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Warming and Cooling in the Bay of Biscay
deCastro, M., Gomez-Gesteira, M., Alvarez, I. and Gesteira, J.L.G. 2009. Present warming within the context of cooling-warming cycles observed since 1854 in the Bay of Biscay. Continental Shelf Research 29: 1053-1059.

What was done
The authors employed two different sea surface temperature (SST) datasets to reconstruct the SST history of the Bay Biscay for the period 1854-2007: an extended reconstructed SST history obtained from NOAA/OAR/ESRL PSD of Boulder, Colorado, USA, for the period 1854-1997, and weekly mean SST data obtained from nighttime measurements made by Advanced Very-High Resolution Radiometers onboard NOAA satellites for the period 1985-2006. This work was done, in their words, in order "to put the intensity of the present warming trend within the context of the last two centuries."

What was learned
DeCastro et al. report that "two consecutive warming-cooling cycles were detected during the period 1854-2007: cooling from 1867 to 1910 (-0.14C per decade); warming from 1910 to 1945 (0.17C per decade); cooling from 1945 to 1974 (-0.10C per decade); and warming from 1974 to 2007 (0.22C per decade)."

What it means
In discussing their results, the four Spanish scientists state that "the present warming period (1974-2007) is on the same order of magnitude although slightly more intense than the one observed from 1910 to 1945." However, they conclude that "this fact does not permit elucidating the possible anthropogenic influence on the present day warming, which still remains an open question." This conclusion, in their words, "is consistent with the analysis carried out by Hodson et al. (2008) for the North Atlantic," who also concluded that "current 'warm era conditions' do not eclipse prior 'warm' conditions during the instrumental record," and that, with respect to sea surface temperature, "the North Atlantic remains within the envelope of previous recorded conditions."

Hobson, V.J., McMahon, C.R., Richardson, A. and Hays, G.C. 2008. Ocean surface warming: The North Atlantic remains within the envelope of previous recorded conditions. Deep-Sea Research I 55: 155-162.

Reviewed 23 September 2009