Global Warming Effects Of CO2 Could Be Less Than Foreseen By IPCC


According to the most accurate predictions on increasing CO2 levels and effects on the climate, published this week in Science, the Earth’s temperature will rise less than expected even if current levels of CO2 emissions continue.

The new prediction lowers the maximum increase in temperature from 4.5K to 2.6K, below that expected by the Intergovernmental Panel on Climate Change (IPCC), and discards the possibility of increases superior to 6K if CO2 levels in the atmosphere double in comparison to preindustrial levels.

Climate sensitivity measures how Earth’s surface temperature is affected by changes in the atmosphere. Scientists have developed models to calculate climate sensitivity in relation to an increase in CO2, i.e. to calculate how temperature would rise depending on the increase in CO2 concentration in the atmosphere.

According to the latest report by the Intergovernmental Panel on Climate Change (IPCC), if CO2 concentrations in the atmosphere doubled in relation to preindustrial levels, the temperature of the Earth’s surface would rise an average of 3K. This is a probabilistic estimation and scientists point out a 66% chance of a rise between 2 and 4.5K, and a not negligible chance of reaching a 6K increase. Nevertheless, scientists have not been able to narrow down this estimation in the past 32 years.

A research published this week in Science, in which UAB researcher Antoni Rosell took part, significantly reduces the temperature increase predicted by IPCC. According to the research, the average increase in temperature could be of 2.3K. It also shortens the difference between minimum and maximum temperature increase, with a 66% chance of it ranging from 1.7K to 2.6K and in no way reaching more than a 6K increase. The data is lower than that offered by the Intergovernmental Panel on Climate Change (IPCC) in its latest report in 2007.

Researchers arrived at these results by reconstructing temperatures from the Ice Age (21,000 years ago) using climate simulation models. The Ice Age is a very adequate climate period with which to make predictions on the effect of the rise of CO2 levels in the atmosphere and rises in temperature, given that concentrations of greenhouse gases were far lower than those found immediately before the preindustrial era (little over a century ago), and because surface temperatures and characteristics of the atmosphere at that period are well known thanks to palaeoclimate reconstructions.

According to the authors, “if climate restrictions 20,000 years ago can be applied to future predictions, as can be seen in the model, the probabilities of extreme climate changes in the near future are low compared to what was believed until now”. Nevertheless, scientists do emphasise the fact that global warming is real and that the increase in atmospheric CO2 will have important effects.

The research, which included the participation of Antoni Rosell, ICREA researcher of the UAB Institute for Environmental Science and Technology, was directed by researchers from Oregon State University, and included members of Princeton University, Harvard University, Cornell University, and University of Oregon. Funding for the research was provided by the US National Science Foundation.

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