New studies say the warming to be expected from the doubling of carbon dioxide (CO2) between now and 150 years from now is going to be one-sixth of previous UN Climate Panel estimates, according to Lord Monckton, a one-time journalist, businessman and former policy adviser to British Prime Minister Margaret Thatcher.

"Half a degree Celsius in 150 years. Not much to write home about," he told reporters in Calgary on Thursday.

The forecast comes as a result of new methods of measurements, as science has moved away from computer modelling to direct measurements of what's going on in the atmosphere, he explained.

Monckton, currently chief policy adviser for the Science and Public Policy Institute, was in town to present his Apocalypse Cancelled: The Overheated Hype behind Global Warming presentation to a lunchtime crowd of about 300.

The global warming scare is having catastrophic effects as it's leading to the creation of public policy that ultimately harms people, he said.