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The strong weak sun

10 Apr 2019 | Science Notes

A new study in the Proceedings of the National Academy of Sciences finds a surprisingly strong solar influence on wind and rainfall in the tropical Pacific. It’s surprising because, the American Association for the Advancement of Science’s EurekAlert! story goes out of its way to say, “the surface temperature imprint of solar cycle barely reaches 0.1 K in a solar maximum - almost 8 times weaker than the global warming trends observed in the 20th century” and, it adds pointedly, “numerous claims” about the sun’s influence “did not survive proper statistical scrutiny”. So the sun isn’t important. Except because facts are facts there must be some other mechanism that amplifies the sun’s influence. So it is important.

The reason the sun’s influence on climate is so controversial is that there’s only so much warming since 1880 to attribute to all factors combined. And therefore CO2 is fighting Mr. Sun and others for a share of a fixed pie. And the less impact CO2 has, the less those scary charts turn upward at the end as atmospheric CO2 rises.

EurekAlert! Is of course correct that the sun’s output of heat doesn’t vary much over solar cycles. But people like Fritz Vahrenholt and Sebastian Lüning, pointing to surprisingly strong correlations between solar activity and temperature over a far longer period than CO2 seems to correlate with temperature, have argued in The Neglected Sun (in German the even more evocative Die kalte Sonne) that a different mechanism is in play: the far larger fluctuations in the sun’s magnetic field over a solar cycle. They say the sun’s magnetic field plays a large role in screening out cosmic rays which, in turn, play a large role in the formation of clouds that potentially either trap or reflect incoming solar radiation. This is also known as the Svensmark effect, named for Danish physicist Henrik Svensmark who has been studying it for decades. But don't scientists know everything there is to know about the sun's magnetic field? Far from it--as they only just learned it is ten times stronger than previously believed.

Watts Up With That reports another study in Nature Climate Change, also reported in EurekAlert! saying the recent intensification of the Walker Circulation has now definitively been ascribed to natural not human influences, ending “a long-standing debate”. Evidently the intensification drove sea level increases in the western tropical Pacific and also contributed to the infamous hiatus. And that computer models tended to say warming should weaken the Walker Circulation and it didn’t happen although it turns out that instead of consensus there’s a big spread in the models here.

The upshot? Well, situation complex, too soon to tell, but “The study concludes that the observed strengthening of the Walker circulation from about 1990-2013 and its impact on western Pacific sea level, eastern Pacific cooling, drought in the Southwestern United States, was a naturally occurring phenomenon, which does not stand in contrast to the notion of projected anthropogenic climate change.” So whatever the evidence may say, humans are responsible because, you know, they have to be.

To repeat, whatever rise in temperature in the 20th century is due to a more active sun shielding our planet from cosmic rays, or any other natural cause, can’t also be attributed to CO2, which requires the modelers to adjust their estimate of the “forcing” impact of CO2 downward which makes the more alarming predictions fizzle out.

And we can’t have that.

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