Aug. 29 (UPI) -- New analysis of centuries-old trees in South America has revealed a strong correlation between wildfires and periods of warming.
The history of Earth's climate features frequent fluctuations in global temperatures, including many periods of warming. In modern history, periods of warming have occurred more frequently -- interrupted by shorter and shorter periods of more and more moderate cooling.
By comparing evidence of wildfire scarring among tree rings with climate records, scientists can tease out the relationship between fire and climate change.
In the most recent study, researchers at Portland State University surveyed evidence of wildfire scarring among 1,767 trees spread across 97 South American sites, including trees from a range of ecosystems. The evidence revealed a strengthening relationship between periods of warming and wildfire frequency.
Scientists shared their findings this week in the journal PNAS.
The South American climate is heavily influenced by the climate oscillation known as the Southern Annular Mode. SAM brings warm, dry weather and westerly wind patterns. SAM has become increasingly active over the last century. As a result, South America has experienced an increase in wildfire activity.
The oldest trees surveyed as part of the study prove the pattern has held for several centuries.
"We found that wildfire activity over the centuries has been increasingly favored by the warm phases of SAM going back to 1665," PSU geography professor Andrés Holz said in a news release.
Holz and his colleagues say the impact of rising greenhouse gas concentrations in Earth's atmosphere will strengthen the connection between warm periods and wildfire activity in the 21st century.