(CNN) The US Department of Transportation appears to have wiped pages with information about climate change from its website.

CNN found at least two pages previously dedicated to detailing the possible impacts of climate change on the transportation sector -- a key source of greenhouse gas emissions -- that apparently have been cleared from the federal agency's website. At least one of the pages was designed to serve as a "one-stop source of information on transportation and climate issues," making it easy for people to find and access the information.

Now when users click the link for the Transportation Department's "Transportation and Climate Change Clearinghouse" and "Climate Change Impacts" pages, they are greeted with the message, "Access denied. You are not authorized to access this page."

Based on an archival web search, it appears both pages disappeared from the department's website on October 3 or 4.

A spokesman for the Transportation Department told CNN the information on those pages had been removed because it was outdated.

This isn't the first time the Trump administration has suppressed climate change information online, so the disappearance of the two links is raising questions for some.

Michael Halpern, deputy director of the Union of Concerned Scientists, said that while there is still some climate change information on the agency's website, he is particularly concerned about the disappearance of the Transportation and Climate Change Clearinghouse page, which contained climate change information all in one place on the massive government website.

"Putting information in various places versus all in one place makes it more difficult to find the information," Halpern said. "It's a symbolic move that says this administration is deprioritizing communicating about climate science. You have to look at this in the context of the different ways science is being sidelined."

The Environmental Data and Governance Initiative -- a group that monitors federal agency websites and changes to those sites, along with archiving environmental data on federal government websites -- has identified at least 16 instances of climate change information being scrubbed from federal government websites under the Trump administration.

In January, CNN reported on a study by the group that found the administration had eliminated or replaced references to climate change, renewable energy and similar topics on federal agency websites including the Department of Energy, the Environmental Protection Agency, the Interior Department, the State Department and the Department of Transportation.

In August 2017, CNN reported on internal emails from the US Department of Agriculture that outlined a list of language changes its employees should use when describing their work. One email obtained by CNN advised employees of the department's Natural Resources Conservation Service to avoid the term "climate change" and to instead use "weather extremes."

The clearinghouse page on the Department of Transportation website included information on greenhouse gas reduction strategies, along with "potential impacts of climate change on transportation infrastructure, and approaches for integrating climate change considerations into transportation decision making."

"While transportation is crucial to our economy and our personal lives, as a sector it is also a significant source of greenhouse gas (GHG) emissions," the archived webpage reads. "Based on current GHG emission reporting guidelines, the transportation sector directly accounted for about 28 percent of total U.S. GHG emissions in 2006."

The archived clearinghouse page says the transportation sector has been one of the fastest growing sources of greenhouse gases in the US.

The impacts page highlighted several papers and studies on the issue, according to an archived version. One focused on the affects that climate change may have on Atlantic coast cities' transportation infrastructure. "The study uses multiple data sources to identify the potential impact of sea level rise on land and transportation infrastructure along the Atlantic coast, from Florida to New York. The study creates maps of land and transportation infrastructure that, without protection, could be inundated regularly by the ocean or be at risk of periodic inundation due to storm surge under a range of sea level rise scenarios," an archived version of the page reads.

After reviewing the web pages the department took down, Gretchen Gehrke, who is in charge of website monitoring for the Environmental Data and Governance Initiative, told CNN: "The content of the page cites papers and workshops from 2001-2010. Interestingly, this webpage is solely devoted to listing resources, which is a webpage that one would expect to be updated regularly with additions of new resources. As the page doesn't present a synthesis or insight that would be informed by new information, and doesn't describe any sort of present state (e.g. discussing annual emissions by different sectors) where outdated info could impact interpretation, it is interesting to see access denied to simply a list of resources."

CNN reached out to the department for an explanation of why the two pages have been removed from the agency's website. The agency said in an email, "Web archive procedures at the Department call for web records and applications, in general, to be archived when they no longer serve a purpose. Content that has been administration-specific or not updated in two years is subject to unpublishing to prevent static, outdated web content. In general, the retention schedule for dated reference materials is to archive annually, retaining two full years on the live site."

A search of the department's website turned up several pages older than two years that had not been removed, however. CNN asked the agency why these two specific pages had been pulled and not other, older pages. It said the data on both links is "at least 4 years old and in some cases includes studies over 18 years old."

When asked if the information removed is available elsewhere on the website, the department did not point to any particular pages. However, the agency said "much of this type of information is accessible" on other DOT pages. "The Department creates pages and updates the main site as relevant and up-to-date information is available for individual programs," a spokesman said.

Unlike the scrutiny the EPA and the Interior Department have received under the Trump administration for their own policies and the effect they have on the climate, not much attention has been paid to the Department of Transportation under Secretary Elaine Chao.

Climate change information became inaccessible through the two links a couple of months after the EPA and the DOT proposed loosening fuel economy standards, allowing automakers to sell vehicles with lower gas mileage, potentially increasing greenhouse gas emissions.

In early August Chao said, in a news release on the proposal, "There are compelling reasons for a new rulemaking on fuel economy standards for 2021-2026. More realistic standards will promote a healthy economy by bringing newer, safer, cleaner and more fuel-efficient vehicles to U.S. roads and we look forward to receiving input from the public."

The public comment period for the DOT/EPA proposal was still open when the two pages disappeared from the agency's website, eliminating some of the information commenters could have used to inform their opinions.

On September 28, The Washington Post published an article that found, buried in a draft National Highway Traffic Safety Administration document dated July 2018, an assessment that the Earth would warm a whopping 7 degrees Fahrenheit by the end of the century with or without the newly proposed reduction in fuel standards. Days after that story was published, the two climate change pages disappeared from DOT's website.

"The real problem is that the administration has taken down webpages for political reasons and had repeatedly shut down the communication of climate science. So we are all left guessing. If the administration actively encouraged scientists to communicate about climate science this would not even be an issue at all," said Halpern, of the Union of Concerned Scientists.