With all the stories about the record-breaking cold air, the unbelievably heavy snow in Buffalo, and other frigid weather conditions, it is not surprising that I have been asked where all this cold air is coming from, particularly so early in the winter season.  To answer this, you need to look at where the air is coming from.  The flow this year has brought us air that originated in the Siberian high plains region.  This year the region has seen record levels of snow and cold temperatures for so early in their winter.  The mass of air that has moved through the US Central Plains and down into the South formed above this record snowfall, creating a brutally cold and dry pool of air.  Often, as the air moves away from the area where it formed, it modifies as it passes over bare ground that is warmer and moister than Siberia.  This year, however, the extensive snow cover in North America has insulated the ground from interacting with the Siberian air mass, allowing it to move much farther south than usual with little modification.  The Northern Hemisphere snow and ice map below shows the extent of snow across both Asia and North America.

Source: US National Ice Center
Source: US National Ice Center

The weather pattern that has directed all this cold air to us is called an “omega block”, which takes its name from the shape of the air flow, which looks like the Greek letter Omega.  You can read about this weather pattern in this Slate article.  Slate also has a separate article which explains the relationship of the Omega block to the “Polar Vortex”, an often misused phrase that has been used by popular media outlets in recent years to describe cold outbreaks.

In spite of all the hype, the cold conditions this year do not prove that global warming is a hoax.  This is weather, not climate (see this Washington Post article).  Weather describes short-term atmospheric conditions, where climate describes long-term patterns.  Weather is like your mood; climate is like your personality.  Or like a smart 7th grade 4-H student once told me, climate is the clothes in your closet, but weather is what you put on today.  You can read a good commentary about this at the Washington Post (here).  In fact, if you use the Climate Reanalyzer web site at https://cci-reanalyzer.org/DailySummary/, you can see that even though we are in the deep freeze in the lower 48 states, Alaska is well above normal in temperature, and the earth as a whole is 0.4 degrees C above the 1979-2000 baseline.

 

Source: Climate Reanalyzer
Source: Climate Reanalyzer

The biggest question remaining is where the record-setting snowfall in Siberia came from.  Like many climate questions, it is hard to pin it on a specific set of causes.  Climatologists are looking at the impacts of less sea ice in the Arctic as well as the impact of several volcanic eruptions which have occurred in the last few months, potentially cooling the atmosphere through reflection of sunlight back to space.  But it will take time to unravel how this pattern set up.  In the meanwhile, warmer air should return for the next few days before the next cold blast enters the US.  Let the roller coaster continue!