In 2023 and 2024, the hottest years on record, more than 78 million acres of forests burned around the globe. The fires sent veils of smoke and several billion tons of carbon dioxide into the atmosphere, subjecting millions of people to poor air quality. Extreme forest-fire years are becoming more common because of climate change, new research suggests. Boreal forests lost more than two times the canopy area in 2023-24 compared with the period between 2002 and 2022, the study found. Tropical forests saw three times as much loss, and North American forests lost nearly four times as much canopy, mostly because of Canada’s wildfires. Significant losses were in remote forests, far from human activities. That isolation suggests fires are increasing primarily because of climate change, said Calum Cunningham, a fire geographer at the University of Tasmania who was not involved with the study. “Chronic changes in climate are making these forests more conducive to burning,” Dr. Cunningham said. [a paid subscription is required to read this article]