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North America sees deep freeze, but the climate keeps warming

polar vortex

Chicago during the polar vortex, Creative Commons: Edward Stojakovic, 2014

Freezing weather conditions have gripped a large portion of the US and Canada this week, with temperatures reaching extreme lows such as -32° Fahrenheit (-35° Celsius) in North Dakota and -15° F (-26° C) in Minneapolis, Indianapolis and Chicago. At least 12 deaths are blamed on the unusually cold temperatures.

The cold weather this week in North America is no indication, however, that climate change has halted.

In fact, emerging research indicates that the cold snap may be yet another example of the ‘global weirding’ of weather caused by climate change and warming in the Arctic.

Abnormal conditions in the Arctic fueled by climate change could be wreaking havoc on the global weather system. Researchers have identified a weather pattern called ‘warm Arctic, cold continents’ that is a symptom of climate change.

A wind pattern known as the polar vortex circles the Arctic, keeping cold air locked at the pole. Sometimes, the pattern of the vortex is weakened and broken. When that happens, the cold air that normally circles the Arctic flows south, causing unusually low temperatures in the continents, including North America and Europe.

The polar vortex is weakened when the Arctic experiences unusually warm temperatures that disrupt its normal pattern. This has indeed been the case in recent years, as climate change has caused the Arctic to experience above-average temperatures and record breaking ice melt in the summer months over recent years. As the ice melts, the exposed ocean waters absorb additional heat. In the winter, the ocean releases that heat back into the atmosphere, causing the weakening of the polar vortex.

In fact, data from this past decade is beginning to show that when the Arctic sees high rates of ice melt in the summer, the normally steady circle of the polar vortex tends to be weakened during the following winter, and cold temperature events are more likely surge south.

While the causes and implications of a weakened polar vortex continue to be studied, the overwhelming weight of the data still shows very little doubt that the planet is warming due to human greenhouse gas emissions. Above all, the fact remains that climate change is measured across the entire planet, over the course of decades and centuries — and the science shows ‘unequivocally’ that the climate is warming because of rising emissions of greenhouse gases.

The unusually cold weather now hitting North America is part of a larger landscape of extreme weather around the world. It is accompanied by abnormally high temperatures across Alaska, Scandinavia and Russia. In the southern hemisphere, Australia is experiencing an intense heat wave just after it reported that 2013 was the hottest year on record for the nation.

Additionally, long-term weather patterns are more indicative of the rise in global temperatures — regardless of the weather on any given day.

Analysis by Climate Central shows that the number of extremely cold nights in US cities has steadily decreased since 1970, from Los Angeles to Detroit to Miami. Despite the deep freeze hitting this week, winters are in fact getting warmer in the US.

November 2013 was the 345th consecutive month with temperatures above the historic average. And based on early global calculations, 2013 is expected to rank among the 10 hottest years since 1850.

According to the World Meteorological Organization (WMO), the decade from 2001 to 2010 was the hottest decade ever since temperature measurements began.

As humans continue to pump greenhouse gases into the atmosphere, the unprecedented rise of global temperatures, and the extreme weather caused by it, continues unabated.  

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