Canadian heat wave linked to human-caused climate change

Canadian scientists have concluded that the recent heat wave in Ontario, Quebec, and the Atlantic provinces was linked to human-induced climate change. For the first time, they used a rapid assessment model to evaluate the connection between weather extremes and climate change.

In June, when a three-day heat wave began in Ontario, exceeding average temperatures by 13°F, the Canadian Ministry of Environment launched a pilot tool to identify which extreme weather events are results of human-caused climate change. At that time, Canadian climatologists highlighted that the system generates results quickly and is the first globally.

The rapid attribution system was tested during the June heat wave, which moved from Ontario to Quebec, where temperatures were even 18°F higher than usual, and then to the Atlantic provinces, where temperatures exceeded norms by 19°F. According to the Canadian Ministry of Environment and Climate Change, the analysis showed that human-caused climate change substantially increased the likelihood of such weather extremes. It was estimated that the probability of the June heat wave was two to ten times higher due to human activity.

The Canadian rapid assessment model uses data from two different historical periods and creates simulations of two contrasting climates: the contemporary climate and the late 19th-century climate before significant industrial impact on global warming. When extreme weather events occur, climatologists can compare data on similar events in both models, estimating the extent to which human activity influences their current likelihood.

"By carefully analyzing the differences between these climate simulations, we can calculate how much the probability of the observed event has changed," explained senior scientist at the Ministry of Environment and Climate Change Greg Flato.

The new tool enabled an evaluation of the situation between June 17 and 20, when in eastern Ontario, the average maximum temperatures were 84°F, 13°F higher than normal; in northern Quebec, they were 71°F, 13°F higher than normal; in southern Quebec, they reached 85°F, 19°F higher than normal; and in the Atlantic provinces, the heat wave caused temperatures to climb to 79°F, 19°F higher than normal.

The analysis highlighted exceptionally high temperatures, higher-than-average nighttime temperatures, and high humidity. In Canadian weather forecasts, two temperature values are given: the expected and the perceived temperature, which humidity influences.

It was disclosed that the analysis of heat waves is a pilot application of the model. It will be used for seventeen regions of Canada where higher-than-normal temperatures have already been recorded. The next phase of work will involve constructing similar comparative models for extremely low temperatures and heavy precipitation.

The Canadian Ministry of Environment and Climate Change emphasizes that the use of attribution models has practical significance. It allows national and local authorities to better plan and respond more quickly during weather extremes and enables more efficient recovery after potential damages.