At the end of October, 222 people died in floods in Valencia, Spain. During the summer, over 1,700 people lost their lives in a heatwave that hit Spain, Portugal, and Morocco. In September 2023, the Daniel depression devastated the Libyan shores, causing over 14,000 deaths.
Deadly heatwaves, oceanic heatwaves, and devastating floods: the countries along the Mediterranean Sea are highly exposed to global warming and its consequences. Here are the explanations in maps and graphs.
A Region Heating Up Faster Than the Global Average
2023 was announced as the hottest year, with a global temperature increase of +1.45°C compared to pre-industrial temperatures. On November 11, the World Meteorological Organization (WMO) announced that 2024 was on track to break this record with a global temperature rise of +1.54°C. This warming, caused by excessive greenhouse gas emissions from human activities, is not uniform. The Mediterranean basin, a transitional zone between the atmospheric circulation regimes of mid-latitudes and subtropical areas, is warming 20% faster than the rest of the world. It is considered a climate change hotspot.
Oceanic Heatwaves
This temperature rise affects both the atmosphere and surface waters of seas and oceans. Oceans absorb 30% of carbon dioxide emissions and 93% of the excess heat due to global warming.
On August 15, 2024, the median daily surface temperature of the Mediterranean Sea reached 28.90°C, surpassing the previous record of 28.71°C measured on July 24, 2023, according to the Catalan institute Icatmar. In comparison, during the heatwave summer of 2003, the daily median was 28.25°C. When surface water temperatures remain higher than average for at least five consecutive days, they are referred to as oceanic heatwaves.
According to a study conducted by researchers from the National Center for Meteorological Research (CNRM – Météo-France/CNRS) between 1982 and 2017, these heatwaves last on average fifteen days, with an average intensity of 0.6°C above the threshold. In recent decades, the duration, extent, and intensity of these phenomena have increased. The summers of 2003, 2012, 2015, and 2017 saw the most severe oceanic heatwaves recorded. The last two years have since broken these records.
Mediterranean episodes are weather phenomena characteristic of the northern Mediterranean climate during autumn and winter. They are marked by significant rainfall over a short period, exceeding 100 millimeters and up to 500 millimeters locally—equivalent to several months’ worth of rainfall in just a few days, or even hours.
Climate change is intensifying these episodes.
Jet streams form at high altitudes, horizontally, at the boundary between air masses of different temperatures and pressures.
The jet stream and its disturbances move north in summer and south in winter. In autumn, disturbances more easily reach the Mediterranean region.
Throughout the year, jet streams oscillate more or less strongly. A cold air mass can detach and move to lower latitudes. This is called a « cold drop. »
With the warming of the Mediterranean, the air masses at the surface are warmer and more humid.
The wind pushes the warm, humid air from the sea onto the land. It meets the colder air at higher altitudes, making the atmosphere unstable. This instability causes the warm air to rise. The presence of mountains amplifies this rising phenomenon.
As it rises, the warm air cools. The water vapor it contains condenses and falls as precipitation. This is a thunderstorm.
A thunderstorm is usually a short-duration phenomenon. It can be isolated (due to the relief or the warming of the soil in summer) or organized in a line (the « squall line »).
The temperature difference between the unstable warm air rising and the cold, dense air descending continues to fuel the storm. This is called a stationary thunderstorm.
As the cold air descends, it pushes the warm air near the thunderstorm cloud. This warm air may rise again, encountering cold air at high altitudes.
A new storm forms in almost the same place. This cycle repeats until the temperature difference between the surface and upper air masses decreases, stabilizing the atmosphere.
The accumulation of precipitation in the same area can lead to flooding. Several factors can amplify this risk: the nature of the terrain (mountains, valleys), soil artificialization, or their dryness, which promotes runoff.
More Intense Phenomena in Densely Populated Areas
Today, 540 million people live around the Mediterranean. Between 1960 and 2023, the population doubled. Urban areas (131 million inhabitants) absorb the largest portion of population growth, particularly on the southern and eastern coasts. It is estimated that by 2050, the population of Mediterranean countries will reach 635 million people, according to a medium scenario (UN, Plan Bleu).
The increase in meteorological risks—particularly Mediterranean episodes—heightens the vulnerability of hundreds of millions of people who are unprepared for such violent events, mostly along the coast and, to a lesser extent, in the hinterland.
Vulnerability of Coastal Urban Areas
Flooding risk is significant in coastal urban areas. In recent decades, urbanization has led to the occupation of flood-prone areas and major riverbeds, the eradication of wetlands that mitigate floods, and soil impermeabilization. These factors multiply the material and human hazards during Mediterranean episodes. The near-absence of tides has also allowed populations to settle very close to the shore. Rising sea levels, 2.8 millimeters per year between 1990 and 2018, thus expose these populations to a greater risk of marine submersion and coastal erosion.
Floods and river floods are not the only harmful effects of climate change for populations. Intense heatwaves have been occurring at a rapid pace in recent years. Although the Mediterranean climate is naturally marked by high summer temperatures due to hot air from the Sahara, heat records are being broken every year on both sides of the Mediterranean.
Weather station records show a continuous rise in temperatures since the 1990s, with an acceleration in recent years.
The Dangers of Extreme Temperatures
On August 11, 2021, in Syracuse, Sicily, the temperature reached 48.8°C: a new record for continental Europe, according to the WMO. On August 11, 2023, the thermometer reached 50.4°C in Agadir, Morocco. These extreme temperatures raise concerns about their sustainability for the human body, with the risk of hyperthermia potentially causing death among the most vulnerable people (infants, pregnant women, the elderly, etc.). The impact of extreme temperatures on ecosystems is also devastating: intensified droughts due to greater evaporation, risks of water shortages, soil impermeabilization, and conditions conducive to the ignition of forest fires that threaten flora, fauna, and public safety.
The Mediterranean shores are not exposed to the same risks. The north and west currently accumulate the most worrying signals.
The Northern Shore Exposed to Heatwaves
Analysis by Le Monde of the CatNat database, which records climate events since 2001, shows that heatwaves have become more frequent since 2015 for all Mediterranean countries. Italy, France, Spain, and Greece have experienced multiple heatwaves per year since 2021. This observation is supported by the rise in the average maximum temperatures in these countries, particularly France and Spain, with respective increases of +2.45°C and +2.27°C between 1950 and 2022 (Copernicus). The 2022 report from the Intergovernmental Panel on Climate Change (IPCC) forecasts a global temperature rise for all Mediterranean countries in the future, regardless of the warming scenario chosen.
Overall Less Water to the West…
Floods remain the most frequent natural disasters. According to the World Bank, they represent 30% to over 50% of natural disasters recorded in Mediterranean countries between 1980 and 2020. Although the Mediterranean climate is characterized by large variability in annual rainfall, the total annual rainfall observed is decreasing, particularly for countries in the Maghreb, Spain, Italy, and southern France.
…But Floods Caused by More Intense Rainfall
Rainfall records have been broken in the last two years. Spain set its national rainfall record in 2024 during a Mediterranean episode on October 29, with 771 millimeters of water in Turis, near Valencia. According to ClimaMeter, an international consortium for attributing extreme weather events to climate change, these exceptional weather conditions are mainly attributed to warming. In France, a Cevennes episode on October 16-17 dropped 694 millimeters of rain in 24 hours at Mayres (Ardèche). Emilia-Romagna, Italy, has experienced three major rainy episodes in fifteen months, leading to the evacuation of thousands of people in Bologna and its surroundings. According to the IPCC’s sixth report, these intense rainfall episodes are multiplying on the northern shore, potentially accompanied by an increase in sudden floods.
The Western Mediterranean at Risk of Aridification
The western and southern shores are more exposed to the risk of critical drought, leading to severe water shortages for populations and agricultural production. Morocco is experiencing its sixth consecutive year of drought, while Algeria and Tunisia have been affected for two consecutive years. Andalusia (Spain) has also been under drought conditions for six years, as has the Pyrénées-Orientales department in France since 2022. The IPCC’s sixth report predicts that these droughts will become more severe, frequent, and prolonged, even with moderate warming.
If no action is taken to reduce greenhouse gas emissions and slow the ongoing warming, according to the IPCC projections and regardless of climate change trajectories, Mediterranean countries and their populations will face more climate
