US environmental regulators Thursday rejected a series of challenges to the science behind climate change, reaffirming that global warming is real and the result of man-made pollution.

The Environmental Protection Agency (EPA) ruling was welcomed by US climate groups and comes after a number of recent controversies over the workings of climate scientists provided fodder for sceptics around the world.

The EPA reaffirmed its 2009 'endangerment finding', which for the first time declared climate change a threat to public health and could serve as a basis for the US government taking action to reduce pollution.

Opponents had argued that the 'Climategate' scandal, involving errors discovered in a 2007 international climate report and emails leaked last year from a British university, had placed in doubt the science behind climate change.

The EPA rejected 10 separate challenges to its endangerment finding. EPA chief Lisa Jackson said that the ruling was 'based on years of science from the US and around the world'.

The finding allows the agency to move ahead with specific actions to reduce US emissions of greenhouse gases blamed for global warming, including new limits on pollution from vehicles. Critics argue the EPA is acting without the approval of lawmakers, who are locked in a fierce debate over the direction of US climate policy.

'It is time to move beyond this year's contrived controversies over climate science,' said Eileen Claussen, head of the US-based Pew Centre on Global Climate Change.