Is There Global Warming? No and Yes

The Telegraph has an article today, Doha: Global warming is slowing down, says Met Office, which contains this graph:

The article explains:

Dr Peter Stott, Head of Climate Monitoring and Attribution at the Met Office, said the past decade has been the warmest on record.

But he pointed out that warming has slowed down since 2000, in comparison to the rapid warming of the world since the 1970s.

"Although the first decade of the 21st century was the warmest on record, warming has not been as rapid since 2000 as over the longer period since the 1970s," he said.

Scott is hedging with "… has not been as rapid …" In short, the warming trend line from 2001 to 2012 is negligible. So, if by "global warming" we mean a more or less relentless upward trendline over a few years …a decade in this case …, then there was no global warming.

However, Scott also reminds us:

"Dr Stott warned that global warming could speed up again at any time, and insisted that the general pattern of warming is not in doubt."

A momentary plateau of a few years does not negate a long-term trend. So, if "global warming" means a more or less relentess upward trendline over a period of more than a few years, then there is global warming. So is there global warming? No and yes.

But this raises an important question. When does a short-term trend become a long-term trend, prompting a rethink about climate models? Ten years? Twenty years? Fifty years? Last month, Judith Curry, in response to controversial reports about the global warming plateau, explained that climate models typically do not predict decade-long global warming stalls. (See: 'Pause': Waving the Italian Flag) She reports that prominent scientists have said that a plateau or decline in global temperatures of fifteen or more years would be grounds for rethinking climate models. The last eleven years have been flat, and even going back fifteen years to 1997, the rate of warming is much slower than models suggested it would be. She is not disputing long-term warming but suggests that climate models may not be as robust as advertised. It will be interesting to see how the climate science community responds if the past decade's trend continues for three or four more years or how skeptics respond if temperatures begin to soar in the same timeframe.