Araucaria araucana trees in northern Patagonia, Argentina, used in the study, can live 1,000 years. Ricardo Villalba, Argentine Institute of Snow, Glacier and Environmental Sciences
South America has experienced an “unprecedented” increase in extreme weather events over the past century, according to a new analysis of 600 years of tree-ring records published in the journal Proceedings of the National Academy of Sciences.
Researchers used the tree-ring data to reconstruct changes in soil moisture over time, part of the new South American Drought Atlas, and found that there has been a dramatic rise in severe droughts and periods of extreme rainfall in central and southern South America dating back to the 1960s.
Tree-ring records are often used as proxy data sources for past climate conditions, as the width of the rings, which show annual tree growth, varies with changes in precipitation. Tree rings are generally wider when there is increased soil moisture and narrower during drier periods. The researchers validated their tree-ring analysis against existing written records of droughts and floods.
The study authors note that the increase in extreme weather could be caused by a combination of both human-induced climate change and natural climate variability. However, the new atlas “highlights the acute vulnerability of South America to extreme climate events,” lead author Mariano Morales said in a statement. For example, an ongoing decade-long drought in Chile and Argentina is one of the worst on record and could result in “the potential collapse of food systems,” according to Morales. Meanwhile, other regions of South America have seen frequent periods of heavy rainfall, including the La Plata basin in Uruguay.
“Everything is consistent with the idea that you’ll be intensifying both wet and dry events with global warming,” said Jason Smerdon, a co-author of the study and a climate scientist at Columbia University’s Lamont-Doherty Earth Observatory.
The researchers hope that the extended 600-year record will help scientists better understand the impacts of human activity on extreme hydroclimate events. The research group also plans to expand its atlas to include more South American countries and additional years of reconstructed climate records.
—Elisheva Mittelman
