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March 27, 2018

Arctic Sea Ice Has Been Declining, But Maybe Not Why Critics Think

 

The New York Times reports, “Arctic Sea Ice Missed a Record Low This Winter. Barely.” 

Arctic sea ice grows in the winter and declines in the summer. The winter sea ice “maximums” and summer “minimums” have been on a gradual, though somewhat sporadic, decline since the 1990s. Many climate scientists and apparently nearly all media see that decline as a result of man-made global warming.  

Maybe, but multiple factors affect the climate, including major oscillations, which may have little or nothing to do with CO2 emissions. 

People may be familiar with the El Niño/La Niña pattern, known as the El Niño Southern Oscillation (ENSO). That’s the warming (El Niño) and cooling (La Niña) of the western equatorial Pacific Ocean that can have a big impact on U.S. weather, especially in the southern half. 

Surface waters will warm for a while and then transition to a neutral or cool phase and then reverse, referred to as “oscillations.” Climate scientists can track the changes, but they concede they don’t understand oscillations very well.  

The ENSO isn’t alone. Meet the Atlantic Multidecadal Oscillation (AMO) and the Pacific Decadal Oscillation (PDO). Large portions of the northern Atlantic and Pacific Oceans undergo periodic rising and falling temperatures and apparently have for millennia—without the help of humans. 

El Niños and La Niñas typically last nine to 12 months, though they can go on for years. 

By contrast, the PDO and AMO warm and cool phases tend to last much longer; 20 to 30 years for the PDO and 50 to 80 years for the AMO. 

As the two charts show, both the PDO and the AMO have been in a warm phase for some years, though the AMO may be transitioning into a cool phase again. 

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Could surrounding the Arctic with warm water for decades at a time have an impact on Arctic sea ice? And when the PDO and AMO return to a cool phase, could we see Arctic sea ice begin to grow again? 

I discussed this issue with a climate scientist who spends his life tracking the polar ice patterns. He responded, “Certainly there will be some [PDO] effect on sea ice, such as in the Bering Sea.  But that influence seems to be less pronounced than the effects of variability in the Arctic Oscillation (AO) and North Atlantic Oscillation (NAO) and something called the Arctic Dipole Anomaly.” 

His conclusion: “Short answer: We don't have all the answers yet, but it is clear that the sea ice is getting hit from both sides—from the top (warmer atmosphere) and the bottom (warmer ocean) and there is big variability from year to year linked to atmospheric (NAO, AO, PDO, DA) and oceanic circulation patterns.” 

The point is that the climate is very—VERY—complex. If the experts don’t have all the answers, be leery of media people (and politicians) who assert they do.


 

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