In a move that contradicted nearly three decades of military planning, the Trump administration in December backed away from calling climate change a national security threat.

On Friday, a bipartisan group of 106 House members sent a letter to the president asking him to reconsider.

Conspicuously absent from the National Security Strategy report released last month was any mention of climate issues critical to national security, like how extreme weather drives conflict or how rising sea levels are a looming danger for coastal military facilities.

But lawmakers in their letter to the president quoted Defense Secretary James Mattis, who said at his confirmation hearing, “The effects of a changing climate... will impact our security situation.” He added that leaving climate change out of the discussion “represents a significant step backwards on this issue and discredits those who deal in scientific fact.”

President Obama’s 2015 National Security Strategy mentioned “climate change” 13 times across 35 pages and had “Confront Climate Change” listed as a security priority.

“Climate change is an urgent and growing threat to our national security, contributing to increased natural disasters, refugee flows, and conflicts over basic resources like food and water,” according to the Obama administration report.

Trump’s report mentions “climate” four times but refers to climate change only once, to criticize how addressing it hurts fossil fuels. “Climate policies will continue to shape the global energy system. U.S. leadership is indispensable to countering an anti-growth energy agenda that is detrimental to U.S. economic and energy security interests,” it says.

The softening on climate change as a national security threat is part of an ongoing effort to dismantle climate change efforts across all government agencies. But it is at odds with the 2018 National Defense Authorization Act, which Trump signed into law earlier this month. The $700 billion law describes climate change as a “direct threat” to US national security.

The military has long considered climate change a “threat multiplier,” with assessments dating back to 1990 observing that “nearly all areas of operational effectiveness are threatened by these environmental changes should they occur.” In 2014, the US Department of Defense published a climate change adaptation road map, oblivious to the political wrangling on the issue and writing that “rising global temperatures, changing precipitation patterns, climbing sea levels, and more extreme weather events will intensify the challenges of global instability, hunger, poverty, and conflict.”

Higher oceans, for example, menace 128 military bases. A 2016 report from the Union of Concerned Scientists found that the largest naval installation in the world, Naval Station Norfolk, will face water levels that are between 4.5 feet and 7 feet higher in this century.

The new report also furthers the administration’s mission to promote and protect fossil fuel interests at every possible opportunity. It claims that future energy demand will continue to be met with fossil fuels, and that the United States will be an increasingly dominant provider of these resources. At the same time, the country will continue to cut greenhouse gas emissions via energy efficiency and technology improvements.

However, the new National Security Strategy doesn’t preclude the military from factoring climate change into its calculus. Already, facilities like Naval Station Norfolk are lifting piers above projected flood levels, while units like the Navy SEALs are working toward becoming net-zero energy users. Bases are also aggressively deploying renewable energy and cutting their electricity and water use with efficiency upgrades.

And the military will likely remain a driver of climate science, from operating satellite instruments to modeling humanity’s effects on the climate.