Tree rings show a climatic anomaly that began in the 20th century

(ORDO NEWS) — Look carefully, and tree rings can tell quite a lot – including changes in the moisture content of the soil in which they grow.

Scientists have gathered data for 600 years to understand recent climate changes, including a weather anomaly that was first noticed in the mid-20th century.

The new entries comprise the latest edition of the South American Drought Atlas (SADA), showing moisture variability over the past six centuries, backed up by other historical records. Meanwhile, periods between intense droughts have increased since the 1930s, and from the 60s drought occurred every ten years.

The rings cannot tell us the cause of the droughts, but the researchers behind the publication hope the article will be a useful guide for use in combination with other data sets and observations.

This new edition of SADA highlights changes in Argentina, Chile, Uruguay, Paraguay, most of Bolivia, southern Brazil, and Peru, using data collected locally from a total of 286 trees.

South America is “acutely vulnerable” to extreme climate events, and recent droughts have indeed led to a difficult agricultural situation in vast areas of the continent. Some food systems are now in danger of collapse.

However, the current picture is mixed: while some parts of Argentina and Chile have one of the most severe droughts in history, an abnormally high rainfall is observed in the regions of the southeastern part of the continent.

Researchers have identified three key factors that have influenced climate fluctuations over the past sixty years: cyclical shifts in sea surface temperature over the Pacific Ocean and the Atlantic, the belt of westerly winds around Antarctica, and the Hadley cell phenomenon that distributes warm and humid air from the equator.

Researchers argue that greenhouse gas emissions and the continuing legacy of ozone-depleting chemicals affect these key factors and can affect the climate change that is now observed in South America.

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