For many people, especially people in the South, the Arctic eruption that has gripped the country’s heartland over the past week is the kind of cold that occurs only once in a century. Countless record temperatures have been set. Conditions overwhelm the Texas Power Network, electricity cut off to millions and water pipes bursting, and ‘ humanitarian crisis.
But because climate change over the past decade has generally caused warmer winters and that global heat records exceed the past decade by 2 to 1, this historic cold momentum may seem counter-intuitive. It is not. In fact, paradoxically, a warmer climate has actually contributed to the extreme cold.
The science of meteorology has come a long way in the last few decades, so much so that meteorologists saw this extreme winter weather coming many weeks ahead of time. This is because this extreme pattern was caused by a large and recognizable phenomenon that unfolded in the Arctic at the beginning of the year, called Sudden Stratospheric Warming, or SSW.
CBS News saw an example of the wild winter weather here January 7 articlewhich explained how temperatures in the atmosphere high above the North Pole warmed by 100 degrees Fahrenheit during a few days in late December and early January – it jumped from minus 110 degrees Fahrenheit to minus 10.
SSWs are a natural occurrence that occurs every few winters and indicate extreme weather in subsequent weeks. This is because when the North Pole warms up rapidly, it disrupts a rotating mass of cold air – the polar vortex – a semi-permanent weather system that is present every winter.
Normally, the jet stream winds around the vortex and acts as a lasso of different kinds, holding the cold air inside. But as it gets warmer in the Arctic, the jet stream weakens and lengthens, allowing the cold air to subside south.
This allows a broad mountain of warm air to form over the North Pole, temporarily displacing the cold vortex. The warm mountain serves as an atmospheric block and directs the jet stream and bitterly cold air southward.
Although this bitterly cold air mass for the upper Midwest was certainly memorable, it was not entirely uncommon for them. The record set back in 1899 was much broader in the northern United States.
What made this particular situation historic was that the core of the cold air – a stretch of the polar vortex – plunged farther south than it ever did: a full 4,000 kilometers from its usual home near the North Pole.
As a result, hundreds of daily record lows were set in the south-central plains states over the past week. Dozens of records of all time were also set as the unprecedented cold gripped cities and towns that were not used to and unprepared for the bitter explosion. The animated loop below shows monthly records in dark blue dots and record colds in black dots.
It produced some amazing footage. A frozen waterfall in the Ozarks of Arkansas.
And frozen swamps in Louisiana.
This is despite a long-term trend in which winters across the US have become warmer and the cold has become less and less. In Minneapolis-St. Paul, for example, rose the coldest temperature of the year by 12.1 degrees Fahrenheit from 1970 to 2020.
The recent extreme weather was not only limited in the US. If the beam current in one region is extreme, it is often extremely extreme around the world. In Saudi Arabia, snow-covered camels provided a rare but not unheard of sight.
Snow also fell in Jerusalem and parts of Jordan and Syria, while record heat simultaneously affected other parts of the Middle East such as Iraq, where temperatures rose to 93 degrees in winter.
How to connect the extreme cold and the extreme heat
While this extreme cold coupled with extreme heat may seem strange, it is actually what meteorologists would expect from a wavy jet stream. Think of it this way: what goes up must come down. When the atmosphere forces cold air southward, there must be an equal and opposite reaction forcing warm air northward. When air masses are displaced to places they do not normally visit, the extreme weather and the effects it has on society follow.
A number of climate scientists believe that climate change may not only make sudden stratospheric warming more likely, but that climate change itself may have a similar effect in the Arctic, as it also causes significant warming. Due to human-caused climate change, the arctic area is getting warmer at three times the rate of the world average.
The undulating jet stream theory, as it relates to climate change, is pioneering work by Dr. Jennifer Francis by Woodwell Climate Research Center. The theory makes logical sense: Arctic warming reduces the gradient between hot and cold air and thus weakens the temperature contrast mechanism that drives the strength of the jet stream. This results in a weaker, more undulating jet stream, which is likely to spill its cold air southward.
The theory has since been accepted by many other climate scientists, who regard the seemingly increasing extremes, such as this latest bitter explosion, as a sign that the theory is deserving. But a significant group of other scientists doubt the impact of climate change and Arctic reinforcement on the jet stream.
This is partly because the atmosphere is very noisy and climate models are not yet able to reproduce the finer details of a complex system. It was therefore a challenge to find evidence to finally prove or disprove the theory. But many years of meteorologists believe that the logic, the research, and the qualitative evidence they observed are sufficient to make the case.
What all meteorologists and climate scientists can agree on is this extreme event triggered by a sudden stratospheric warming. That was the driving force.
For those who are tired of the cold and snow, good news: the extreme pattern seems to have almost run its course. The world will soon return to a more normal pattern. This does not rule out the outbreak of cold air and snowstorms for the US in the spring, but it should cause the weather to return to normal to some extent.