In 1992, diplomats and scientists at the United Nations negotiated the first-ever treaty intended to tackle the scientific phenomenon now known as climate change. This brought the issue to the forefront and led to a series of conferences that would occur almost every year for the next 30 years. Short Wave host Emily Kwong talks to freelance climate reporter, Dan Charles, about how those at the conference wrote a clear and ambitious goal that they didn't even fully understand.Email the show at shortwave@npr.org.