During his campaign for president, Donald Trump promised to end action on climate change and kill the climate treaty adopted in 2015 in Paris. To truly understand why that’s such a big deal—perhaps the biggest deal ever—you need to think about a few things. Yes, you need to think about the oft-repeated but nonetheless true and alarming statistics: 2014 was the hottest year ever recorded till 2015 snatched the crown—till 2016 obliterated the record.