Counter-intuitively, although the sun has been going through a period of decreased activity over the last few years, a new study in Nature claims that there’s been an increase in the amount of visible light and near-infrared energy:
New data indicates that changes in the Sun’s output of energy were a major factor in the global temperature increases seen in recent years. The research will be unwelcome among hardcore green activists, as it downplays the influence of human-driven carbon emissions.
As the Sun has shown decreased levels of activity during the past decade, it had been generally thought that it was warming the Earth less, not more. Thus, scientists considered that temperature rises seen in global databases must mean that human-caused greenhouse gas emissions — in particular of CO2 — must be exerting a powerful warming effect.
Now, however, boffins working at Imperial College in London (and one in Colorado) have analysed detailed sunlight readings taken from 2004 to 2007 by NASA’s Solar Radiation and Climate Experiment (SORCE) satellite. They found that although the Sun was putting out less energy overall than usual, in line with observations showing decreased sunspot activity, it actually emitted more in the key visible-light and near-infrared wavelengths.
These shorter wavelength forms of radiated heat penetrate the atmosphere particularly well to heat up the Earth’s surface — just as the same frequencies get in through car windows to heat up its interior. The hot seats and dashboard — in this case the seas, landmasses etc — then radiate their own increased warmth via conduction, convection and longer-wave infrared, which can’t escape the way the shortwave energy came in. This is why the car, and the planet, become so hot.
Thus the Sun, though it was unusually calm in the back half of the last decade, was actually warming the planet much more strongly than before.
If this research is confirmed, it certainly provides a lot of ammunition to the folks who don’t want to spend huge sums to try to cut down carbon emissions.
