Drivers and Patterns of Extreme Future Summer Warming

Abstract:

In a warmer future climate, climate simulations predict that some land areas will experience excessive mean warming during summer. This excessive mean warming intensifies the severity of heat waves or droughts, which exposes the population of affected areas to heat-related risks such as heat strokes. Extreme land warming has been connected to near-surface feedbacks, but we suggest that tropospheric lapse-rate changes also play a role. We analyze potential causes for the spatial summer warming patterns on a global scale. For the European region, we perform idealized simulations to isolate drivers of surface warming patterns and reinforce our findings using further climate model ensembles on global and regional scales. We will present in detail how the enhanced Mediterranean summer warming is mainly caused by tropospheric lapse-rate changes, while surface feedbacks are less important. Additionally, we will show that lapse-rate changes regulate the extent of summer warming globally across land areas in the mid-latitudes and tropics. Thus, tropospheric temperature changes need to be considered together with surface feedbacks when assessing the causes of surface warming patterns.