This year’s polar vortex doesn’t disprove climate change, it’s another example of its extreme impacts
Next Generation Science Standards:
Key Vocabulary: Climate, air pressure, jet stream, temperature, weather, heat energy, positive-feedback loop
Just in time for Puxatawney Phil to make his prediction for the arrival of spring, the last full week of January has brought a polar vortex to the continental United States and with it the coldest temperatures of the year. Around 200 million Americans across the Midwest and have experienced absolutely brutal temperatures 20° to 40° F below average. Lows reached -6° in Detroit, -20° in Chicago and -30° in Minneapolis, without factoring in the wind chill. The US postal service has stopped delivering mail, thousands of flights have been delayed or canceled and power outages put anyone without electricity at the risk of frostbite and hypothermia.
The abnormally cold air in the US comes at a time of abnormal weather conditions across the world. At the same time some of the country’s biggest peddlers of misinformation have taken the opportunity to crow that cold weather in January disproves climate change, Australia is in the middle of a historic heat wave, with temperatures soaring past 118° F. 2018 was the 4th warmest year on record and recent extreme weather events from Hurricane Florence to the drought in Florida has more Americans than ever concerned about climate change. Which begs the question: what is causing the Polar Vortex in the middle of a global warming event?
What is the polar vortex?
The atmosphere above the surface of the Earth circulates based on the phenomenon that as air warms, it becomes less dense and rises in the atmosphere, where it then cools, becomes denser and sinks. Despite how weather can change, even drastically from day to day, these patterns are fairly constant. Since temperatures are coldest above the poles, the air here sinks, forming a high-pressure system and, like every other high-pressure system on Earth, it rotates.
This system of cold, dense air spinning around each end of the Earth is what meteorologists call the polar vortex. The strongest winds of the vortex are found at around 60 degrees latitude, where the cold air of the poles meets warmer air from closer to the equator. This border between continent-size masses air forms the jet stream, a narrow, fast-moving air current in the troposphere around 60,000 feet from the surface. This river of air acts as a border, keeping the frigid arctic air from moving towards the equator and its strength depends on the differences in temperature between the cold and warm systems. The greater the difference in temperature between the two air masses, the faster the air moves and the stronger the jet stream.
As you may imagine, the strength of the jet stream has a lot of influence on the weather patterns around the world. When a jet stream is strong and well defined, the bitter arctic air is contained at the poles. However, when the system weakens, the cold, bitter air cannot be contained and spills down into the lower latitudes. Meteorologists noticed a weakening of the jet stream several weeks ago. Since then, the mass of arctic air became disorganized, pushing the record-breaking, dangerously cold air southward. Things have gotten so cold that the Curiosity rover on Mars, a planet 50 million miles farther from the Sun, registered warmer temperatures than some parts of the Midwest.
The effects of climate change
While the strength of the jet stream fluctuates, both from year to year and from season to season, climate change is beginning to disrupt the system. As the entire planet warms, the Arctic is doing so at an accelerated rate. The sea ice that surrounds the North Pole becomes less dense each year, increasing the amount of heat energy absorbed by the surrounding water. This has formed a positive feedback loop – the Arctic has warmed a full 2° Celcius more than the rest of the globe.
Warmer water temperatures at the poles will weaken the high-pressure system and the jet stream that keeps cold air over the Arctic. If the polar vortex continues to weaken, it could allow for some of the coldest air on Earth to slip southward more often. We should expect cold temperatures in winter and no single weather event can give us a clear indication of any changes to our climate. But extreme and volatile weather events including this week’s polar vortex and the hurricanes, droughts, floods, and heat waves seen over the last few years line up with what researchers are forecasting for a warmer world.
The biggest risk posed by such low temperatures is frostbite, which can set in a matter of minutes in sub-freezing wind chills. If you are to go out of doors, dress in layers and limit the amount of skin exposed to the elements. Electric bills are likely to go up as extra electricity is used to keep homes warm. Not only is this expensive, but the extra demand can burden power generators, causing some to shut down when they are needed most. However, a cold snap this severe can be downright deadly for the elderly and homeless. Already 6 people have died to due the cold and nearly half a million people in the US are currently experiencing homelessness and not all will have access to services or shelters.
It seems that global warming may bring to the US some of the coldest weather on Earth.
A previous verison of this article said that the a low-pressure system forms at the poles, when in fact it is a high-pressure system. The correction has been made.