In a twist that deepens the complexities of the impacts of “global warming,” a new study featured in Science Magazine reports that the warmer-than-average summers it is causing may be linked to colder and more extreme winter weather in the Northern Hemisphere.

The general consensus among climate scientists is that global average temperatures have been rising since the 1800s, with more extreme warming evident in the past 40 years. However, winters in the Northern Hemisphere have actually become colder on average in some places, including southern Canada, the eastern US and northern Eurasia, for instance England’s record setting cold streak in December 2010.

The study, authored by Judah Cohen and colleagues, examines climate and weather data to estimate Eurasian snow cover, which they speculate may have been – and may continue to be – a trigger for colder and more extreme winters in the Northern Hemisphere.

Increased autumn snow cover in Eurasian regions such as Siberia, the authors say, could strengthen a semi-permanent high-pressure system that reinforces a climate phenomenon called the Arctic Oscillation, which steers frigid air southward to mid-latitude regions throughout the winter.

Rather than show a direct causal relationship between warm summers and colder winters, the study presents a compelling set of facts that will enable climate scientists to examine these trends in future studies. The researchers suggest that climate cycles such as the El Niño-Southern Oscillation do not accurately explain regional cooling trends experienced in the Northern Hemisphere over the past couple of decades.

In summary, by developing a better understanding of autumn snow cover variability and incorporating such data into climate models, scientists may be able to better predict winter weather forecasts in the Northern Hemisphere.

This data may also deepen our comprehension of the complex phenomenon of global warming, including the fact that it may be more helpful to refer to it by the term used by US President Barack Obama’s chief climate scientist John Holdren: “global climate disruption,” as people are less confused by weather extremes when it is framed this way.

ACT released its Climate Change Adaptation and Extreme Weather report in September 2009. The report, authored by Dr. Gordon McBean, comments that climate change adaptation in smaller communities will be more effective with access to current, downscaled climate modelling and monitoring. If autumn snow cover variability leads to regional cooling in parts of Canada, decision-makers can use this data to better prepare, protect and safeguard Canadian communities against the impacts of extreme weather.

Article created with ACT researcher Timothy Shah