In our ongoing series on the book Canary in a Climate World, Chapters 4 and 5 are by Professor Nir Shaviv of the Hebrew University of Jerusalem and Dr. Henrik Svensmark of the Danish Technical University respectively. And especially as they were written independently about work done independently, in combination they present a remarkably powerful argument that the sun has played a major role in the Earth’s climate variations, not just over the past century but over hundreds of millions of years. Both authors’ account of how they discovered the mechanism, how they gathered the evidence to prove its validity, and how they validated their ideas by testing it against widely-varying data sets, shows science at its best. Including that they did not take care to make their stories coincide at every point at the cost of suppressing uncertainty. Sadly, the story of how the IPCC and the rest of the climate establishment responded shows science at its worst.

The manner in which their research is mutually reinforcing is especially revealing because Shaviv and Svensmark came to the topic from opposite directions. Shaviv was interested in astronomical events over millions of years, Svensmark in the physics of cloud formation over days to weeks. But both were drawn to look at the role of cosmic rays, the constant shower of high energy particles bombarding our solar system from distant supernovae, because of a vital point about how fluctuations in solar activity affects climate.

When the sun is more active, as climate orthodoxy is quick to point out, the change in direct total solar irradiance on the Earth is trivial and hence could only exert a small direct influence on our climate. But crucially, the output of “solar wind”, a steady stream of charged particles (a complex mix but mostly electrons, protons and alpha particles), changes a great deal, so if solar wind affects climate then a more active or less active sun can have a large impact. And according to these researchers, it does affect climate through a powerful if indirect mechanism.

Specifically, the solar wind partially shields the Earth from “cosmic rays”, another shower of charged particles (mostly protons and atomic nuclei) that hit our planet from outside the solar system and even from outside the Milky Way and generally with much higher kinetic energy. Which matters because the cosmic rays that do get through the solar-wind shield then affect clouds.

In his research Svensmark hypothesized, then investigated, that cosmic rays interact with sulphur dioxide molecules in the atmosphere to produce large particles that become Cloud Condensation Nuclei (CCN), on which water droplets cling and create the seeds for clouds to form, clouds whose primary effect is to reflect heat rather than trapping it. If true, then it means that when the sun gets more active and a stronger solar wind screens out more cosmic rays, it diminishes cloud formation, which in turn serves as an indirect amplifier of the incoming solar radiation.

In one of those effects climate orthodoxy loves when it applies to CO2 but shuns when they concern natural phenomena, the outcome is that the small increase in direct incoming heat from a more active sun is boosted by the reduction in cooling cloud formation also resulting from that same more active sun, resulting in a large increase in temperature. So as Gertrude Stein was wont to say, “Interesting if true.” And it’s not just Svensmark whose research suggests that it is true.

For his part Shaviv had already seen a close correspondence between extraterrestrial conditions and temperature proxies over very long time scales, hundreds of millions of years, associated with passage of our solar system through the spiral arms of the Milky Way galaxy and thus encountering more intense cosmic rays. And of course it must be true that if cosmic rays have a significant impact on temperature then (a) it isn’t all CO2 and (b) anything that has a significant impact on cosmic rays will necessarily have a significant impact on temperature. Such as solar activity. And there’s more.

Shaviv also hypothesized, and later demonstrated, that cosmic ray changes during solar cycles correlated closely with sea level changes that were caused by temperature cycles. Which if true must mean that those cosmic ray changes, and hence the solar cycles, were correlated closely with temperature cycles. And since only a lackwit would suggest that a warming planet was making the sun more active, it stands to reason that a more active sun was warming the planet. And if it has done so dependably over very long periods of time, it is impossible to argue that the more active sun of the late 20^th century had no impact on the temperature increase that happened simultaneously.

To make the theory even more persuasive and, one would have assumed, fascinating to researchers and granting organizations alike, Svensmark found evidence that cloud formation responded to so-called Forbush events in which a sudden dramatic increase in solar wind, often associated with a solar “geomagnetic storm”, caused a sudden dramatic decrease in cosmic rays. And yes, he was able to secure funding to conduct high precision experiments that found direct evidence explaining the physics and chemistry involved.

So far so good, right? No. Here the story takes a dark turn because instead of attracting scholarly interest the solar hypothesis ran straight into the buzz saw of climate activism. If the sun explains even a fraction of modern warming, it leaves less for CO2. Which must not be because of the intellectual knock-on effects. The less warming is attributable to CO2, the lower the climate sensitivity should be in models, and the less our emissions can be blamed. And both Shaviv and Svensmark talk in their chapters about the struggles they have gone through to fund their work and to push back against the professional disparagement and marginalization caused by their findings.

The IPCC in particular has consistently either ignored their work or leapt at their critics’ dismissals without ever actually evaluating the evidence. Which sadly is what we have come to expect in climate science. But if what Shaviv and Svensmark and their coauthors have discovered is real, nature will eventually have the last word. Or second-last, because the IPCC will be the last to admit it.