Amplification of the Temperature Seasonality in the Mediterranean Region Under Anthropogenic Climate Change.

Amplified warming in the Mediterranean region in summer, corresponding to strengthening temperature seasonality (Tseasonality), increases the frequency and intensity of heatwaves and endangers both human health and ecosystems. However, previous studies have not found a detectable signal of anthropogenic forcing in changes in Tseasonality in the Mediterranean and the contribution from human activities is unclear. Here, we show that signals of anthropogenic forcing and greenhouse gas forcing can be detected for the period 1950–2014, the signals of anthropogenic and natural forcing are separable, and the contribution of anthropogenic forcing is 74% using the optimal fingerprinting approach. Future projections based on attribution constraints indicated that Tseasonality will continue to strengthen by more than 2°C by 2100, which is much worse than predicted by direct model output. These results are important for understanding and projecting the impacts of human activities on Tseasonality and related summer heatwaves in the future. Plain Language Summary: The temperature seasonality, also known as the amplitude of the annual cycle of temperature, is important for human societies and ecosystems. The amplified summer warming enhances the temperature seasonality in the Mediterranean region, which is vulnerable to climate change. In this study, we detected signals of human influences on changes in the temperature seasonality in this region and further quantified the contribution of anthropogenic forcing using a formal detection and attribution technique. Future projections were then carried out based on attribution constraints and the results showed a much faster increase in the temperature seasonality than direct model output. The result highlights the importance of reducing greenhouse gas emissions for this region. Key Points: The anthropogenic forcing signal was detected in the strengthening temperature seasonality in the Mediterranean regionAnthropogenic forcing was found to play a major role in changes in the temperature seasonalityFuture projections based on attribution constraints indicate an enhancement in the temperature seasonality faster than direct model output [ABSTRACT FROM AUTHOR]