Yet another fear among scientists and climate activists has become reality in the era of Trump.

Decades of research and data about carbon emissions, other greenhouse gases, and more was hidden from the U.S. Environmental Protection Agency (EPA) website by the Trump administration late Friday as the sprawling climate change webpage goes under "review."

Adding insult to injury, this comes on the eve of the People's Climate March.

Climate change activists have been wringing their hands ever since Inauguration Day, fearing that the new administration would do something just like this. The EPA has been chipping away at climate change mentions on its website since January, but Friday's takedown is the biggest, and most disturbing step yet.

The webpage, which has been in existence for more than 20 years, explained what climate change is, what caused it and how it affects your health, among other things. In contrast to what Trump and his EPA administrator, Scott Pruitt, have said about climate change (they don't believe it's man-made), the webpage notes many times how humans have contributed to climate change.

"Research indicates that natural causes do not explain most observed warming, especially warming since the mid-20th century. Rather, it is extremely likely that human activities have been the dominant cause of that warming," the webpage read, according to an archived version captured before Friday.

Starting Friday evening, going to EPA.gov/climate and EPA.gov/climatechange sent visitors to a landing page that said, "This page is being updated." In an agency statement about the website changes, there's no mention of removing all the content, even if temporarily.

"The process, which involves updating language to reflect the approach of new leadership, is intended to ensure that the public can use the website to understand the agency's current efforts," the EPA's statement reads, adding in the last line that "content related to climate and regulation is also under review."

At the very end of a Friday news dump: @EPA might take climate change information off its website pic.twitter.com/Gngh62R5sJ — Timothy Cama (@Timothy_Cama) April 28, 2017

While the climate landing page was down, certain climate-related sections could still be found through a Google search. For example, a section about climate indicators was still live as of Friday evening.

"While it remains to be seen how information and information access will change as the EPA site is updated, it is concerning that this overhaul was not announced until the same day that pages like the Climate Change page, which serve as important public resources, were already becoming unavailable," said the Environmental Data and Governance Website Tracking Initiative, a nonprofit group closely tracking changes to climate information across the federal government, in a statement.

"The timing of this overhaul cuts off availability when access to trusted information about the science behind climate change will be necessary to enable a conversation about our changing climate," the group stated.

Trump has made climate denying statements in the past, calling global warming a hoax. More recently he walked them back, claiming that climate change was naturally occurring and not man-made. Trump's EPA chief, Scott Pruitt, is a noted climate-change denier.

The administration is seeking to make deep cuts to the EPA's budget and personnel, potential involving thousands of layoffs and the gutting of its climate science programs, which could leave few qualified people left to update the climate science page in the next few years.

The scientific findings presented on the EPA climate change website were used by many in the media and the scientific community to contradict claims Pruitt made in a CNBC interview on March 9, in which he said that carbon dioxide does not act as a "control knob," or thermostat, on the planet's climate:

"I think that measuring with precision human activity on the climate is something very challenging to do and there's tremendous disagreement about the degree of impact, so no, I would not agree that it's a primary contributor to the global warming that we see," Pruitt said.

"But we don't know that yet, as far as... we need to continue the debate and continue the review and the analysis," he said.

On eve of #climatemarch, Trump EPA releases quiet, mumbling press release signaling censorship of climate change content from EPA website. https://t.co/MUxAIf5XMs — John Walke (@jwalkenrdc) April 28, 2017

The EPA's inspector general is investigating whether Pruitt's statement's violated agency policy because they departed so much from the agency's own scientific findings.

The EPA has a link back to an archived view of the site from before Trump took office on Jan. 19. That's exactly one day before Trump took over. But more recent archived versions of the site are available, such as this screenshot of the climate page from March 17.

Earlier Friday, Trump signed an executive order that expands offshore drilling in the Arctic and Atlantic Oceans, something the Obama administration fought to curtail. The administration has been working to roll back Obama's other climate change programs, including the EPA's Clean Power Plan, which would restrict greenhouse gas emissions from power plants.

The website review may be aimed at bringing the site in line with such an agenda, but any editing of scientific information would run counter to the history of the site and the mission of the EPA.

Information about the website changes have been murky, with the administration's statement leaving much to be desired in terms of detail. There's no timeline on when the changes will be made either.

Climate activists have already begun voicing their concerns on social media, and this is sure to fire them up as they ready for Saturday's big climate march.

Mashable science editor Andrew Freedman contributed reporting for this story.