California's drought is worst for
1,200 years - but worse is to come, warn scientists
·
Current short-term drought
worse than any previous span of consecutive years of drought without
reprieve
·
It comes as California is
experiencing a wet start to December that could result in 12-inches (30 cm) of
rain and severe snow over next two weeks
·
Experts say there is 'no doubt'
we are entering a new era where humans have changed the climate system
California's three year drought is the worst seen for over 1200
years, researchers have found.
Scientists looking at the
cumulative effects of temperature, low precipitation and other factors said
that it all adds up to the worst conditions in more than a millennium.
The also claim that worse could
be to come, with droughts almost certain to occur again in the future.
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The dry bed of the Stevens Creek
Reservoir in California: A combination of record high temperatures and sparse
rainfall during California'sthree-year drought have produced the worst
conditions in 1,200 years.
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A combination of record high
temperatures and sparse rainfall during California's three-year drought have
produced the worst conditions in 1,200 years, according to a study accepted for
publication by the American Geophysical Union (AGU).
'The current California drought
is exceptionally severe in the context of at least the last millennium and is
driven by reduced though not unprecedented precipitation and record high
temperatures,' the report's authors said in the study released late Thursday.
The study by the University of
Minnesota and the Woods Hole Oceanographic Institution said that warm, dry
conditions have shrunk the supply of surface water from reservoirs, streams and
the Sierra Nevada snowpack in the state, even as demand from people and farms
has gone up, resulting in unprecedented scarcity.
Daniel Griffin, an assistant professor
in the Department of Geography, Environment and Society at the University of
Minnesota, and Kevin Anchukaitis, an assistant scientist at Woods Hole
Oceanographic Institution, asked the question, 'How unusual is the ongoing
California drought?' and collected new tree-ring samples from blue oak trees in
southern and central California.
'California's old blue oaks are as close to nature's rain gauges
as we get,' says Griffin.
'They thrive in some of the
driest environments where trees can grow in California.'
These trees are particularly
sensitive to moisture changes and their tree rings display moisture
fluctuations vividly.
'We were genuinely surprised at
the result,' says Griffin, a NOAA Climate & Global Change Fellow and former
WHOI postdoctoral scholar.
'This is California - drought
happens.
'Time and again, the most common
result in tree-ring studies is that drought episodes in the past were more
extreme than those of more recent eras.
'This time, however, the result
was different.
'One thing is clear, drought is
going to continue to happen.
'This is the kind of thing we get
to see in the future.'
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The low water level of
California's Lake Kaweah, February 5, 2014. Now in its third straight year of
unprecedented drought, California is experiencing its driest year on record,
dating back 119 years and possible the worst in the past 500 years.
Stanford
scientists explain the state of California's drought
While there is good evidence of
past sustained, multi-decadal droughts or so-called 'megadroughts'' in
California, the authors say those past episodes were probably punctuated by
occasional wet years, even if the cumulative effect over decades was one of
overall drying.
The current short-term drought
appears to be worse than any previous span of consecutive years of drought
without reprieve.
It comes as California is
experiencing a wet start to December that could result in 12-inches (30 cm) of
rain and yards (meters) of snow over the next two weeks, according to the
forecasting service Accuweather.
In October, the AGU published a
study by NASA's Goddard Institute for Space Studies in New York City saying
that the 1934 U.S. drought, which caused the upheaval known as the Dust Bowl,
was the worst in 1,000 years.
With an exceptionally wet winter,
parts of California might emerge from the drought this year. 'But there is no
doubt,' cautions Anchukaitis, 'that we are entering a new era where
human-wrought changes to the climate system will become important for
determining the severity of droughts and their consequences for coupled human
and natural systems.'
