Michael Mann and Stefan Rahmstorf claim the Gulf Stream is slowing due to Greenland ice melt, except reality says otherwise
Anthony Watts / 1 day ago March 24, 2015
UPDATED – see below
From your “Day after Tomorrow” department (where a slowing Gulf Stream turned NYC into an icebox) comes this claim from the bowels of Mannian Science. Unfortunately, it looks to be of the caliber of Mann’s Hockey Schtick science.
As WUWT reported on a peer reviewed paper last year, H. Thomas Rossby says: URI oceanographer refutes claims that climate change is slowing pace of Gulf Stream saying in a paper published in Geophysical Research Letters:
“The ADCP measures currents at very high accuracy, and so through the repeat measurements we take year after year, we have a very powerful tool by which to monitor the strength of the current,” said Rossby. “There are variations of the current over time that are natural — and yes, we need to understand these better — but we find absolutely no evidence that suggests that the Gulf Stream is slowing down.”
Of course, Rahmstorf and Mann don’t list Rossby’s study in their references, nor seem to use the “highly accurate” ADCP data. Instead they use a model along with [proxies, reconstructions, and] the highly interpolated GISS data to come to the conclusions they want. So, it isn’t surprising they are chasing phantoms in their study. They claim (in Figure 1 from their paper) that this cold spot south of Greenland is caused by meltwater from Greenland and it is evidence of a slowed circulation:
ITS YOUR FAVORITE IMAGE RAT !!!!!
 Linear trends of surface temperature since AD 1901. Based on the temperature data of NASA GISS (ref. 48). a, Global equal area map (Hammer projection) for 1901–2013; white indicates insufficient data. b, Same analysis for the North Atlantic sector for 1901–2000. In addition to the observed temperature trends b also shows the grid points (black circles) of the subpolar-gyre region for which time series are shown in Figs 3 and 5, as well as the model-average 2 °C cooling contour (white) from a climate model intercomparison1 in which the models were subject to a strong AMOC reduction induced by adding a freshwater anomaly to the northern Atlantic. The geographic extent of the model-predicted temperature response to an AMOC reduction coincides well with the region of observed twentieth-century cooling. The models are forced more strongly and cooling extends further west as a result of shutting down Labrador Sea convection, which has only briefly happened in the real world so far. (Note that the second cooling patch in central Africa is in a region of poor data coverage and may be an artefact of data inhomogeneities.)
Rest here :
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