The Biophysical Impacts of Deforestation on Precipitation: Results from the CMIP6 Model Intercomparison

Abstract

Deforestation can impact precipitation through biophysical processes and such effects are commonly examined by models. However, previous studies mostly conduct deforestation experiments with a single model and the simulated precipitation responses to deforestation diverge across studies. In this study, eleven earth system models are used to robustly examine the biophysical impacts of deforestation on precipitation, precipitation extremes and the seasonal pattern of the rainy season through a comparison of a control simulation and an idealized global deforestation simulation with clearings of 20 million km2 of forests. The multimodel mean suggests decreased precipitation, reduced frequency and intensity of heavy precipitation and shortened duration of rainy seasons over deforested areas. The deforestation effects can even propagate to some regions that are remote from deforested areas, e.g., the tropical and subtropical oceans and the Arctic Ocean. Nevertheless, the eleven models do not fully agree on the precipitation changes almost everywhere. In general, the models exhibit higher consistency over the deforested areas and a few regions outside the deforested areas (e.g., the subtropical oceans) but lower consistency over other regions. Such intermodel spread mostly results from divergent responses of evapotranspiration and atmospheric moisture convergence to deforestation across the models. One of the models that has multiple simulation members also reveals considerable spread of the precipitation responses to deforestation across the members due to internal model variability. This study highlights the necessity of robustly examining precipitation responses to deforestation based on multiple models and each model with multiple simulation members.

Local and Non‐Local Biophysical Impacts of Deforestation on Global Temperature During Boreal Summer: CMIP6‐LUMIP Multimodel Analysis

“…Recently, the Land Use Model Intercomparison Project (LUMIP, Lawrence et al., 2016) multimodel simulations, which were part of the Coupled Model Intercomparison Project Phase 6 (CMIP6, Eyring et al., 2016), were conducted to understand the impacts of land use and land cover change (LULCC) on climate (Boysen et al., 2020; Luo et al., 2022). Boysen et al.…”

“…Recently, the Land Use Model Intercomparison Project (LUMIP, Lawrence et al, 2016) multimodel simulations, which were part of the Coupled Model Intercomparison Project Phase 6 (CMIP6, Eyring et al, 2016), were conducted to understand the impacts of land use and land cover change (LULCC) on climate (Boysen et al, 2020;Luo et al, 2022). Boysen et al (2020) first utilized the CMIP6-LUMIP multimodel simulations to examine the biophysical effect of large scale deforestation and found that the impacts of deforestation vary in sign (i.e., a switch of sign from tropical warming to extratropical cooling located around 22.6°N).…”

Is land use producing robust signals in future projections from Earth system models, all else being equal?

“…Work on average temperature and precipitation changes under LUC, mostly using idealized deforestation experiments with a background of a stationary, pre-industrial climate, has already revealed the difficulty of finding a robust signal across models in terms of patterns and at times even sign of changes. The more robust effects are in the direction of a cooling and drying effect of deforestation (Boysen et al 2020, Luo et al 2022, Yu and Leng 2022 but with disparities among models on the size and significance of these changes. Here we present results from an analysis that attempts to maximize the LUC signal: we focus on changes by the end of the century, averaged over regions where LUC differences are largest and most consistent across ESMs.…”

Observed and simulated local climate responses to tropical 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.…”