The journal Science has published a letter defending the integrity of climate science, signed by 255 members of the U.S. National Academy of Sciences.

"We are deeply disturbed by the recent escalation of political assaults on scientists in general and on climate scientists in particular," the letter reads.

The letter, signed by leading scientists, including 11 Nobel laureates, confirms that the conclusions of climate science — that human behaviour is changing the planet's climate — are based on the work of thousands of scientists.

"There is compelling, comprehensive and consistent objective evidence that humans are changing the climate in ways that threaten our societies and the ecosystems on which we depend," the letter says.

In particular, the letter says, the evidence shows that, "the planet is warming due to increased concentrations of heat-trapping gases in our atmosphere," and "most of the increase in the concentration of these gases over the last century is due to human activities."

"A snowy winter in Washington does not alter this fact."

The letter was signed by scientists from 53 different disciplines, from environmental science to geophysics, to microbial biology.

"Society has two choices: we can ignore the science and hide our heads in the sand and hope we are lucky, or we can act in the public interest to reduce the threat of global climate change quickly and substantively," the letter reads.

The letter comes in response to growing political pressure on climate scientists, particularly in the wake of the release of more than 1,000 emails stolen from the University of East Anglia's climatic research unit.

Letter calls for end of 'McCarthy-like threats'

Critics of climate science said the emails showed that researchers had been fudging data and suppressing findings that did not agree with the conclusion that climate change is occurring and is the result of human activity.

The incident was dubbed "climategate" by various commentators.

The letter called "for an end to 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."

In April, an independent panel of experts recommended by the Royal Society found that the climate research unit at the University of East Anglia did not engage in "scientific malpractice."

The panel did not analyze whether the researchers' conclusions were correct but investigated the scientific process at the research unit and found "absolutely no evidence of any impropriety."