US faces worst droughts in 1,000 years, predict scientists

The US south-west and the Great Plains
will face decade-long droughts far worse
than any experienced over the last 1,000
years because of climate change,
researchers said on Thursday.
The coming drought age – caused by higher
temperatures under climate change – will
make it nearly impossible to carry on with
current life-as-normal conditions across a
vast swathe of the country.
The droughts will be far worse than the
one in California – or those seen in ancient
times, such as the calamity that led to the
decline of the Anasazi civilizations in the
13 century, the researchers said.
“The 21 century projections make the
[previous] mega-droughts seem like quaint
walks through the garden of Eden,” said
Jason Smerdon, a co-author and climate
scientist at Columbia University’s Lamont-
Doherty Earth Observatory.
Researchers have long known that the
south-west and Great Plains will dry out
over the second half of the 21 century
because of rising temperatures under
climate change.
But this was the first time researchers
found those droughts would be far worse
even than those seen over the millennia.
The years since 2000 give only a small
indication of the punishment ahead. In
parts of Arizona, California, Nevada, New
Mexico, Oklahoma and Texas, 11 of those
years have been drought years.
As many as 64 million people were
affected by those droughts, according to
Nasa projections.
Those conditions have produced lasting
consequences. In California, now
undergoing its fourth year of drought – and
the worst dry spell in 1,200 years, farmers
have sold off herds. Growers have
abandoned fields. Cities have imposed
water rationing.
But future droughts could be even more
disruptive, because they will likely drag
on for decades, not years.
“We haven’t seen this kind of prolonged
drought even certainly in modern US
history,” Smerdon said. “What this study
has shown is the likelihood that multi-
decadal events comprising year after year
after year of extreme dry events could be
something in our future.”
The study, Unprecedented 21 -Century
Drought Risk in the American Southwest
and Central Plains, was published in a
new online journal Science Advances.
The researchers said the effects of drought
would likely be exacerbated by population
growth in the south-west and rising
demands for water.
Already current demands for water – for
agriculture and for daily life – have
drastically reduced groundwater sources
in California and across the south-west.
Under the current warming trajectory, the
south-west and Great Plains could expect
to see chronic water shortages, making it
impossible to carry out farming and
ranching under current methods.
“Given the likelihood of a much drier
future and increasing water resources
demand, groundwater loss and higher
temperatures will likely exacerbate the
impacts of future droughts, presenting a
major adaptation challenge,” the paper
said.
The researchers used data derived from
tree rings, whose growth patterns show the
effects of dry and wet years, sampled
across North America, and soil moisture,
rainfall and evaporation records, and 17
climate models to study the effects of
future temperature rise on the region.