Currently CO2 makes up about 390 parts per million of the atmosphere.
The assumption of the global warming alarmists has been that a doubling of CO2 from pre-industrial levels, from about 290 ppm to about 580 ppm, would drive the world over a ‘tipping point.’ So much heat would be captured, they claim, that the atmosphere would warm by as much as ten degrees, mass extinctions would occur, polar ice caps would melt, sea level would rise catastrophically, etc, etc.
These claims are made despite the fact that it is well established that the world has been through periods of very much higher CO2 than at present (over 1000 ppm) with no ill effects.
Now researchers Mark Pagani, Matthew Huber et al have shown that when the deep antarctic ice was formed some 34 milion years ago, atmospheric CO2 was about 600 ppm – well beyond the alarmists’ supposed polar ice melting tipping point:
By analysing ancient algae found in deep-sea core samples, Professor Matthew Huber and his colleagues determined that the mile-thick ice which now covers the south polar continent formed around 34 million years ago. At that stage the atmosphere held much more CO2 than it does now, some 600 parts per million (ppm) as opposed to today’s level of 390 ppm.
There is often concern that the Antarctic ice sheet might melt due to global warming (though in fact, despite much publicity over losses of ice from the Western peninsula, Antarctic ice has been steadily increasing in extent for the last 40 years). It would seem that this is highly unlikely given current and near-future levels of atmospheric CO2: at current rates of increase it will take a century at least to reach 600 ppm, the level at which the ice sheet formed itself, and higher levels would be needed to actually start it melting.