The sun gets short shrift in the computer climate models used to buttress the mainstream view of anthropogenic (human-caused) global warming. That’s because the climate change narrative, which links warming almost entirely to our emissions of greenhouse gases, trivializes the contributions to global warming from all other sources. According to its Fifth Assessment Report, the IPCC attributes no more than a few percent of total global warming to the sun’s influence.
That may be the narrative but it’s not one universally endorsed by solar scientists. Although some, such as solar physicist Mike Lockwood, adhere to the conventional wisdom on CO2, others, such as mathematical physicist Nicola Scafetta, think instead that the sun has an appreciable impact on the earth’s climate. In disputing the conventional wisdom, Scafetta points to our poor understanding of indirect solar effects as opposed to the direct effect of the sun’s radiation, and to analytical models of the sun that oversimplify its behavior. Furthermore, a lack of detailed historical data prior to the recent observational satellite era casts doubt on the accuracy and reliability of the IPCC estimates.
I’ve long felt sorry for solar scientists, whose once highly respectable field of research before climate became an issue has been marginalized by the majority of climate scientists. And solar scientists who are climate change skeptics have had to endure not only loss of prestige, but also difficulty in obtaining research funding because their work doesn’t support the consensus on global warming. But it appears that the tide may be turning at last.
Judging from recent scientific publications, the number of papers affirming a strong sun-climate link is on the rise. From 93 papers in 2014 examining such a link, almost as many were published in the first half of 2017 alone. The 2017 number represents about 7% of all research papers in solar science over the same period (Figure 1 here) and about 16% of all papers on computer climate models during that time (Figure 4 here).
This rising tide of papers linking the sun to climate change may be why UK climate scientists in 2015 attempted to silence the researcher who led a team predicting a slowdown in solar activity after 2020. Northumbria University’s Valentina Zharkova had dared to propose that the average monthly number of sunspots will soon drop to nearly zero, based on a model in which a drastic falloff is expected in the sun’s magnetic field. Other solar researchers have made the same prediction using different approaches.
Sunspots are small dark blotches on the sun caused by intense magnetic turbulence on the sun’s surface. Together with the sun’s heat and light, the number of sunspots goes up and down during the approximately 11-year solar cycle. But the maximum number of sunspots seen in a cycle has recently been declining. The last time they disappeared altogether was during the so-called Maunder Minimum, a 70-year cool period in the 17th and 18th centuries forming part of the Little Ice Age.
While Zharkova’s research paper actually said nothing about climate, climate scientists quickly latched onto the implication that a period of global cooling might be ahead and demanded that the Royal Astronomical Society – at whose meeting she had originally presented her findings – withdraw her press release. Fortunately, the Society refused to accede to this attack on science at the time, although the press release has since been removed from the Web. Just last month, Zharkova’s group refuted criticisms of its methodology by another prominent solar scientist.
Apart from such direct effects, indirect solar effects due to the sun’s ultraviolet (UV) radiation or cosmic rays from deep space could also contribute to global warming. In both cases, some sort of feedback mechanism would be needed to amplify what would otherwise be tiny perturbations to global temperatures. However, what’s not generally well known is that the warming predicted by computer climate models comes from assumed water vapor amplification of the modest temperature increase caused by CO2 acting alone. Speculative candidates for amplification of solar warming involve changes in cloud cover as well as the earth’s ozone layer.
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