Global warming and cooling linked to the sunspot cycle

PLANET-wide heating and cooling of the atmosphere during the 11-year sunspot cycle has been measured for the first time. Climate-change sceptics may seize on the findings as evidence that the sun's variability can explain global warming - but mathematician Ka-Kit Tung says quite the contrary is true.

Tung and colleague Charles Camp, both of the University of Washington in Seattle, analysed satellite data on solar radiation and surface temperatures over the past 50 years, covering four-and-a-half solar cycles. They found that global average temperatures oscillated by almost 0.2 °C between high and low points in the cycle, nearly twice the amplitude of previous estimates (Geophysical Research Letters, DOI: 10.1029/2007GL030207).

The finding adds to the evidence that mainstream climate models are right about the likely extent of future human-generated warming, Tung says. It also effectively rules out some lower estimates in those models.
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