Storm Daniel: The Crucial Role of Record-Breaking Mediterranean Temperatures in Intensifying the Region's Most Devastating Storm
A recent study by IMEDEA (CSIC-UIB) and UIB reveals the role of unusually high sea surface temperatures in intensifying Storm Daniel, the deadliest cyclone ever recorded in the Mediterranean region.
Storm Daniel, formed from a low-pressure system on September 4, 2023, rapidly evolved into a medicane—a Mediterranean cyclone with tropical characteristics.
During its course, it unleashed unprecedented rainfall: over 700 mm fell in just 18 hours in Greece, while 414 mm were recorded in a single day in Al-Bayda, Libya. These extreme downpours caused critical infrastructure to collapse, triggering a humanitarian catastrophe. The devastation included an estimated 4,000–10,000 fatalities and over $20 billion in economic losses.
A study published in the prestigious journal npj Climate and Atmospheric Science by researchers from the Mediterranean Institute for Advanced Studies (IMEDEA, CSIC-UIB) and the University of the Balearic Islands (UIB) identifies exceptionally high sea surface temperatures (SSTs)—up to 5.5°C above historical averages—as the primary factor behind the storm's intensification. These elevated temperatures provided additional energy and moisture, enhancing the cyclone's strength and associated extreme rainfall.
Behind the storm: methodologies and findings
To understand the impact of the Mediterranean's high temperatures on Storm Daniel, scientists employed an advanced climate model, Weather Research and Forecasting (WRF). This allowed them to simulate two scenarios: one with the actual 2023 conditions and another excluding global warming's effects on SSTs.
Key findings from the study include:
- Record-breaking rainfall: Warmer sea temperatures injected more moisture into the atmosphere, resulting in unprecedented rainfall. Greece saw historical precipitation records shattered, while Libya experienced even more destructive downpours as the storm took on tropical characteristics.
- Climate change as a key driver: Researchers confirmed that global warming significantly contributed to the Mediterranean's extreme SSTs, intensifying both the storm’s force and its impacts. Without these temperature anomalies, the storm would have been far less severe.
- Accurate simulations: The climate model successfully replicated the rainfall patterns observed during the storm, validating the methodology and highlighting the importance of such tools for anticipating extreme weather events.
Long-term implications
The Mediterranean has experienced a sustained warming trend in recent years, with record-breaking SSTs during the warm months of 2022 and 2023. This warming not only intensifies tropical-like storms like Daniel but also amplifies other extreme phenomena such as heatwaves and heavy rainfall in Central Europe.
“Without such high sea temperatures, Storm Daniel would not have produced such extraordinarily intense rainfall,” notes Daniel Argüeso Barriga, one of the study's authors.
Next steps in research and climate response
The team underscores the urgency of:
- Enhancing climate models to incorporate real-time air-sea interactions validated by high-resolution data.
- Strengthening international collaboration to share meteorological data and improve forecasting and response to extreme events.
- Deepening research on SSTs’ role in similar phenomena, such as extreme rainfall in Central Europe or tropical cyclones in other regions.
As Mediterranean temperatures continue to rise due to climate change, the region is likely to face more intense storms. Adapting to this new climate reality will require investing in early warning systems, resilient infrastructure, and science-based climate policies to mitigate the impacts of such events.
Link to the study: https://www.nature.com/articles/s41612-024-00872-2