Future summer warming pattern under climate change is affected by lapse-rate changes

Roman Brogli,Silje Lund Sørland,Nico Kröner,Christoph Schär

doi:10.5194/wcd-2-1093-2021

Roman Brogli, Silje Lund Sørland + Show 2 more

Open Access

https://doi.org/10.5194/wcd-2-1093-2021

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Abstract

Abstract. Greenhouse-gas-driven global temperature change projections exhibit spatial variations, meaning that certain land areas will experience substantially enhanced or reduced surface warming. It is vital to understand enhanced regional warming anomalies as they locally increase heat-related risks to human health and ecosystems. We argue that tropospheric lapse-rate changes play a key role in shaping the future summer warming pattern around the globe in mid-latitudes and the tropics. We present multiple lines of evidence supporting this finding based on idealized simulations over Europe, as well as regional and global climate model ensembles. All simulations consistently show that the vertical distribution of tropospheric summer warming is different in regions characterized by enhanced or reduced surface warming. Enhanced warming is projected where lapse-rate changes are small, implying that the surface and the upper troposphere experience similar warming. On the other hand, strong lapse-rate changes cause a concentration of warming in the upper troposphere and reduced warming near the surface. The varying magnitude of lapse-rate changes is governed by the temperature dependence of the moist-adiabatic lapse rate and the available tropospheric humidity. We conclude that tropospheric temperature changes should be considered along with surface processes when assessing the causes of surface warming patterns.

Highlights

Rising greenhouse gas emissions will lead to climate warming on a global scale
We conclude that tropospheric temperature changes should be considered along with surface processes when assessing the causes of surface warming patterns
We find that variations in the vertical warming with climate change, given by atmospheric lapse-rate changes, are decisive for the understanding of enhanced or reduced regional greenhouse-gas-driven surface warming during summer

Summary

Introduction

Rising greenhouse gas emissions will lead to climate warming on a global scale. the warming on regional to local scales is what directly affects people (Sutton et al, 2015). In the mid-latitudes and tropics, land areas warm more than the ocean, as seen in observations and climate simulations (Byrne and O’Gorman, 2018; Chadwick et al, 2019). Many hot spots of amplified warming are arid or semi-arid areas. Such land surface warming hot spots are often assumed to be primarily caused by changes in the partitioning of surface energy fluxes (Huang et al, 2017a, b; Barcikowska et al, 2020), but it is unclear if this surface perspective is sufficient in explaining the regional warming differences (Byrne and O’Gorman, 2013a; Berg et al, 2016; Koutroulis, 2019)

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