Syria and California have both recently suffered their worst-ever droughts, exacerbated by global warming. Syria鈥檚 may have helped trigger its bloody civil war, but not California鈥檚, which instead brought vermin invasions and wildfire. The difference points to the resilience that will be needed in a warming world.
of the University of California, Santa Barbara, and his colleagues analysed Syrian weather data since 1931, and found steadily less winter rainfall, which is crucial for crops, and higher temperatures, which dry soils faster. The only explanation for such a change over that timescale lies in man-made greenhouse emissions, says Kelley. Climate models, his team found, consistently predict such changes for the Fertile Crescent, the Middle Eastern area that includes Syria and Iraq.
The researchers used a statistical technique to separate the long-term drying that appeared linked to climbing CO2 emissions, from yearly, natural ups and downs in precipitation. Those natural variations led to the occasional drought by themselves, says Kelley. But, he adds, 鈥渢he long-term drying trends exacerbated the recent drought, making it the most severe in the observed record.鈥� Crops failed from 2006 to 2009 in Syria鈥檚 northeastern region that is its breadbasket 鈥� then when rains returned, they triggered an explosion of yellow rust, a wheat fungus, that .
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Since 2011, California has also been suffering its worst drought on record Climate models do not predict less rainfall for the state, but do forecast that years of naturally low rainfall will be more likely to be unusually warm, say and colleagues at Stanford University. They report that, as in Syria, higher temperatures in recent times have exacerbated the impact of naturally dry years, making them more deadly to crops.
Unlike California, however, Syria tipped into civil war in 2011, which has been .
Using satellite images, Kelley鈥檚 team confirms that over-pumping of ground water in north-eastern Syria because of government subsidies for wheat production depleted a source of irrigation that farmers could otherwise have used when rains failed. Meanwhile, the Syrian government slashed food and fuel subsidies. 鈥淭his resulted in agricultural collapse and mass migration,鈥� says Kelley.
When relief failed to arrive over the next two years 鈥� , because the local mostly Kurdish population opposed Syrian president Bashar al-Assad 鈥� up to 1.3 million the north-east and into Syria鈥檚 urban slums, which already hosted a million refugees from Iraq.
Civil unrest
As a result of the drought, grain prices rose 27 per cent between 2008 and 2010, and mass migration into slums with few job opportunities meant that unemployment soared in a mostly 鈥� a recipe for unrest. Cities affected included Homs and Hama, where protests began in 2011.
Other investigators have linked climate stress and civil unrest . 鈥淭his is plausible,鈥� says of Woods Hole Oceanographic Institution in Massachusetts. 鈥淧lacing stress on a society tends to make violence more likely.鈥� But he whether that means such links are always important. The existing political unrest in the Middle East, he observes, might have led to violence in Syria even without a drought.
Kelley agrees there is no one cause for the violence 鈥� but cites who blamed the drought for 鈥減ushing people toward revolution鈥�.
Drought-stricken California, meanwhile, has been hit by , but no mass migration or violence. The difference, says Kelley, is resilience, the ability of a social system to absorb shocks and still function. 鈥淪yria鈥檚 vulnerability was very high before the drought,鈥� he says. 鈥淐alifornia has much higher resilience.鈥� Many societies at risk of climate shocks might benefit from understanding that resilience 鈥� and how to bolster it.
鈥淢any factors contributed to the unrest,鈥� says Mahmoud Solh, head of the International Center for Agricultural Research in the Dry Areas. Poverty played a role, he says, and the drought exacerbated poverty, while the government did not do enough to help farmers. It was trying to stop the overuse of groundwater by diverting water from the Euphrates into the region, he says 鈥� a project now halted by fighting.
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