The Black Summer bushfires may have contributed to the following triple La Nina, with smoke from large-scale events having some similarities to impacts caused by volcanic eruptions, researchers have found. 
 
A triple La Nina is not common and the first in the 2020-22 streak was poorly forecast and was unusual as it didn’t follow a strong El Nino. The climate driver contributed to last year's record flooding.
 
Climate scientists at the National Centre for Atmospheric Research (NCAR) in Boulder, Colorado, incorporated satellite data for bushfire smoke into model simulations, with results suggesting the bushfires were an important contribution to the string of La Nina events. 
 
“Many people quickly forgot about the Australian fires, especially as the covid pandemic exploded, but the Earth system has a long memory, and the impacts of the fires lingered for years,” scientist and study lead author John Fasullo says on an NCAR news website. 
 
The research published in Science Advances says the “Australian wildfire season” that started in late 2019 and continued into the next year was exceptional in both its severity and particulate emissions. 
 
Previous research has looked at the impact of major southern hemisphere volcanic eruptions and the emergence of La Nina conditions. 
 
The bulk of the bushfire emissions didn’t reach the altitudes of those caused by eruptions and acted differently to influence the climate. But the emissions brightened cloud decks across the Southern Hemisphere, especially near Peru, and the ultimate net result, according to the study, was a cooling of the Tropical Pacific Ocean, where La Ninas form, over multiple years. 
 
“The relevance of wildfire-aerosol-cloud interactions to both climate seasonal prediction and long-term projection underscores the need to better represent wildfire-climate couplings in models,” the research says. 
 
The research was funded by the US National Science Foundation, which is NCAR’s sponsor, NASA, and the US Department of Energy. 
 
NCAR says wildfires are getting larger and more intense in the western US and many regions around the world with far-reaching consequences. 
 
The study is available here.