At first glance, California and Syria appear to have little in common other than Mediterranean climates.
But two new studies – focusing on severe droughts in these places half a planet apart – highlight a yawning gap in the abilities of developed and many developing countries to adapt to the effects of climate change.
Each study, appearing in the current issue of the Proceedings of the National Academy of Sciences, documents ways in which global warming is boosting the likelihood of additional droughts as severe and prolonged as those the two have experienced.
But they also "are identifying the importance of risk and extreme events," says Noah Diffenbaugh, a researcher at Stanford University in California, and the lead author of the paper focusing on California's intense drought.
That risk, he explains, involves not just increases in the probability of extreme events, but "in the vulnerability of people and ecosystems that are in harm's way when those physical climate hazards occur." That vulnerability is influenced by farm, land-use, and water-management policies, other social, political, and economic factors, and population growth.
As geographically distant as the two regions are, they are even further apart in their economic ability to respond and adapt to severe changes in climate. Some adaptive strategies that have worked in affluent California would be hard to implement for poorer nations, such as Syria. Beyond differences in wealth and the behavior of the climate itself, political, social, and economic factors may be as important in determining potential for adaptation and the success of those efforts as changes to the climate itself.
These studies highlight the challenges international aid organizations are likely to face as distinct regions need specific intervention strategies, even when the challenges they face are strikingly similar.
In Syria's case, researchers say, decades of unsustainable farm, land, and water-use policies collided with a three-year drought that began in 2006-07 and was the driest drought on record. The confluence helped feed the instability leading to the country's civil war, according to the Syria study, by prompting up to 1.5 million people to leave farms and rural communities to the outskirts of cities, where ramshackle exurbs lacked basic services and became centers of unrest.
This interplay of climate, social, and political factors in compounding risks from climate extremes has received heightened attention in recent years.
The last round of reports from the Intergovernmental Panel on Climate Change, released in 2013 and '14, placed a new emphasis on the need to focus on the full range of factors that influence the risks from global warming.
The interplay also looms over efforts to help developing countries adapt to the effects of global warming.
Negotiators are working on mechanisms for channeling aid to developing countries for green development and adaptation as part of the effort to produce a new global climate treaty by the end of this year, notes Heather Coleman, climate-change policy manager for Oxfam America, a nongovernmental organization involved in a range of global development issues.
Among the aid provisions: Countries seeking money for green-development or adaptation will have to show they can responsibly oversee the money and must meet requirements for accountability and transparency in how the money is used.
"Countries that are unable to demonstrate they can meet those standards will not be able to access those funds," she says, even if the need is great.
Although they are poles apart in myriad ways, California and Syria share similar general climatic traits. Both have a rainy season that runs from mid-fall through late winter or early spring. Farmers in both places draw heavily – researchers say unsustainably – on groundwater.
With the Sierra Nevada falling within California's borders, however, networks of reservoirs capture runoff from melting mountain snowpack to get farmers and cities through the summer. Syrian farmers, meanwhile, have tended to rely focus on dry-land crops that can thrive with the seasonal rains, notes Richard Seager, who focuses on drought research at Columbia University's Lamont-Doherty Earth Observatory in Palisades, N.Y., and was a member of the team involved in the Syria study.
In both places, long-term warming has boosted the chances of prolonged, severe drought by increasing the periods where gradually rising temperatures coincide with periods of scant precipitation, the researchers say.
Prolonged periods of warmer temperatures tend to evaporate what little moisture may be available in the soil when precipitation is scarce. A prolonged drop in rain and snowfall may be traceable to natural swings in climate. But warming due to rising levels of greenhouse gases in the atmosphere from burning fossil fuels – and climate feedbacks that reinforce the warming – raise the likelihood for the overlap between unusual dry spells and warming.
For Syria, warming has doubled or tripled the likelihood of debilitating droughts compared with what one might expect from natural variability, according to the team studying that country's droughts. For California, warming has virtually ensured that over the next several decades the annual dry season also will be extremely warm, boosting the chances for more droughts on the scale of the drought California currently is enduring.
Yet the Golden State – politically stable and wealthy, with a $2-trillion economy – has been implementing various water conservation measures over several decades and is exploring ways to ramp up its adaptation measures.
There are plenty of adaptation ideas for Syria – embroiled in a civil war and with a gross domestic product that by some estimates falls south of $64 billion.
Four years ago, for instance, the International Food Policy Research Institute in Washington outlined adaptation options for Syria, ranging from diversifying its economy so that non-farm jobs are available for a growing population to improved grazing and irrigation practices down on the farm.
But "the political and social conditions will make it hard to do any adaptation," Dr. Seager says, noting that it's not just a Syrian issue, but a regional one as well.
The Fertile Crescent and Levant are areas where global warming's signal – warmer and drier – is emerging from the static of natural variability, he says. Concerns over water and the potential for conflict that could arise there over it have long been a concern.
Opportunities for increased adaptation efforts exist. For instance, international agreements governing water rights between countries such as Turkey, Syria, and Iraq exist, he notes.
But when countries such as Syria "are in this degree of disarray, it's going to be hard to use those to strengthen adaptation," he says.