Some considerations about the climate variability and change in the Mediterranean region
[eng] Climate change has many effects, and while global warming caused by human activity is widely recognised, regional-scale changes are particularly important yet uncertain. To effectively communicate, plan protective measures, and adapt to these changes, it is crucial to improve the regional clim...
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| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2025 |
| País: | España |
| Institución: | Universidad de Barcelona |
| Repositorio: | Dipòsit Digital de la UB |
| OAI Identifier: | oai:diposit.ub.edu:2445/225933 |
| Acceso en línea: | https://hdl.handle.net/2445/225933 http://hdl.handle.net/10803/696388 |
| Access Level: | acceso abierto |
| Palabra clave: | Climatologia Clima mediterrani Canvi climàtic Climatology Mediterranean climate Climatic change |
| Sumario: | [eng] Climate change has many effects, and while global warming caused by human activity is widely recognised, regional-scale changes are particularly important yet uncertain. To effectively communicate, plan protective measures, and adapt to these changes, it is crucial to improve the regional climate information and expand the knowledge of regional climate variability. This thesis focuses on the Mediterranean region, not only because it is where we are located, but also due to its high population density, distinct climate, and the expected intensification of climate change beyond the global average. The thesis begins with an analysis of temperature and precipitation projections from the latest phase of the Coupled Model Intercomparison Project (CMIP6). It considers multiple sources of uncertainty, including different climate models and emission scenarios, and compares the results with those from the previous CMIP5 multi-model set. Findings confirm that the Mediterranean is a climate-change hotspot, showing significant warming and drying trends, especially in summer. Despite differences in global warming projections, CMIP6 projects a warmer future than CMIP5, the pat-tern of amplified regional warming remains consistent. Uncertainty increases toward the end of the 21st Century, driven by the differences in emission scenarios, under-scoring the urgent need for mitigation efforts. Without emission reductions, summer mean temperatures (JJA) could rise by up to 8◦CZ by 2100. Precipitation projections vary widely, but drying trends become clearer under higher emission scenarios, highlighting the region’s future vulnerability to drought and water shortages. The study employs weighting methodologies on the multi-model ensembles to constrain their sampling and performance issues. The thesis then examines the near-term climate in the region, focusing on methods to estimate Mediterranean summer temperatures over the next 20 years from CMIP6 projections. At this timescale, internal climate variability plays a dominant role in uncertainty. The study evaluates different methods that incorporate internal variability by selecting simulations that match the recent climate state. This comparative assessment of constraining methods for short-term climate projections is novel and provides a framework for testing them against observational data. Results show that effectiveness varies depending on the method used and the area considered within the Mediterranean region. Selection approaches based on sea surface temperatures appear promising for improving the estimates but require further refinement for reliability. The research highlights the importance of evaluating the methods to estimate future climate against past observations. Given the complexity of the constraining methodologies that attempt to capture internal variability in uninitialized simulations, the study proposes a framework to improve the understanding of the results and guide future constraining techniques. The thesis concludes addressing another process that affects the Mediterranean climate and has received little attention: the Saharan warm air intrusions, which are not necessarily linked to dust storms and transport. These intrusions can impact extreme temperatures across large parts of the Euro-Mediterranean region throughout the year. The study identifies a rising trend in these events during summer, winter, and autumn over the historical period. It also identifies large-scale atmospheric circulation patterns associated with their occurrence. Understanding these mechanisms could improve climate estimates and serve as an additional metric for evaluating climate models. Initial results indicate that CMIP6 models perform in a variety of ways when reproducing the historical frequency, seasonality, and trends of the intrusion events. This research explores open questions about the Mediterranean climate, enhances understanding of its variability, and proposes ways to improve the quality of available climate information using climate simulations and observational products. |
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