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Sunday, 7 August 2011

Global Warming update: Arctic 'tipping point' may not be reached

OK, let's not beat about the bush, won't be reached. Danish scientists writing in Science magazine report that the extent of sea ice around Greenland was far less 5,000 years ago than it is today, and we didn't reach a tipping point whereby the absence of ice caused a loss of albedo and runaway climate conditions.

So if there was no runaway positive feedback 5,000 years ago, why should there be any runaway positive feedback now?  The simple answer is that there won't be.

The longer answer is that the amount of energy reaching the Arctic region is so small that it the loss of albedo from the melting of the ice is extremely unlikely to have any effect on global temperatures.  Think about it.  Any light (solar radiation) reaching the polar regions is coming in at a very shallow angle relative to the horizon and is thus relatively weak compared to the light at the equator.  Also it has to come through more atmosphere, so the amount of heating effect is very small.  That figures that is why it is so cold.

Also a lot of the heating effect at the North Pole is not due to solar effects.  The temperature at the poles is driven by the amount of radiant and convected energy lost into space less the amount of incoming radiation and the heating effect from below the surface.  Have you ever wondered why temperatures at the North Pole are higher than those at the South Pole?  Or why the North Pole can be ice free, but the South Pole never has bare rock?  Simple.  The North Pole lies in the Arctic Ocean where sea currents can transport heat faster than it travels through the geology of the South Pole.  So if we ignore the heating effect of Arctic Ocean currents we can hypothesize that the temperature at the North Pole would be about the same as the South Pole, which implies that the insolation has very little heating effect, so the effect of a little less albedo would be peanuts.

In other words, the temperature of  the North Pole is dominated by the temperature of sea currents not solar effects and the likelihood of any positive feedback is limited. And that is just common sense.

1 comment:

A K Haart said...

Great summary. It really is that simple.