by Robert Maynard
In the past several articles have been posted here at True North Reports indicating that factors such as sun activity may be more decisive drivers of climate change than human generated CO2 and that the magnitude of the change predicted has been grossly overestimated. Now even the Intergovernmental Panel on Climate Change is in the process of scaling back the substance of their predictions, if not the hysteria in their rhetoric. Here is an excerpt for an article that appeared in The Economist:
“THAT report is going to scare the wits out of everyone,” said Yvo de Boer recently. He is a former United Nations chief climate negotiator and was talking about the forthcoming fifth assessment by the Intergovernmental Panel on Climate Change (IPCC). With two months to go before the assessment is to be published, however, one sign suggests it might be less terrifying than it could have been.
The sign in question is about climate sensitivity. This is the measure used by researchers of how much they expect the world’s average temperature to increase in response to particular increases in levels of carbon dioxide in the atmosphere. According to one table from the unpublished report, which was seen by The Economist (above), at CO2 concentrations of between 425 parts per million and 485 ppm, temperatures in 2100 would be 1.3-1.7°C above their pre-industrial levels. That seems lower than the IPCC’s previous assessment, made in 2007. Then, it thought concentrations of 445-490 ppm were likely to result in a rise in temperature of 2.0-2.4°C.
The two findings are not strictly comparable. The 2007 report talks about equilibrium temperatures in the very long term (over centuries); the forthcoming one talks about them in 2100. But the practical distinction would not be great so long as concentrations of CO2 and other greenhouse-gas emissions were stable or falling by 2100. It is clear that some IPCC scientists think the projected rise in CO2 levels might not have such a big warming effect as was once thought.