Source: Crowdflower. http://www.crowdflower.com/open-data-library Contributors evaluated tweets for belief in the existence of global warming or climate change. The possible answers were "Yes" if the tweet suggests global warming is occuring, "No" if the tweet suggests global warming is not occuring, and "I can't tell" if the wtweet is ambiguous or unrelated to global warming. We also provide a confidence score for the classification of each tweet.