Arid and very dry phases much more common in the Americas than thought

Periods of drought in the Americas would be surprisingly common according to a study conducted by Columbia University paleoclimatologist Nathan Steiger. The scientist has in fact analyzed the tree trunk rings and found, as he explains in his study in Science Advances, several evidence that very dry climatic phases, such as those involving California this year or Chile in recent years, are actually very common.

The speech would be related to at least the last 12,000 years. According to the researcher, these very dry climatic phases have in common an abnormally very cold phase in the eastern Pacific Ocean and a process also known as La Niña.
Moreover, these analyses, making a projection into the future, suggest that further periods of extreme aridity could also involve the entire west coast of the Americas.

This study follows other studies that analyzed dead tree stumps located in the middle of lakes and rivers in Patagonia and the Sierra Nevada in California in the mid-1990s. Trees growing in watercourses or lakes indicated that drought levels so others must have lasted for decades. But it was only with this study, during which the scientist analyzed the tree rings, that the researchers used data covering much larger regions.

In addition, by combining these data with data on corals, ocean sediments and ice cores, the researcher has generated a kind of global vision of how the climate is changing. The research would confirm that from 800 to 1600 A.D., many such arid phases would have occurred in various parts of the world.

In particular the arid phases in the southwest of the United States were influenced by three factors, according to Steiger and the other authors of the study: the area of the North Atlantic Ocean abnormally hot, slight increases in global temperature and La Niña. As far as the arid phases of South America are concerned, it would be mostly only La Niña that would be the main trigger.

Now it remains to be seen how these drought patterns will change with ongoing global warming if it does. It is expected that with a warmer climate the drier phases will increase, but it is not so simple: scientists themselves remain divided on how the current climate change will affect the dry phases of certain areas. The drought that has been seen in Chile in recent years could, in any case, only be a faint example of what could happen in the future with consequences that could be catastrophic.

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