Data provided on websites over the last few weeks seem to indicate that, as the Sun takes a rest during solar Cycle 24, UV Radiation has dropped by about 6%. I think this 6% is quite a drop, especially if you look and see that Total Solar Irradiance (TSI) only varies by between 0.05 to 0.1% over a Solar Cycle. This variation in TSI is thought to be too insignificant to affect climate, but what of the UV Decrease?
It’s well known that the majority of UVB and almost all UVC Radiation is absorbed by the upper atmosphere, mainly by ozone. But this radiation is, after absorption, re-emitted as black body radiation. Black body radiation is taken to be emitted in any direction, which means at least 50% is passed towards space, where it may be absorbed and re-emitted again.
Associated with this drop in UV is a decrease in the diameter of the atmosphere. NASA have said that satellites are experiencing less atmospheric drag when in low orbit (low orbit being between 120 and 200 Km above the surface). This means that there is less atmosphere, at the edges, to intercept UV.
So what if Carbon Dioxide is not the primary driver of climate variations? Perhaps UV plays a much larger role than previously thought. Perhaps, with a suitable lag due to the heatsink that is the oceans, we will see a much larger drop in Global temperature than is currently expected.
If you have any reliable data concerning the absorption and re-emission of UV in the upper atmosphere, I would appreciate seeing it