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Cheers - AE

Thursday, 2 July 2009

Wandering lonely as a cloud.

There's a very interesting post at Watts Up With That about the alternative climate change theory of cloud cover being affected by cosmic rays. I came across this a few years ago and being interested in alternative theories I dropped a few quid on a book called The Chilling Stars by Henrik Svensmark and Nigel Calder. It covers Svensmark's theory pretty well, but it's very much written for the layman. Read the book for the full SP, but the very short version is that it's cooler if there are more clouds and warmer if there are fewer (which fits with the experience of anyone who's noticed the difference between a cloudless day in midsummer and a very overcast day around the same time), but clouds don't just form from nothing. Not easily at any rate. Something is needed to seed the cloud in the same way that raindrops form around a speck of dust or pearls form around something that's got into the shell of the oyster or mussel. Svensmark's theory is that one mechanism for providing this seed for cloud formation is cosmic rays coming through the atmosphere and smacking electrons off air molecules. These free electrons serve as seeds for tiny droplets of natural sulphuric acid to form around, and in turn the droplets of sulphur dioxide are seeds for drops of water vapour... and bingo, extra clouds. And, very importantly for the climate, cosmic rays aren't constant. One of the reasons for this is that the sun's magnetic field affects them, driving more away when it's strong and allowing more into the inner solar system when it weakens*. There's obviously more to it than that and of course the book goes into much more depth, not only of Svensmark's theory but also of how it was developed (just as interesting) and where it sometimes explains historical climate rather better than the man made CO2 theory.

Now despite it's appeal and plausibility it's still just a theory and could be wrong (which is also 100% applicable to the CO2 warming idea, though it's not often you'll find any of its supporters admitting that even as they attack opposing theories for the same thing). And as pointed out on WUWT the warming alarmists of the IPCC and Realclimate etc. claim it's been discredited, but for one thing they were never going to support a theory that would destroy their cosy world and the funding that flows into it, and for another they're not above supporting discredited theories themselves when it does support the cause (Hockey Stick anyone?). And a final point on that, did they actually wait for the theory to even be tested before screaming "discredited"? In my copy of The Chilling Stars (2007 edition) they'd only just begun the process of testing the idea experimentally. Yes, experiments, not computer models - wink wink. One proposed experiment, dubbed CLOUD (a crappy backronym**, but at least easy to remember), was to use a particle accelerator going through a specially constructed chamber as a man made, and presumably therefore controllable, stand in for cosmic rays, the idea being to fill the chamber with different mixtures of air, water vapour and H2SO4 and see if changes in the particle beam can affect the creation of cloud condensation nuclei. It had been hoped that CERN would run the experiment, but when they decided to build the Large Hadron Colliding Black Hole Creating World Squisher CERN didn't have the money to spare. Come back in a few years, they said. To kill time until CLOUD could be built (and they were talking about maybe getting some data in 2010) they designed a smaller scale experiment, small enough to fit in the basement of Danish National Space Centre in fact, that they could run in the meantime using the real cosmic rays that hit the planet all he time. This experiment, called SKY, got going towards the end of 2004. They got some interesting results and had to tweak the theory in places, but generally the results from SKY were positive. Certainly they were enough for CERN to come back to the CLOUD experiment after the LHC funding was taken care of. And that, as posted on Watts Up With That, is about where we are now. CLOUD06 has returned some "encouraging results", on the basis of which CERN have stumped up the money for a larger experiment they're calling CLOUD09. One thing it certainly won't do is prove the cosmic ray theory correct - they're only testing to see if they can increase cloud formation, not whether they actually do, and on top of that no experiment ever proves any theory beyond doubt since the possibility always exists that a rerun may produce results that will hole it massively below the waterline. But as I said before, that applies to man made CO2 theories as well, and it's just as possible that CLOUD or successor research will torpedo them instead.

If you've got the time go read the whole thing at WUWT as well as download the PDF at the bottom of the WUWT post. It's the slides for a presentation on the theory and the experiments, and it gives more background and depth than I have. Not as much as a good read through the book (2008 edition apparently has an extra chapter written more recently than the 07 edition on my shelf) or possibly a video of the presentation being made, but still worth flicking through.

*Which could explain why the Little Ice Age was accompanied by a largely spotless and relatively inactive sun. Fits anyway.
**Oh, if you insist. "Cosmics Leaving OUtdoor Droplets" apparently.
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