A multi-variable constrained ensemble of regional climate projections under multi-scenarios for Portugal – Part I: An overview of impacts on means and extremes

Abstract

Climate projections are a powerful tool that can help decision makers to timely prepare adaptation policies, which may then be efficiently implemented. In this study, a comprehensive analysis of how climate change may affect Portugal (located in a climate change hotspot) is conducted, providing the foundations to the first National Roadmap for Adaptation 2100. A multi-variable ensemble was built and tested, being the baseline for assessing future projections for three different emission scenarios (RCP2.6, RCP4.5, and RCP8.5) throughout the 21st century, accounting for the model’s ability to simulate a set of variables. A warmer and drier future climate is projected for the mainland, being more severe in the interior regions. Even for the optimistic RCP2.6 scenario, results indicate increases in temperature between 1 and 2 °C in comparison with the historical period and can surpass 6 °C in some regions for RCP8.5. Extreme hot events will be more frequent and severe, with maximum temperatures above 45 °C being more common throughout the 21st century. A decline in precipitation is expected mostly in summer and intermediate seasons, with losses above 40 % for the end-of-century. However, an intensification of heavy short-term rainfall events is projected to increase in northern regions. A rising of maximum wind gusts is also expected in these regions. Such projections call for an urgent planning and adaptation measures to safeguard critical sectors of the Portuguese society. Finally, the information here produced and examined constitutes a key example of climate services for mitigation and adaptation in Portugal.