The 2,400-page National Defense Authorization Act that Congress sent to President Trump last week is packed with new military policies and weapons purchases. But also tucked into the voluminous legislation is a warning about climate change, something Trump has openly ridiculed for years.

Changing climate is a “direct threat” to U.S. national security, endangering 128 military bases with sea rise and global destabilization that could fuel terror groups, according to the NDAA, which is a bipartisan compromise struck by the House and Senate.

The bill orders a Pentagon report on the top 10 at-risk bases and what should be done to protect them.

Trump, who has described himself as a climate change skeptic, indicated he will sign the $700 billion policy bill, calling it an historic boost for the military that “could not come at a better time for our nation.” The provision is one among hundreds that offer defense reforms as well as more aircraft, ships and troops.

The language on climate change, almost certain to become law, is a sign that under the new Republican administration, Congress is moving toward more acceptance of the phenomenon being a serious security issue, and that the military will continue efforts to assess and plan for the risks.

Lawmakers have shifted from being a headwind on climate change as a national security issue to being a tailwind, said John Conger, a senior policy adviser with the Center for Climate and Security.

“During the last administration they pushed back — don’t do as much, reduce your funding — now they are saying to do more,” said Conger, who is a former Defense Department deputy comptroller. “I think there is a growing acceptance of the relevance of some of these issues and I think the fact that they put language in the bill reflects that.”

It is not the first time Congress has ordered up a report on the topic. The Senate Appropriations Committee required an assessment on climate change from the Pentagon in 2015 that found it is a security risk and said combatant commanders were already figuring forecasts into their planning.

But Conger said the new NDAA report is a shift because it requires the military to say how it will shore up the at-risk bases and what the cost may be.

Rep. Jim Langevin, D-R.I., a member of the House Armed Services Committee, proposed the legislation this year and added it to an early version of the NDAA.

“Congress has ignored this issue for far too long, and I hope this provision represents a turning point on climate change denial in Washington, D.C.,” Langevin said when the bill was passed.

It survived the bill’s markup in the Republican majority House committee and a floor debate, and was eventually adopted by an NDAA conference committee headed by Sen. John McCain, R-Ariz., and Rep. Mac Thornberry, R-Texas.

Still, it remains an open question how the Trump administration might treat climate change as a defense issue.

Before becoming president, Trump criticized climate change as a hoax. And although he has since appeared to moderate that view, his Environmental Protection Agency has removed references to it. But the White House also approved the release this month of a major multi-agency report finding humans are the main driver of changing climates.

There was widespread acknowledgement of climate change under the Barack Obama administration following skepticism from the George W. Bush administration, and that coincided with an uptick in the Pentagon work on the issue as a security risk, including strategic climate change roadmaps.

Despite shifting political winds, the military has been discussing the implications of climate change since the 1990s and the urgency has only seemed to increase in recent years. The melting sea ice in the Arctic and the race to counter Russian influence in the region has become a major and very public security challenge for the Pentagon and for the Coast Guard.

“When politics affects the debate of what you can and cannot pay attention to or everything we do in this space is somehow politicized, it throws a wrench into the pragmatic apolitical instincts of the military,” Conger said. “The military’s goal is to be pragmatic and apolitical.”

The Trump administration has opposed regulating emissions, which most climate scientists believe are fueling changes. That may remain its limited focus when it comes to the Pentagon's work, Conger said.

“It is a much bigger thing to tell the DoD that they cannot take a risk factor [climate change] into account and I suspect they won’t try,” he said. “I suspect that the White House will let DoD be and go and do their mission without prioritizing this particular aspect of it.”