Extreme fire weather - EurekAlert

Researchers model the regional impacts of specific anthropogenic activities and their influence on extreme fire weather risk.

While research has long concluded that anthropogenic activity and its products -- including greenhouse gas emissions, biomass burning, industrial aerosols (a.k.a. air pollution) and land-use changes -- raise the risk of extreme fire weather, the specific roles and influences of these activities was still unclear.

By disentangling the effects of those man-made factors the researchers were able to tease out the roles these activities have had in generating an increasingly fire-friendly climate around the world and the risk of extreme fire weather in decades to come.

Using state-of-the-art climate model simulations available from NCAR, the researchers analyzed the climate under various combinations of climate influences from 1920-2100, allowing them to isolate individual effects and their impacts on extreme fire weather risk?

By 2005, emissions raised the risk of extreme fire weather by 20% from preindustrial levels in western and eastern North America, the Mediterranean, Southeast Asia and the Amazon.

The researchers predict that by 2080, greenhouse gas emissions are expected to raise the risk of extreme wildfire by at least 50% in western North America, equatorial Africa, Southeast Asia and Australia, while doubling it in the Mediterranean, southern Africa, eastern North America and the Amazon.

Meanwhile, biomass burning and land-use changes have more regional impacts that amplify greenhouse gas-driven warming, according to the study -- notably a 30% increase of extreme fire weather risk over the Amazon and western north America during the 20th century caused by biomass burning.

Land use changes, the study found, also amplified the likelihood of extreme fire weather in western Australia and the Amazon.

The role of industrial aerosols has been more complex in the 20th century, actually reducing the risk of extreme fire weather by approximately 30% in the Amazon and Mediterranean, but amplifying it by at least 10% in southeast Asia and Western North America, the researchers found.

The cooling effect may still be present in regions such as the Horn of Africa, Central America and the northeast Amazon, where aerosols have not been reduced to pre-industrial levels.

Aerosols may still compete with greenhouse gas warming effects in the Mediterranean, western North America and parts of the Amazon, but the researchers expect this effect to dissipate over most of the globe by 2080, due to cleanup efforts and increased greenhouse gas-driven warming!

Southeast Asia meanwhile, "where aerosols emissions are expected to continue," may see a weakening of the annual monsoon, drier conditions and an increase in extreme fire weather.