A strong storm might not be climate change. Bad year, like BC’s in 2021? Weather experts saw it coming

First came the heat dome. Then the forest fires. Then torrential rains led to flooding and landslides.

In this year alone, British Columbia has become the punching bag of not one, but three extreme weather events – undeniable proof, some say, that climate change is happening and that humans are paying the price for our failure. of attention.

Detractors will claim that there has always been extreme weather: heat waves in 1941 and 1998; forest fires in 1998, 2017 and 2018; floods in 1983 and 2003.

Climate change researchers say British Columbia was predictable to be hit by increasingly frequent and intense weather events. The forest fire seasons in 2017, 2018 and 2021, for example, were the three worst in the province’s history.

But were the specific events of this past year due to climate change? That’s something that scientists say is extremely difficult to pin down.

The challenge, experts say, is that understanding climate change is about understanding trends over longer periods of time, not in individual instances.

Those who study climate change can largely predict British Columbia’s recurring extreme weather events, they say, but it is considerably more difficult to point out that these particular heat waves, wildfires or floods are the direct result of climate change.

While the flooding that currently rips through bridges and highways in southern British Columbia, and the wildfires that ravaged the interior earlier this year, and the “heat dome” before that, are interconnected and are all manifestations of a climate changing, it’s nearly impossible to attribute specific individual events to climate change, says Elizabeth Wolkovich, associate professor of Forest and Conservation Sciences at the University of British Columbia.

“There are many weather events and there are extreme weather events naturally in any weather system,” she says.

“What we can do is estimate the highest probability of those events occurring, given what we know about how we have altered the climate system as humans.”

One way to think about it may be to use the metaphor of an unnamed baseball player, a power hitter on steroids.

We can see how many home runs that player hit before starting steroids. And we can predict (and observe) that after he started taking steroids, the number of home runs he hit increased significantly.

But we can’t point to the home run he hit in the bottom of the seventh against St. Louis and say that that particular home run was hit by steroid use. We don’t know that, absent steroids, he would not have hit that home run.

Attributing climate change to unique natural events works the same way. We can say that we will see more heat waves and wildfires, scientists predicted this 20 or 30 years ago, says Wolkovich, and we can see that we are experiencing more frequent extreme weather events.

But we can’t point to a particular heat wave and say that that particular one was caused by climate change.

“What we can do is say that we are much, much, much more likely to have these heat waves, something that was well predicted by all the models beforehand,” says Wolkovich.

Think of a bell curve of average temperatures, says Kent Moore, a professor of atmospheric physics on the Mississauga campus of the University of Toronto.

In the middle, at the height of the hood, are the most frequent temperatures. On the left and right are the extremes of hot and cold, respectively.

When the global mean temperature rises one degree, which is how much it has increased since 1900, the peak of the bell moves to the right. But climate models show that something else is happening on the hot side of the curve.

“What’s happening with climate change is that in addition to moving the average … we have the idea that the warm end of the bell curve is spreading a little further,” says Moore.

The consequence of that, he says, is that those extremely higher temperatures will occur more frequently. Instead of having a strange heat wave two percent of the time, we could have one five percent of the time.

Even outside of those extreme weather events, a one degree rise in average global temperature has huge consequences.

One of the first things that happens when the temperature rises is that the air can hold more water vapor.

That water vapor is one of the main drivers of weather systems around the world. As you put more water vapor into the atmosphere, more intense storms occur, among other things.

BC, indeed much of the West Coast, is on the receiving end of what scientists call “atmospheric rivers” or, more colorfully, “the pineapple express.” These are wind systems that rotate counterclockwise over the Pacific, picking up water vapor in the warm waters near Hawaii and spewing the water when it hits the mountains and colder temperatures on the west coast of America. North.

These atmospheric rivers are huge: they can carry more than twice the amount of water that flows through the Amazon. That’s enough water to fill 188 Olympic swimming pools per second.

And when temperatures rise in the water off Hawaii, even by one degree, that means much more water vapor (scientists don’t know exactly how much) is being absorbed into the atmosphere, which means more water will fall in BC. later.

What we can also see is that the impact of individual events has been magnified by climate change.

BC is in a kind of feedback loop. Climate change predicts more heat waves. Those heat waves cause dry air, droughts, and drier lands, all of which combine to warm the atmosphere a bit more. That also creates the ideal conditions for wildfires.

And when those fires come, they tear a lot of vegetation off the slopes, which means that when the winter rains come, themselves reinforced by a greater uptake of water, without the vegetation to mitigate the impact, we have landslides and rocks.

Studies of the 2017 wildfires in British Columbia, the second worst wildfire season in the province’s history, underscore this point. The researchers found that there were the same number of fires in BC as before climate change. But in 2017, because the ground is so much drier and the air so much warmer, those fires turn into large fires that spread quickly and are much more difficult to control.

So some of the weather events that we are seeing may be events that we would have seen before climate change, but due to climate change, the impact of those events is much greater.

And scientists say, barring some radical changes that bring us closer to a global zero-emissions scenario, things will get worse before they get better.

“We are not stationed here. We keep warming up. We are testing what the future holds, ”says Wolkovich.

“And that is why researchers are so concerned. It’s not because we have a crystal ball and can tell you for sure how bad it could get. It’s because we know how bad it has already gotten. “