Global Dimming

Last night, the ABC's Four Corners program broadcast a BBC Panorama documentary about a recently discovered phenomena called 'Global Dimming.'

No, this is not about the global intellectual decline since the right wingers took the political ascendancy. It's much more frightening than that.

'Global Dimming' is the gradual reduction over the past 50 years of sunlight reaching the earth due to atmospheric pollution. Apparently, man made particles in the atmosphere cause solar energy to be reflected away to space rather than warm the globe. Measurements have shown that light reaching the earth has declined by up to 20% in some regions.

In these circumstances you'd expect the world would be cooling. In fact, the opposite has happened, and the globe has become warmer due to increased carbon dioxide in the atmosphere.

The implications are that the calculated effect of extra carbon-dioxide in the air has been understated due to the effect of Global Dimming. As technology improves, the burning of fossil fuels now creates less particulate matter, lessening the cooling effect. Global warming may accelerate much faster than previously thought.

Instead of five degrees average increase in temperatures by the end of the century, it may be double that amount. Those levels would see the melting of the Greenland icecap, resulting in a five metre rise in sea levels, and the destruction of equatorial rain forrests.

The time window in which the world can act to prevent runaway global warming due to C02 emissions may be much shorter than previously calculated.