Half a Degree Matters: Mean Climate and Climate Extremes Responses to 1.5 °C and 2 °C Global Warming Levels in Türkiye

Résumé fourni par la source

The Paris Agreement aims to limit global warming to well below 2 °C while pursuing efforts to restrict it to 1.5 °C, as exceeding these thresholds may intensify climate-related risks. Understanding climate responses to an additional half-degree of warming remains critical for adaptation planning. Accordingly, the implications of an additional 0.5 °C warming from 1.5 °C to 2 °C over Türkiye were evaluated using 10 km resolution RegCM4.4 simulations driven by the MPI-ESM-MR and HadGEM2-ES models. Temperature- and precipitation-related indicators were analyzed, including mean temperature (Tmean), tropical nights (TN), discomfort index (DI), total precipitation (TP), the simple daily intensity index (SDII), extreme precipitation days (R90P), dry periods lasting at least five consecutive days (CDD5), and consecutive dry days (CDD). The results indicate that the additional 0.5 °C warming does not affect all climate indicators equally, with the strongest responses observed in temperature-related indicators. Temperature-related indicators, particularly TN and DI, show clear and consistent increases, indicating strong sensitivity to additional warming. By contrast, precipitation-related indicators display more heterogeneous and model-dependent responses, with RCM-HG generally projecting increases in precipitation and intensity, while RCM-MPI suggests decreases in certain regions and seasons. The signal-to-noise ratio (SNR) analysis further indicates greater robustness of annual temperature-related changes, whereas inter-model sign agreement varies among indices and seasons, with complete agreement for Tmean. The findings provide a scientific basis for regionally tailored adaptation planning in Türkiye and highlight the potential for reducing climate risks by limiting warming to lower levels.