Narrator: A new NASA study predicts that by the end of the 21st Century,
the American Southwest and Great Plains are likely to experience
longer and more severe droughts than at any other time
in the last thousand years.
Cook: So recent droughts like the ongoing drought in California or in the Southwest, or even
historical droughts like the dustbowl in the 1930s. These are naturally-occurring droughts that
typically last several years or sometimes almost a decade. In our projections what we're seeing
is that with climate change, many of these types of droughts will likely last for
20. 30. sometimes even 40 years. Even exceeding the duration of
the long-term intense mega-droughts that characterized the really arid
time period known as the Medieval Climate Anomaly.
Narrator: So how can we peer into the planet’s future? Researchers combined natural
harnessed the processing capabilities of powerful supercomputers.
The scientists looked at a thousand years of tree ring data
and compared those records with soil moisture data from
17 different climate models. in order to extend this information into the future.
The models all show a drier world thanks to increased temperatures
from human induced climate change.
Cook: These computer simulations, these climate models, really represent our best understand of
the physics and the workings of the climate system. They're tested extensively against
observations, and at the end of the day if we want to investigate future climate,
they're really the only tool that we have to use.
Narrator: How bad these droughts are likely to get has a lot to do with how much greenhouse gas emissions
humans generate in coming years. Scientists looked at two different possibilities.
First, a “business as usual” scenario where world-wide
greenhouse gas emissions continue on their current course.
In this case the future risk of lengthy droughts rises to 80%.
lternatively, if the world were to take aggressive actions to reduce
emissions, the models still show drying, but the trends will be less severe.
In either scenario, droughts could
potentially have major impacts in a region already facing water management concerns.
Cook: These droughts really represent events that no
in the history of the United States has ever had to deal with.
And so even in the modern era droughts such as the ongoing droughts in California
and the Southwest, these normal droughts act as major stresses
on resources in the region, so we expect with these much longer droughts, it's going to be
even more impactful and cause even more problems for agriculture
and ecosystems in the region.
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