Global WarmingWater

Global Drought Predicted by Century's End – "Unprecedented Consequences"

By the 2030’s, more and more regions across our planet will be entering drought conditions, according to a recently published study by the National Center for Atmospheric Research (NCAR) at the University of Colorado, Boulder. This dryness trend, which encompasses much of the temperate and tropical Western Hemisphere along with large areas of Eurasia and most of Africa and Australia, will continue to increase through the final decades of the 21st Century.

Combining data from 22 different computer models and data from previous published studies and drought indexes, NCAR researcher Aiguo Dai found that by the 2030’s — within most of our lifetimes — global warming will create increasing dryness over much of the planet.  Some regions will experience  severe, dry conditions that have rarely been seen in recorded history.

Dai also found that some northern regions, such as Scandinavia, Alaska, part of Russia and Canada, will actually grow wetter/cooler, but not so much as to counteract the general drying trend over most of the planet’s land areas.

Here is a break down of regions that will be hardest hit, according to the study*:

  • Much of Latin America, including large sections of Mexico and Brazil
  • Regions bordering the Mediterranean Sea, which could become especially dry
  • Large parts of Southwest Asia
  • Most of Africa and Australia, with particularly dry conditions in regions of Africa
  • Southeast Asia, including parts of China and neighboring countries

Also: by 2030, the western two-thirds of the United States will be “significantly dryer”.

Dai does caution that his predictions are based on current GHG emission data. Other factors could influence this trend (i.e., either decrease it or augment it), such as El Nino, and human factors like better land management practices and the adoption of climate remediation strategies (including geoengineering), or, tragically, a failure to adopt comprehensive carbon emission policies.

This trend, if it does indeed develop as predicted, will have great, perhaps perilous, consequence for much of the world’s people. It spells a dramatic reduction in water resources worldwide. As it stands right now, more the 100 million people in this world lack  “water security” (i.e., are water “insecure”; some estimates are ten times higher) and another startling 4 billion + face increasing water insecurity (see my previous post on this topic).

Net Primary Production decreased over the last decade

Another climate-impacting consequence of this global drying trend will be less carbon dioxide sequestered by plants and vegetation, as drought conditions reduce the total area and “net primary production” of land-based vegetation. Net primary production (NPP) is a quantity that estimates the amount of atmospheric carbon “fixed” by plants and thus converted into biomass. Less NPP means more carbon remains in the atmosphere (excluding ocean absorption of CO2, which is reaching its limits), and hence the risk of further warming increases. This is another, deeply important, “ecosystem service” that often gets overlooked.

Indeed, this decline in NPP already seems to be occurring; according to a recently published study (Zhao, Running, Science, 20 August 2010), the last decade (2000 – 2009) saw droughts worldwide reducing global NPP by .55 petagrams (a petagram is a 1 followed by 15 zeros, or, over half a quadrillion grams). This general NPP reduction trend persisted despite some regional increases in NPP, as over the Northern Hemisphere.

One can see how the reciprocal interaction of increasing drought conditions and reduced NPP could generate one of those positive feedback cycles that climate scientists speak of with greater frequency these days.

Read the World Science article here.

To learn more about the ‘hows’ and ‘whys’ of climate research, and “Science serving society,” visit the NCAR website.

*This section (bullet list of areas impacted by drought) is quoted directly from the University Corporation Atmospheric Research (UCAR) website.

Photo Credit: Tomas Castelazo; CC – BY 3.0

Chart: NCAR

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