"This could be the start of another ramping up of warming."

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Known as the Pacific Decadal Oscillation, the El Nino-like pattern typically lasts 15-30 years and is understood to operate as an accelerator on global surface temperatures during its positive phase – and a brake during its negative phase – as the ocean takes up fluctuating amounts of the extra heat being trapped by rising greenhouse gas emissions.
"It certainly could be an early sign of a change but you'd probably want to see another year or two before it's a genuine phase shift," Matthew England, a professor at the University of NSW's Climate Change Research Centre, said. "This could be the start of another ramping up of warming." 

The last positive phase of the PDO, also known as the Interdecadal Pacific Oscillation, ran from about 1978 to 1998, a period of a rapid increase of surface temperatures. Since then, temperature increases have flattened out, despite an increase in greenhouse gases, as oceans have taken up more of the excess heat. 

Even with the negative-PDO drag - worth about 0.2 degrees in global average air temperatures a decade - 2005 and 2010 both topped the 1998 record annual global temperatures. The first 11 months of 2014 were the warmest on record and with ocean temperatures remaining exceptionally warm, this year is very likely to set a fresh high, according to NOAA, the Bureau of Meteorology and other agencies. 

In positive-PDO periods, the tropical Pacific is relatively warm and north of about 20 degrees latitude, it should be cool, said Shayne McGregor, a UNSW research fellow, said: "It's definitely consistent with what we've seen in tropics."

(SMH)