J. Geophys. Res. 113, D14S16 (2008)

Credit: US FISH & WILDLIFE SERVICE

Smoke from wildfires in northern boreal forests might give the Arctic a respite from its rapid warming, say scientists. Tiny particles in smoke can scatter and absorb sunlight, temporarily cooling the Earth's surface.

A team from the University of Colorado and the US National Oceanic and Atmospheric Administration studied the climatic impact of smoke from severe wildfires that raged throughout Alaska and western Canada in 2004, burning 57,000 square kilometres of forested land. Robert Stone and colleagues used data from a climate observatory near Barrow, Alaska, where the smoke was at times thick enough to reduce visibility to less than 2 kilometres. During passage of the smoke plume, scattering and absorption of the sun's rays was many times higher than is typical in summer, suggesting that wildfires could cool the Arctic for weeks to months at a time. Modelling showed that such an effect would ultimately depend on factors such as the concentration of the smoke particles, the position of the Sun and the brightness of the land and ocean surface.

Scenarios of future global warming suggest that North American wildfires are likely to become more frequent, and could thus have an increasing role in the Arctic climate.