The recent surge in frequency of extra-tropical storms or ‘Medicanes’, formed over the Mediterranean Sea, has sparked a considerable amount of concern amongst scientists worldwide. These researchers indicate that this is a direct consequence of human-induced climate change and are worried about the potential implications on vulnerable populations.
Understanding Medicanes
Medicanes are tropical-like cyclones that develop over the Mediterranean Sea. Unlike typical cyclones, these occur infrequently due to the sea’s shallow waters and the surrounding dry climate. Generally observed during fall or winter, medicanes usually take place once or twice annually. A medicane named Lanos, which hit Greece’s coast on September 18, 2020, resulted in excessive rainfall and severe flooding in Greece and the surrounding islands.
Comparing Medicanes with Tropical Cyclones
Contrary to tropical cyclones, hurricanes, and typhoons that occur in warmer waters, medicanes form in relatively colder conditions. Such storms have cold cores compared to the warm cores of tropical cyclones, yet are warmer than extra-tropical cyclones. Typically smaller in diameter, medicanes exhibit lower wind speeds than true tropical cyclones. In some instances, warm-cored tropical cyclones can transform into cold-cored extratropical cyclones, and very rarely, vice versa. One such unusual event occurred in November 2011, leading to significant flooding and loss of life in Spain, Italy, and France.
Increased Occurrence of Medicanes
Over the past half-century, there has been a steady rise in the number of medicanes. Remarkably, two such storms in 2005 and 2012 originated over the Black Sea, a much smaller water body than the Mediterranean. Global warming plays a significant role in increasing these storms’ intensity as it leads to warmer sea surface temperatures in the Mediterranean. This allows the storms to adopt more tropical appearances and characteristics, thereby enhancing the wind speeds and causing heavier rainfall.
Impact of La Niña on Medicanes
According to the World Meteorological Organization, this year marked a mild La Niña. Although La Niña typically reduces the number of landfalling hurricanes, the current hurricane season has remained very active. It is evident that global warming is modifying the impacts of El Niño Southern Oscillation (ENSO) in all oceans, including the Mediterranean. La Niña, the cooling phase of the ENSO cycle, is defined by the unusual cooling of the central and east-central equatorial Pacific Ocean.
Warnings from the Intergovernmental Panel on Climate Change (IPCC)
The IPCC’s 2019 Special Report on the Ocean and Cryosphere in a Changing Climate warns of rising temperatures and increased frequency of extreme El Niño and La Niña events.
Potential Threats of Medicanes
The increasing frequency of medicanes poses significant threats to vulnerable populations residing in North Africa, potentially triggering human migration. Additionally, these storms could pose considerable challenges for European nations, including Italy and Greece.