Canada links June heat wave to climate change with new attribution analysis

For the first time, the Canadian government has conducted a rapid analysis of a period of extreme heat and linked it to human-caused climate change.

Analysis by Environment and Climate Change Canada (ECCC) found that the likelihood of a heat wave in Ontario, Quebec and Atlantic Canada between June 17 and 20 is two to ten times greater due to climate change.

“In all regions, the likelihood of this event was greatly increased by human influence on the climate,” Greg Flato, a senior researcher with Environment and Climate Change Canada, said at a briefing for reporters.

The analysis noted abnormally high daytime temperatures, high humidity and warmer than normal nighttime lows. Bathurst and Saint John, NB, in particular, set records for the highest temperature since data was first collected in the 1870s.

The ECCC research is the start of a pilot project, in which researchers will analyze weather data and climate model simulations to compare how these types of events have changed between today’s climate and the cooler pre-industrial climate.

“By carefully analyzing the differences between these simulated climates, we can calculate how much the probability of an observed event has changed,” he said.

Flato said the ongoing heat wave in Western Canada will also be analyzed, as will others in the future. The department will expand this system to analyze other extreme weather events, he said. Another ECCC scientist said the rapid attribution system is based on peer-reviewed techniques.

‘Not a one-off study’

The findings add to a growing field of research known as rapid attribution, in which scientists use models to quickly determine the extent to which climate change is linked to extreme weather events, such as heat waves, floods and storms.

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The federal government’s commitment to continued attribution work marks a “very significant development,” said Frederike Otto, co-founder of World Weather Attribution (WWA), a U.K.-based group that conducts attribution research.

“If you don’t just do a one-off study, but do it regularly, it obviously helps to see how things have already changed, but also how quickly they are changing.”

According to Otto, other countries have also conducted attribution studies, but Canada appears to be the first country to commit to doing so on an ongoing basis.

Attribution studies do not provide a definitive answer to the question of whether climate change caused a specific weather event, but they do indicate the statistical probability that climate change caused a specific weather event and the extent to which it made the event worse. (In some cases, natural weather patterns, such as El Niño, also play a role in driving up temperatures.)

According to Otto, the findings can help governments make better decisions, such as planting trees in places where it is very hot in a city or ensuring cool spaces for vulnerable population groups.

“If you know that the heat wave you are experiencing now is not the result of God or just bad luck of nature, but that it is something that you actually expect every 10 years or so, then that means you have to have infrastructure that can cope with these heat levels,” Otto said.

In the past, WWA has certain that climate change has more than doubled the likelihood of the conditions that led to Quebec’s record-breaking wildfire season, and calculated that the devastating 2021 heat wave in Western Canada would occur every five to 10 years in a world that has warmed by 2 degrees Celsius.

Such studies are not directly peer reviewed and published in scientific journals, given the effort to release the information shortly after an event, but are based on peer-reviewed modeling techniques—and many are eventually published, the WWA said.

‘A lever to take the conversation to a higher level’

Sarah Henderson, scientific director of the environmental health division at the British Columbia Centre for Disease Control, said studies like this “can reinforce the message that climate change is affecting the health and well-being of Canadians.”

WATCH | Dangerous heat breaks temperature records in US:

Dangerous heat breaks temperature records in US

A heat wave has brought record high temperatures to California and Nevada that are already significantly higher than last year. The heat has people looking for ways to stay cool and firefighters working to prevent wildfires from spreading.

“It just serves to put these events in the context of climate change for the public and for public health professionals,” she said.

“It’s a way to move the conversation forward and ensure that climate change is never left out of the discussion about extreme heat.”

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