A polar bear plays in the water. (Jim Lo Scalzo/EPA-EFE)

Michael Morell was deputy director and twice acting director of the Central Intelligence Agency from 2010 to 2013. Benjamin Haas is a student at Stanford Law School and a former intelligence officer in the Army.

President Trump, who has played down and outright denied climate change, has drawn widespread criticism from both the scientific community and the public by announcing his intention to withdraw from the Paris climate accord.

And now, Congress has joined the critique of Trump's views — at least indirectly — by passing legislation affirming its belief that climate change is a national security threat. On Thursday, that bill was presented to the president for his signature. This is an interesting moment for Trump, who must now decide whether to stand up for his stance on climate change and the Paris agreement.

The National Defense Authorization Act (NDAA) for 2018 contains a provision making clear that "the sense of Congress" is that "climate change is a direct threat to the national security of the United States." The provision cites statements from authoritative figures including Defense Secretary Jim Mattis, former defense secretary Robert Gates, Chairman of the Joint Chiefs of Staff Gen. Joseph F. Dunford Jr. and the Office of the Director of National Intelligence.

The legislation calls upon the Defense Department to submit a report within a year of the NDAA's enactment, outlining the effects that climate change will have on military installations and the interests of senior military commanders around the world. To be sure, the provision does not invoke congressional funding power, refer to the Paris agreement or explicitly address the role that humans play in causing climate change. Yet without a doubt, the bipartisan statement by Congress is forthright and represents an encouraging step in the right direction.

At first blush, Trump may view the provision unfavorably. He might accordingly consider including a signing statement expressing his disagreement with the provision, instead of plainly acknowledging climate change as a national security threat with his signature. Alternatively, he might avoid the issue by allowing the NDAA to become law after 10 days without his signature. Or perhaps he could use this opportunity — however unlikely — to reverse course and address in earnest the national security challenges presented by climate change.

The reasons why climate change is a national security threat are numerous and well established. It is, of course, one of just a few threats carrying the potential for true global catastrophe, as it could eventually make our planet uninhabitable. But beyond this sobering reality, climate change serves as a "threat multiplier," to borrow language from a 2014 Pentagon report. It increases the risk of resource conflicts, both between and within states. It will lead to troublesome waves of humans migrating in search of food and water. It will facilitate the spread of diseases, possibly leading to epidemics and pandemics. It will lead to failed states. It will feed the recruitment of terrorists. It even threatens our military bases due to rising sea levels, among other things.

In addition, the Defense Department, the intelligence community and the Department of Homeland Security will have to dedicate finite resources to assessing and addressing threats caused or exacerbated by climate change, including humanitarian crises and extreme weather disasters. But if climate change were mitigated, these resources could instead be directed toward other national and international priorities.

When the intelligence community and the military warn of the national security risks associated with climate change, they do so without a political agenda. Their only agenda is providing impartial analysis and recommendations for the sake of our nation's security interests. Besides, this issue is now bipartisan: Last year, a group of U.S. House members formed the Climate Solutions Caucus, which can only be joined if members bring along someone from the other party. Membership in the caucus is growing.

The president should follow suit. To continue disregarding the perils of climate change would be an affront to the professionals whose assessments strongly suggest that he should act otherwise. It would also eschew his presidential responsibility to prevent and confront national security threats in good faith.

It was mildly reassuring when the administration, perhaps reluctantly, did not impede the release of an extensive, multi-agency climate change report last month. Signing the NDAA without any objections on the climate change issue would be another small but constructive step for Trump.

If he does this, perhaps he might be willing to marshal national resources in the effort to blunt climate change by properly addressing and prioritizing the issue in the administration's forthcoming national security strategy. And if he does that, maybe — eventually — he could get back in step with the international community by recommitting to the Paris agreement.