Human-caused warming made the heavy rainfall up to 10 times more likely in Greece, Bulgaria and Türkiye and up to 50 times more likely in Libya, with building in flood plains, poor dam maintenance and other local factors turning the extreme weather into a humanitarian disaster.
Heavy rainfall, which caused devastation in large parts of the Mediterranean in early September, was made more likely to happen by climate change resulting from greenhouse gas emissions, according to rapid analysis by an international team of climate scientists from the World Weather Attribution group. The study also found that the destruction caused by the heavy rain was much greater due to factors that included construction in flood-prone areas, deforestation, and the consequences of the conflict in Libya.
In early September, a cut-off low which affected Spain and a low-pressure system named Storm Daniel, which formed in the Eastern Mediterranean, brought large amounts of rain over a 10-day period to several countries, including Spain, Greece, Bulgaria, Türkiye and Libya. The heavy rain led to massive floods across the region, killing four people in Bulgaria, five in Spain, seven in Türkiye, and 17 in Greece.
The greatest disaster occurred in Libya, where the floods caused the collapse of two dams. While the exact number of casualties is still not clear, there are currently 3,958 confirmed deaths in Derna alone and 170 people elsewhere in Libya, with over 10,000 people still missing.
To quantify the effect of climate change on the heavy rain in the region, scientists analysed climate data and computer model simulations to compare the climate as it is today, after about 1.2°C of global warming since the late 1800s, with the climate of the past, following peer-reviewed methods.
The scientists divided their analysis in three regions: Libya, where the analysis focused on the northeast part of the country, where most of the rainfall fell; Greece, Bulgaria and Türkiye, where the analysis looked at maximum rainfall over four consecutive days; and Spain, where most of the rain fell in just a few hours.
For Libya, the scientists found that human-caused climate change made the event up to 50 times more likely to happen, with up to 50% more rain during the period, as a result of human-caused greenhouse gas emissions. The event is still extremely unusual, and can only be expected to occur around once in 300-600 years, in the current climate.
For Greece, Bulgaria and Türkiye, the analysis showed that climate change made the heavy rain up to 10 times more likely to happen, with up to 40% more rain, as a result of human activities that have warmed the planet. For this large region, which encompasses parts of the three countries, the event is now reasonably common, and can be expected about once every 10 years, meaning it has a 10% chance of happening each year. For central Greece, where most of the impacts took place, the event is less probable and only expected to happen once every 80-100 years, equivalent to a 1-1.25% chance of happening each year.
In Spain, where most of the rain fell in just a few hours, the scientists estimated that such heavy rainfall is expected once every 40 years, but they could not conduct a full attribution analysis as the available climate models poorly represent heavy rainfall on timescales shorter than a day.
These findings have large mathematical uncertainties, as the events occurred over relatively small areas, and most climate models do not represent rainfall on these small scales well. While the scientists cannot completely rule out the possibility that climate change has not affected the likelihood and intensity of events like these, they are confident that it did play a role for several reasons: increased temperatures generally lead to heavier rainfall and studies project heavier rain in the region as temperatures rise; they could find no evidence of factors that might be making heavy rain less likely and balancing the influence of climate change; and weather station data in the region shows a trend towards heavier rain. Because of the limits in the models, the scientists did not give a central estimate of the influence of climate change, as they have done in previous studies, instead giving an upper-bound of the effect.
A key finding of the study is that the very large impacts observed in some of the regions were caused by a combination of high vulnerability of the population and their exposure to the event. In the affected area in Central Greece, most of the cities and communities and a large part of the infrastructure are located in flood-prone areas. In Libya, a combination of several factors including long-lasting armed conflict, political instability, potential design flaws and poor maintenance of dams all contributed to the disaster. The interaction of these factors, and the very heavy rain that was worsened by climate change, created the extreme destruction.
The study was conducted by 13 researchers as part of the World Weather Attribution group, including scientists from universities and research centres in Greece, the Netherlands, the United Kingdom and the United States.
Vassiliki Kotroni, Research Director at the National Observatory of Athens, said: “The extreme rainfall amounts that affected central Greece and their devastating effects are a breaking point in the way we should re-organise the early warning systems towards impact-based alerts, the Civil Protection response capacity, and the design of resilient infrastructures in the era of climate change.”
Friederike Otto, Senior Lecturer in Climate Science at Grantham Institute – Climate Change and the Environment, Imperial College London, said: “The Mediterranean is a hotspot of climate change-fueled hazards. After a summer of devastating heatwaves and wildfires with a very clear climate change fingerprint, quantifying the contribution of global warming to these floods proved more challenging. But there is absolutely no doubt that reducing vulnerability and increasing resilience to all types of extreme weather is paramount for saving lives in the future.”
Julie Arrighi, Director at the Red Cross Red Crescent Climate Centre, said: “This devastating disaster shows how climate change-fueled extreme weather events are combining with human factors to create even bigger impacts, as more people, assets and infrastructure are exposed and vulnerable to flood risks. However, there are practical solutions that can help us prevent these disasters from becoming routine such as strengthened emergency management, improved impact-based forecasts and warning systems, and infrastructure that is designed for the future climate.”
Ben, refugee from Darfur and founder of ‘Refugee Network Libya’, said: “Mercy and forgiveness to all victims of the painful natural tragedy in eastern Libya, Derna. We have lost countless migrants as a result of the painful Hurricane Daniel, and I do not know why the media is silent about what we are experiencing in Libya.
“We, as the Refugee Network Libya, want to highlight to communities around the world (Europe) that we are dying in Libya, because of EU and Italy’s support for Libya. These western governments should instead provide support to evacuate migrants, because Libya is not safe for us.
“The warnings from scientists about natural disasters also show that we are in real danger in Libya. Our homes as refugees are uninhabitable. As for the prisons, they are all in non-strategic locations that are at risk in light of this disaster. Here, we demand the release of all refugees. We are in real danger in Libya.”
Gorden Isler, spokesperson for civil search and rescue organisation Sea-Eye, said: “As well as taking thousands of lives, the horrific floods in Libya. are compounding an already catastrophic humanitarian emergency. Those forced to flee by the disaster will join the ranks of displaced people who are routinely imprisoned, exploited, tortured, and sold into slavery.
“While our crews encounter people risking death at sea to flee Libya on every mission, Europe maintains the fiction that Libya is a “safe third country” for refugees. And even when they flee Libya; refugees are violently dragged back to danger by the so-called ‘Libyan Coast Guard’, an institution dependent on funding from Europe.
“This latest emergency demonstrates the need for urgent action from European states to address both the causes and consequences of climate disasters. This must include ending border control deals that cost lives and destabilise the region; and instead putting those resources into helping people.”
Nadia Bloemendaal, Assistant professor on extreme weather risk at the Institute for Environmental Studies and the Royal Netherlands Meteorological Institute, said: “Storm Daniel is the latest example of a very impactful Mediterranean hurricane (medicane). Daniel’s wind speeds peaked at 83 km/h over the open waters. But most impacts from Daniel are due to the unprecedented rainfall totals it brought onshore in Greece and Libya. These high rainfall totals were directly caused by the warm Mediterranean Sea waters, and resulted in rainfall totals of over 750 mm and 400 mm over Greece and Libya, respectively.
“The largest impacts of Daniel are now seen in the Libyan port city of Derna, where a combination of factors has now led to the significant impacts that are starting to unfold. First of all, Derna is located in an estuary of the Wadi Derna River, a river that runs from the mountains in the desert to the Mediterranean Sea. As dry ground barely takes up any moisture, Daniel’s excessive rainfall that fell in the mountains directly ended up in the river, leading to a sudden and substantial rise of the river’s water level.
“Secondly, two dams that were built in the Wadi Derna had been poorly maintained in the last few decades. This directly contributed to the two dams breaching early Monday morning. Third, many houses and apartment complexes in Derna were built directly alongside the river. When the dams breached and the water came surging into the city, these houses and apartments collapsed under the force of the water.
“And finally, and perhaps most importantly, Libya has very poor economic and political conditions to provide adequate flood early warning systems. As the dams breached early Monday morning, many people were caught off guard by the sudden flood rushing into the city, as they were still sleeping.”
Thuy-Binh Nguyen, Climate Adaptation Specialist at the CARE Climate Justice Centre, said: “The images coming out of Libya defy belief, but this tragedy is a very real and predictable consequence of what happens when climate change collides and intertwines with other factors. The devastation caused by floods following storm Daniel can be seen as the combined effects of climate change, prolonged conflict and environmental degradation. The victims of these compounding risks were ordinary people, who, despite already dealing with severe stress, were just trying to live their lives. Leaders must recognize that climate change exacerbates existing vulnerabilities, and there is an urgent need to strengthen early warning systems, invest in disaster risk reduction policies and actions, and fully finance the resilience of vulnerable communities.”
Jamie Williams, senior policy advisor for poverty reduction at Islamic Relief, said: “The floods that have hit Libya, where at least 11,300 people have died is a rising trend in more intense and frequent disasters taking place across the world due to climate change. Extreme weather events will be testing infrastructure more often and more severely as the globe heats and climate systems break down. We must learn from Libya that these events can happen anywhere and anytime.
“Twenty out of Libya’s 22 districts exhibit significant vulnerability to direct climate-related hazards. The districts with the highest levels of vulnerability include Zawiya, Murqub, Jufra, Wadi al Shatii, and Sirte. As these impacts intensify, urgent measures are imperative to safeguard the lives of Libya’s citizens. Urgent intervention is needed to repair and fortify flood defence and drainage infrastructure.
“Stable governance is needed to enforce life-saving planning regulations and strengthen monitoring and early warning systems.”
Iskander Erzini Vernoit, co-founding director at the IMAL Initiative, a North African climate thinktank based in Rabat, Morocco, said: “While acknowledging the role played by local infrastructure management and underinvestment, this unspeakable catastrophe also illustrates the mounting losses and damages borne by African and Arab nations. It underscores the need for developed countries, as the historically responsible polluters, to increase their overall finance for developing countries beyond the decades-old target of 0.7% of GDP.”
Ali Salem Eddenjal, Director, Research & Studies, Libyan National Meteorological Centre and IPCC focal point, said: “The devastating floods in Libya are a glaring example of how climate change is affecting predictable weather patterns in Africa and the surrounding areas. From Malawi and Mozambique to present-day Libya, these incidents are becoming more widespread. Although the general orientation of Libya precipitation, among Northern African countries, is trending towards dryness, rainfall extremes events are expected to increase in intensity because of Global Warming and Climate Change. Such events will be accompanied with destruction and life losses under shoddy infrastructure and poor urban design.
“This is a strong plea for Western nations to reduce emissions in order to safeguard those in Africa who are most at risk. This is also an opportunity to set up early warning systems around the globe to stop similar calamities from happening again. The Libyan floods call for more investment in meteorology, such as getting support for some capacity building to improve Met Services and the quality of research work on climate, climate change, weather extremes and climate events as well as early warning systems in Libya.”
Fadhel Kaboub, Economist, President of the Global Institute for Sustainable Prosperity and Associate Professor of Economics at Denison University, said: “The tragic loss of life and destruction caused by storm Daniel in Libya is a stark reminder of the urgency to deal with climate change by rapidly scaling up climate adaptation efforts in the region. The Loss and Damage fund must be made operational and fully funded before the end of this year. The global community needs to design a systemic approach to transfer technology, know-how, and financial resources to help those who are the least responsible for, and the most impacted by, climate change to adapt and build resilience so we can avoid such tragedies in the future.
“It is pure madness to see hundreds of billions of dollars go into new fossil fuel infrastructure and subsidies when we should be negotiating a just transition framework under a Fossil Fuel Non-Proliferation Treaty to end the root cause of this climate crisis.”
