Monday, August 17, 2015

Global Warming Hiatus And Internal Natural Climate Variability

This is worth sharing. A short but useful explanation of the global warming "hiatus" and the natural variability of different atmosphere-ocean phenomenon that influence global mean surface temperature (GMST) trends.

From the article-
Every decade since the 1960s has been warmer than the one before, with 2000 to 2009 by far the warmest decade on record (see the figure). However, the role of human-induced climate change has been discounted by some, owing to a markedly reduced increase in global mean surface temperature (GMST) from 1998 through 2013, known as the hiatus (1–3). The upward trend has resumed in 2014, now the warmest year on record, with 2015 temperatures on course for another record-hot year. Although Earth's climate is undoubtedly warming, weather-related and internal natural climate variability can temporarily overwhelm global warming in any given year or even decade, especially locally.

And an excerpt about the role of the Pacific Decadal Oscillation-

There is also strong decadal variability in the Pacific Ocean, part of which is the Pacific Decadal Oscillation (PDO) (see the figure, panel B). The PDO is closely related to the Interdecadal Pacific Oscillation (IPO) but has more of a Northern Hemisphere focus. Observations and models show that the PDO is a key player in the two recent hiatus periods (2). Major changes in trade-winds, sea-level pressure, sea level, rainfall, and storm locations throughout the Pacific and Pacific-rim countries extend into the southern oceans and across the Arctic into the Atlantic (7–9). The wind changes alter ocean currents, ocean convection, and overturning, for example affecting the Atlantic Meridional Overturning Circulation (10). As a result, more heat is sequestered in the deep ocean during the negative phase of the PDO (1, 6, 9, 11, 12). GMST therefore increases during the positive phase of the PDO but stagnates during its negative phase (see the figure) (13).

more here..

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