Climate scientists agree that human activity has been changing our planet’s climate over the long term. Without serious policy changes, scientists expect devastating consequences in many regions. Environmentalists have been campaigning for effective policy changes for more than two decades. The world’s governments have been negotiating since 1995 as parties to the United Nations Framework Convention on Climate Change (UNFCCC). These talks have not yet produced agreements that are sufficiently effective in curbing greenhouse gas emissions or helping the world adapt to climate impacts. Some effort has shifted to partial measures by national governments, provinces, cities and private companies, which together, also fall far short of the need identified by science so far.