GOP presidential frontrunner Donald Trump laid out his foreign policy platform on Wednesday in a speech covering national security threats that ranged from ISIS to North Korea. But what about an issue that the Pentagon considers one of the biggest threats of the coming decades: climate change? The only time he addressed it was to mock it.

“Our military is depleted, and we’re asking our generals and military leaders to worry about –” Trump said, pausing before delivering the punch line, “global warming.”

Trump failed to touch on the landmark 196-nation Paris agreement, in which nations pledged emissions cuts and finance to act on “an urgent and potentially irreversible threat.” What we do know about Trump’s opinion of the agreement is from December, when Trump called Obama’s Paris remarks “one of the dumbest things I’ve ever seen, or perhaps most naive.” The candidate is known for conflating weather and climate, stating that global warming was “created by and for the Chinese,” and flat-out denying the scientific consensus about climate change.

Trump could formally pull the U.S. out of the agreement, or simply fail to deliver on Obama’s pledges; it’s tough to ever guess what he’s going to do next.

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Let’s put aside Trump’s views on climate science for a minute and focus on the pure politics of this. Climate change may be just one issue on a long list of diplomatic conflicts that Trump would have upon entering the White House, but pulling from the Paris deal alone would be huge: Trump is prepared to take the United States in the opposite direction of every single one of our allies. And he hasn’t told us yet how he will engage in trade talks and tackle migration crises while the rest of the world recognizes these issues are linked to climate change.

By ignoring climate change, Trump is ignoring the advice of America’s military experts. The Pentagon itself, with Defense Secretary Chuck Hagel at the helm, warned in 2014 that climate change would directly contribute to security risks for U.S. relations abroad. Last year, a study commissioned by the G7 countries found that climate change, which poses a threat to both global and economic security, has become “the ultimate threat multiplier” for regions that are already facing another type of threat.

Trump just isn’t listening.