Shaviv and Miskolczi

Nir’s 2005 paper “On climate response to changes in the cosmic ray flux and radiative budget”, available as pdf here, provides a solid case linking cosmic ray flux (CRF) variations to global climate change. The effect is consistent over hugely different timescales, using completely different indicators — from cosmic sources of CRF at the Phanerozoic, to the shortest time scale of the 11-yr solar cycle. The fit is extraordinary. The statistics competent. The bottom line?

Thus, anthropogenic sources alone contributed to a warming of 0.14 ± 0.36 K since the beginning of the 20th Century. Using our estimate, we find Tsolar = 0.47 ± 0.19 K. We therefore find that the combined solar and anthropogenic sources were responsible for an increase of 0.61 ± 0.42 K. This should be compared with the observed 0.57 ± 0.17 K increase in global surface temperature [IPCC, 2001].

In other words, changes in solar forcing, amplified by changes in cloud albedo due to CRF variations, account for a whopping 80% of the temperature increase seen since 1900. The rest, 20%, can be attributed to AGW.

I thought it would be interesting to see if Shaviv’s theory fits together with Miskolczi’s. Miskolczi’s is a theory of constant optical IR depth for the atmosphere, a consequence being that fluctuations in climate mostly come about through changes in solar forcing, i.e. short wave SW in, not effects of IR absorbers on long wave out. Even if you are not happy with all aspects of his theory, I want to look at it from the point of view of a theory explaining why IR absorbers like CO2 might not have as a strong an effect on global temperature as the IPCC scientists assert.

Shaviv explains that the CRF variations bring about changes in the % cover of low altitude clouds (LACC), changing the optical depth for both IR and SW. However, the effects are not equal.

This result is also reasonable considering that the total long wavelength heating effect of LACC was estimated to be 3.5Wm−2 [Hartmann et al., 1992], while cloud albedo is responsible for a globally averaged cooling of 20Wm−2, implying that changes in albedo will likely be more important for changing the radiative budget arising from LACC variations.

That is, by far the greatest effect of variations in LACC are on the SW, reflecting more sunlight away when cloud cover increases, thus shading and reducing the solar isolation at the surface. So while Miskolczi says global warming can’t be due to long wave variation, because the system optimizes for stability at that wavelength, Shaviv says there is a variation in solar input, amplified 5 to 7 times by cloud cover, and it explains temperature variation far better than GHG’s across all known time scales.

The two theories are both consistent and complementary, providing the strongest basis so far, for a natural and not human explanation for global warming.