Deadly ‘medieval mega-droughts’ that last for DECADES could hit America
CLIMATE change threatens to bring a string of deadly droughts to the United States not seen since Medieval times.
That’s the stark warning issued Wednesday by scientists, who say mega-droughts lasting decades could plague the American Southwest if global warming continues.
Some suggest the region may already be at the precipice of one of its worst mega-droughts in 1,000 years.
The extreme dry spells last for longer than 20 years and cause rivers to run dry, while forests become tinderboxes waiting for a spark.
A dozen mega-droughts hit the Southwest United States from the 9th to 15th Centuries, but they mysteriously stopped around 1600.
Researchers at Columbia University in New York, USA, set out to better understand why.
Climate change could spark a mega-drought in the Southwest United States (stock)[/caption]
And after number crunching climate and ocean temperature data from the past 2,000 years, they reckon they’ve finally cracked it.
A trio of complex climate changes must be in play to trigger a mega-drought, the team writes in a new study.
Firstly, the Atlantic Ocean must be warmer than usual. Secondly, a string of severe and frequent “La Niña” events – cool tropical sea temperatures that can dry up parts of the globe near the equator – have to occur.
Finally, the planet must be absorbing more sunlight than it reflects back into space, causing surface temperatures to ratchet up.
Scientists suggest repeated La Niña events were most likely responsible for America’s Medieval droughts.
And they warn there are more of the deadly dry spells to come.
Mega-droughts are dry spells that last for more than two decades (stock)[/caption]
What is a mega-drought?
Here's everything you need to know…
- A mega-drought is a deadly dry spell lasting two decades or longer
- During one of the droughts, rains dry up while rivers and lakes evaporate
- Forests and fields become extremely susceptible to wildfires
- The US has seen an extended period without any mega-droughts
- Following a string of them in Medieval times, the last occured one in the 16th century
- However, scientists have warned climate change could bring the mega-droughts back
- That’s because higher global termperatures are drying up the American Southwest
If climate change continues, the American Southwest will see more mega-droughts as the region dries out with rising global temperatures.
This will cause more sunlight to be absorbed than reflected, making mega-droughts more likely if and when a La Niña event occurs in future.
Currently, the United States is hit by a La Niña event once every two to seven years.
“Because you increase the baseline aridity, in the future when you have a big La Niña, or several of them in a row, it could lead to mega-droughts in the American West,” said study lead scientist Nathan Steiger.
Some scientists believe the American Southwest is already at the precipice of another mega-drought.
A record-breaking period of aridity set in around the year 2000 that continues to this day could be the beginnings of a decades-long dry spell, researchers, also from Columbia University, warned at a meeting of the American Geophysical Union last year.
The research was published in the journal Science Advances.
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In other news, the next five years are to be the hottest ever with soaring temperatures bringing droughts, floods and hurricanes, according to experts.
The world’s water supply is reportedly shrinking as drought-like conditions on Earth become the “new normal”.
Here are history’s deadliest heatwaves – featuring wildfires, melting streets and tens of thousands of fatalities.
Are you worried about climate change? Let us know in the comments!
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