A new Intergovernmental Panel on Climate Change (IPCC) report was released on Friday, and it’s more confident than ever the climate change is mainly being caused by human activity.
Since the previous report in 2007, the IPCC has raised the probability that human activities, largely the constant burning of fossil fuels, have been the chief cause of global warming since the middle of last century. The term “extremely likely” has been used for the first time, which means at least 95% probability, up from “very likely”, or 90%, in the previous report. The new probability rating means that scientists are as confident that humans are causing climate change as they are that smoking causes cancer. Pretty, damn, confident. And let’s not forget that the IPCC is very cautious in its published findings.
The IPCC said that humans have now emitted more than half the 1 trillion tonne “carbon budget” scientists have estimated to be the maximum to keep global warming to the “safe” level of under 2 degrees celsius.
In terms of projected warming this century, the IPPC says that a doubling of CO2 concentrations in the air would lead to global warming of between 1.5 and 4.5 degrees. The lowest number is lower than the 2 degrees projected in 2007, but the new range is the same as the reports released before 2007. New, more advanced computer models have been used and do not directly compare with earlier models from more than a decade ago.
The panel also says that sea levels are likely to rise by between 26 and 82 cm by late this century, which is higher than the 18 to 59cm projected back in 2001. Melting in Greenland and Antarctica was not fully accounted for in previous projections. The worst case projection is that sea levels could rise by 98cm by 2100.
U.N. Secretary-General Ban Ki-moon has said that the study should be yet another call-to-action for governments around the world, especially in relation to reaching the planned and long-awaited U.N. climate accord in 2015.
The last word should go to climate scientist Michael Mann, Director of the Earth Systems Science Center at Penn State, who has said when asked for a headline about the report, “Jury In: Climate Change Real, Caused by Us, and a Threat We Must Deal With”.
Image: IPCC Working Group. Global average surface temperature change to date in degrees Celsius.