Hola amigos: A VUELO DE UN QUINDE EL BLOG., la Agencia Espacial NASA, nos informa que el aumento de las emisiones de carbono a la atmósfera, originará megasequias en los llanos estadounidenses, parece que recién están entendiendo que ellos son los primeros contaminantes del espacio, y justamente su propio territorio será víctima de esas emisiones del Efecto Invernadero: Las sequías en los EE.UU. suroeste y llanos centrales durante la última mitad de este siglo podrían ser más seco y más largo que las condiciones de sequía se ven en esas regiones en los últimos 1.000 años, según un nuevo estudio de la NASA.
El estudio, publicado el jueves en la revista: the journal Science Advances, se basa en las proyecciones de varios modelos climáticos, incluyendo uno patrocinado por la NASA. Los que se encuentran el aumento continuado de investigación en las emisiones de gases de efecto invernadero producidos por el hombre eleva el riesgo de sequías severas en estas regiones.
NASA scientists used tree rings to understand past
droughts and climate models incorporating soil moisture data to estimate future
drought risk in the 21st century.
Image Credit:
NASA's Goddard Space Flight
Center
Feature Link:
Droughts in the U.S. Southwest and Central Plains during the last half of
this century could be drier and longer than drought conditions seen in those
regions in the last 1,000 years, according to a new NASA study.
Youtube Override:
Soil moisture 30 cm below ground projected through
2100 for two emissions scenarios. Brown is drier and blue is wetter than the
20th c. average. RCP 4.5 assumes reduced CO2 emissions. RCP 8.5 is "business as
usual."
Image Credit:
NASA's Goddard Space Flight
Center
Feature Link:
The study, published Thursday in the journal Science Advances, is based on
projections from several climate models, including one sponsored by NASA. The
research found continued increases in human-produced greenhouse gas emissions
drives up the risk of severe droughts in these regions.
Soil moisture 30 cm below ground projected through
2100 for high emissions scenario RCP 8.5. The soil moisture data are
standardized to the Palmer Drought Severity Index and are deviations from the
20th century average.
Image Credit:
NASA's Goddard Space Flight
Center
"Natural droughts like the 1930s Dust Bowl and the current drought in the
Southwest have historically lasted maybe a decade or a little less," said Ben
Cook, climate scientist at NASA's Goddard Institute for Space Studies and the
Lamont-Doherty Earth Observatory at Columbia University in New York City, and
lead author of the study. "What these results are saying is we're going to get a
drought similar to those events, but it is probably going to last at least 30 to
35 years."
Soil moisture 30 cm below ground projected through
2100 for moderate emissions scenario RCP 4.5. The soil moisture data are
standardized to the Palmer Drought Severity Index and are deviations from the
20th century average.
Image Credit:
NASA's Goddard Space Flight
Center
According to Cook, the current likelihood of a megadrought, a drought lasting
more than three decades, is 12 percent. If greenhouse gas emissions stop
increasing in the mid-21st century, Cook and his colleagues project the
likelihood of megadrought to reach more than 60 percent.
However, if greenhouse gas emissions continue to increase along current
trajectories throughout the 21st century, there is an 80 percent likelihood of a
decades-long megadrought in the Southwest and Central Plains between the years
2050 and 2099.
The scientists analyzed a drought severity index and two soil moisture data
sets from 17 climate models that were run for both emissions scenarios. The high
emissions scenario projects the equivalent of an atmospheric carbon dioxide
concentration of 1,370 parts per million (ppm) by 2100, while the moderate
emissions scenario projects the equivalent of 650 ppm by 2100. Currently, the
atmosphere contains 400 ppm of CO2.
In the Southwest, climate change would likely cause reduced rainfall and
increased temperatures that will evaporate more water from the soil. In the
Central Plains, drying would largely be caused by the same temperature-driven
increase in evaporation.
The Fifth Assessment Report, issued by the United Nations Intergovernmental
Panel on Climate Change (IPCC) in 2013, synthesized the available scientific
studies and reported that increases in evaporation over arid lands are likely
throughout the 21st century. But the IPCC report had low confidence in projected
changes to soil moisture, one of the main indicators of drought.
Until this study, much of the previous research included analysis of only one
drought indicator and results from fewer climate models, Cook said, making this
a more robust drought projection than any previously published.
"What I think really stands out in the paper is the consistency between
different metrics of soil moisture and the findings across all the different
climate models," said Kevin Anchukaitis, a climate scientist at the Woods Hole
Oceanographic Institution in Woods Hole, Massachusetts, who was not involved in
the study. "It is rare to see all signs pointing so unwaveringly toward the same
result, in this case a highly elevated risk of future megadroughts in the United
States."
This study also is the first to compare future drought projections directly
to drought records from the last 1,000 years.
"We can't really understand the full variability and the full dynamics of
drought over western North America by focusing only on the last century or so,"
Cook said. "We have to go to the paleoclimate record, looking at these much
longer timescales, when much more extreme and extensive drought events happened,
to really come up with an appreciation for the full potential drought dynamics
in the system."
Modern measurements of drought indicators go back about 150 years. Cook and
his colleagues used a well-established tree-ring database to study older
droughts. Centuries-old trees allow a look back into the distant past. Tree
species like oak and bristle cone pines grow more in wet years, leaving wider
rings, and vice versa for drought years. By comparing the modern drought
measurements to tree rings in the 20th century for a baseline, the tree rings
can be used to establish moisture conditions over the past 1,000 years.
The scientists were interested in megadroughts that took place between 1100
and 1300 in North America. These medieval-period droughts, on a year-to-year
basis, were no worse than droughts seen in the recent past. But they lasted, in
some cases, 30 to 50 years.
When these past megadroughts are compared side-by-side with computer model
projections of the 21st century, both the moderate and business-as-usual
emissions scenarios are drier, and the risk of droughts lasting 30 years or
longer increases significantly.
Connecting the past, present and future in this way shows that 21st century
droughts in the region are likely to be even worse than those seen in medieval
times, according to Anchukaitis.
"Those droughts had profound ramifications for societies living in North
America at the time. These findings require us to think about how we would adapt
if even more severe droughts lasting over a decade were to occur in our future,"
Anchukaitis said.
NASA monitors Earth's vital signs from land, air and space with a fleet of
satellites and ambitious airborne and ground-based observation campaigns. NASA
develops new ways to observe and study Earth's interconnected natural systems
with long-term data records and computer analysis tools to better see how our
planet is changing. The agency shares this unique knowledge with the global
community and works with institutions in the United States and around the world
that contribute to understanding and protecting our home planet.
For more information about NASA's Earth science activities, visit:
NASA
Guillermo Gonzalo Sánchez Achutegui
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