Dr Andrew Glikson, Earth and paleo-climate scientist at the Australian National University, writes: As predicted by the IPCC-2001 report, global warming trends tracking toward 2100 are likely to be expressed by an increase in weather variability. Expect these to include a series of heat waves, fires, floods, hurricanes and cold fronts, the consequence of an increase in the energy level (temperature) of the atmosphere/ocean system:
For the uninitiated, the weather and the climate are not to be confused. Weather events comprise transient and regional variations in atmospheric conditions on a scale of a few days to few weeks, whereas climate trends occur on a global multi-annual to decade-long time scales.
The effects of global warming, at a mean of +0.8 degrees C since the early 20th century but +4 to +5 degrees C in the polar regions, include enhanced collision of warm and cold air masses, which can perpetrate snow storms. The current North Atlantic freeze is no exception.
As displayed in NASA’s November 2010 global temperature map, the freezing of western Europe and northeast America are contrasted with an overall warming of Canada and Siberia. Those areas have warmed by more than +4 degrees C relative to the 1951-1980 baseline, the factor which underlies the rapid melting of Arctic sea ice and the Greenland ice cap. Does this look like global cooling?
In the North Atlantic wind patterns and storm tracks are affected by the North Atlantic Oscillation (NAO) and the Arctic Oscillation (AO). The NAO is controlled by the Azores High (descending dry air) and the Iceland Low (rising moist air). The AO represents the changing relations between the Arctic High and mid-latitude Highs. When the NAO polarity weakens cold Arctic fronts penetrate the North Atlantic.
According to Petoukhov and Semenov (2010) of the Potsdam Institute of Climate Impact, advanced melting of the eastern Arctic sea ice:
“… causes some regional heating of the lower levels of air – which may lead to strong anomalies in atmospheric airstreams, triggering an overall cooling of the northern continents… These anomalies could triple the probability of cold winter extremes in Europe and northern Asia”.
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These authors further state:
“Our simulations reveal a rather pronounced nonlinear response of air temperatures and winds to the changes of sea-ice cover” and “It ranges from warming to cooling to warming again, as sea ice decreases. An abrupt transition between different regimes of the atmospheric circulation in the sub-polar and polar regions may be very likely. Warming of the air over the Barents-Kara Sea seems to bring cold winter winds to Europe.”
The increase in extreme weather patterns is represented on a plot of the NAO index versus time (the lower the index the greater the opportunity for Arctic fronts to penetrate the Atlantic Ocean). Note the onset of extreme warm and freezing weather events in 1970 and 2010:
It is not clear whether the decreased polarity between the Azores High and the Iceland Low may also be related to a weakening of the North Atlantic Thermohaline Current (NATC), emanating from the Gulf Stream. If and when the NATC collapses, the North Atlantic would undergo longer term cooling, while the continents continue to warm, a development compared perhaps to the Holocene Optimum (8500 years ago) or to the Younger Dryas (12,900 years ago).
Inherently individual extreme weather events are difficult to relate to longer term climate trends. However the temporal increase in floods and cyclones and in the temporal increase in the amplitude of the NAO tell a story. Similar trends appear to hold regarding the frequency and intensity of heat waves and fires and of floods, which may include the recent flooding in Australia, as a consequence of increased evaporation in the oceans.
As stated by Dr. Nathan Lewis, Professor of Chemistry, California Institute of Technology:
“You see the Earth has a 35 year thermal inertia and so what we’re doing now is only the beginning because we’re waiting 35 years even to see the effects of what we did 35 years ago. So it would be another 30 years until we started to really see, even at the only 380 parts per million level [of C02-e atmospheric concentration] that we’re doing now, what those effects are. And we’ll be at 550 [parts per million of C02-e concentration] by then — or more — and it’s never been above 300. So there’s a serious debate over whether that will be very bad or not, very bad, but all we know is no matter what we do when we get there there’s no turning back.”