“…the Planet acts a little bit like your own body. I mean in response to temperature. If your temperature goes up by three or four degrees you are getting into life-threatening stress. Five degrees you are probably dead, three-and-a-half you may be going into delirium. If your temperature drops by about two or three degrees, you are suffering hypothermia. You have a very narrow temperature scale within which to operate. Your body is very sensitive to small changes in temperature. So is the Planet. Just five degrees marks the difference between a mile and a half of ice over Ottawa and the bustling capital city we know today! Five degrees, that is all. So in that sense, global sensitivity to temperature change is extremely high.
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“We are not just doomed to go past the supposed 2 degree safety barrier, but we are already committed to over 6 degrees Centigrade warming – just with our current greenhouse gases in the atmosphere!
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“At present the CO2 concentration stands at 400 ppm. If it is thought to be safe to go up to 440 ppm, then we have a good budget to play with. There is still plenty of room in the sky-fill site. However, if we don’t use the inadequate computer models, and instead apply the real Earth System Sensitivity, then we were already committed to passing the 2°C ceiling when CO2 concentration stood at 334 ppm. That was back in 1978. We have already overspent the budget by a large amount!
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“National promises … concerning reduction in CO2 emissions, have been tabled ahead of the COP21 in Paris. Those promises look like pushing us to about 700 ppm by the end of the century (if they are implemented, and there is no guarantee about that whatsoever!). Business as usual is driving us up towards 800 or 900 ppm up here. If we cannot improve the level of promised emissions reduction, then “We might hit 4°C” predicts the IPCC using its low value for sensitivity.
“But if we use the full Earth System Sensitivity to examine the way the climate behaves at the level of 700 ppm. We are not looking at something around 4°C, but an increase of more like 10°C. That is twice the temperature shift between the ice ages and the pre-industrial benchmark. If we are not able to cut back on our current “business as usual” behaviour, then the temperature rise increases to more like 12 or even 15°C, (and two or three times that amount in the Arctic!) Good bye all the ice on earth. Welcome to something like 90 feet of sea level rise, or even more when all the Greenland ice-cap and the whole of the Antarctic ice sheet melts. Civilisation would have collapsed and we would have evacuated London and New York well before then!”
