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2015-02-26. Cold Pacific Ocean is offsetting global warming.

posted Feb 28, 2015, 10:54 AM by Alan Gould
By Carolyn Gramling, Science. For GSS Climate Change chapter 7. Excerpt: ...Greenhouse gases, particularly carbon dioxide, continue to be pumped into the atmosphere, but sometime around 1998, the rise in Earth’s average temperatures slowed, deviating from the rates predicted by models. ...a new study suggests that natural cycles in the Pacific Ocean are the culprit. Since the end of last El Niño warming event of 1997 to 1998, the tropical Pacific Ocean has been in a relatively cool phase—strong enough to offset the warming created by greenhouse gas emissions. But, this is just a temporary balm: When the switch flips and the waters turn warm again, the researchers say, Earth will likely continue warming. “What this study addresses is what’s better described as a false pause, or slowdown,” rather than a hiatus in warming, says climate scientist Michael Mann of Pennsylvania State University, University Park. ...One of the biggest lingering issues in the global warming slowdown is the full impact of the natural temperature cycles of Earth’s oceans. The waters of the Pacific flip back and forth between warm and cool as part of a 16- to 20-year-long cycle known as the Pacific Decadal Oscillation. That oscillation includes the 3- to 7-year-long warm El Niño/cold La Niña cycle. Overprinted on that is a longer term oscillation of sea surface temperatures in the Pacific, a cycle that lasts perhaps 50 to 70 years. Similarly, in the Atlantic, sea surface temperatures go through a long-term natural cycle (the Atlantic Multidecadal Oscillation) that lasts about 50 to 70 years. ...Since the late 1990s, the Pacific Decadal Oscillation has been in a cool phase....  http://news.sciencemag.org/climate/2015/02/cold-pacific-ocean-offsetting-global-warming.