Climate change made deadly Mediterranean rains up to 50 times more likely

Scientists now dare to correlate specific meteorological events and climate change.

Oliver Thansan
Oliver Thansan
18 September 2023 Monday 16:27
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Climate change made deadly Mediterranean rains up to 50 times more likely

Scientists now dare to correlate specific meteorological events and climate change. Before they shied away from this type of attribution. The latest assessment in this regard indicates that warming resulting from human activities has made it possible for an event of extremely heavy, deadly rains such as the one recently recorded in Greece, Bulgaria and Turkey to be currently up to 10 times more likely under current circumstances than if the change did not exist. climate. And in the case of Libya, that probability is up to 50 times higher. In this country, furthermore, building on floodplains, poor dam maintenance, and other local factors turn extreme weather into a humanitarian disaster.

Climate change resulting from human activities caused the episode of heavy rains recorded in much of the Mediterranean at the beginning of September to increase the degree of probability of its occurrence.

This is according to a rapid analysis carried out by an international team of climate scientists from the World Weather Attribution group.

The study also found that the destruction caused by the heavy rains was much greater due to factors including construction in flood-prone areas, deforestation and the fallout from the conflict in Libya.

In early September, a depression that affected Spain and a low pressure system called Storm Daniel, which formed in the eastern Mediterranean, caused large amounts of rain over a 10-day period in several countries, including Spain, Greece and Bulgaria, Turkey and Libya.

Heavy rain caused massive flooding across the region, resulting in four deaths in Bulgaria, five in Spain, seven in Turkey and 17 in Greece.

However, the biggest disaster occurred in Libya, where flooding caused two reservoirs to collapse. While the exact number of victims is still unclear, there are currently 3,958 confirmed deaths in Derna alone and 170 people in other parts of Libya, while more than 10,000 people remain missing.

To assess the effect of climate change on heavy rainfall in this region, scientists analyzed climate data and computer model simulations to compare the current climate – which has seen almost 1.2°C of global warming since the late 19th century. with the climate of the past, following peer-reviewed methods.

The scientists divided their analysis into three regions: Libya, where the analysis focused on the northeastern part of the country, the area where most of the rainfall fell; Greece, Bulgaria and Turkey, where the analysis looked at maximum rainfall for four consecutive days; and Spain, where most of the rain fell in just a few hours.

In the case of Libya, scientists discovered that human-caused climate change made this event up to 50 times more likely, and up to 50% more rainfall was measured during that period as a result of greenhouse gas emissions. greenhouse gases caused by man. An event like this can only be expected to occur once every 300 to 600 years in the current climate.

Likewise, in the case of Greece, Bulgaria and Turkey, climate change made such heavy rains up to 10 times more likely, and up to 40% more rainfall was recorded as a result of human activities that have warmed the planet.

For this large region, covering parts of all three countries, this event is now relatively common and can be expected to occur approximately once every 10 years, meaning it has a 10% chance of occurring each year. For central Greece, where most of the impacts took place, such an event is less likely and is only expected to occur once every 80-100 years, which equates to a 1 to 1.25% chance that it could occur every anus.

In Spain, where most of the rain fell in just a few hours; Scientists estimated that such a heavy rainfall event could be expected to occur once every 40 years, but they were unable to perform a full attribution analysis because available climate models poorly represent heavy rainfall on time scales as short as of one day.

However, scientists highlight that all these findings are surrounded by large mathematical uncertainties, since the events occurred in relatively small areas and most climate models do not represent precipitation well on these very small scales.

Although they cannot completely rule out the possibility that climate change has not affected the probability and intensity of events like these, they are certain that it has, for several reasons. First, they highlight that rising temperatures generally lead to heavier rainfall and that studies project heavier rainfall in the region as temperatures rise. Likewise, they could not find evidence of factors that could be making heavy rains less likely and thus balance the influence of climate change. And thirdly, data from weather stations in the region show a trend towards heavier rains. Due to the limitations of the models, the scientists did not give a central or mean estimate of the influence of climate change, as they had done in previous studies, but instead gave an upper limit of the effect.

A key finding of the study is that the large impacts observed in some of the regions were caused by a combination of high population vulnerability and exposure to the event. In the affected area of ​​central Greece, most cities and communities and much of the infrastructure are located in flood-prone areas. In Libya, a combination of several factors, including a long-running armed conflict, political instability, potential design flaws, and poor dam maintenance, contributed to the disaster. The interaction of these factors and heavy rains made worse by climate change created extreme destruction.

The study was carried out by 13 researchers as part of the World Weather Attribution group, including scientists from universities and research centers in Greece, the Netherlands, the United Kingdom and the United Kingdom.

“The Mediterranean is a focus of dangers caused by climate change. After a summer of devastating heatwaves and wildfires with a very clear footprint of climate change, quantifying the contribution of global warming to these floods was a challenge,” said Friederike Otto, senior lecturer in climate science at Imperial College London. “But there is absolutely no doubt that reducing vulnerability and increasing resilience to all types of extreme weather conditions is essential to saving lives in the future,” she adds.

“This devastating disaster shows how extreme weather events driven by climate change combine with human factors to create even greater impacts, as more people, assets and infrastructure become exposed and vulnerable to flood risks,” said Julie Arrighi, director of the Red Cross and Red Crescent Climate Centre. "However, there are practical solutions that can help us prevent these disasters from becoming routine, such as strengthened emergency management, better forecasts and warning systems based on the impact, and infrastructure designed for the future climate,” he added

“The extreme rainfall that affected central Greece and its devastating effects are a turning point in the way we must reorganize early warning systems towards impact-based alerts, the response capacity of Civil Protection and the design of resilient infrastructure. in the climate era. Change,” said Vassiliki Kotroni, research director at the National Observatory of Athens.