The Great Global Warming Swindle: Response

Richard Betts

15th March, 2007

The key argument mounted by Martin Durkin in the Channel 4 documentary, ‘The Great Global Warming Swindle’, was that the sun’s activity had more to do with global warming than levels of carbon dioxide in the atmosphere.

We asked Dr Richard Betts of the Met Office Hadley Centre to explain the scientific evidence for why the sun is not to blame for current climate change. He responded:

"Although the sun can play a part in climate change, there is overwhelming scientific evidence that it is not the cause of the climate warming that we have seen over recent decades.

There have been proposed 2 mechanisms for how the sun might might be influencing climate. The first is that changes in the amount of solar radiation given off by the sun might be to blame. Solar irradiance has been monitored continuously for the last 28 years, and although an 11-year cycle has been well-established, no significant long-term trend has been detected over that period. The warming trend in global temperatures over recent decades therefore cannot be explained by changes in solar irradiance, simply because there has been no overall change in solar irradiance over that time.

Earlier records show an increase in solar irradiance in the early part of the Twentieth Century, followed by a brief decrease before the current period of no significant trend. Global temperatures also underwent a warming until around...

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