Mild temperatures, cold rain, and snowless sidewalks have characterized winter in Toronto this time around. So far.
Consultation with a calendar reveals that Groundhog Day falls very near the precise midway point between the winter solstice and the spring equinox. Strange, then, that the day is supposed to herald—depending on the relative shyness of a few arbitrarily chosen and unwitting rodents—the early onset of spring.
This year, regardless of the mixed verdicts returned Wiarton, Ontario; Punxsutawney, Pennsylvania; and Shubenacadie, Nova Scotia this morning, residents of Toronto can be forgiven for wondering when exactly their winter will be arriving.
As of January 31, just 25.4 cm of snow had fallen on Toronto this winter, barely a third of the 68.4 cm we’ve usually seen by that time. On 12 separate occasions this season, the temperature has not cracked the freezing mark all day, while temperatures had dropped below freezing 42 times by this point last year. And the average temperature in the city last month was more than four degrees warmer than a normal January.
If this season does have something to show, it is running out of time to show it.
“There have been winters that have been milder but they had more snow. You’ve had winters that have [had] less snow but they were colder,” says David Phillips, senior climatologist for Environment Canada. “But when you really describe the full effect of winter and the look and the shape of winter,” he continues, “in many ways this one stands alone.”
Things have been so balmy, Phillips says, because the jet stream which separates warm air in the south from cold air in the north is in an unusual position for this time of year. Instead of meandering, as it tends to do in the winter, as far south as Texas and Tennessee, it is running straight across the continent at a far more northerly latitude, Phillips says, “like a ribbon stretched from British Columbia to Labrador.”
The jet stream is under the influence of something called Arctic oscillation, a phenomenon which is exactly what it sounds like. High pressure in the Arctic allows cold air to push the jet stream south (called a negative oscillation), while high pressure in the mid-latitudes can keep Arctic air at bay (a positive oscillation), as is happening now.
“What is weather?” Phillips answers his own question, to illustrate why the jet stream’s position also explains our lack of snow: “Weather is when the warm air dukes it out with the cold air.” The jet stream’s expected, snaking path across the continent ordinarily provides for plenty of conflict between those two combatants. Not so this year. “The fact that we’re not seeing this thrust northward, and this dipping southward, is the reason why we’re also seeing less precipitation,” he says.
But this explanation raises other questions. Sandi Duncan, of Farmers’ Almanac—whose lone prognosticator (known by the pseudonym Caleb Weatherbee) uses a nearly 200-year-old mathematical and astronomical formula to make his annual weather predictions—also cites Arctic oscillation as being behind the season’s aberrant weather.
But she is at a loss to explain why that oscillation is positive this year.
“Mother Nature does like to throw curveballs every once in a while,” Duncan says. “I think weather is one of those unknowns that, even as far advanced as we get, we may not be able to figure out the exact whys and hows.”
Phillips is also stumped. “It’s easy to describe what we’re getting,” he says. “It’s not easy to say why we’re getting it.”
But he believes there is a strong possibility that what we are seeing this winter, and with unstable weather here in general, is a consequence of global warming and melting Arctic ice. “There’s no normal weather anymore; it’s one extreme to the other,” he says. [Arctic ice] is one of the major climate controls of this planet … The Arctic ice is the refrigerant of the world. And when it disappears, when it’s thinner, [with] less volume, when it’s [a] smaller area, then you should expect profound changes to our weather. And I think we’re seeing that.”
Whatever the reasons for the weather until now, both Duncan and Phillips caution that plenty of this winter still remains in store, and it may well bring with it cold and storms. “Don’t give up on winter yet,” Phillips advises, despite Environment Canada models he says predict more unseasonably mild temperatures this month. “You shouldn’t write the obituary on winter as we’re going into February.”