Since the 1980s, climate science and mass media have transformed into an increasingly politicized sphere. In the United States, Conservatives and Liberals understand global warming differently. Democrats often accept the evidence for global warming and think that it's caused by humans, while not many Republicans believe this. Democrats and liberals have higher and more steady trust in scientists, while conservative Republicans’ trust in scientists has been declining. However, in the United Kingdom, mass media do not have nearly the impact on people's opinions as in the United States. They have a different attitude towards the environment which prompted them to approve the Kyoto Protocol, which works to reduce carbon dioxide emissions, while the U.S., the world's largest creator of carbon dioxide, has not done so.