When it comes to climate change, there is one fairly well-understood extreme that will affect humans in the decades to come: heat.
Scientists know that climate change will see events like hurricanes, droughts, floods and heat waves increase in frequency or intensity. But when it comes to heat waves, in particular, it’s already being seen across the world with deadly consequences.
According to a recent study published in the journal The Lancet, more than five million deaths annually between 2000 and 2019 were associated with “non-optimal temperatures,” with roughly 500,000 of these deaths related to heat.
While many of these deaths occur in tropical countries, heat waves are beginning to affect more northerly climes.
During the heat wave that suffocated British Columbia at the end of June into the first week of July, more than 800 people died in the province.
For comparison, in the same period last year, there were 232 deaths, according to B.C. Coroners Service’s chief medical officer, Dr. Jatinder Baidwan. The coroner’s office is continuing to investigate all of the deaths to nail down exactly how many were heat-related.
While we know that daytime temperatures are rising, in some regions — specifically in parts of Ontario and Quebec — nighttime temperatures are warming faster.
Those warmer nights mean our bodies don’t have any time to cool off. For people with health issues like heart disease or asthma, for example, this can be extremely problematic and potentially deadly.
“Our bodies were not designed to put up with environmental heats that exceed the high 30s,” Dr, Baidwan said.
“If you think about it, what happens to an air conditioning unit? When you stress it, it builds up with lots of ice on the outside and then it stops working. And in some ways, that’s a great analogy for what happens to our bodies. With extreme heat, we just find it really hard to do the usual homeostatic sort of mechanisms and protocols that happen in our body.”
The heat wave that affected the Pacific Northwest was highly unusual — a one in 1,000-year occurrence, according to a recent analysis by the group World Weather Attribution, a collection of scientists who analyze severe weather events.
However, parts of eastern Canada, including Ontario and Quebec, are seeing more frequent heat waves and tropical nights, defined as nighttime temperatures 20 C or higher.
For example, according to the Climate Atlas of Canada, the number of tropical nights in Toronto averaged roughly 6.9 annually from 1976 to 2005. With climate change, under a scenario where carbon emissions decline substantially, that is expected to climb to 17.6 annually from 2021 to 2050.
If current rates of carbon emissions continue, the average number of tropical nights in Toronto is expected to hit 20.6 annually from 2021 to 2050. From 2051 to 2080, under the two different scenarios for emissions, the average number would rise to 26.4 and 42.8 respectively.
In 2018, a heat wave blanketed Montreal from June 29 to July 5; temperatures averaged roughly 34 C during the day. Nighttime temperatures didn’t fall below 20 C. In all, 66 people died.
“We’re seeing an increase in hot extremes in Canada that’s larger than the global mean warming,” said Nathan Gillet, a research scientist with Environment and Climate Change Canada.
“The average warming in Canada is about twice the global mean warming. And the heat extremes are also increasing at a similar rate. And it’s not just the hottest, maximum temperatures, but the minimum temperatures, the nighttime minimums that are also increasing.”
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