See Candidate Page Joe Biden, Climate Climate tweets on Biden 11/20/19 “[Climate change] is the existential threat to humanity. It is the number one issue.”@JoeBiden responds during the climate segment in the #DemDebate pic.twitter.com/8Dv0zSuAmH— LCV – League of Conservation Voters 🌎 (@LCVoters) November 21, 2019