Aerosol radiative effects on the global land carbon sink

This project will use state-of-the-art satellite observations and global models to evaluate the role of aerosol radiative effects on the land carbon sink. Atmospheric CO2 concentrations have increased by 50% since the Industrial Revolution (from 278ppm in 1750 to over 420ppm in 2022), contributing about 80% of the total anthropogenic radiative forcing on climate. This dramatic increase has so far been mitigated by the land and ocean carbon sinks absorbing over half of the total CO2 emitted by human activities (Friedlingstein et al., 2022). Accurate estimates of these carbon sinks is essential for projecting future climate change and developing effective climate policies. However, many global vegetation models used in current global carbon budget assessments do not include a full representation of important processes such as diffuse light fertilisation (see Fig. 1; Mercado et al., 2009; Rap et al., 2018). As a result, a "budget imbalance" term is currently needed to close the carbon budget equation. The large variability of this carbon budget imbalance is believed to be caused by errors in the land carbon sink (Friedlingstein et al., 2022). The overarching aim of the project is to improve our understanding of how aerosol particles affect the land carbon sink. In particular, the project will investigate the role of competing effects on the land carbon sink due to the variability in temperature, precipitation and diffuse radiation on semi-decadal timescales. The approach will involve a combination of remote sensing analysis (e.g. Global Ecosystem Dynamics Investigation - GEDI (Hancock et al., 2019); Clouds and the Earth's Radiant Energy System - CERES) and model simulations (i.e. aerosol, radiation and vegetation models, together with UK Earth System Model - UKESM simulations).
Within the diverse supervision team we have the ability to observe and simulate biosphere-atmosphere interactions in a more comprehensive way than ever before. This project will therefore provide a unique opportunity to employ state-of-the-art satellite observations and global models to answer a series of key questions. While relatively flexible to allow for your interests, the project will involve:
-A comprehensive assessment of global forest structure and above-ground biomass density using remote sensing products (e.g. GEDI, ICESat-2, NISAR).
- Using satellite observations to constrain simulated semi-decadal Net Primary Productivity trends, including via advanced computer techniques (e.g. bias correction and data-driven algorithms).
- Exploring the role of anthropogenic aerosol and other pollutants (e.g. ozone) on the efficiency of UKESM simulated ecosystem feedbacks.
- Investigating the effect of changes in temperature, precipitation and atmospheric CO2 on biosphere-atmosphere interactions in the UKESM model.