A critique on Veizer’s Celestial Climate Driver

In a paper in Geoscience Canada, Veizer (2005) states that ‘the multitude of empirical observations favours celestial phenomena as the most important driver of terrestrial climate on most time scales‘. This paper was cited by a contributor to a debate on the website openDemocracy . In short, the argument is that the cosmic ray flux (CRF, also denoted as ‘GCR’ – galactic cosmic rays – in some papers) is the most important factor affecting our climate. Since this issue is likely to crop up from time to time, it is worth taking a closer look at the Veizer (2005) paper ( Here is a link to short summary, but the actual paper requires subscription). [Update: The actual paper is now available as supplemental material on the Geoscience Canada website.] I will try to show that CRF explanation for the recent global warming is easy to rule out.

One of the main planks of the argument that CRF is responsible for the most recent warming is based on figure 14b in Veizer (2005), where there appears to be a trend in CRF from eg Climax neutron monitor (also, see plots at this URL). This CRF-curve was a surprise to me, and furthermore, it’s at odds with CRF-evolution presented in figure 17 in the very same paper (showing no systematic change) – how can these accounts be so different? The inconsistency becomes even more apparent when it is argued that the ‘balloon and satellite data ([Veizer, 2005] Fig. 17) do not show any clear temperature trend… Instead, their interannual temperature oscillations correlate clearly with … CRF’ (p. 22, 2nd column). Again, no long-term trend in the CRF-data. It has been argued earlier on RealClimate that there is no long-term trend in the modern CRF measurements. The lack of systematic trends in CRF and other solar activity proxies is well-known and published in the scientific literature (eg. Richardson et al, 2002). In fact, the CRF curves presented by some of the key cosmic-ray hypothesis proponents, Marsh & Svensmark, do not exhibit any trend, yet it has been claimed that CRF is responsible for the most recent warming (Marsh & Svensmark say that the wiggles correlate, but don’t discuss the [or lack of] observed trends).

There are other aspects which appear as problematic for the CRF-interpretation for the recent global warming. First of all, according to IPCC (2001) the night-time temperatures have in general increased more than the day-time temperature (the diurnal temperature range, DTR, has decreased in most areas, except over middle Canada, and parts of southern Africa, south-west Asia, Europe, and the western tropical Pacific Islands). Since individual clouds have a life time of hours, and the CRF-interpretation involves changes in the reflected light as well as ionisation, a climatic response from change in CRF is hypothetically almost instantaneous, and it is a challenge to explain why the night side (where there is no sunlight and hence reflection cannot play a role) warms more strongly than the dayside, if the CRF were to drive the recent warming trend. Another equally important challenge is the fact that there are pronounced ~11-year variations in the CRF, but the presence of ~11-year variations in the global mean temperature are much less pronounced than the trend over the 3–4 most recent decades. If the CRF were so important (and the cloud response near-instantaneous) why do we not see more pronounced ~11-year variations in the global mean temperature?

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