A few days ago, a possible record temperature of 38 degrees Celsius was recorded north of the Arctic Circle. In the area affected by the heat wave, more than 70 weather stations that have been measuring temperature since at least the 1960s have recorded temperatures equal to or exceeding the established records.
Can we really make a connection between climate change and these extraordinary heat waves?
Several records were broken
The Canadian temperature record ever set at 45°C was set on July 5, 1937 in Saskatchewan. He died three days in a row in Lytton, British Columbia. It was 46.6°C on June 27, 47.9°C on June 28 and 49.5°C on June 29. The news made headlines in foreign media.
Several temperature records have also been broken in the Northwest Territories. In the United States, temperature records have also fallen in Seattle, Portland, and others.
Another amazing fact: The temperatures were much warmer than usual at this time of year. For example, temperatures above normal by 20°C were recorded in Portland, USA.
In Canada, extreme temperatures and drying up of vegetation have increased the risk of wildfires. Hundreds of wildfires have been reported in British Columbia since the beginning of July.
On Monday July 5, there were about 200 active fires, a third of which were deemed out of control. A forest fire destroyed the village of Lytton by 90%, forcing its residents to evacuate in a short time.
Thermal dome phenomenon
Anticyclones (high pressure systems) are usually associated with good weather and clear skies. However, when a high pressure system stays in one area for a long time due to “atmospheric blockage”, preventing it from moving, this situation can lead to a heat wave. In the case of the heat wave that hit western North America, high pressure lasted for a week over the affected areas.
The atmospheric embolism that caused this heat dome is known as an ‘omega embolism’. It is usually this type of blockage that causes heat waves in this area. The high pressure system has reached record values; However, these values ​​were well below the observed maximum temperatures.
This heat wave was so unheard of, that meteorologists wondered if this event, so well predicted by atmospheric models, was a typical error.
public health issue
This exceptional heat wave had significant impacts on the health of the affected population. Because these areas are unaccustomed to high temperatures, residents are less prepared to face extreme heat. For example, a BC Hydro report released last year found that the number of homes with air conditioners in British Columbia is 34%.
Between June 25 and July 1, 2021, British Columbia reported 719 sudden and unexpected deaths (note that these are preliminary results), which is three times more than normal over the same period. It is possible that the heat wave contributed significantly to this increase in deaths, but it is not yet clear how many deaths can be attributed to it. In most cases, these were elderly people who lived alone in private housing without adequate ventilation.
Another negative consequence of the heat wave is the deterioration of air quality because the atmospheric conditions associated with heat waves (the stability of the lower layers of the atmosphere, high temperature, the presence of sunlight and weak winds) are favorable for formation and concentration. of air pollutants such as ozone and fine particles. In fact, smoke from wildfires contributes to further deterioration of air quality.
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