Chemistry-albedo feedbacks from reforestation partially offset CO2 removal benefits
- 1School of Biosciences, University of Sheffield; Sheffield, S10 2TN, United Kingdom.
- 2Centre for Atmospheric Science, Yusuf Hamied Department of Chemistry, University of Cambridge; Cambridge, CB2 1EW, United Kingdom.
- 3National Centre for Atmospheric Science, Yusuf Hamied Department of Chemistry, University of Cambridge; Cambridge, CB2 1EW, United Kingdom.
- 4Institute for Climate and Atmospheric Science, School of Earth and Environment, University of Leeds, Leeds LS2 9JT, United Kingdom.
- 5Leverhulme Centre for Climate Change Mitigation, School of Biosciences, University of Sheffield, Sheffield, United Kingdom.
- 6NCAR Earth System Laboratory, Climate and Global Dynamics Division, National Center for Atmospheric Research; Boulder, CO, USA
Reforestation is widely proposed for carbon dioxide (CO2) removal but the impact on climate, via atmospheric composition and surface albedo changes, remains relatively unexplored. Using two Earth System models, UKESM1 and CESM2, we compare scenarios where existing forests expand to a near biophysical limit (with croplands fixed at 2015 to preserve food production) with SSP1-2.6 and SSP3-7.0 at 2050 and 2095.
In the reforestation scenario, global BVOC emissions are 18% (35%) higher than SSP3-7.0 at 2050 (2095) and 8% (12%) higher than SSP1-2.6. The resulting increases to secondary organic aerosols and aerosol scattering, from BVOC emission changes, drive a negative radiative forcing (RF). However, this is outweighed by the positive RF from increases to methane and ozone and decreases to surface albedo.
The net RF is equivalent to CO2 increases of 13 (32) ppm relative to SSP3-7.0 at 2050 (2095) and 3 (8) ppm relative to SSP1-2.6. These indirect factors offset ~25% of the additional CO2 removal arising from reforestation relative to SSP3-7.0 and ~10% relative to SSP1-2.6. This highlights the importance of assessing the full response of the Earth System to reforestation, rather than just the potential CO2 removal.
How to cite: Weber, J., King, J. A., Abraham, N. L., Grosvenor, D. P., Beerling, D. J., Lawrence, P., and Val Martin, M.: Chemistry-albedo feedbacks from reforestation partially offset CO2 removal benefits, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-8236, https://doi.org/10.5194/egusphere-egu23-8236, 2023.
