It will be hard keeping an eye on the members' progress, since the group is made of up entities from various industries. But Bloomberg hopes to make things easier by launching a process called "America's Pledge" that gives the participants a way to combine and quantify their emissions reduction. If you're wondering who's taking part in the project, We Are Still In's official website has a list of all the signatories. They include 13 Democratic and Republican governors, 19 state attorneys general, over 200 mayors and 183 colleges and universities across the country.

Among the 900-plus names under the "Businesses and Investors" section, you'll find a number of familiar companies, such as Apple, Facebook, Google, Microsoft, Adobe, Airbnb, eBay, HP, Lyft, Uber, Spotify, Twitter, Tumblr and Yahoo. Tesla is also part the group, which doesn't really come as a surprise, seeing as its head honcho, Elon Musk, left the president's council when he announced the country's withdrawal from the agreement.