Impact on short-lived climate forcers increases projected warming due to deforestation

Abstract

The climate impact of deforestation depends on the relative strength of several biogeochemical and biogeophysical effects. In addition to affecting the exchange of carbon dioxide (CO₂) and moisture with the atmosphere and surface albedo, vegetation emits biogenic volatile organic compounds (BVOCs) that alter the formation of short-lived climate forcers (SLCFs), which include aerosol, ozone and methane. Here we show that a scenario of complete global deforestation results in a net positive radiative forcing (RF; 0.12 W m^-2) from SLCFs, with the negative RF from decreases in ozone and methane concentrations partially offsetting the positive aerosol RF. Combining RFs due to CO₂, surface albedo and SLCFs suggests that global deforestation could cause 0.8 K warming after 100 years, with SLCFs contributing 8% of the effect. However, deforestation as projected by the RCP8.5 scenario leads to zero net RF from SLCF, primarily due to nonlinearities in the aerosol indirect effect.

Fig. 1

Global annual mean radiative forcings due to changes in the concentrations of short-lived climate forcers (SLCFs) under global (a) and regional (b–d) deforestation scenarios. Bars represent the net radiative forcing from SLCFs (orange) and the aerosol direct radiative forcing (DRF; in red), first aerosol indirect radiative forcing (IRF; in blue) and RF due to changes in O₃ (green) and CH₄ (purple)

Fig. 2

Aerosol radiative effects due to global deforestation. Direct radiative forcing (a) and first indirect radiative forcing (b)

Fig. 3

Temperature changes due to deforestation. Net temperature changes after 20 years (a) and 100 years (b) for the global and regional deforestation scenarios, with and without the impacts of SLCFs