When the North Atlantic Caught a Chill - Surface cooling could have pushed down temperatures in the Northern Hemisphere 40 years ago.""The sudden cooling event [of 0.3 °C ] that Thompson and his colleagues report1 on page 444 of this issue [September 23] could help to solve a mystery: a prominent drop in the global mean surface temperature record around the same time. The ocean cooling, which may have resulted from a shift in currents, also offers a reminder of the North Atlantic's outsize role in climate."
Excellent background information is available in this text:
Atmosphere, ocean, and climate dynamics : an introductory text / John Marshall and R. Alan Plumb. Elsevier Academic Press, c2008. Science Library QC880.4.A8 A877 2007 [plus 7 other copies in OhioLINK]