Canada releases first results from rapid extreme weather event attribution system

July 9, 2024 – Gatineau, Quebec

Understanding the causes and risks of extreme weather events can help us make informed decisions to protect our health, safety, and the long-term well-being of our communities. The science of calculating how much human-caused climate change has influenced extreme weather events is known as extreme weather event attribution.

Today, Environment and Climate Change Canada released the first results generated, using its pilot rapid extreme weather event attribution system. The system compares climate simulations to reveal how human-caused climate change affected the likelihood of an extreme weather event.

Using this system, Environment and Climate Change Canada scientists analyzed the heat waves experienced in Eastern Ontario, Northern and Southern Quebec, and Atlantic Canada during June. In all instances, the analysis determined that human-caused climate change made these heat waves much more likely:

• Eastern Ontario: From June 17 to 19, 2024, a heat wave reached a peak temperature of 29.0 degrees Celsius averaged over the region, which is 7.4 degrees Celsius above normal.
• Southern Quebec: From June 18 to 20, 2024, a heat wave reached a peak temperature of 29.5 degrees Celsius averaged over the region, which is 10.7 degrees Celsius above normal.
• Northern Quebec: From June 18 to 20, 2024, a heat wave reached a peak temperature of 21.5 degrees Celsius averaged over the region, which is 7.2 degrees Celsius above normal.
• Atlantic Canada: From June 18 to 20, 2024, a heat wave reached a peak temperature of 26.1 degrees Celsius averaged over the region, which is 10.6 degrees Celsius above normal.

The rapid extreme weather event attribution system compares two simulated climates with different atmospheric compositions:

• The climate of the late 1800s, before the major impacts of the Industrial Revolution
• The climate of today

A comparison of the two climates reveals the degree to which human activity increased the likelihood of a heat wave.

We urge the public to regularly monitor weather forecasts, take all weather alerts seriously, and get prepared for weather-related events by developing an emergency plan and being ready to adjust their travel plans. Canadians can download the WeatherCAN app to receive weather alert notifications directly on their mobile devices. Alerts help Canadians prepare to face severe weather events, save lives, and reduce the impacts on property and livelihoods.