December 31, 2010
By: Nick Engelfried
As many parts of the US gear up for what looks to be another cold and snowy winter, it seems counterintuitive to believe the planet is growing warmer. However the findings of climate scientists over the last couple years have shown that colder winters in parts of the North America, Europe, and Asia can actually be expected to occur partly as a consequence of climate change. Rather than undermining the scientific data in support of global warming, the harsh winter season facing many highly populated areas are more likely a preview of how climate change is re-shaping the world we live in.
The key to understanding colder winters in a time of global warming is realizing the overall warming of the planet will affect global weather patterns in strange and sometimes paradoxical ways. For example the winter of 2005 and ’06 was an exceptionally cold one for Japan and several eastern European countries. Yet globally 2005 was among the warmest years on record, and this may in fact have contributed to winter storms in these temperate regions. According to Japan’s Agency for Marine-Earth Science and Technology, relatively warm temperatures over the Arctic in 2005 caused northern wind patterns to shift, meaning cold Arctic air blew down into Japan and Europe and contributed to a colder winter.
Similarly as ice continues to melt in the Arctic, there is more liquid water available to evaporate and fall back on the Earth as precipitation. This has caused an increase in winter snowfall in Siberia—a vast area that affects global weather patterns. More white snow cover in Siberia means more heat is reflected back into space, causing a local cooling affect that again changes wind and weather patterns around the world. The growing cool patch above Siberia has been shown to impact the flow of the jet stream—one of the most important wind currents on the planet. Changing energy patterns in the atmosphere tip the jet stream in such a way that it blows Arctic air down into eastern North America and parts of Eurasia.
Meanwhile as climate change causes cold and snowy winters at a local level, the overall trend of global warming continues. The decade spanning the ten years from 2000 to 2009 was the warmest since record keeping began in 1880. In November the US National Oceanic and Atmospheric Administration reported 2010 is on-track to be the warmest year on record, and will certainly end up being counted as one of the top few warmest. A certain amount of year to year variation in temperature will always occur, but the overall trend toward increased warming due to human activities is clear.
So why are so many local impacts of changes in global weather patterns traced back to a warming Arctic? At least part of the reason is that the Arctic is feeling the effect of global warming much faster than most other parts of the world, with the result that dramatic changes in Arctic conditions reverberate throughout the globe. Climate scientists have long predicted the Arctic would warm faster than other parts of the planet as greenhouse gases continue to accumulate in the atmosphere. This is already happening, and scientists say the Arctic has warmed about two to three times faster than the rest of the planet.
The cold winter which many parts of the US are likely to experience this year is a reminder of just how complex global weather patterns are, and how changes in climate brought on by human activities can affect the planet in unexpected ways. If you find yourself kept home be stormy snow conditions this winter, just remember: these local weather condition may be traceable back to a melting Arctic, and a steadily warming Earth.
Photo credit: Michael Dolan