Posted by Olive Heffernan on behalf of Quirin Schiermeier
The sun, despite claims to the contrary, is not a factor in recent climate change.
Nature had a news article last week about a paper – and the reactions to it – by Mike Lockwood and Claus Froehlich. Their comprehensive (and conclusive) (re)-analysis of solar trends concludes that the sum of natural changes in solar activity since 1985 would have cooled our climate, were it not for the strong warming effect of increased greenhouse gas concentrations.
That is surprising inasmuch the data are by not what you would call a scientific breakthrough. Indeed, most climate scientists will hardly consider the findings particularly new or surprising. Granted, bringing into line solar observations and measurements (and associated theories) collected during the 20th century is anything but trivial. But no matter how one looks at the issue, existing data were long supposed sufficient to disprove the only seemingly reasonable idea that global warming might be the natural result of increased solar activity.
Lockwood and Froehlich’s study does however go a step further. The two find that the correlation between solar activity and temperature trends post-1985 is actually negative. This means that changes to the sun (including cosmic ray intensity, for that matter) have contributed Less than Zero to the recent sharp rise in average global temperatures.
End of debate? Unfortunately no, I would guess. The inaptly so-named ‘climate sceptics’ who are keen to let mankind off the global warming hook, will not easily abandon this battle-tried warhorse. A natural sun-climate link, albeit invisible and unverifiable, is just the most persuasive among the set of quasi-plausible arguments with which upright eco-optimists attempt to dismiss as a (left-wing? anti-liberal?) conspiracy theory mankind’s responsibility for global warming. The ‘Great Global Warming Swindle’ documentary, to be aired tomorrow in Australia, is just the most-recent example of such attempts to argue that climate change is the effect of the sun.
To further confuse things and the public, solar changes do seem to have had an impact on past climates. Moreover, it is at least not impossible that cosmic ray intensity does influences clouds and climate. There’s nothing wrong with investigating these things – that’s how science goes. But blaming the sun for recent global warming is no science-backed position anymore – it is deliberate disinformation.