Another day, another depressing “it’s worse than we thought” story…
Green Car Congress: New MIT Analysis Finds Global Warming Could Be Double Previous Estimates:
A new comprehensive MIT study of the probabilistic projections of climate change in this century found that absent aggressive intervention, warming will likely be about twice as severe as previously estimated by the MIT model six years ago.
The new projections, published this month in the American Meteorological Society’s Journal of Climate, indicate a median probability of surface warming of 5.2 °C by 2100, with a 90% probability range of 3.5 to 7.4 degrees. This can be compared to a median projected increase in the 2003 study of 2.4 degrees.
However, if recently published data, suggesting stronger 20th century ocean warming, are used to determine the input climate parameters, the median projected warning at the end of the 21st century is only 4.1 °C. Nevertheless all our simulations have a much smaller probability of warming less than 2.4°C, than implied by the lower bound of the IPCC AR4 projected likely range for the A1FI scenario, which has forcing very similar to our median projection.
-Sokolov et al. (2009)The difference is caused by several factors rather than any single big change. Among these are improved economic modeling and newer economic data showing less chance of low emissions than had been projected in the earlier scenarios. Other changes include accounting for the past masking of underlying warming by the cooling induced by 20th century volcanoes, and for emissions of soot, which can add to the warming effect. In addition, measurements of deep ocean temperature rises, which enable estimates of how fast heat and carbon dioxide are removed from the atmosphere and transferred to the ocean depths, imply lower transfer rates than previously estimated.
See MIT’s press release, “Climate change odds much worse than thought”
