13th November 2013

'Missing heat' discovery prompts new estimate of global warming

An interdisciplinary team of researchers have found ‘missing heat’ in the climate system – casting doubt on suggestions that global warming has slowed or stopped over the past decade.

Observational data on which climate records are based cover only 84 percent of the planet – with Polar regions and parts of Africa largely excluded. However, Dr Kevin Cowtan, computational scientist at the University of York, and Robert Way, cryosphere specialist and PhD student at the University of Ottawa, have managed to reconstruct the ‘missing’ 16 percent. They achieved this using a combination of observations from satellites and surface data from weather stations and ships on the peripheries of the unsampled regions.

Their new research – published in the Quarterly Journal of the Royal Meteorological Society – shows that the Arctic is warming about eight times faster than the rest of the planet. Previous studies by the UK Met Office based on the HadCRUT4 dataset (which only covers about five-sixths of the globe), have suggested that global warming has slowed significantly since 1997. This new research, however, which adds the ‘missing’ data, indicates that the rate of warming since 1997 has been two and a half times greater than shown in the Met Office studies.

Evidence for the rapid warming of the Arctic includes observations from high latitude weather stations, radiosonde and satellite observations of temperatures in the lower atmosphere, along with reanalysis of historical data.

“There’s a perception that global warming has stopped but, in fact, our data suggests otherwise," said Cowtan. "But the reality is that 16 years is too short a period to draw a reliable conclusion.”

Robert Way added: “Changes in Arctic sea ice and glaciers over the past decade clearly support the results of our study. By producing a truly global temperature record, we aim to better understand the drivers of recent climate change.”

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