The scientists also found that climate change, caused primarily by burning fossil fuels, made the total severity of Quebec's fire season to the end of July around 50% more intense.

Fire severity reflects how difficult a fire is to suppress once it has been sparked, and is a commonly used metric to assess fire weather on monthly or longer timescales.

The scientists wanted to "understand how climate change affects us, to connect... the experience of people with the usually relatively abstract signs of climate change", said Dr Friederike Otto, co-founder of the World Weather Attribution (WWA) group behind the analysis.

Dorothy Heinrich from the Red Cross Red Crescent Climate Centre, who was also involved in the study, said the fires had "significant direct impacts on communities, the ones that needed to be evacuated, the ones in towns that have been burned" as well as impacts further afield like air pollution.

Swirling smoke from the fires left millions of people in the US and Canada breathing unhealthy air, turned the New York sky orange, and even reached Spain.

This year's devastating wildfire season has been Canada's worst in history.

Already, nearly 14 million hectares have burned, an area larger than Greece and nearly double the previous record of 7.6 million hectares set in 1989.

The study, which has not been peer-reviewed but uses peer reviewed methods, focused specifically on one region in the Canadian province of Quebec, which recorded an exceptionally high number of wildfires in May and June.

Wildfires are common in Canada's western provinces, but this year the eastern provinces of Nova Scotia, Quebec and parts of Ontario reeled from out-of-control wildfires.

More than 10,000 people were evacuated from their homes in Quebec alone.

The scientists used weather data and computer model simulations to compare the climate of the past with that of today, after about 1.2C of global warming since the late 1800s.

To assess the effect of hot and dry weather conditions between January and the end of July that drove the fires, the scientists calculated the "Cumulative Daily Severity Rating", to conclude that seasons of this severity have been made at least seven times more likely to occur.

They also looked at the fire weather conditions - influenced by temperature, wind, humidity and precipitation - when they were at their peak, which is when fires spread very rapidly, and found they were made twice as likely by climate change.

They say both figures are likely underestimates, and are expected to increase if the planet continues to warm.

Dr Otto, also a senior lecturer at Imperial College London, said the key finding is climate change is a "really important driver" of the conditions that fuelled such fires.

Current policies put the world on course for around 2.4-2.7C of warming by the end of this century, according to Climate Action Tracker.

Caroline Brouillette, executive director of campaign group Climate Action Network Canada, said: "The science plainly shows that the climate crisis is making the unrelenting impacts we've seen this summer more frequent and more extreme, while polls show that Canadians are connecting the dots: most Canadians believe that climate change is to blame for the wildfires."

WWA publishes its attribution studies soon after the event, rather than waiting for a roughly two-year peer-review process, in the hopes it can influence urgent policy decisions on things like relocating and rebuilding.