The controversy over the science of global warming is mainly over the extent of human contribution to warming, as well as a dispute over predictions of near-future warming and its effect on human beings and the environment.
Among registered U.S. voters, opinion is split down the middle, with 75% of Democrats believing that "the science is settled" in favor of the view of the IPCC, and 73% of Republicans believing that there is no scientific proof. Both main party candidates for president in the 2008 election, John McCain and Barack Obama, have stated publicly that the issue is real and urgent.
The Stern Review, commissioned by the UK Government to look into the economic effects of climate change, concluded that if left unchecked climate change would cost 5% of GDP per year. "In contrast, the costs of action to reduce greenhouse gas emissions to avoid the worst impacts of climate change can be limited to around 1% of global GDP each year."