DEBATE about the reality of a two-decade pause in global warming and what it means has made its way from the sceptical fringe to the mainstream.

In a lengthy article this week, The Economist magazine said if climate scientists were credit-rating agencies, then climate sensitivity - the way climate reacts to changes in carbon-dioxide levels - would be on negative watch but not yet downgraded.

Another paper published by leading climate scientist James Hansen, the head of NASA's Goddard Institute for Space Studies, says the lower than expected temperature rise between 2000 and the present could be explained by increased emissions from burning coal.

For Hansen the pause is a fact, but it's good news that probably won't last.

International Panel on Climate Change chairman Rajendra Pachauri recently told The Weekend Australian the hiatus would have to last 30 to 40 years "at least" to break the long-term warming trend.


But the fact that global surface temperatures have not followed the expected global warming pattern is now widely accepted.

Research by Ed Hawkins of University of Reading shows surface temperatures since 2005 are already at the low end of the range projections derived from 20 climate models and if they remain flat, they will fall outside the models' range within a few years.

"The global temperature standstill shows that climate models are diverging from observations," says David Whitehouse of the Global Warming Policy Foundation.

"If we have not passed it already, we are on the threshold of global observations becoming incompatible with the consensus theory of climate change," he says.

Whitehouse argues that whatever has happened to make temperatures remain constant requires an explanation because the pause in temperature rise has occurred despite a sharp increase in global carbon emissions.

The Economist says the world has added roughly 100 billion tonnes of carbon to the atmosphere between 2000 and 2010, about one-quarter of all the carbon dioxide put there by humans since 1750. This mismatch between rising greenhouse gas emissions and not-rising temperatures is among the biggest puzzles in climate science just now, The Economist article says.

"But it does not mean global warming is a delusion."


http://www.theaustralian.com.au/news/features/twenty-year-hiatus-in-rising-temperatures-has-climate-scientists-puzzled/story-e6f