Over many decades industry has released a huge quantity of aerosol particles that reflect incoming sunlight right around the planet's northern hemisphere. Consisting of a mixture of exhaust fumes, smoke and dust it reduces global warming by reflecting sunlight back into space and shields us from some of the sun's radiation.
This phenomenon is known as "global dimming". It can reduce heating locally by between 2-3°C. It has allowed us to continue business as usual by disguising the enormous impact we are having on the earth. Because the true impact of greenhouse gasses has not yet been felt, many scientists believe that we may already have passed the point of no return.
This dimming is transient stuff. It could disappear in a few days if there were an economic downturn or a reduction in fossil fuel use. This would leave us fully exposed to the heat of the global greenhouse.
The proof came when all airplanes were grounded for three days after the September 11 attack on the Twin Towers. Investigation found that temperatures then rose by 1.3°C due to the loss of aeroplane contrails.
As James Lovelock said, "we are in a fool's paradise, accidentally kept cool by smoke."
But if the glaciers melt or any other tipping point gets triggered, and life in industrial cities becomes untenable, there would be a severe industrial downturn. Then the aerosol would fall out of the atmosphere in a very short time, and the global temperature could take a sudden enormous leap upwards.
It was for this reason that Lovelock wrote The Revenge of Gaia and warned in The Independent that the world has already passed the point of no return for climate change, and that civilisation as we know it is now unlikely to survive. He suggests that efforts to counter global warming cannot succeed because we would be ambushed by global dimming. Therefore human society will probably face disaster to a worse extent, and on a faster timescale, than anybody realises.
He wrote "Before this century is over, billions of us will die, and the few breeding pairs of people that survive will be in the Arctic where the climate may remain tolerable."
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