Nir Shaviv was actually born after WWII (a first on this list), and has a decidedly non-white-man-sounding name, though I think Jews are considered white now, right? Right. He’s a white man. It doesn’t really matter.
Anyhoo, Shaviv seems to actually have some climate-science cred, via astrophysics. In 2003 he published a theory accounting for global temperature variance having something to do with our solar system’s passage through the Milky Way’s galactic arms. Thing is, in the paper making this case, his object of study isn’t the current drivers of climate change, but the drivers of climate change over the past 500 million years. And while he finds that, over that period, “at least 66% of the variance in the paleotemperature trend could be attributed to CRF variations likely due to solar system passages through the spiral arms of the galaxy,” that doesn’t imply that 66%+ of every variability is attributable to a cause. Basic statistics. And he acknowledges as much:
As a final qualification, we emphasize that our conclusion about the dominance of the CRF over climate variability is valid only on multimillion year time scales. At shorter time scales, other climatic factors may play an important role.
Even its relatively benign claim was seen as problematic by…
- STEFAN RAHMSTORF, Potsdam Institute for Climate Impact Research, Germany;
- DAVID ARCHER, University of Chicago, Ill.;
- DENTON S. EBEL, American Museum of Natural History, N.Y.;
- OTTO EUGSTER, University of Bern, Switzerland;
- JEAN JOUZEL, Institut Pierre Simon Laplace/LSCE, Saclay, France;
- DOUGLAS MARAUN,Potsdam University, Germany;
- URS NEU, Swiss Academy of Sciences,Bern;
- GAVIN A.SCHMIDT,NASA GISS and Center for Climate Systems Research,Columbia University,N.Y.;
- JEFF SEVERINGHAUS, Scripps Institution of Oceanography,San Diego,Calif.;
- ANDREW J.WEAVER,University of Victoria, B.C.,Canada; and
- JIM ZACHOS, University of California, Santa Cruz
…who published a review in Eos that concluded,
Two main conclusions result from our analysis of Shaviv and Veizer [2003].The first is that the correlation of CRF and climate over the past 520 m.y. appears to not hold up under scrutiny. Even if we accept the questionable assumption that meteorite clusters give information on CRF variations, we find that the evidence for a link between CRF and climate amounts to little more than a similarity in the average periods of the CRF variations and a heavily smoothed temperature reconstruction. Phase agreement is poor.The authors applied several adjustments to the data to artificially enhanc the correlation.We thus find that the existence of a correlation has not been convincingly demonstrated.
Our second conclusion is independent of the first.Whether there is a link of CRF and temperature or not, the authors’ estimate of the effect of a CO2 doubling on climate is highly questionable. It is based on a simple and incomplete regression analysis that implicitly assumes that climate variations on time scales of millions of years, for different configurations of continents and ocean currents,for much higher CO2 levels than at present, and with unaccounted causes and contributing factors,can give direct quantitative information about the effect of rapid CO2 doubling from pre-industrial climate.The complexity and non-linearity of the climate system does not allow such a simple statistical derivation of climate sensitivity without a physical understanding of the key processes and feedbacks.We thus conclude that Shaviv and Veizer [2003] provide no cause for revising current estimates of climate sensitivity to CO2.
Undeterred, Shaviv has taken to the Internet, self-publishing a number of anti-anthropogenic polemics on his website (e.g.).
In the example, he argues that while there is, in fact, an impressive correlation between CO2 levels and global temperatures over not only the last 400 thousand years, but over the last century, the causality is ambiguous. Anyway, blah blah, “we don’t fully understand the aerosol effect on cloud formation!” QUESTIONS QUESTIONS QUESTIONS and then he points out that there’s ALSO been a correlation between the last century’s increase in temperatures and an increase in solar activity, to which he elsewhere attributes something like half of the century’s warming.
He’s been in a fight over this with Michael Lockwood (meteorology prof at the University of Reading) and Claus Froehlich (of the World Radiation Centre in Switzerland) who argue that solar outputs since the 80s have actually been at historic lows, while the warming effect has continued. Here’s the actual paper. And here’s a 2010 inter-disciplinary lit. review (well cited) substantiating the conclusion that solar variation falls short of accounting for recent temperature changes.
Shaviv responded to Lockwood and Froehlich’s findings in a memo published by a self-described “conservative” science blog called “Reference Frame,” but no where else that I can find.
As for ulterior motives, he apparently wrote to SourceWatch “if you’re looking for dark secrets about my funding…you’ll find none,” and it doesn’t appear that they have.
Conclusion: This guy’s got more cred than anyone yet, but his respected work doesn’t appear hugely relevant to the current climate situation, and his work that does relate to it seems not particularly respected in the scientific community, which begs the question — is this really the best they can do?
PS – I’ve asked r/AskScience if they can comment on his credibility within the scientific community on this subject. Will update if/when I get any good responses.
Updated: From “FormerlyTurnipHunter,” who is an expert in “Quantum Information/Quantum Computing/Quantum Optics”:
Not every skeptic or denialist is an outright crackpot. Some scientists do really think they found a different mechanism to explain global warming and they should be taken seriously.
However, these skeptics’ theories usually don’t hold up to even the most cursory scrutiny. This is also the case for Shaviv’s theory on cosmic rays. He is not the only one propagating cosmic rays as the main cause for warming btw., there’s also Svensmark.
Their physics is not completely wrong, their [sic] is definitely a link between cosmic rays and cloud cover, which in turn influences the climate. The problem however is that the cosmic ray theory can’t explain the warming over the last three decades, in which solar activity was decreasing.
So why would these scientists still hold on to their theories despite a lack of evidence? I don’t know, but I’m a scientist myself and I know how hard it is to let go of your ideas sometimes. Especially when there’s a big enough lobby happy to believe you and give you money to talk about this research of yours.
According to desmogblog, a great resource on climate denialism, Shaviv at least doesn’t deny anthropogenic warming completely, he just places our contribution at roughly 1/3 (its more like 3/4).
So instead of a paid denier like many others I would say he’s simply a mediocre scientist who won’t let go of a disproven theory.
