Climate Change – News and Comments
An active Sun cools the world? How daft!
Valiant efforts of British physicists to deny that the Sun is important in climate change have always been good for a laugh. Names like Mike Lockwood and Arnold Wolfendale spring to mind. But with what she’s published in today’s Nature a professor at Imperial College London, Joanna Haigh, wins the my Gag of the Year prize.
The 200-year-old problem for solar-terrestrial physicists is to explain why the historical record shows strong and persistent links between solar activity and climate change over decades, centuries and millennia. Variations in visible light won’t do the job. The only mechanism powerful enough is Svensmark’s hypothesis about cosmic rays governing low cloud cover – see http://calderup.wordpress.com/category/3b-the-svensmark-hypothesis/ .
Haigh has never gone along with Svensmark, preferring instead to focus on ultraviolet light from the Sun, which does vary more than the visible light, and generally to minimize solar effects on climate. But in her new paper she offers to tear everything up and scatter it to the wind, because a satellite measured an increase in the intensity of visible light between 2004 and 2007, when solar activity was in decline. From the paper:
Daily measurements of the solar spectrum between 0.2 mm and 2.4 mm, made by the Spectral Irradiance Monitor (SIM) instrument on the Solar Radiation and Climate Experiment (SORCE) satellite3 since April 2004, have revealed that over this declining phase of the solar cycle there was a four to six times larger decline in ultraviolet than would have been predicted on the basis of our previous understanding. This reduction was partially compensated in the total solar output by an increase in radiation at visible wavelengths.
As summarized in an ICL press release:
The researchers used satellite data and computer modelling to analyse how the spectrum of radiation and the amount of energy from the Sun has been changing since 2004. Instruments on the SORCE satellite have been measuring the Sun’s energy output at many different wavelengths. The researchers fed the data from SORCE into an existing computer model of the Earth’s atmosphere and compared their results with the results obtained using earlier, less comprehensive, data on the solar spectrum.
And the implications?
Overall solar activity has been increasing over the past century, so the researchers believe it is possible that during this period, the Sun has been contributing a small cooling effect, rather than a small warming effect as had previously been thought.
Let’s say that the satellite results are surprising, but as they concern solar irradiance and not variations in cosmic rays, there’s no reason to expect a big climatic impact. And Haigh’s wish to invert the active Sun’s influence from positive to negative does nothing to explain all the historical data on solar activity and climate change, going back to William Herschel, 1801, and the link between sunspots and the price of wheat.
And I’m afraid that just as Al Gore had to share his Nobel Prize with the Pachauri Gang, Haigh must split my award of three raspberries with the editors of Nature and with the BBC’s environmental team.
Suppose someone offered to Nature a paper saying, “We’ve got three years of satellite data here and a computer model suggesting that an increase in carbon dioxide in the atmosphere cools the world.” Would Nature publish it? Would the BBC greet it with enthusiasm and carry the remark on its website, “The view that carbon dioxide may be driving modern-day climate change has clouded policy discussions”?
You may doubt it, yet the doughty Richard Black of the BBC, who has made a career of rubbishing the solar contribution to climate change, uses the flimsy Haigh report to try to put the knife in once again: “The view that the Sun may be driving modern-day climate change has clouded policy discussions.”
J.D. Haigh et al. “An influence of solar spectral variations on radiative forcing of climate” Nature, 467, 696 ff., 7 October 2010
ICL press release: http://www.alphagalileo.org/ViewItem.aspx?ItemId=86915&CultureCode=en
BBC website item by Richard Black: http://www.bbc.co.uk/news/science-environment-11480916