Ice Ages - some speculation

13 Jan 2011

At www.sciencebits.com/ice-ages there is an article by Nir Shaviv, a youngish scientist, if his picture is up to date, that has been making waves the past few years. He sees a connection between solar activity and the terrestrial climate as the solar wind varies in strength and effects the amount of cosmic rays reaching earth from outside the solar system. He maintains that cosmic rays dominate the troposheric ionisation process and therefore increased solar activity will relate into reduced ionisation - reducing low altitude cloud cover. These clouds have a cooling effect, he thinks, so less clouds = a warmer climate.

If this was so we should expect climatic variation as our solar system orbits within our galaxy, he says, for the simple reason the density of cosmic rays is not uniform. They tend to concentrate in the galactic spiral arms - as a result of the belief that supernovae, or dying stars, have a propensity to occur on the edges of the galaxy. The solar system, he seems to suggest, crosses a spiral arm every 135 million years (with a 25 million year give either way) and this coincides with the occurrence of Ice Age epochs on earth at about every 145 million years.

Now, Shaviv has suggested, and has been misquoted often he says, that we are nearing the end of the current Ice Age epoch - but we are not at the end he emphasises. The fact that he thinks cosmic rays might be the principle climate driver over the geological time-scale is upsetting for climate scientists who insist that it is C02. It would seem that in his hypothesis the recent warming trend, over a very short period of geological time, might also be attributable to increased solar activity which diminished the cosmic ray influx reaching the surface of the earth. Shaviv laments being misquoted once again, saying the recent warming trend has absolutely nothing to do with spiral arms. A short 30 year warming trend has its origins here in the solar system - not in outer space. Needless to say climate scientists have debunked his ideas and he is largely seen as a sceptic.