Former CIA director R. James Woolsey, who has warned of the national security implications of climate change and advocated for the U.S. to shift toward more clean energy use, joined GOP presidential nominee Donald Trump‘s team as senior national security advisor. Trump has consistently denied climate change poses a problem or a threat. But Woolsey said Trump “understands the magnitude of the threats we face and is holding his cards close to the vest.”

Last fall, Woolsey joined dozens of other military, national security and foreign policy leaders on a statement calling for U.S. leadership to “tackle [climate change] by mobilizing the strength and ingenuity of the U.S. government and business community to seek effective, financially sound approaches.” In 2010, he said “there’s enough consensus that human-generated global warming gas emissions are beginning to have an effect… Next year might be cooler than this year but that doesn’t mean the trend isn’t there.”