One of the more ludicrous conceits in American political discourse is the microscopic boundaries of the term "national security." In elite circles, "national security" generally refers to the use of military force to topple some tinpot dictatorship or meddle in a chaotic civil war, most often in the Middle East somewhere. Hundreds of billions are spent, tens of thousands die, the region is left radically destabilized, and the assumption that American military force is by definition good is ever more ironclad.

But if national security means anything at all, it surely includes maintaining the actual physical existence of the country. There are only two things that pose a clear and present existential danger to the United States: nuclear war, and climate change.

President Trump is not just failing to prevent climate change. He is actively aiding and abetting the enemy: by denying that climate change actually exists, and by dismantling his predecessor's halting efforts to preserve the country.

Though nuclear war has a greater destructive potential, climate change is the greater threat, because nothing is being done to arrest it. All that must be done to head off nuclear war is preserve the status quo of mutually assured destruction. Given tensions with Russia and global nuclear proliferation, this is really important, without question. But the basic policy framework to prevent large-scale nuclear exchange from the Cold War is manifestly still functioning, and there's little reason to think it can't continue to do so indefinitely.

A tremendously dangerous level of global warming, by contrast, is already headed directly for us, and we have no plan to stop it. The logic of climate change is simple — either we construct a global policy to smash down emissions as fast as possible, or we lock in serious harm to human society. The longer we procrastinate, the greater the harms, and the worse the risk of total civilizational immolation. High enough mankind-driven warming risks tripping self-reinforcing warming feedback loops that rapidly drive temperatures up 4-6 or more degrees Celsius. That is the stuff of nightmares, with vast swathes of American territory (not to mention whole large nations) drowned by hundreds of feet of sea level rise, mass extinction, plummeting crop yields, loss of fresh water sources, drought, desertification, and endless extreme weather. At that point only hellishly risky and untried geoengineering schemes would be our only hope.

Hurricane Sandy did $75 billion of damage in 2012. Imagine something equally damaging or worse happening every few weeks, all while agricultural productivity has crashed, the oceans are filled with nothing but jellyfish, and the surviving refugees from what used to be Miami are wandering the wasted hinterlands.

A prudent, conservative climate security approach for the United States would mean a crash program of decarbonization aimed at cutting emissions by about 10 percent per year, both to do our part for global emissions control and as a diplomatic strategy of leading by example.

Instead, President Trump announced last week that he would abolish President Obama's Clean Power Plan, the most significant American effort by far to cut greenhouse emissions. While itself totally inadequate to the scale of the problem, it was at least going in the right direction. But it's not remotely surprising given that Trump has selected an oil company lickspittle as the head of the Environmental Protection Agency, and wants to cut its budget by a third.

Conservatives constantly cite the 1938 appeasement policy of Neville Chamberlain as one of history's biggest acts of cowardice. Their case is overstated, but what Trump is doing is leagues beyond anything Chamberlain did. This is as if, in addition to allowing Hitler to annex the Sudetenland, the British had also given him half the U.K.'s navy and installed Hermann Göring as foreign secretary.

Denying the fact of climate change, like Trump and most conservatives do, will not avail them in the eyes of history. Future generations will remember this president and his party as having done their utmost to burn this country to the ground.