The non-scientists among you may be aware of a climate science paper just published in the journal Nature. According to the popular press and broadcast media, this shows that the Sun’s role in global warming is possibly less than had been thought.
Journalists and information consumers must be very bored indeed if they feel the need to embellish good science in this way.
I say possibly, above, but of course this caveat hasn’t made its way into many of the mainstream media reports. The paper by Imperial College London physicist Joanna Haigh and others makes it perfectly clear that the conclusions are based on just three years of data, and this is not enough to draw firm conclusions.
If the subject interests you, then you can read Richard Black’s account on the BBC News website, or other of the more substantial reports out there in medialand. But what marks out even these relatively well-written pieces is the submersion of the science under a blanket of political comment. In the past 24 hours the entire spectrum of opinion from doom-monger environmentalists to nut-job climate deniers has weighed in on the work of Haigh et al., yet I suspect that few of these partisans have actually read the paper, or, indeed, have a genuine interest in the science.
So what is the science telling us?
The Sun works on a roughly 11-year cycle, and emits radiation at many wavelengths, including ultraviolet and the visible light apparent to our human senses. Different wavelengths work on the Earth’s atmosphere in different ways through complex chemical interactions, and the proportion of radiation emitted by the Sun in the various wavelength bands changes within and across solar cycles. From the limited dataset analysed by Haigh and her colleagues, we see that a fall in UV affects ozone concentrations in the upper atmosphere. But the observed drop in UV comes with a rise in visible radiation from the Sun, and the net effect is a warming of the lower atmosphere.
There is nothing controversial about this, nor is it “counter-intuitive”, as some have claimed, including the Nature press release writer. All it requires is that we grapple simultaneously with more than one cause-effect concept. What the new study shows is how the balance between visible and UV radiation changes within a solar cycle, and how important is it to account for this complexity in ‘radiative forcing’ within climate models used to predict future temperatures.
This is excellent science, yet within a day of its publication the science has been distorted for political ends. If there is just one thing you take with you from your reading of either the Nature paper or news media accounts of the work, it is this: the results tell us something about solar variations within an 11-year solar cycle. No claims are being made about secular (i.e., long-term) climate change, and the intention is to use the results to improve the accuracy of climate models by better accounting for shorter-term variations in UV and visible radiation from the Sun.
Haigh et al., “An influence of solar spectral variations on radiative forcing of climate”, Nature 467, 696 (2010)
Rolando R Garcia, “Solar surprise?”, Nature 467, 668 (2010)