Killer heat doesn’t boost mortality rate

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Last week, Statistics Canada released a study of the impact of extreme heat events on mortality in 12 large Canadian cities. To great fanfare in media reports, it concluded extreme heat events caused an increase of 900 deaths over the 20 years 2000-2020. In other words, despite all the breathless reporting about” killer heat waves,” no one bothered to calculate that this averages just over 45 deaths a year. Relative to the 21 million people living in these 12 cities, the increase in annual mortality equals a microscopic 0.0002 per cent of their population. You are twice as likely to die from tuberculosis. Your hernia has a 10 times greater chance of killing you than a heat wave does.

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What’s more, almost all the increased deaths attributed to extreme heat were in Montreal and Toronto. Apparently, this is because more people in these cities live in apartments, which typically have less air conditioning. For the rest of Canada, the impact of heat waves on mortality was mostly a non-event.

Statcan’s results actually found extreme heat had less impact than other studies have found. If you read the report all the way through, it concludes that “the average longer-term impacts of extreme heat events on mortality were considerably smaller than those previously estimated” by other researchers. This is partly because past studies have focused on extreme heat events that were known to have led to higher mortality. The field of climate research is littered in this way with a bias to producing sensational results designed to persuade more than inform.

Part of the problem is that the summary of the study (which is all that many people will read) highlights that “extreme heat has significant impacts on mortality” and that “past research has analyzed the degree to which non-accidental mortality increases during single extreme heat events” but it doesn’t include the finding that the results were in fact much lower than in most other studies.

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The bigger problem is that most research into heat waves and mortality misleads by ignoring the reduction in deaths due to milder winters. An unspoken assumption of such studies is that climate change only results in more deaths during heat waves. In fact, cold weather is much harder on humans. It increases the risk of strokes, heart attacks and respiratory diseases, as Bjorn Lomborg pointed out in his 2020 book False Alarm: How Climate Change Panic Costs Us Trillions, Hurts the Poor, and Fails to Fix the Planet.

Lomborg criticizes research that only addresses mortality from hot weather. Studying heat waves exclusively is misleading because “First, hearing only about deaths caused by heat means we end up believing things are much worse, leading to more fear. Second, it means we focus too little on the bigger and often stubborn problem of cold deaths.” A balanced approach for Statcan would have been to address the overall impact of climate change on total mortality, which likely would have supported Lomborg’s conclusion that “reducing death from heat is easier than reducing death from cold.”

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More broadly, colder weather is associated with poor harvests that can result in social problems, food riots and even armed conflict as populations seek to secure food supplies. If lower mortality is the overriding goal, the lesson of the 20th century is that higher incomes are the best way of improving health care outcomes and dramatically lowering the death rate.

The media is not solely to blame for the confusion and misinterpretation of Statcan’s study. The agency’s summary contributed to the muddle, both because it did not place its results in the context of other studies and because it failed to clearly state the total mortality count. As a result, some media outlets reported the total death toll was 670, because Statcan enumerated 670 non-accidental deaths, 115 cardiovascular deaths and 115 respiratory-related deaths without providing a total. It is as if Statcan listed the components of GDP without tallying the total, which is an invitation to the confusion and misinformation statistical agencies are supposed to avoid.

Financial Post

Philip Cross is a senior fellow at the Macdonald-Laurier Institute.

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