Ice Age theories warming up

Dedicated global warmers hoping that the solar magetic theory cannot possibly be right should look at Recently opposite directed trends in climate forcings and the global mean surface temperature (Proceedings of the Royal Society A, July 13, 2007) by Mike Lockwood, a physicist at the Rutherford Appleton laboratory (and strongly in the global warming camp) and Claus Frolich, of the word radiation centre in Davos, Switzerland.

Lockwood and Davos use the first two pages of their paper to acknowledge the mass of evidence for the influence of changes in the sun’s magnetic field on climate, including the key work of Gerard Bond of the Lamont-Doherty Earth Observatory of Colombia University and nine others which linked solar activity to changes in drift ice in the North Atlantic over thousands of years (Persistent Solar Influence on North Atlantic Climate During the Holocene, Science, December 7, 2001). After waving around a lot of graphs and numbers, however, the pair conclude that the link breaks down in 1985, with the implication being that the warming after that must be due to industrial gases.

That conclusion has been heavily challenged but we will not linger on that issue. The point is that solar magnetic fields affect climate. One other often cited piece of evidence is that of the depths of the little ice age (a cold period last centuries up to the 1850s) was associated with an absence of sun spots. The link may be deep indeed, as shown by an interesting although still speculative paper by Charles A. Perry, of the US Geological Survey, and Swiss scientist Kenneth J. Hsu - Geophysical, archaeological and historical evidence support a solar-output model for climate change (Proceedings of the National Academy of Sciences, November 7, 2000; available online).

The paper presents evidence of larger and longer cycles in the sun than just the 11 year basic sunspot cycle, and that the cycles fall into a noticeable pattern. The two scientists then extrapolate that work to suppose that there are 13 individual cycles, ranging from 11 years through to 90,000 years, or the length of an ice age.

Using the end of the last ice age as an anchor point, they combined all those cycles to give a pattern which follows the highlights of known climate history including the holocene maximum, medieval warm period and little ice age. No need to bother with orbital cycles at all. The warm periods are when one or more than one cycles are up, cold periods are when they are down. Far more importantly the analysis also forecasts a sharp fall in solar activity off a peak sometime after 2000, and that seems to have happened, albeit a few years later which is not bad considering the scale of the work. As has been widely reported the sun’s 11 cycle stopped mysteriously in 2007 with no sunpots for long periods and then only two or three. The spots are not building up into a peak. (A last check as this was being written showed none at all.)

Perry and Hsu’s work also indicates that the present intergalacial, which has proved so comfortable for humans, will last another 10,000 years with occasional bouts of colder climate which may happen from now thanks to the fall of in solar activity. Whatever affect industrial activity is supposed to have had on climate may well be swamped by natural cooling. Cannot possibly happen you say? We shall see.