The Montreal Protocol was a successful international treaty to protect the Ozone Layer, so there is some precedence for countries coming together to protect our environment:
I kind of disagree with this one. The number is high, but a bunch of countries haven't signed it
(As of 2016, eight Annex 2 states have not ratified the treaty: China, Egypt, Iran, Israel and the United States have signed but not ratified the Treaty; India, North Korea and Pakistan have not signed it.) [[0]