The drought that played a role in triggering the catastrophic Syrian Civil War was the worst such climate event in at least the past 900 years, according to a new study published this week.

The study bolsters the conclusions from other research that found that because of human-made global warming, the drought was made three times more likely to occur, and that it was one of a number of factors that led to the outbreak of hostilities in 2011.

The new study examined tree-ring records showing the annual precipitation history from recent years back to the year 1100, across an area stretching from southern Europe to northern Africa to the Levant region of the Middle East.

Drought index for the past six months in the Levant region. Reds/oranges show below average precipitation. Image: NASA

The Levant region encompasses Cyprus, Israel, Jordan, Lebanon, Palestine, Syria, and Turkey.

The study, published in the Journal of Geophysical Research-Atmospheres, found that in the western Mediterranean, recent droughts have not yet departed from their natural variability, but in the east, including Syria, they have.

The drought, along with other factors, forced about 1.5 million rural residents to urban areas in Syria to look for work.





The conclusion about the Levant drought in particular increases confidence in computer model projections of future climate conditions.

These projections almost unanimously show a much drier Middle East, northern Africa and Southern Europe, as weather patterns shift in response to a warming climate.

This is a worrisome prediction for the Pentagon and intelligence community, who see water stress and population growth as two factors that are likely to tip the scale toward more conflict and humanitarian crises in the coming decades.

The roots of the Syrian civil war, which according to a recent estimate has killed at least 470,000 people and helped set in motion one of the most significant human migrations on record, can be traced in part to the drought. The drought, along with other factors, forced about 1.5 million rural residents, including farmers, to urban areas in Syria to look for work, including Aleppo and Damascus.

The government's inadequate response to the drought and resulting massive internal displacement was one of a series of events that helped spark what was initially a series of uprisings against the government of President Bashar Al-Assad, but soon turned into a devastating, all-out civil war.

A view of Aleppo, Syria, on Feb. 18, 2016. Image: Iliya Pitalev/Sputnik via AP

For example, government policies encouraged the unsustainable use of water resources and provided inadequate aid to displaced persons.

Richard Seager, a researcher at Columbia University's Lamont Doherty Observatory in New York, who co-authored a landmark 2015 study on the Syria drought and civil war but was not involved in the this study, said the new study helps back up the earlier work.

"[The study] truly backs up our contention... that the Syria drought was unusual and influenced by human-driven climate change. As such, it places more confidence in model projections that drying will continue and intensify across Middle East in coming decades and, yes, cause more trouble in a water scarce area," he said in an email to Mashable.

There is a vigorous debate in the climate community and among researchers who study the factors that lead to social conflict regarding how climate change may increase the odds for future conflicts. The bottom line is that, even in the case of the Syrian drought, a climate event did not directly cause a civil war. But it was an important factor.

"It is important that the national security community is taking climate variability and climate change seriously as both a present and future threat multiplier," said Kevin Anchukaitis, a researcher at the University of Arizona and a co-author of the new study.

"However, I want to also voice a caveat here, which is that the actual literature on climate and conflict — particularly with respect to water — also suggests that competition over limited water actually leads in many instances to cooperation, not conflict," he wrote in an email to Mashable.

Global warming worsened recent drought

The new study — from researchers at NASA, the Lamont Doherty Earth Observatory in New York and other institutions — used different methods than previous studies and showed that manmade global warming likely worsened the most recent drought, making it more intense than similar events in the past.

Re-centered (zero mean from 1100–2012 CE) time series of a drought index (scPDSI) for WestMED, Greece, and the Levant region. Red lines represent smoothed versions using a 10-year loess smoother. Image: Cook et al. 2015

In other words, global warming-amplified droughts are not a phenomenon solely for the future inhabitants of the Middle East to deal with. Such droughts are, in all likelihood, already here.

The reason why this part of the world is getting drier is thought to lie in a northward movement of subtropical dry zones, areas that used to be confined to north-central Africa. These regions are prone to sinking air masses, which dry out the air and stifle any precipitation.

To arrive at their conclusions, the researchers used a database known as the Old World Drought Atlas.

For this study, they took 106 tree-ring time series from northern Africa to Greece and all the way to Syria to reconstruct a drought index across the European-Mediterranean region during the past millennium. Their analysis showed that the index accurately captured drought history in this region, after comparing it to other data, such as historical texts.

For January 2012, brown shades show the decrease in water storage from the 2002-2015 average in the Mediterranean region. Units in centimeters. Image: NASA/ Goddard Scientific Visualization Studio

The study found that the 1998-2012 period was drier than the previous driest interval in the time period in question, which occurred during the years from 1205 to 1219.

The study concluded that the drought in the Levant during the 1998 to 2012 period had an 89 percent likelihood that it was the driest 15-year period of the last 900 years, and a 98 percent likelihood that it was the driest 15-year period of the last 500 years.

While the study does not allow scientists to quantify the size of the manmade global warming influence on droughts in the Levant region, it does show that the "recent dry extremes are exceptional relative to natural variability during the last millennium," the study states.

"This offers some independent support for recent studies concluding that [human-made] climate change has had a significant influence," the study states.

As Seager put it, "a long-term decline in winter precipitation in the eastern Mediterranean region made the drought worse and the trend is consistent with model projections of regional precipitation change under global warming."

In other words, this Syrian drought, and the cataclysmic conflict that has been a related result, may be just the beginning of a long period of water stress and instability in the once-fertile Levant region.