American climatologist Michael Mann has been at the heart of the war of words over climate change for the last 15 years.

The author of the book The Hockey Stick and the Climate Wars, in which he examines who is behind the campaigns to discredit scientists who believe in global warming, argues it is cheaper to wean ourselves from fossil fuels than to pay for the damage caused by global warming.

Known for his scientific analysis of temperature records over the last 1,000 years, his "hockey stick" graph depicting the impact of climate change and global warming became a defining symbol of man's influence on the environment.

In an interview on CBC-TV’s The Lang & O’Leary Exchange, Mann said the evidence for climate change is mounting, despite fluctuations caused by El Nino and volcanic events.

“Evidence for human influence on climate change just becomes stronger with each additional year of data that ... comes in,” he said.

“Indeed we’re seeing unprecedented warmth, we’re seeing unprecedented melt of sea ice up in the Arctic.”

Mann, who works at the Earth Systems Science Centre at Penn State University, issues a call to citizens to wake up and demand action from leaders before it’s too late.

“Will we commit to a level of dangerous interference with the climate that commits us to rapid melting of the ice sheets, to abrupt changes in drought patterns,” he said.

“The fear is that we may approach one of these climate tipping points before we approach the other tipping point – the tipping point in the public consciousness – the recognition that through the emissions we are making now, we are locking in global warming and climate change for decades to come.”

He argues that not acting to slow global warming is already costing the economy – through damage from extreme weather events, drought, wildfire and flooding.

It would be cheaper to take action, he argues, but the public debate is being poisoned by climate deniers funded by powerful private interests.

Mann is a perennial target of climate change deniers, the subject of physical threats, mocking YouTube videos, Republican politicians and chat shows accusing him of shoddy science.

His emails with researchers at the Climatic Research Unit in East Anglia were part of an international controversy when they were leaked by hackers in 2009.

Mann laments the “huge gulf” between acceptance of climate change in the scientific community and the doubt in the political sphere.

“Here in the U.S. we have a House of Representatives with a science committee led by a Republican politicians that don’t even accept that climate change is real,” he said.