Climate change significantly increased the likelihood of the devastating storm that struck the Libyan city of Derna, resulting in thousands of casualties, according to experts.

Climate scientists from the World Weather Attribution group found that human-caused greenhouse-gas emissions led to up to 50% more rainfall, making the storm up to 50 times more probable.

The report also highlighted that years of regional conflicts made the population more susceptible to flooding, escalating the extreme weather event into a full-fledged humanitarian catastrophe.

The researchers used computer simulations to evaluate the increased likelihood of such a storm due to the 1.1°C of warming already caused by climate change. However, they emphasized that limited data, especially in Libya, introduced substantial uncertainties into their findings.

Storm Daniel, responsible for the deadly rains in Greece, Bulgaria, and Turkey, had already dumped 910mm (35in) of rain, resulting in 28 fatalities. The study revealed that climate change made such an event up to 10 times more probable, bringing 40% more rainfall.

Intense storms of this nature are becoming relatively common in the region, occurring approximately once every 10 years, the study cautioned.

However, the weather event in northern Libya was far more exceptional, producing a storm of intensity expected to occur only once every 300-600 years in that region.

As Storm Daniel slowly traversed the Mediterranean, it absorbed extra energy from sea temperatures 2-3 degrees above the September average.

Kostas Lagouvardos from the National Observatory of Athens explained, "Storm Daniel was a low-pressure weather system, as we usually have in the Mediterranean. It was not very deep, but it was very early in the season and remained stagnant over the south Ionian Sea for four to five days."

This additional warmth fueled stronger winds and allowed the air to hold more moisture. When it struck the northern coast of Libya, it unleashed an estimated 400mm of rain on Derna in just 24 hours, an astonishing figure compared to the city's average September rainfall of 1.5mm, according to Nasa's Earth Observatory.

The catastrophic impact demonstrated how extreme weather can intersect with vulnerable populations, leading to devastating consequences, the scientists noted.

In Libya, the ousting of Colonel Muammar Gaddafi in 2011 was followed by political instability and civil war. Two aging and poorly maintained dams were situated upstream of Derna, and many homes were constructed in flood-prone areas. When the dams ruptured, tens of millions of cubic meters of water inundated the city, wiping out entire neighborhoods.

The researchers acknowledged that their findings had significant mathematical uncertainties due to the relatively small affected areas, limited data availability, and the challenge of accurately representing small-scale rainfall in most climate models. However, they remained confident that climate change played a substantial role, given the strong evidence linking higher temperatures to heavier rainfall and the known intensification of weather systems like Storm Daniel due to climate change. Photo by Syed Wali Peeran, Wikimedia commons.