A recent study led by the National Center for Atmospheric Research (NCAR) has revealed that the devastating wildfires that ravaged Australia in 2019-2020 had far-reaching consequences, including contributing to a multi-year La Nina event in the Tropical Pacific. Published in the journal Science Advances, the research sheds light on the lingering impacts of the fires and their unexpected connection to climate patterns.
The study, conducted by NCAR scientist John Fasullo and his team, utilized advanced computer modeling to investigate the climate impacts of the Australian wildfires. They found that the emissions from the fires, which spread across the Southern Hemisphere, set off a series of climate interactions. Unlike volcanic eruptions, the wildfire emissions did not cool the climate directly by reflecting sunlight but instead led to the formation of aerosols that brightened cloud decks across the Southern Hemisphere.
The brightened clouds, particularly off the coast of Peru, caused cooling and drying of the air in the region, which ultimately shifted the convergence zone of the northern and southern trade winds. This resulted in the cooling of the Tropical Pacific Ocean, where the La Nina event developed and persisted for three consecutive winters.
The occurrence of a La Nina event for three consecutive winters is rare, and what makes this recent streak even more unusual is that it did not follow a strong El Nino, which typically precedes La Nina. The researchers noted that previous studies have established that various events in the Earth system, such as volcanic eruptions or aerosol emissions, can influence the likelihood of a La Nina event.
The findings of this study have important implications for seasonal climate forecasts. The researchers emphasized the significance of using coupled Earth system models, which incorporate both the atmosphere and the ocean, as forecasting tools. They also highlighted the long-lasting impacts of natural disasters like wildfires, emphasizing that the Earth system has a long memory.
The study serves as a reminder that seemingly localized events can have global consequences. The catastrophic Australian wildfires, often overshadowed by the COVID-19 pandemic, played a role in shaping climate patterns thousands of miles away. Understanding these connections is crucial for improving our ability to predict and mitigate the impacts of climate phenomena like La Nina, ultimately helping us better prepare for and adapt to a changing climate.