More than 250 US scientists, including 11 Nobel laureates, have published an open letter defending climate change research.
The letter, which appears in Science, follows increasing hostility to climate change science in the wake of the release of hacked emails from the University of East Anglia and errors made by the Intergovernmental Panel on Climate Change (IPCC).
The scientists, all members of the US National Academy of Sciences, accuse their opponents of "McCarthy-like threats of criminal prosecution against our colleagues based on innuendo and guilt by association, the harassment of scientists by politicians seeking distractions to avoid taking action, and the outright lies being spread about them."
Much of the controversy stems from a lack of scientific understanding on the part of the general public, they say.
"There is always some uncertainty associated with scientific conclusions; science never absolutely proves anything," says the letter.
"When someone says that society should wait until scientists are absolutely certain before taking any action, it is the same as saying society should never take action."
Well-established theories which have not been successfully challenged can be spoken of as facts, they say - and climate change falls into this category. Heat-trapping gases are indeed warming the planet, and most of this increase is due to human activity.