Climate change "undoubtedly" played a role in Libyan floods that killed over 11,000 people: experts

A devastating flood that tore through eastern Libya has left at least 11,300 people dead and thousands more still missing. The deadly downpour began over the weekend when torrential downpours from Cyclone Daniel caused two upstream river dams to burst. The nearby city of Derna was overwhelmed, and reporters describe miles upon miles filed with distraught survivors and debris. It is reportedly Africa's deadliest storm in recorded history and the most lethal natural disaster so far this year.

The storm began over the Ionian Sea and damaged a few other countries on its way to Libya, including Bulgaria and Turkey. In Greece, Daniel killed 16 people and swamped the country's agricultural center, the effects of which will be felt of years to come, Politico reported, putting additional strain on a region already struggling under climate change. But Libya has by far taken the worst damage from the storm, with an estimated 30 million cubic metres of water released when the dams gave way.

"Hundreds of body bags now line Derna's mud-caked streets, awaiting mass burials, as traumatised and grieving residents search mangled buildings for missing loved ones and bulldozers clear streets of debris and mountains of sand," France 24 reported. The death toll is could rise as high as 20,000, according to Derna's mayor.

There are many factors that contributed to this devastation — and experts agree climate change was likely the primary catalyst.

To know for sure, a direct study of the Libyan floods would be required, climate scientist Dr. Stephanie Herring pointed out, noting that "increases in heavy rainfall (or extreme precipitation) such as observed in Libya are consistent with what we expect in a warmer world, and consistent with what we are already observing in many regions across the planet including regions here in the U.S." The National Oceanic and Atmospheric Administration (NOAA) scientist then broke down the process which causes this to happen.

"In general, as the Earth's temperature rises, more water evaporates from the surface into the atmosphere," Herring explained. "Warmer air can hold more moisture, so there is an increase in the amount of water vapor in the atmosphere and can result in more extreme precipitation events."

Other scientists agree. According to Dr. Michael E. Mann, a professor of Earth and Environmental Science at the University of Pennsylvania, "the atmosphere has on average about 7% more water vapor because of the warming that has occurred so far. That means that every rainfall event is on average about 7% greater, but modeling studies have shown that the effect can be even greater than that (sometimes 20% or 30%) because stronger storms entrain more moisture into them."

Unfortunately, climate change is not only making the storms more intense; it makes them last longer.

"In summer, as our own research has shown, human-caused climate change is favoring stalled weather systems that remain in place for longer periods of time, leading to more persistent heat and flooding events," Mann explained.

Like Herring and Mann, Dr. Kevin E. Trenberth — a distinguished scholar at the National Center for Atmospheric Research who has written about water vapor and extreme weather — told Salon by email that climate change was "undoubtedly" a component in heavy rains that bombarded the Libyan dams. Yet he emphasized another variable, one that is highly specific to the context of the Libyan flood: Poor implementation of effective emergency policies by Libyan government authorities.

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Trenberth attributed the disaster in no small part to those factors, pointing to "failing infrastructure (2 dams) and its management." His views were echoed by Petteri Taalas, head of the United Nation's World Meteorological Organization, who told reporters that government officials "could have issued the warnings and the emergency management forces would have been able to carry out the evacuation of the people, and we could have avoided most of the human casualties."

Michael Wehner, a senior scientist in the Computational Research Division at the Lawrence Berkeley National Laboratory, connected the question of climate change's impact on the floods very specifically to those dams. Until scientists know more about how those dams broke down and why, they cannot deduce the extent to which climate change was a factor as opposed to more immediate forms of human error.

"As the flood was caused by the two dam breaks, the critical question is whether those dams would have failed in a less severe storm without climate change," Wehner explained. "This is an extremely difficult question that may or may not be answerable depending on how much is known about the dams. Hence such an analysis would require experts on these particular dams."

Herring also concluded that the next step for scientists trying to piece together the horrors of the flood is actually examining other drivers of the event, such as the atmospheric circulation patterns. Yet even though it is impossible to predict exactly how much climate change contributed to this specific event, none of the scientists deny that our warmer planet now has more atmospheric water vapor, and that this will ultimately cause more extreme weather.

"Not specific to the Libya event, but I'll add that NOAA and the scientific community have collected a robust body of evidence such that now, per the IPCC, it is considered 'established fact' that some extremes are changing in a warmer world," Herring said. "While we do have the ability to answer your first question of 'to what extent', the scientific community still struggles to do this in a timely manner for a broad range of events. It takes a great deal of scientific investment to perform these studies, and there isn't the capacity to do this rapidly for every event."