It’s cold outside, as you may have noticed. After a very brief interlude late last week, we’re back into the deep minuses by midweek. Though we’ve now entered March, spring is not in the air.
There is, however, considerable heat being generated in the ongoing debate about the role of climate change in the polar vortex that’s had us in its icy grip this winter.
Those who label climate change models a hoax say freezing temperatures negate the idea of global warming. Ignoring the fact that much of the planet has been experiencing the flip side of the coin – from blistering hot weather and drought in Australia to milder temperatures in Scandinavia and flooding in the UK – there is the issue of confusing today’s weather with decades-long trends.
Scientists, in their usual cautious way, don’t draw any conclusions from this frigid patch of weather. What they will say, however, is that the vortex’s migration south, bringing the cold all the way down to the Gulf Coast, is in keeping with what we might expect from the warming we’ve seen in the Arctic.
It works like this. The westerly winds of the jet stream, serving as a divide between cold air to the north and tropical air to the south, normally travel at a good clip. Some scientists postulate that the warming of the Arctic and melting of the ice cap reduce the temperature gap between the cold north and warm south, causing the jet stream to slow down. Instead of a straight stream with rapids, it becomes more an oxbow river, meandering along. The polar vortex is then permitted to move further south, and to linger longer – and we’ve seen a whole bunch of cold air lingering so far this winter.
Rutgers University professor Jennifer Francis has been monitoring the goings-on.
“Occasionally, the polar vortex can shift well south of its typical position, or a significant piece of the larger spin can break off and plunge south into the U.S. In the case of the outbreak this winter, a big southward dip, or trough, in the jet stream has been parked over the eastern two thirds of the United States for several weeks, allowing a large piece of the vortex to break off and move south over Ontario and the northern Great Lakes,” she notes.
“We can’t say these extremes are happening because of climate change, but we can say that they’re more likely because of climate change.”
While this winter has been extremely cold, our short-term memories also come into play in our assessment of the weather. The last decade has been particularly warm, offering up winters some years that hardly warrant the label, with little snow and milder temperatures. We come to think of that as normal, though the kind of weather we’re seeing this season is not unfamiliar to those who’ve been around more than a couple of decades.
Still, there’s no denying there’s been a shift. Those who warn us of the dangers of climate change have much to say about the kind of extreme weather we’re seeing more of. We’re not to confuse today’s weather with the big picture of climate, but every anomaly adds to the evidence.
If climate models are on target, we can expect more extreme weather ahead, even putting aside the human contribution to global warming/climate change.
Ontario falls prey to a number of natural hazards: drought, heat waves, floods, rain, snow and ice storms, tornadoes, and even hurricanes, although they’re rare. Small changes in average climate conditions are expected to generate significant changes in extreme events.
It’s likely to be a bumpy ride. Best to buckle up.