteered their time — and computer servers — to save and store government data stored on the websites of the Environmental Protection Agency, NASA, NOAA, and the United States Geological Survey. Those websites keep records of key climate data such as atmospheric temperature trends, greenhouse gas emissions levels, and sea level rise.

The scientist gatherings have been organized by 314 Action — a nonprofit group named for the first three numbers of the mathematical concept Pi — which aims to make science more accessible to the public.

“The government has done a great job of collecting and maintaining climate change data on these websites located all across the federal government,” said Shaughnessy Naughton, the founder of 314 Action. “The concern is that the data may no longer be publicly available, and then that they may no longer gather the data. It’s a lot easier to deny climate change when you don’t have data.”