Solar variations not behind global warming: study

They concluded that the rapid rise in global mean temperatures seen since the late 1980s could not be ascribed to solar variability, whatever mechanism was invoked.

Britain's Royal Society -- one of the world's oldest scientific academies, founded in 1660 -- said the new research was an important rebuff to climate change skeptics.

"At present there is a small minority which is seeking to deliberately confuse the public on the causes of climate change. They are often misrepresenting the science, when the reality is that the evidence is getting stronger every day," it said in a statement.

The 10 warmest years in the past 150 years have all been since 1990 and a United Nations climate panel, drawing on the work of 2,500 scientists, said this year it was "very likely" human activities were the main cause.

The panel gave a "best estimate" that temperatures would rise 1.8 to 4.0 degrees Celsius (3.2 to 7.8 Fahrenheit) this century.