Syria’s 1998-2012 drought likely its most severe in more than 900 years
“After the release of the Old World Drought Atlas last year, we have been eagerly awaiting research like this that places recent droughts in the context of variability over the past millennium, far longer than the century or so that can be analyzed with weather station records,” said Richard Seager, a climate scientist at Lamont and co-author of the 2015 Syria drought study.
“Cook and colleagues’ result is consistent with human-driven climate change and drying of the Middle East having contributed to the severity of the drought. This also raises confidence in climate models that indicate the eastern Mediterranean will be a hot spot of aridification due to rising greenhouse gases and that this change is already underway,” Seager said.
Mediterranean climate patterns
Across the Mediterranean, the new study shows some basic patterns. Large droughts tend to affect both the west end of the Mediterranean and the east end at the same time. North and South tend to be the opposite: When Turkey and the Anatolian region are wetter than normal, coastal Libya, Egypt, and the Levant tend to be drier than normal. The study highlights several periods of persistent drought across the entire Mediterranean region during the Medieval period, including in the 1100s, 1200s, and 1300s, but the scientists found no evidence of megadroughts of more than 30 years as studies have shown in North America during that time.
Some unusual patterns also appear that provide fodder for future research. For example, a nearly two-decade period of excessive rain from 1125 to 1142 in what today would be Spain, Morocco, Algeria, Tunisia, Italy, the Balkans, and Turkey occurred at the same time as extended drought across much of North America. That suggests that there could have been a large-scale shift in atmospheric circulation across the Atlantic, possibly related to sea surface temperatures, the authors write.
This new ability to see how periods of drought and extreme wetness play out across the Mediterranean basin over a millennium can help provide better evaluations of climate model simulations, Cook said. Climate model simulation, in turn, may tell scientists more about the dynamics and the drivers of different drought events.
“Even if you don’t care about climate change, our instrumental records are pretty short, so our understanding of natural variability is pretty limited by the last 100 years of data. These longer paleo records allow us to better characterize natural variability to really better understand, for example, how often droughts of a certain magnitude would happen even without climate change,” Cook said.
Columbia U notes that the Old World Drought Atlas was created from the analysis of thousands of tree ring samples collected into local chronologies. In the Levant, tree ring scientists have been able to date existing forests and timber beams and cedar flooring in ancient buildings going back to the 1300s. Older chronologies from within a 1,000 kilometer radius help to fill in details for the region going farther back in time.
— Read more in Benjamin I. Cook et al., “Spatiotemporal drought variability in the Mediterranean over the last 900 years,” Journal of Geophysical Research: Atmospheres (4 March 2016) (DOI: 10.1002/2015JD023929
