Data shows city was part of a minority of the Earth’s surface that was merely warmer than average

This article was written by Kate Allen and was published in the Toronto Star on September 23, 2023.

The planet is getting hotter — that’s undeniable. But amidst this trend, the summer of 2023 was exceptional. In June, July and August, the average global temperatures shredded previous highs.

So many parts of the world saw heat records broken that it would be hard to list them all — places as far apart as Peru, Japan and Algeria all sweltered. Of course, many parts of Canada seared, too.

But not Toronto. Summer 2023 here was not that remarkable.

There were some hot stretches, for sure. But no heat records were broken — not even close. We logged an almost exactly average number of very hot days, compared to historic norms. So what’s going on?

Toronto has not been spared from the effects of climate change. Year to year there is lots of variability, but each decade has been trending hotter. In short: we got lucky. When will that luck run out? Scientists are typically a restrained bunch. But this summer they did not hold back: “Astonishing” was a word one used in July. “Extraordinary,” another said that same month.

“Totally unprecedented and terrifying,” a third scientist tweeted around the same time.

They were reacting to heat records toppling worldwide as huge swaths of the globe baked under extreme temperatures. When they made these remarks, in early July, it had been an exceptionally hot week, following an exceptionally hot month — the hottest June on record globally.

But the records didn’t stop falling then. July earned the dubious designation of being the hottest month since the advent of modern instrumentation and record-keeping, according to both U.S. and European climate agencies. August did not slack: it was the hottest August ever, too. What stunned scientists was not just how many records fell, but by how much.

Normally, a record-breaking month might be a few hundredths of a degree hotter than the last. But this summer felled records by much bigger margins, and the Northern Hemisphere summer as a whole was almost 1.5 degrees hotter than the historic average — a symbolic threshold and a scary preview.

Every country’s current heat-related death toll is likely a massive undercount. Doctors and scientists call extreme heat the “silent killer,” because it so often strikes by exacerbating other conditions, and is rarely the cause listed on a death certificate. One study looked at how many more people died than normal in Europe last summer and concluded that more than 61,000 people were killed from heat-related causes alone.

Billions of data points go into these monthly global averages: they are calculated by processing temperature data from thousands of land-based weather stations, ocean buoys, ships and more. The final figure blends data from both poles, the equator, and everywhere in between.

To drive the global average that high, a lot of the world had to be a lot hotter than normal. But not everywhere followed the trend: a few small pockets were just average, or even cold, and a minority of the Earth’s surface was merely warmer than average, but not much warmer than average or truly record-breaking. Toronto was nestled among that minority.

We did have heat waves in July and early September, but by historical norms, summer 2023 was dead average. Between 1976 and 2005, Toronto had an average of 12 “very hot days,” defined as days the mercury hit at least 30 C, according to the Climate Atlas of Canada. That’s exactly how many there have been as of this week.

“It’s a little bit like looking at the performance of a baseball player like Babe Ruth,” explains Bill Merryfield, a research scientist for Environment and Climate Change Canada who specializes in longterm predictions.

“If you look at one particular game, he might happen to strike out four times. And if that’s the only data you get, you would probably conclude he was a pretty lousy batter. But if you look at an entire season or better yet, an entire career, you get a much clearer picture.”

Next summer might be average again. It might be a hot one — especially because El Niño, a natural climate pattern that acts like turning up the global thermostat, began ramping up this past spring, and usually exerts its strongest influence the year after. It could even be cold.

But climate change is loading the dice, making hot summers more likely, and pushing how hot those summers are into higher extremes.

In a future where the world reins in carbon emissions significantly, Toronto is predicted to get about 28 “very hot” 30-plus degree days a year by 2050, according to the Climate Atlas — more than double the current number.

In a future where we keep burning fossil fuels and pumping large amounts of greenhouse gases into the atmosphere, we could get as many as 80 very hot days a year by 2080. Many other parts of Canada were not as lucky as Toronto this summer. Nine weather stations across five provinces and territories saw all-time maximum temperature records fall, according to data provided by Environment and Climate Change Canada.

One of those was in Norman Wells, a town in the Northwest Territories. It hit 37.9 C in early July — hotter than Toronto ever got by several degrees, even though the town sits not far below the Arctic Circle. All nine of the record-breaking weather stations were in the North, where climate change is happening faster than in southern latitudes.

In B.C., many places struggled with far hotter temperatures than Toronto as they also battled wildfires. These extremes hit just two years after the last brutal summer in the province, in 2021, when a heat dome killed 619 people and the hottest temperature ever recorded in Canada was measured in Lytton, one day before the town burned to the ground.

Torontonians should not take this mercifully average summer as a sign that this city will be spared from climate change’s effects in the future, experts say.

Until recently, in B.C. and the rest of the Pacific Northwest, “there was a sense that perhaps that also might be a bit of a climate refuge. But certainly what happened in the summer of 2021 … really kind of dispelled that sense,” says Merryfield. “So I don’t think there’s any particular reason to think that climate impacts in Toronto won’t be substantial.”

July earned the dubious designation of being the hottest month since the advent of modern instrumentation and recordkeeping, according to both U.S. and European climate agencies. August did not slack: it was the hottest August ever, too