A drought in Russia led to riots in Egypt. Fires in Canada fueled deadly pollution in Spain. Extreme weather can have knock-on effects in faraway places that are not well understood and rarely accounted for in planning, a new paper warns.

The unprecedented wildfires that burned across Canada in 2023 not only scorched 70,000 square miles of forest, but also unleashed massive plumes of smoke that clouded skies from Chicago to New York to parts of Europe. The spike in pollution contributed to the deaths of more than 22,000 Europeans, according to one estimate.