Global Warming: Caused by the sun or CO2?

The March 5, 2009 version of ICECAP has an article, “It’s the Sun, stupid!” by Dr. Willie Soon, a solar and climate scientist at the Harvard-Smithsonian Center for Astrophysics. The subtitle indicates his position: “New direct evidence demonstrate that changes in solar activity influence climate” Below are some key quotes from his article.

Between 1645 and 1715, sunspots were very rare and temperatures were low. Then sunspot frequency grew until, between 1930 and 2000, the Sun was more active than at almost any time in the last 10,000 years. The oceans can cause up to several decades of delay before air temperatures respond fully to this solar “Grand Maximum.” Now that the Sun is becoming less active again, global temperatures have fallen for seven years.

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The close relationships between the abrupt ups and downs of solar activity and of temperature that I have identified occur locally in coastal Greenland; regionally in the Arctic Pacific and north Atlantic; and hemispherically for the whole circum-Arctic, suggesting that changes in solar activity drive Arctic and perhaps even global climate.

There is no such match between the steady rise in atmospheric CO2 concentration and the often dramatic ups and downs of surface temperatures in and around the Arctic.

I recently discovered direct evidence that changes in solar activity have influenced what has been called the “conveyor-belt” circulation of the great Atlantic Ocean currents over the past 240 years. For instance, solar-driven changes in temperature, and in the volume of freshwater output from the Arctic, cause variations in sea surface temperature in the tropical Atlantic 5-20 years later.

These previously undocumented results have been published in the journal Physical Geography. They make it difficult to maintain that changes in solar activity play an insignificant role in climate change, especially over the Arctic.

The hallmark of good science is the testing of a plausible hypothesis that is then either supported or rejected by the evidence. The evidence in my paper is consistent with the hypothesis that the Sun causes climatic change in the Arctic.

It invalidates the hypothesis that CO2 is a major cause of observed climate change – and raises serious questions about the wisdom of imposing cap-and-trade or other policies that would cripple energy production and economic activity, in the name of “preventing catastrophic climate change.

Bill Clinton used to sum up politics by saying, “It’s the economy, stupid!” Now we can fairly sum up climate change by saying, “It’s the Sun, stupid!”

To me the key statement is: “The hallmark of good science is the testing of a plausible hypothesis that is then either supported or rejected by the evidence.” Unfortunately, those who blame global warming on carbon dioxide released by human activities have politicized science to the point where discussion of plausible counter hypotheses like this is actively discouraged, even demonized.