Putin says 'nobody knows' causes of global climate change

Russian President Vladimir Putin on Thursday said "nobody knows" what causes climate change, appearing to cast doubt over whether global warming was of man-made origin and stating it may be due to cosmological processes. "Nobody knows the origins of global climate change," Putin told reporters at the start of his marathon end-of-year news conference.

"We know that in the history of our Earth there have been periods of warming and cooling and it could depend on processes in the universe," he added.