Assessing the Intensity of Heatwaves in a Warming Climate at the Urban Scale: A Case Study of the Metropolitan Area of Barcelona

Given that more than half of the world's population currently resides in cities, further understanding of the potential impact of future climate change on urban areas is needed. In this regard, we project recent heatwave (HW) episodes in the Metropolitan Area of Barcelona (AMB) with future climate conditions until 2100 using the pseudo global warming method. First, we determine all the HWs that occurred in the AMB during the last climatological period of 30 years (1991–2020) and simulate each individual event using the Weather and Research Forecasting (WRF) model at high-resolution. Then, these historical HW events are resimulated with the modified atmospheric conditions of the midcentury (2041–2070) and the end of the century (2071–2100) according to the scenario SSP3-7.0, in which CO₂ emissions are projected to almost double from current levels by 2100 following a low emission reduction scenario. In the AMB, HW intensity is expected to increase by 2.5°C and 4.2°C in the mid- and end-of-the-century periods, respectively. Higher temperatures are related to the stationary and stable synoptic pattern, which, among the four analyzed, is projected to experience the greatest intensification in the future. The geopotential height at 500 hPa could increase up to 100 geopotential meters (gpm) by the end of the century, leading to values up to 6,050 gpm, which indicates changes in thermodynamic and dynamic effects resulting in potentially warmer HW episodes. The results obtained can aid in understanding the expected changes for this century, which could facilitate the formulation of heat mitigation and adaptation strategies, particularly for the most exposed areas.