The biogeophysical effects of idealized land cover and land management changes in Earth system models

Abstract

Abstract. Land cover and land management change (LCLMC) has been highlighted for its critical role in mitigation scenarios, both in terms of global mitigation and local adaptation. Yet, the climate effect of individual LCLMC options, their dependence on the background climate and the local vs. non-local responses are still poorly understood across different Earth system models (ESMs). Here we simulate the climatic effects of LCLMC using three state-of-the-art ESMs, including the Community Earth System Model (CESM), the Max Planck Institute for Meteorology Earth System Model (MPI-ESM) and the European Consortium Earth System Model (EC-EARTH). We assess the LCLMC effects using the following four idealized experiments: (i) a fully afforested world, (ii) a world fully covered by cropland, (ii) a fully afforested world with extensive wood harvesting and (iv) a full-cropland world with extensive irrigation. In these idealized sensitivity experiments, performed under present-day climate conditions, the effects of the different LCLMC strategies represent an upper bound for the potential of global mitigation and local adaptation. To disentangle the local and non-local effects from the LCLMC, a checkerboard-like LCLMC perturbation, i.e. alternating grid boxes with and without LCLMC, is applied. The local effects of deforestation on surface temperature are largely consistent across the ESMs and the observations, with a cooling in boreal latitudes and a warming in the tropics. However, the energy balance components driving the change in surface temperature show less consistency across the ESMs and the observations. Additionally, some biases exist in specific ESMs, such as a strong albedo response in CESM mid-latitudes and a soil-thawing-driven warming in boreal latitudes in EC-EARTH. The non-local effects on surface temperature are broadly consistent across ESMs for afforestation, though larger model uncertainty exists for cropland expansion. Irrigation clearly induces a cooling effect; however, the ESMs disagree whether these are mainly local or non-local effects. Wood harvesting is found to have no discernible biogeophysical effects on climate. Overall, our results underline the potential of ensemble simulations to inform decision making regarding future climate consequences of land-based mitigation and adaptation strategies.

Observed and simulated local climate responses to tropical deforestation

“…Our analysis focused on assessing the simulated local climate response to tropical deforestation and understanding how this depends on the modelled treatment of the land surface change. Tropical deforestation drives changes to the local energy balance that are dominated by changes in the turbulent energy flux (Boysen et al 2020, De Hertog et al 2023. Our analysis shows a large disagreement in the simulated response of ET flux to deforestation.…”

“…Climate models have different representations of the land surface and the biophysical responses to land cover change, leading to different simulations of the climate response to land cover change (Boisier et al 2015, Boysen et al 2020, Baker et al 2021a, Luo et al 2022, De Hertog et al 2023. Most models agree that deforestation in the tropics causes local surface warming but disagree on the magnitude of the temperature response (Winckler et al 2019b, Boysen et al 2020.…”

Changes in Land Cover and Management Affect Heat Stress and Labor Capacity

“…Below, we provide a short description of the conducted sensitivity experiments on LCLMC. A detailed description of the model simulations can be found in (De Hertog et al., 2023).…”

“…Increasing evidence reveals that land cover and land management change (LCLMC) can have a substantial impact on climate through the biogeophysical effects resulting from modifications of the radiative, aerodynamic and thermodynamic properties of the land surface (Chen & Dirmeyer, 2019; De Hertog et al., 2023; de Vrese et al., 2016; Pongratz et al., 2021; Thiery et al., 2017). Biogeophysical effects can be local and non‐local.…”

“…Specifically, we investigate the effectiveness of LCLMC as adaptation strategies for reducing heat stress. Our global analysis builds upon the results from stylized global sensitivity experiments for three LCLMC practices (a) cropland expansion, (b) irrigation expansion, and (c) afforestation, which are described and analyzed in (De Hertog et al., 2023). To directly separate between local and non‐local effects of LCLMC, the checkerboard approach developed by Winckler et al.…”