People walk with face covers at Jaffa Gate near the Tower of David in Jerusalem, Sept. 8, 2015, as a sandstorm hit across Israel. (Yonatan Sindel/Flash90)

(JTA) — A recent 14-year dry spell in the Middle East was the worst drought in the past 900 years, according to a new NASA study.

The American space agency’s researchers examined records of rings of trees in several Mediterranean countries to determine patterns of dry and wet years across a span of nine centuries. In the study published this week, they concluded that the years from 1998 to 2012 were drier than any other period, and that the drought was likely caused by humans, the Associated Press reported.

The study’s lead author Ben Cook said the range of extreme weather events in the eastern Mediterranean has varied widely in the past nine centuries, but the past two decades stand out.

Israel also experienced a severe drought, but its effects were significantly dampened by its array of six desalination plants.

When the sixth plant in Ashdod goes into full production, Israel’s desalination plants will reach 600 million cubic meters of water — which is nearly 70 percent of Israel’s domestic water consumption. According to a government decision, by 2020 the desalination plants should reach a capacity of 750 million cubic meters.

Cook, the Nasa scientist, said the Middle East drought “falls outside the range of natural variability.”

Cook is a climate scientist at NASA’s Goddard Institute for Space Studies and the Lamont Doherty Earth Observatory at Columbia University in New York City.

The researchers used records of tree rings in Northern Africa, Greece, Lebanon, Jordan, Syria and Turkey, and combined the data with records from Spain, southern France and Italy to examine patterns of drought across time in the region.

They studied rings of trees, both living and dead, that were sampled all over the region. Rings in the trunks of trees represent years. Thin rings indicate dry years; thick rings show years when water was abundant.

Cook said the research supported other studies indicating human causes of extreme climate events.

The water shortage was one of several contributing factors that worsened the situation in Syria in the lead-up to the outbreak of that country’s devastating civil war in 2011.

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