Speranza (2026) Long-term trend in temperature, precipitation and evapotranspiration in three small mediterranean Italian islands: Pantelleria, Ponza and Ustica

Identification

• Journal: Theoretical and Applied Climatology
• Year: 2026
• Date: 2026-01-01
• Authors: A. Speranza
• DOI: 10.1007/s00704-025-06002-z

Research Groups

IMAA, Istituto di Metodologie per l’Analisi Ambientale, CNR

Short Summary

This study investigates long-term trends in temperature, precipitation, and evapotranspiration on three small Mediterranean Italian islands (Pantelleria, Ponza, Ustica) over 68-72 years, revealing significant warming across all islands and persistent rainfall deficits in Pantelleria and Ustica, highlighting their vulnerability to climate change.

Objective

• To examine the long-term trends in mean, maximum, and minimum temperature, total precipitation, and evapotranspiration across three small Mediterranean Italian islands (Pantelleria, Ponza, and Ustica) to assess climate change impacts on these ultraperipheral internal areas.

Study Configuration

• Spatial Scale: Three small Mediterranean Italian islands: Pantelleria (84.55 km²), Ustica (8.24 km²), and Ponza (10.16 km²).
• Temporal Scale:
  • Temperature (mean, maximum, minimum): 72 years (1951–2022)
  • Total precipitation and evapotranspiration: 68 years (1951–2018)

Methodology and Data

• Models used:
  • Principal Component Analysis (PCA) for dimensionality reduction and visualization.
  • Mann-Kendall test and Sen’s slope estimator for trend analysis (monthly and annual).
  • Random Forests (missForest function) and Kalman smoothing (na_kalman function) for missing data imputation.
  • Seasonal ARIMA model (auto.arima function) for time series analysis (used in Kalman smoothing).
  • Harmonic linear multiple regression model (with bootstrap regression) for annual temperature trend estimation.
  • Modified Hargreaves equation for reference evapotranspiration (ET₀) estimation.
• Data sources:
  • SCIA – Sistema Nazionale per l’Elaborazione e Diffusione di Dati Climatici (ISPRA).

Main Results

• Temperature:
  • Significant positive annual trends in mean temperature: Pantelleria (0.0308 °C/year), Ustica (0.0363 °C/year), Ponza (0.0311 °C/year).
  • Significant positive annual trends in maximum temperature: Pantelleria (0.0264 °C/year), Ustica (0.0463 °C/year), Ponza (0.0328 °C/year).
  • Significant positive annual trends in minimum temperature: Pantelleria (0.0353 °C/year), Ustica (0.0263 °C/year), Ponza (0.0297 °C/year).
  • Monthly trends generally showed higher slopes in August and lower slopes in February for all temperature types.
  • In Pantelleria, minimum temperature increased more rapidly than maximum temperature; in Ustica and Ponza, maximum temperature increased more rapidly.
• Precipitation:
  • Significant positive annual trends in total precipitation: Pantelleria (4.04 mm/year), Ustica (2.08 mm/year).
  • Ponza showed no significant statistical annual trend in precipitation.
  • Monthly precipitation in Pantelleria showed significant positive trends in February, March, September, November, and December.
  • Ustica showed a significant positive monthly trend only in September.
  • Ponza showed no significant monthly precipitation trends.
• Evapotranspiration:
  • Significant positive annual trend in evapotranspiration only in Ustica (3.16 mm/year). No significant annual trend in Pantelleria or Ponza.
  • Ustica exhibited significant positive monthly evapotranspiration trends across all months, with the highest slope in August.
  • Pantelleria showed significant negative monthly evapotranspiration trends in February, November, and December.
  • Ponza showed significant positive monthly trends in March and December, and a negative trend in July.
• Water Balance:
  • Pantelleria and Ustica exhibit an annual rainfall deficit, where evapotranspiration (734.83 mm/year and 701.55 mm/year, respectively) exceeds total precipitation (508.2 mm/year and 465 mm/year, respectively).
  • In Ustica, the increasing evapotranspiration trend is likely to exacerbate the rainfall deficit.
  • Ponza does not show a rainfall deficit, with precipitation (633.6 mm/year) exceeding evapotranspiration (588.14 mm/year).

Contributions

This study provides a comprehensive long-term (68-72 years) analysis of temperature, precipitation, and evapotranspiration trends for three specific small, ultraperipheral Italian Mediterranean islands, addressing a recognized gap in regional climate models and studies for small islands. It highlights the unique and spatially heterogeneous impacts of climate change on these vulnerable ecosystems and communities, emphasizing the need for tailored climate resilience strategies.

Funding

The author declares that no funds, grants, or other support were received during the preparation of this manuscript.

Citation

@article{Speranza2026Longterm,
  author = {Speranza, A.},
  title = {Long-term trend in temperature, precipitation and evapotranspiration in three small mediterranean Italian islands: Pantelleria, Ponza and Ustica},
  journal = {Theoretical and Applied Climatology},
  year = {2026},
  doi = {10.1007/s00704-025-06002-z},
  url = {https://doi.org/10.1007/s00704-025-06002-z}
}