NASA climate study warns of unprecedented North American drought

California is in the midst of its worst
drought in over 1,200 years, exacerbated
by record hot temperatures. A new study
led by Benjamin Cook at NASA GISS
examines how drought intensity in North
America will change in a hotter world, and
finds that things will only get worse.
Global warming intensifies drought in
several ways. In increases evaporation
from soil and reservoirs. In increases water
demand. It makes precipitation fall more
as rain and less as snow, which is
problematic for regions like California that
rely on snowpack melt to refill reservoirs
throughout the year. It also makes the
snowpack melt earlier in the year. The
record heat has intensified the current
California drought by about 36%, and the
planet will only continue to get hotter.
The study finds that drought intensity will
increase, but could be manageable if we
follow a path that involves slowing global
warming by cutting carbon pollution.
However, decades-long mega-droughts in
North America could be much worse than
those experienced during medieval times,
which led to the decline of native
populations, if we continue on our current
business-as-usual path.
Jason Smerdon, a co-author and climate
scientist at Columbia University’s Lamont-
Doherty Earth Observatory, described the
implications of the study in stark terms,
The 21 century projections make the
[previous] mega-droughts seem like quaint
walks through the garden of Eden
The mega-droughts are projected to hit the
main agricultural regions in the United
States – both California and the Midwest
“ breadbasket.” The chronic water
shortages that are anticipated in these
regions under the business-as-usual
scenario would make farming, as well as
ranching in the American southwest,
nearly impossible.
This study reveals the flaw that underlies
the ‘CO2 is plant food’ myth. While some
types of plants benefit from a high-CO2
environment in a greenhouse where we
can control all other variables, in the
global climate, carbon pollution has other
consequences. Among these are higher
temperatures and more intense droughts,
which are not good for plants or
agriculture.
It’s another example of the risks we face in
a hotter world. This is an important time
in human history, where we’re at a fork in
the road. If we follow the business-as-
usual path, we move towards a future with
extremely disruptive climate
consequences, like mega-droughts and
water shortages in major agricultural
regions. If we follow the path to cut carbon
pollution, we significantly reduce the risks
of disruptive climate change.