In my recent post called The UK Floods I mentioned some research work that seemed to point to sunspot activity and cosmic rays as being responsible in some measure for changes in climate. Now a BBC News item refutes that theory and places the blame for climate change firmly back on human activity. And while the sunspot/cosmic ray theory points to a possible dramatic cooling being on the cards, the BBC item favours good old global warming again.

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The Canadian National Post article I originally cited now has only restricted access (a subscription is required to view it), but I’ve found the article reprinted at martinfrost.wa. To briefly re-cap: it was written by R. Timothy Patterson, professor and director of the Ottawa-Carleton Geoscience Centre, Department of Earth Sciences, Carleton University. His research into the amount of fish scales and tiny animals found preserved in mud deposits in western Canadian fjords found striking correspondences with past changes in the output of the Sun and the strength of the Solar Wind, which in turn affected the amount of cosmic rays reaching the Earth from deep space. He claims that those variations precipitated periods of dramatic climate change here on Earth — and rather than a heating of the Earth being on the cards, Patterson warns that his mud cores indicate that a period of cooling is far more likely to be the next big event to strike us.

Now Richard Black of the BBC reports:

A new scientific study concludes that changes in the Sun’s output cannot be causing modern-day climate change. It shows that for the last 20 years, the Sun’s output has declined, yet temperatures on Earth have risen. It also shows that modern temperatures are not determined by the Sun’s effect on cosmic rays, as has been claimed. Writing in the Royal Society’s journal Proceedings A, the researchers say cosmic rays may have affected climate in the past, but not the present. “This should settle the debate,” said Mike Lockwood, from the UK’s Rutherford-Appleton Laboratory, who carried out the new analysis together with Claus Froehlich from the World Radiation Center in Switzerland.

The scientists’ main approach on this new analysis was simple: to look at solar output and cosmic ray intensity over the last 30-40 years, and compare those trends with the graph for global average surface temperature, which has risen by about 0.4C over the period. The Sun varies on a cycle of about 11 years between periods of high and low activity. But that cycle comes on top of longer-term trends; and most of the 20th Century saw a slight but steady increase in solar output. However, in about 1985, that trend appears to have reversed, with solar output declining. Yet this period has seen temperatures rise as fast as – if not faster than – any time during the previous 100 years.

“This paper re-enforces the fact that the warming in the last 20 to 40 years can’t have been caused by solar activity,” said Dr Piers Forster from Leeds University, a leading contributor to this year’s Intergovernmental Panel on Climate Change (IPCC) assessment of climate science.

The organisation was criticised by some for not taking into account the cosmic ray hypothesis. While the BBC News item doesn’t mention Patterson’s research into the mud deposits of western Canada, it does name Henrik Svensmark and Eigil Friis-Christensen of the Danish National Space Center. Their decade-long research on cosmic rays was explained in 2006 at Space Daily — but rather than getting down and dirty in the mud here on Earth, they’ve been looking at exploding stars deep in space and re-creating the resultant exotic cosmic particles in reaction chambers to observe their behaviour.

The BBC News item says that Mike Lockwood’s analysis appears to have put a large, probably fatal nail in this intriguing and elegant hypothesis.

Lockwood is quoted as saying: I do think there is a cosmic ray effect on cloud cover. It works in clean maritime air where there isn’t much else for water vapour to condense around. It might even have had a significant effect on pre-industrial climate; but you cannot apply it to what we’re seeing now, because we’re in a completely different ball game.

So it seems that, for the time being at least, we are firmly back in the frame as being the main cause of climate change. But will we ultimately experience global warming, or global cooling? Personally, I think the jury’s still out.

Our politicians need to know which one to prepare for, and soon — because spending whatever funds they allocate for our protection on the wrong outcome will surely be as utterly catastrophic as the event itself.

Read my Climate Change posts in chronological order by using the Climate Change Log.

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