Cosmic ray global warming debunked; deep ocean conveyors rethought

Paul Raven @ 18-05-2009

sun, clouds and seaOne of the more popular alternatives to anthropic global warming theories has been the cosmic ray hypothesis – the notion that changes in the sun’s output of cosmic rays are responsible for the planet’s recent changes in temperature. However, it’s always been short on evidence (much shorter than the theories it is intended to topple, funnily enough), and now new research has put another nail in its coffin lid:

In research published in Geophysical Research Letters, and highlighted in the May 1 edition of Science, Adams and Pierce report the first atmospheric simulations of changes in atmospheric ions and particle formation resulting from variations in the sun and cosmic rays. They find that changes in the concentration of particles that affect clouds are 100 times too small to affect the climate.

[…]

Despite remaining questions, Adams and Pierce feel confident that this hypothesis should be laid to rest. “No computer simulation of something as complex as the atmosphere will ever be perfect,” Adams said. “Proponents of the cosmic ray hypothesis will probably try to question these results, but the effect is so weak in our model that it is hard for us to see this basic result changing.”

As the researchers point out, these results are based on a computerised model of phenomena, and it could (and doubtless will) be asserted that it may not have any bearing on reality. In the absence of a model of similar complexity and expertise that supports the solar wind warming theory, however, I think I’m going to accept it as having been laid to rest. YMMV. [via DailyGalaxy]

While we’re talking about complex climate models, though, it looks like some rethinking will be required with respect to the ways in which deep-ocean circulation functions; experiments involving the dispersal of sensor-laden floats have revealed that a ‘conveyor belt’ of cold water flowing southward from the Labrador Sea doesn’t actually form a loop with the Gulf Stream as previously assumed.

I’d lying if I said I totally understood what this means (I’m not an oceanographer, nor do I play one on television), but what’s clear is that scientists aren’t just cherry-picking evidence that suits their models; they’re actively looking to improve the accuracy of their calculations all the time. Who’d have thought, eh? [via SlashDot; image by notsogoodphotography]

[Welcome back, JasperPants. ;)]


Study finds little solar link to cloud formation, not the driver of climate change?

Tomas Martin @ 03-04-2008

A pretty picture fo the sun, which doesn\'t look like it\'s causing global warmingTwo of the major criticisms of global warming theory I’ve seen recently have been that a) 1998 was actually the hottest year on record and since then it’s been cooler and b) that solar winds and cosmic rays are driving the climate change process, not human emissions.

These are valid points and scientists have been spending a lot of time researching their impact. Lancaster University have just released a major report on the latter, concluding from 20 years of data that global temperatures have little influence from solar activity. The original hypothesis, by Danish scientist Henrik Svensmark, hypothesized that when the 11 year cycle of solar wind is weak, more cosmic rays make it through the earth’s atmosphere, making more clouds and cooling the earth. Correspondingly, when solar wind is strong, Svensmark’s theory expected more global warming. However, with solar winds currently near their minimum, global temperatures are still high. The Lancaster study used three different experimental methods to find little correlation between the two, contradicting Svensmark’s theory, which was heavily cited in the documentary ‘The Great Global Warming Swindle’.

Related to this discussion is the citing of 1998, the hottest year on record, as proof that global temperatures are going down. This is a compelling argument on the surface but when you look at other global weather patterns the reason for the difference in numbers becomes apparent. 1998 was incredibly hot in main part because it was in an El Nino cycle, in which the warming of the Pacific Ocean disrupts weather patterns. Today however, we are in the midst of a significantly strong La Nina event, the sister condition that dampens global temperatures. This means that whilst it will still likely be in the top ten hottest years, 2008 will not be a very hot year, due to that effect.

Both the cosmic ray and 1998 hypotheses were picked up as proof that global warming doesn’t exist. These criticisms are important because by either disproving or proving them to be right, our understanding of this science improves. When the outlying criticisms of climate change are themselves shown to be lacking, the consensus grows stronger and vice versa. Like all cutting edge science, it’s a learning process.

UPDATE: you can read the Lancaster paper here, whilst some of Svensmark’s papers are available on his website, although I can’t find any after 2001.

[via BBC Science, picture by Feuillu]