Ottawa and other cities in eastern Canada have been experiencing abnormally cold temperatures this past week. Last Wednesday was the coldest day in 8 years dropping down to a downright bone-chilling -30 degrees C. Meanwhile Britain is suffering through some of it’s worst winter snow storms in years. How can this be happening when climate scientists tell us the world is warming?
The first thing to remember is that there is a difference between climate and weather. What we are interested in are long-term trends not isolated weather events. And the long term trends are clear. The last decade saw average global temperatures that were the warmest ever recorded. 2012 was the warmest ever in the continental U.S. Extreme weather such as drought, heat waves, flooding and wildfires are also on the rise. Then there is the Arctic ice cap, which shrank to it’s smallest size ever recorded this past summer.
Second, as it turns out, the recent spate of cold weather may very well be related to climate change. Here’s how: by changing the temperature balance between the Arctic and mid-latitudes, rapid Arctic warming is altering the course of the jet stream, which steers weather systems from west to east around the hemisphere. The Arctic has been warming about twice as fast as the rest of the Northern Hemisphere, due to a combination of human emissions of greenhouse gases and unique feedbacks built into the Arctic climate system.
A recent study, by Jennifer Francis of Rutgers University and Stephen Vavrus of the University of Wisconsin-Madison, ties rapid Arctic climate change to high-impact, extreme weather events in the U.S. and Europe. The jet stream, the study says, is becoming “wavier,” with steeper troughs and higher ridges. Weather systems are progressing more slowly, raising the chances for long-duration extreme events, like droughts, floods, and heat waves.
“[The] tendency for weather to hang around longer is going to favor extreme weather conditions that are related to persistent weather patterns,” said Francis, the study’s lead author.
Check out the video above to see a visual depiction of how the jet stream works and how it is being altered by human-caused climate change.