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 in terms of both 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 four idealized experiments: (i) a fully afforested world, (ii) a world fully covered by cropland, (iii) 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 regarding whether these are mainly local or non-local effects. Wood harvesting is found to have no discernible biogeophysical effects on climate. Our results overall underline the potential of ensemble simulations to inform decision-making regarding future climate consequences of land-based mitigation and adaptation strategies.

How do afforestation and BECCS differ in their impacts on the land carbon cycle and surface climate?

“…The choice of the CDR method impacts climate globally and regionally via the biogeophysical effects of land cover change 29,31−33 . The spatial patterns of biogeophysical effects of BECCS and AR experiments are largely consistent with existing studies 29,32 , but we extend the scope to the context of bioenergy crops, as well as AR on the low carbon-content ecosystems. The biogeophysical effects are dominated by radiative mechanisms (related to the shortwave and longwave radiative processes at surface) over high and mid-latitudes of the Northern Hemisphere and non-radiative mechanisms (related to the sensible, latent and ground surface heat uxes) in the areas south of those.…”

“…However, these studies are predominantly based on IAMs that have only a simple or limited representation of Earth System processes with low sectoral and geographical details and thus cannot fully account for carbon-climate feedbacks on the CDR potentials of BECCS and AR 3,16,21,25,26 . Several studies are based on the intermediate complexity models or Earth System Models (ESM) with a more spatially-resolved and detailed representation of processes compare the land-based CDR methods in terms of their CDR potentials and interactions with the Earth System processes 20,21,[27][28][29] . One study investigates biogeochemical (carbon cycle) feedbacks of land-based mitigation options and demonstrates that AR is more bene cial than BECCS in areas of high vegetation and soil carbon contents due to avoided LUC emissions 28 .…”

“…One study investigates biogeochemical (carbon cycle) feedbacks of land-based mitigation options and demonstrates that AR is more bene cial than BECCS in areas of high vegetation and soil carbon contents due to avoided LUC emissions 28 . Another study investigates the biogeophysical (climate) effects and shows that CDR bene ts of AR over cropland deployment might be offset by its global warming effect 29 . There is a need to explore the CDR potentials of land-based methods and their interactions with global and regional Earth System processes under socially-relevant mitigation pathways.…”

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

“…Yet, in line with CESM and MPI‐ESM, the local effects of cropland expansion induce a moderate local warming effect in the tropics due to decreased evapotranspiration (De Hertog et al. (2023)). The increase of ESI in the tropics is substantially less pronounced than the temperature response because of decreased humidity (Figure S2 in Supporting Information S1).…”

“…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.…”