Thursday, 20 September 2012

A partial vindication

The following comes from a press release from the University of Reading (UK). "Natural climate variations could explain up to 30% of the loss in Arctic sea ice since the 1970s, scientists have found. "Sea ice coverage at the North Pole has shrunk dramatically over the past 40 years. The ice is now more than a third smaller each September following the summer melt than it was in the 1970s. This affects wildlife, while potentially opening up new northern sea routes and controversial opportunities for oil and gas exploration. "Scientists at the University of Reading and the Japan Agency for Marine Earth Science and Technology (JAMSTEC) have found that some of the reduction in ice since 1979 - between 5% and 30% - may be linked to the Atlantic Multi-decadal Oscillation (AMO), a cycle of warming and cooling in the North Atlantic, which repeats every 65-80 years and has been in a warming phase since the mid 1970s." In my previous post "Climate and The Atlantic Multidecadal Oscillation" I argued that around 50% of the increase in temperature from the mid 1970s to around 2005 was due to the effect of the AMO. The researchers suggest that from 5 to 30% on the loss of Arctic Ice was also due to the AMO. My conjecture and their conclusions are compatible. What is important is the implication for the accuracy of climate models. AOGCMs do not represent the AMO and assume that virtually all warming comes from GHGs (plus a little bit from solar irradiance). So, both the findings of the University of Reading researchers and my model point to the same conclusion: AOGCMS overestimate the effect of GHGs.

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