There is perhaps no issue that Hillary Clinton and Donald Trump disagree more on than global warming. The former thinks that it’s one of the biggest threats to humanity, if not the biggest threat, and the latter says that the Chinese invented global warming in order to get an economic advantage.

Climate change has actually not been a big issue in this hotly contest campaign, and really no substantive issues have gotten all that much discussion in a campaign that has largely centered around the sex lives of people either running or married to a candidate. But the issue shows how starkly different Hillary and The Donald are, and how different their administrations would approach the issue if elected.

Clinton says she would continue Obama’s energy policies, and continue to implement the Clean Power Plan. But Trump pledges to kill any such initiatives, arguing that the impede the economy and global warming isn’t anything to worry about anyway, despite almost all scientists saying it presents a grave threat to the planet.

Trump is actually totally reversing strides Republicans had made toward at least accepting some concessions to deal with global warming and climate change, however small. Sen. John McCain in 2008, when he was the Republican nominee for president, said he would be open to a “cap-and-trade” system to cut back on emissions of carbon dioxide.

But Trump has long dismissed global warming has a complete hoax.

“I’m not a big believer in man-made climate change. They used to call it global warming, they’ve called it extreme weather, they always change the name to encapsulate everything,” Trump told the newspaper. “The problem we have is our businesses are suffering.”

Trump has also said he would cancel the Paris climate agreement, in which countries around the globe pledged to cut back on carbon emissions.