Med/Middle East Winter Droughts Becoming More Common; Study Suggests Climate Linkage - CS Monitor

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Winter droughts have become increasingly common in the Mediterranean region, particularly over the past 20 years, and a new study finds that global warming has driven at least half of the change. Drought conditions in this politically explosive region are expected to grow more severe over the course of the century unless countries begin to significantly reduce their emissions of heat-trapping greenhouse gases, particularly carbon dioxide, many researchers say.

Those emissions come from burning fossil fuels, as well as from land-use changes.

Winter storms historically have delivered most of the annual rain and snowfall to the already arid Mediterranean region. Yet precipitation measurements from the region and modeling studies point to a relatively rapid shift in the winter rain and snowfall trends that began in the 1970s, according to the study.

That change could signal that the region "has moved into a new climate regime," says Martin Hoerling, a scientist at the National Oceanic and Atmospheric Administration's Earth Systems Research Laboratory in Boulder, Colo., and the study's lead author.

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http://www.csmonitor.com/Science/2011/1028/Global-warming-Middle-East-s-vital-wet-winters-are-disappearing

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1. NOAA study: Human-caused climate change a major factor in more frequent Mediterranean droughts

(Moderators, please note NOAA Release - copyright concerns are nil.)

http://www.noaanews.noaa.gov/stories2011/20111027_drought.html

NOAA study: Human-caused climate change a major factor in more frequent Mediterranean droughts

October 27, 2011

Wintertime droughts are increasingly common in the Mediterranean region, and human-caused climate change is partly responsible, according to a new analysis by NOAA scientists and colleagues at the Cooperative Institute for Research in Environmental Sciences (CIRES). In the last 20 years, 10 of the driest 12 winters have taken place in the lands surrounding the Mediterranean Sea.

Winter precipitation trends in the Mediterranean region for the period 1902 - 2010.
High Resolution image available at link (Credit: NOAA)

“The magnitude and frequency of the drying that has occurred is too great to be explained by natural variability alone,” said Martin Hoerling, Ph.D. of NOAA’s Earth System Research Laboratory in Boulder, Colo., lead author of a paper published online in the Journal of Climate this month. “This is not encouraging news for a region that already experiences water stress, because it implies natural variability alone is unlikely to return the region’s climate to normal.”

The Mediterranean region accumulates most of its precipitation during the winter, and Hoerling’s team uncovered a pattern of increasing wintertime dryness that stretched from Gibraltar to the Middle East. Scientists used observations and climate models to investigate several possible culprits, including natural variability, a cyclical climate pattern called the North Atlantic Oscillation (NAO), and climate change caused by greenhouse gases released into the atmosphere during fossil fuel use and other human activities.

Climate change from greenhouse gases explained roughly half the increased dryness of 1902-2010, the team found. This means that other processes, none specifically identified in the new investigation, also have contributed to increasing drought frequency in the region.

The team also found agreement between the observed increase in winter droughts and in the projections of climate models that include known increases in greenhouse gases. Both observations and model simulations show a sudden shift to drier conditions in the Mediterranean beginning in the 1970s. The analysis began with the year 1902, the first year of a recorded rainfall dataset.

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Climate is a global phenomenon with global impacts on food prices and water security, and NOAA researchers are engaged in understanding changes in climate across many regions of the world. In the Mediterranean, winter drought has emerged as a new normal that could threaten food security. Lessons learned from studying climate in that region may also be relevant for the U.S. West Coast, which has a similar climate to the Mediterranean region of Europe and North Africa.

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