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Environment: Mediterranean temperature, 1° C warmer in last 25 years

09 January 2025 Last Updated: 09 January 2025

Data from 100 campaigns conducted by ENEA and INGV jointly with the company GNV

The activities conducted by ENEA and INGV as part of the MACMAP project^[1] showed that in 2023 temperatures in the Mediterranean Sea reached the highest thermal value since the beginning of modern records, with an increase in average surface temperature of more than 1°C in 25 years, a progressive increase since 2013 in the southern Tyrrhenian Sea, extending northward, and warming of the deepest layers up to 800 meters.

The outcomes of the research were presented on the occasion of the 25th anniversary of the water temperature survey of the Ligurian and Tyrrhenian seas, along the Genoa-Palermo route, in collaboration with the GNV, the ferry company of the MSC Group. In addition to the increase in average temperature at the surface, the “thermal snapshot” of the Mediterranean, taken over 100 campaigns during which more than 3 thousand probes were launched, also shows an increase in the deeper layers (100-450 meters: +0.4 - +0.6°C; 450-800 m: +0.3 - +0.5°C).

The analysis of the measurements also shows that between 2013 and 2016 the warming excedeed 0.4 °C, followed by a slight decrease and a stationary period in the following years, and then resumed a gradual increase from 2021 until September 2023, when it reached its maximum. For an indication of the magnitude of the phenomenon, it is worth noting both the short time frame in which this variation occurred and the fact that, to induce in the Tyrrhenian Sea the temperature increase measured between 2015 and 2023 in the layer between 200 and 800 m depth would require an amount of energy equal to dozens of times the electricity consumption in Italy in one year.

“The historical series of temperature data along the same route is crucial for climate studies because it allows us to assess its temporal evolution, highlighting possible variations to understand whether there has been warming or cooling along the water column in the monitored area over time,” explained ENEA researchers, including Franco Reseghetti, who recently took leave and personally conducted the campaigns.

“This collaboration is part of GNV's broader sustainability strategy through which we intend, among other things, to actively contributing to preserving biodiversity and the marine ecosystem. We hope to increasingly strengthen this project by taking it to the other routes operated by our Company in the Mediterranean as well. The long-term goal is to use the data collected to ameliorate management of our ships by optimizing, for example, maintenance of hulls and propellers,” said Ivana Melillo, Head of Energy Efficiency at the GNV.

“What does the near future hold? Indications from available models incline toward a possible further increase in water temperatures, but the veracity of these predictions can only be confirmed by the measurements that those involved in this 25-year activity have every intention of continuing to carry out, starting with the 100th campaign scheduled for next December,” said Simona Simoncelli, INGV researcher.

CAMPAIGN HISTORY (1999-2024)

On Sept. 20, 1999, at 19:54:55 UTC, at coordinates 44° 18.793' N, 8° 59.547' E, an ENEA and CNR research team launched a disposable bathythermographic probe (XBT) from the GNV motorship “Excelsior” sailing from Genoa to Palermo. It was the first probe launched to measure the water column temperature along the line now classified as MX04 of the Global Ocean Observing System (GOOS) Ship Of Opportunity Program (SOOP), whose main purpose was, and still is, to acquire data on the upper layers of ocean waters. Collecting data along the line was part of the European Mediterranean Forecasting System Pilot Project (MFSPP) program, coordinated by INGV Professor N. Pinardi and ENEA G.M.R. Manzella as leader, The main goal of the project was developing marine forecasts using near real-time measurements of some parameters of the Mediterranean Sea waters, primarily temperature. The XBT probes were launched from commercial ships operating in the Mediterranean along certain routes passing through areas and basins deemed interesting by the researchers and transmitted as quickly as possible to the research centers participating in the project. These European projects ended in 2006, but sampling on the Genoa - Palermo has continued until today, albeit with some interruptions, mainly by ENEA researchers joined by the INGV thanks to the project MACMAP (A Multidisciplinary Analysis of Climate change indicators in the Mediterranean And Polar regions) that has funded the monitoring activity since 2021. The September 19-20, 2024 campaign celebrated 25 years of these measurements, in which a total of more than 3,000 probes were launched in 100 campaigns. It then happened that the trip was on board the same GNV motor vessel “Excelsior” on which this activity began.

HOW THE CAMPAIGNS ARE CONDUCTED

The measurement campaigns have always used GNV ferry company ships which connect Genoa with Palermo in about 20 hours of navigation at a speed of about 22 knots. During the voyage researchers launch probes at fixed positions (about every 30 minutes): in the first campaigns probes measuring up to 450 m depth were launched, later the probes used allowed measurements down to about 800-850 m. Frequency of campaigns has varied greatly: initially fortnightly and monthly, later 5-6 repetitions each year. Since 2021, 4 campaigns per year have been conducted to study seasonal variability.