Extreme cold
Due to rising temperatures, the duration and intensity of cold spells in Quebec are changing. They have become milder in recent decades, while heat waves have increased in intensity and duration over the same period.
It has also been observed that cold waves last for a shorter period of time, and that the number of cool nights and days has decreased considerably since 1950.
Although 2018 was the coldest year of the 21st century in Quebec, its average temperatures were nevertheless higher than the 20th century average. The exceptional cold that occurred in the north of the province contributed to 2018 being classified this way. However, the summer of that same year set a record as the hottest summer in southern Quebec.
Worldwide
As in Quebec, global trends in the frequency, duration and intensity of extreme cold have been declining since 1950. Greenhouse gases generated by human activities are the main cause.
The climate has gone from a climate balanced between cold and hot extremes to a predominance of heat extremes, i.e. more heat records are now being broken than cold records.
Depending on the region, the effects of greenhouse gases on temperature extremes are moderated or amplified by localized processes, such as:
Snow and ice feedbacks due to the albedo effect
The impacts of land use changes and vegetation cover
Aerosol concentrations
Climate variability
