YES-27-A-25: Greening the North, Changing the Climate: Quantifying BVOC-Mediated Feedbacks from High-Latitude Vegetation Change
Project Description:
In addition to storing carbon, controlling the reflectivity of the land surface and mediating the transfer of moisture to the atmosphere, the presence of forests can influence the atmospheric concentrations of short-lived climate forcers (SLCFs) including ozone, methane and aerosols. Global vegetation emits ~400 – 1000 Teragrams of biogenic volatile organic compounds (BVOCs), including isoprene and monoterpenes, into the air at a rate dependent upon the plant species, temperature, sunlight levels, soil moisture and atmospheric CO2 concentration.
After emission, BVOCs are rapidly oxidised to give a wide range of products, some of which play a key role in the formation and growth of new nanometre sized particles (Riccobono et al., 2014; Zhao et al., 2024), as well as influencing the growth and composition of existing particles in the atmosphere. By scattering solar radiation and acting as seeds for cloud droplet formation (thereby increasing the brightness of clouds), the formation of particles from BVOCs is likely to have a cooling effect on climate (Scott et al., 2014), but not all models agree on the sign of this effect (Weber et al., 2022; Sporre et al., 2020). Due to the complex atmospheric chemistry that BVOCs take part in, their emission can also increase the concentration of ozone and methane, causing a warming that either partially or entirely offsets the aerosol induced cooling (Unger 2014; Scott et al., 2018; Weber et al., 2024).
Since the emission of BVOCs is strongly controlled by temperature there is potential for warming induced feedbacks to occur under climate change that amplify or diminish the initial warming. Such feedbacks are complicated to observe (Yli-Juuti et al., 2021) and current Earth System Models do not agree on the sign or magnitude of the BVOC feedback effect (Thornhill et al., 2021; Blichner et al., 2024), making projections of future climate uncertain.
Rising temperatures and atmospheric CO2 concentrations are already affecting the structure and composition of the vegetated land-surface. At high northern latitudes, as temperatures have risen and the growing season has lengthened, the distribution of tree and shrub cover has shifted (Macander et al., 2022) and in the future, the northern treeline could potentially move polewards by hundreds of kilometres (MacDonald et al., 2008; Montesano et al., 2024). Expansion of boreal tree and shrub cover, alongside rising temperatures, could increase BVOC emissions (Angot et al., 2020) affecting particle, O3 and CH4 concentrations, and ultimately climate. Changes in canopy coverage may also be accompanied by a shift in dominance between broadleaf and needleleaf, and between deciduous and evergreen species (Zhang et al. 2013), altering not only the quantity but the composition of BVOCs that are emitted. Changes to the BVOC emission mixture are important because the oxidation products of different compounds play different roles in the formation and growth of particles in the atmosphere.
Project Aims:
During this project the candidate will:
– Develop the representation of new particle formation involving BVOC oxidation products in the UK’s Earth System Model (UKESM2)
– Conduct a process-based evaluation at multiple stages of the “BVOC emission –> atmospheric composition -> climate impact” feedback chain in UKESM2 using atmospheric observations and satellite data
– Synthesise findings from dynamic global vegetation models to quantify the potential extent of future land cover change at high northern latitudes and evaluate the impact on climate via altered emissions of BVOCs using UKESM2
Skills, Training & Research Group:
You will have a background in environmental science, chemistry, physics, mathematics, physical geography, or natural sciences. You will join the Biosphere – Atmosphere Group (BAG) within the Institute for Climate and Atmospheric Science and become a member of the cross-faculty Leeds Ecosystem, Atmosphere and Forest (LEAF) Centre giving you the opportunity to exchange knowledge with colleagues from across the University of Leeds. You will benefit from the training in both specific technical skills, and in transferable skills provided by the YES-DTN and those offered by the University of Leeds.
References:
Angot, H., et al., 2020, “Biogenic volatile organic compound ambient mixing ratios and emission rates in the Alaskan Arctic tundra”, Biogeosciences, 17, 6219–6236, https://doi.org/10.5194/bg-17-6219-2020
Blichner, S.M., et al., 2024, “Process-evaluation of forest aerosol-cloud-climate feedback shows clear evidence from observations and large uncertainty in models”, Nat. Commun., 15, 969, https://doi.org/10.1038/s41467-024-45001-y
Macander, M. J., et al., 2022, “Time-series maps reveal widespread change in plant functional type cover across Arctic and boreal Alaska and Yukon”, Environ. Res. Lett., 17 054042, https://doi.org/10.1088/1748-9326/ac6965
MacDonald, G. M., et al., 2008, “Climate change and the northern Russian treeline zone”, Philos. Trans. R Soc. B.; 363 (1501), 2283–2299, https://doi.org/10.1098/rstb.2007.2200
Montesano, P.M., et al., 2024, “A shift in transitional forests of the North American boreal will persist through 2100”, Commun. Earth Environ., 5, 290, https://doi.org/10.1038/s43247-024-01454-z
Riccobono, F., et al., 2014, “Oxidation products of biogenic emissions contribute to nucleation of atmospheric particles”, Science, 344, 717–721, https://doi.org/10.1126/science.1243527
Scott, C. E., et al., 2014, “The direct and indirect radiative effects of biogenic secondary organic aerosol”, Atmos. Chem. Phys., 14, 447–470, https://doi.org/10.5194/acp-14-447-2014
Scott, C.E., et al., 2018, “Impact on short-lived climate forcers increases projected warming due to deforestation”, Nat. Commun., 9, 157, https://doi.org/10.1038/s41467-017-02412-4
Sporre, M. K., et al., 2020, “Large difference in aerosol radiative effects from BVOC-SOA treatment in three Earth system models”, Atmos. Chem. Phys., 20, 8953–8973, https://doi.org/10.5194/acp-20-8953-2020
Thornhill, G., et al., 2021, “Climate-driven chemistry and aerosol feedbacks in CMIP6 Earth system models”, Atmos. Chem. Phys., 21, 1105–1126, https://doi.org/10.5194/acp-21-1105-2021
Weber, J., et al., 2022, “Chemistry-driven changes strongly influence climate forcing from vegetation emissions”, Nat. Commun., 13, 7202, https://doi.org/10.1038/s41467-022-34944-9
Yli-Juuti, T., et al., 2021, “Significance of the organic aerosol driven climate feedback in the boreal area”, Nat. Commun., 12, 5637, https://doi.org/10.1038/s41467-021-25850-7
Zhao, B., et al., 2024, “Global variability in atmospheric new particle formation mechanisms”, Nature, 631, 98–105, https://doi.org/10.1038/s41586-024-07547-1