– Step aside, Ivanka.

When it comes to climate change, the biggest influence on President Donald Trump may turn out to be his new chief of staff, John Kelly.

The retired four-star Marine general shares the military's pragmatic view of global warming. Under Kelly's command from 2012 to 2016, U.S. Southern Command played a central role in Pentagon planning for the higher temperatures, more extreme weather and rising sea levels that it sees as threatening national security. Now advocates hope he will bring that view into the White House.

For more than a decade, military leaders have warned that climate change is aggravating social tensions, destabilizing regions and feeding the rise of extremist groups like Al-Qaida and the Islamic State of Iraq and Syria.

Kelly, whom Trump has called "the true star" of his administration, will be up against a cadre of Trump advisers and Cabinet appointees who are either skeptics of or have actively tried to chip away at existing U.S. climate policy. Trump himself has frequently and openly questioned climate change, calling global warming "a hoax" that was "created by and for the Chinese" to hurt U.S. manufacturing.

On Monday, a group of federal scientists, fearful that the White House is actively trying to suppress science related to global warming, went so far as to leak a draft of an extensive climate change study by 13 agencies.

In his new role, Kelly can both reinforce and amplify the views of Secretary of Defense Jim Mattis as he oversees a Pentagon that has long worked to adapt to climate instability both at home and abroad. At his confirmation hearing, Mattis, who also retired from the Marines as a four-star general, called climate change a "driver of instability."

"Kelly hasn't come out and publicly talked about it, but his view is identical to Mattis," said Stephen Cheney, a retired brigadier general in the U.S. Marine Corps and a former colleague and close friend of Kelly's. "And I think that Kelly, if asked by the president, would offer that opinion and would be a supporter of what Mattis has said."

More importantly, Kelly is tightening control over the information that makes it to the president's desk, Cheney said. Trump, who has praised Kelly's leadership at the Department of Homeland Security and considers him a "tough guy," may be more inclined to consider the challenges posed by climate change through the lens of national security.

Under Kelly, Southcom "played a major role in the rollout of the climate change adaptation road map," said John Conger, who served as deputy undersecretary in the Pentagon comptroller's office and assistant secretary of defense for energy, installations and environment under President Barack Obama.

At Southcom, Kelly worked to mitigate security crises caused by extreme weather patterns in Central and South America and the Caribbean. His annual overviews argued that humanitarian assistance for natural disasters was crucial to stabilize the region, and he noted that mass migrations and transnational organized crime were often tied to these natural disasters.

"You can't operate in that region without being aware of how vulnerable these countries are and how climate change is affecting them," said Sherri Goodman, who, under President Bill Clinton, became the Pentagon's first deputy undersecretary of defense for environmental security. "Southcom [under Kelly] had been engaged in bolstering their security, because when they are threatened by rising sea levels and extreme weather it's harder to defend from other threats like narcotrafficking and migration flows."

U.S. military installations themselves are imperiled. Scientists estimate that rising sea levels threaten at least 128 U.S. military bases and installations, nine of which are major hubs for the U.S. Navy. Crucial waterfront installations are facing hundreds of floods a year, and some could be mostly submerged by 2100, according to a report from the Union of Concerned Scientists.

In June, Trump announced that he would withdraw the United States from the Paris climate accord, a move reportedly pushed by White House strategist Steve Bannon. Trump's pick to lead the Environmental Protection Agency, Scott Pruitt, has expressed skepticism about global warming and said during his confirmation hearings that it had leveled off, an assertion refuted by scientists.

But as chief of staff, Kelly, at a minimum, is expected to ensure the president hears from all sides on this issue and others.

"Kelly is going to make sure that the voices that need to be heard are heard," said Andrew Holland, director of studies and senior fellow for energy and climate at the nonpartisan policy organization American Security Project.

And his efforts on this topic may have more success than the much-publicized attempts of the president's daughter, which included sit-downs with Al Gore and Leonardo DiCaprio and enlisting Apple's Tim Cook to speak to her father. Ivanka Trump made climate change one of her signature issues, but her approach seemed to backfire.

"The military's view is 'who cares if there is a scientific debate, what's happening now is real … and we still have to plan for it,' " said Holland.