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Changes in climate extremes in small Pacific Islands from km-scale model simulations

Tiziana Tessadri

Changes in climate extremes in small Pacific Islands from km-scale model simulations.

Rel. Jost-Diedrich Graf Von Hardenberg, Andrea Vito Vacca. Politecnico di Torino, Corso di laurea magistrale in Ingegneria Per L'Ambiente E Il Territorio, 2025

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Abstract:

Pacific Island Countries and Territories (PICTs) are among the most vulnerable regions to climate change due to their small land area, low elevation, high population density, and fragile economies and ecosystems. However, the extent to which climate change will alter the frequency and intensity of extreme events in these territories remains uncertain. This uncertainty arises primarily from the coarse spatial resolution of current-generation general circulation models (GCMs), which are unable to adequately capture the fine-scale morphological and geographical features of the islands. To address this critical knowledge gap, this thesis analyses for the first time kilometer-scale climate simulations from the Destination Earth (DE) Project using the ICON climate model. The high-resolution ICON model (5 km) is compared with two reanalysis datasets, ERA5 (25 km) and BARRA (12 km), to assess the influence of model resolution on the climatology of daily precipitation, daily maximum and minimum temperatures, and selected climate extreme indices (ETCCDI) for 1990–2019. The study area is divided into three domains, land (islands), halo (ocean adjacent to islands), and sea (open ocean). Results show that the three domains exhibit distinct distributions and trends, with higher-resolution data providing a better representation of small-scale climate features. This effect is especially evident in the analysis of ETCCDI indices related extreme temperatures. The analysis of near-future projections using the ICON model under SSP3-7.0 shows significant warming trends in daily minimum and maximum temperatures. Precipitation exhibits a significant positive signal over both the Fiji Islands and the equatorial regions, with the latter showing an opposite-sign change when comparing the historical and projected periods. ETCCDI indices display consistent but steeper trends compared to the historical period. In order to move from regional to point-scale analysis, we further examine projected changes in three representative cities of the region (1990-2039). The results show clear, statistically significant increases in daily temperature and related extremes, while precipitation exhibits a statistically significant increase only over Suva, located in the Fiji Islands. These findings highlight the added value of high-resolution climate simulations for small island regions, where climate change information is vital for adaptation.

Relatori: Jost-Diedrich Graf Von Hardenberg, Andrea Vito Vacca
Anno accademico: 2025/26
Tipo di pubblicazione: Elettronica
Numero di pagine: 84
Soggetti:
Corso di laurea: Corso di laurea magistrale in Ingegneria Per L'Ambiente E Il Territorio
Classe di laurea: Nuovo ordinamento > Laurea magistrale > LM-35 - INGEGNERIA PER L'AMBIENTE E IL TERRITORIO
Aziende collaboratrici: NON SPECIFICATO
URI: http://webthesis.biblio.polito.it/id/eprint/37103
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