How wildfires from Australia affected climate events around the world
New research implicates emissions from the 2019-2020 Australian fires in the three-year super La Niña that fueled droughts in Africa and hurricanes in the Atlantic. Aerosol fallout from the bushfires that burned more than 70,000 square miles of Australia in 2019 and 2020 was so persistent and widespread, that brightened a vast area of clouds over the subtropical Pacific Ocean. Beneath those clouds, the ocean surface and atmosphere cooled, shifting a key tropical rainband northward and pushing the Equatorial Pacific toward an unexpected and prolonged cold phase of the La Niña-El Niño cycle, according to research published today in Science Advances. Fire aerosols are essentially fire dust – microscopic pieces of charred mineral or organic matter that can carry superheated wildfire plumes into the stratosphere and spread across the hemispheres with different climatic effects depending on where they are produced and where they end up. In a new modeling study, scientists have quantified how aerosols from Australian wildfires caused clouds over the tropical Pacific to reflect more sunlight back into space. The cooling effect was equivalent to turning off a 3-watt light bulb over every square meter of ocean area. And that cooling, their data showed, shifted a band of clouds and rain called the Intertropical Convergence Zone towards the north. Together, these effects may have helped trigger a rare three-year La Niña from late 2019 to 2022. The effects of La Niña spread across the globe, intensifying drought and famine in East Africa and preparing the Atlantic Ocean for hurricanes. 2020 became the most active tropical storm season on record with 31 tropical and subtropical systems including 11 storms making landfall in the US, including four isolated in Louisiana. (Bob Berwyn, Incise Climate News)