Canadian scientists link heatwave to human-caused climate changes
Canadian scientists do not doubt that the recent heatwave in Ontario, Quebec, and the Atlantic provinces of the country was linked to human-caused climate changes. For the first time, they used a rapid assessment model to evaluate the connection between extreme weather events and climate change.
In June, a three-day heatwave began in the province of Ontario, exceeding average temperatures for this period by 7 °C. The Canadian Ministry of Environment announced the launch of a pilot tool aimed at explaining which extreme weather events are a result of human-induced climate changes. At that time, Canadian climatologists emphasised that the system was rapidly generating results and was the first in the world.
The rapid attribution system was tested during the June heatwave, which moved from Ontario to Quebec, where temperatures were even 10 °C higher than the norm, and then reached the Atlantic provinces, where the exceedances were 11 °C. According to a statement by the Canadian Ministry of Environment and Climate Change, the analysis of these events showed that human-caused climate changes significantly increased the likelihood of such extreme weather events occurring. It was estimated that the probability of the June heatwave 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 different climates: the contemporary one and the climate of the late 19th century, before industrialisation significantly impacted global warming. When extreme weather events occur, climatologists can compare data from similar events in both models, allowing them to estimate how much human activity influences the likelihood of their occurrence today.
"By comparing those two sets of simulations, we can ask the question for a specific event, like the one we're talking about today, how much has the risk, the probability, the likelihood of such an event been changed by human-made climate change," explained senior scientist at the Ministry of Environment and Climate Change Greg Flato.
The new tool allowed the assessment between 17 and 20 June this year, when in Eastern Ontario, average maximum temperatures were 29 °C, which is 7 °C more than normal. Then, in Northern Quebec, they were 21.5 °C, which is 7 °C more than normal. In Southern Quebec, they increased to 29.5 °C, which is 11 °C more than normal. In the Atlantic provinces, the heatwave caused temperatures to rise to 26 °C, which is 11 °C more than normal.
The analysis highlighted the exceptionally high temperatures, higher-than-average night temperatures, and high humidity. In Canadian weather forecasts, two temperature values are given: the expected and the perceived temperature, which moisture influences.
As revealed, the heatwave analysis is a pilot application of the model. It will be used for seventeen regions in Canada where higher-than-normal temperatures have already been recorded. The next part of the work will involve constructing similar comparative models for extremely low temperatures and heavy precipitation.
The Canadian Ministry of Environment and Climate Change emphasises that attribution models have practical significance because it allows national and local authorities to plan better, respond more quickly during extreme weather events, and enables more effective rebuilding after possible damages.
