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Look closely, and tree rings may show quite a lot — including changes in the soil moisture which the trees are growing in. Now, scientists have gathered 600 years of the data to better understand recent climate change, for example a weather anomaly that was first noticeable in the middle of this 20twentieth century.
The brand new records constitute the most recent edition of this South American Drought Atlas (SADA), showing moisture variability over the last six centuries backed up from other historic documents. Meanwhile, periods between intense droughts have been rising as the 1930therefore, with one drought each ten years being quantified since the’60s.
Exactly what the rings can not tell us is precisely these extremes came about, but the researchers behind the novel are hoping that the record will be a helpful reference point to be used in combination with different sets of information and observations.
“broader intense hydroclimate events are consistent with the effects of human actions, but the Atlas alone doesn’t offer evidence of how much of these observed changes are the result of natural climate variability versus human-induced heating, and” states palaeoclimatologist Mariano Morales from the National Research Council for Science and Technology in Argentina.
This new edition of SADA highlights changes across Argentina, Chile, Uruguay, Paraguay, the majority of Bolivia, southern Brazil, and Peru, using data gathered in the field from a total of 286 trees.
South America comes with an”acute vulnerability” to extreme climate events, according to Morales, and indeed recent droughts have led to a dire scenario for agriculture in vast areas of the country. Food programs are now under threat of collapse.
The present picture is a diverse one however: while parts of Argentina and Chile are suffering among the worst droughts in history, regions in the southeastern area of the continent are experiencing abnormally wet conditions. If the underlying causes aren’t climate change, they certainly look a good deal like climate change.
“We do not want to jump off the cliff and say this is climate change,” says palaeoclimatologist Edward Cook from Columbia University. “There is a lot of natural variability that could mimic human-induced climate change.”
The researchers identify three key factors at play in the swings of the last sixty years or so: perceptible sea-surface temperature shifts over the Pacific and the Atlantic, a belt of westerly winds around Antarctica called the Southern Annular Mode, and also the Hadley cell phenomenon that spreads warm and moist air from the equator.
Shifts which may result from greenhouse gases as well as the ongoing legacy of ozone-depleting compounds are interfering with these vital factors, the investigators say, and potentially feeding to the swings that are now being found in South America.
The SADA team hopes that the tales told from the tree rings may give us a better understanding of long-term climate shifts, modern conditions, and how to plan for the long run. The way that we’re currently treating the planet indicates that our weather extremes won’t be stopping anytime soon.
“What’s in accord with the concept you will be intensifying both moist and dry events with global warming,” claims climate scientist Jason Smerdon, from Columbia University.
The study was published in PNAS.