Climate Science

Shedding Light on the Sun

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Science  15 Sep 2006:
Vol. 313, Issue 5793, pp. 1543
DOI: 10.1126/science.313.5793.1543b

Satellite measurements show that solar irradiance, essentially the amount of energy that reaches Earth, varies over the 11-year solar cycle by ∼0.1%, too small a change to have a noticeable impact on Earth's average temperature. However, a long-standing question in climate science is whether larger solar changes have occurred that might have caused warming over the past century or climate change at some stage of the Holocene (or an even longer span of time).

Bard and Frank provide a thorough critical review of both the problematic evidence for longer changes in solar irradiance and the possible climatic effects these changes could have induced. The authors point out that many proposed connections, for example between the records of cosmogenic nuclides such as 14C and 10Be and records of climate change, are based on correlations—some of which have large and perhaps unappreciated uncertainties—and on imperfect and indirect records. They conclude that there might still be a connection between solar changes and the Medieval Warm Period and Little Ice Age, but that overall solar changes, most of which remain unproven, probably represent a second-order influence on the behavior of Earth's recent climate. — BH

Earth Planet. Sci. Lett. 248, 1 (2006).

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