Periodic Reporting for period 1 - PALEOCARBON (PALEOcene greenhouse climate and the effect of basalt weathering on CARBON sequestration)
Reporting period: 2019-09-01 to 2022-08-31
The 2015 Paris Climate Agreement brought nations together to mitigate anthropogenic climate change, with the aim to keep global temperature rise below 2°C above pre-industrial levels. Artificially enhanced weathering of basalt, driven by intensified geochemical and biological processes that naturally promote the absorption of CO2, is considered as a potentially significant negative emissions technology. However, the impact of climate change and elevated greenhouse conditions on the rate and processes of basalt weathering and the role of plants in mediating this process are unconstrained. This Marie Skłodowska Curie Individual Fellowship aims to address this uncertainty by a multidisciplinary study on silicate weathering of basalts during the Paleocene climatic greenhouse world, using state-of-the-art botanical and geochemical proxies, tools and methods in the PALEOCARBON project. The project will focus on three main objectives: (1) Quantifying elevated Paleocene pCO2, temperature and precipitation levels using fossil leaves; (2) Constraining processes & intensity of silicate weathering and carbon drawdown potential in Paleocene basalts; (3) Quantifying elemental uptake of plants grown in high pCO2 laboratory conditions, to constrain the role of plant in mediating weathering processes. The PALEOCARBON project has the ultimate aim to constrain the fundamental end-member parameters that control the efficiency of (artificially) enhanced weathering as a potential negative carbon emissions technology. The findings suggest that (1) enhanced silicate weathering under elevated atmospheric CO2 levels may act as an important mechanism in stabilising Earth’s atmospheric CO2 levels during past super-greenhouse events as well as during future climate change; (2) plant mediation may play an important role in enhancing silicate weathering rate; (3) the impact of the addition of basaltic materials on plant growth is not necessarily positive, as it may not be a simple nutrient addition or soil remediation effect.
All the work packages (research, training and project management) in the project have been carried out by the fellow, including the three main research work packages. These are: (1) Reconstructing the Paleocene climatic conditions; (2) Constraining processes and intensity of Paleocene NAIP basalt weathering; (3) Quantifying the role of plants in mediating the silicate weathering rate under super-greenhouse climate.
Our results suggest that (1) higher atmospheric CO2 levels (e.g. similar to the Paleocene atmospheric level) increased the average weathering rate of basaltic materials, hence enhancing the associated carbon sequestration; (2) plant growth increased the average weathering rate compared to no plant scenario under a specific climatic condition; (3) adding basaltic materials to soils as carried out in the growth chamber experiment reduced plant growth.
This contribution has been exploited through international scientific conference presentations, invited seminar talks, public engagement/media outreach activities, etc., and is currently being exploited by open access scientific journey publications (in preparation).
Our results suggest that (1) higher atmospheric CO2 levels (e.g. similar to the Paleocene atmospheric level) increased the average weathering rate of basaltic materials, hence enhancing the associated carbon sequestration; (2) plant growth increased the average weathering rate compared to no plant scenario under a specific climatic condition; (3) adding basaltic materials to soils as carried out in the growth chamber experiment reduced plant growth.
This contribution has been exploited through international scientific conference presentations, invited seminar talks, public engagement/media outreach activities, etc., and is currently being exploited by open access scientific journey publications (in preparation).
Silicate weathering has been suggested to play a significant role in modulating atmospheric CO2 and the surface environment throughout Earth history. Mineral reactions associated with silicate weathering have been extensively studied. However, it is unclear how past weathering of silicate rocks, which represented a primary carbon sink in the long-term carbon cycle, evolved and has been modulated under different climatic conditions (e.g. at different atmospheric CO2 levels). It has been widely recognised that plants can enhance silicate weathering, which has been taken into account when quantifying atmospheric CO2 and the long-term carbon cycle over Phanerozoic time. However, processes modulating plant elemental-uptake under varying pCO2 conditions need to be quantitatively studied. This project quantitatively investigates the role of atmospheric CO2 levels and the role of plants in mediating the rate of silicate weathering. This is achieved through the study of Paleogene basalt weathering and silicate weathering under controlled chamber experiment with varying atmospheric CO2 levels, with and without plants.
The results improve our understanding of silicate weathering processes and enable us to better quantify the associated carbon sequestration under high atmospheric pCO2. The results also show the challenges associated with the quantification of carbon sequestration through enhanced silicate weathering and its impacts on plant growth. These have major implications on the future development of enhanced weathering as potential negative emissions technology. The obtained constraints on these processes also provide end member parameters to improve the climate models used to predict future climate change and carbon drawdown scenarios.
The results improve our understanding of silicate weathering processes and enable us to better quantify the associated carbon sequestration under high atmospheric pCO2. The results also show the challenges associated with the quantification of carbon sequestration through enhanced silicate weathering and its impacts on plant growth. These have major implications on the future development of enhanced weathering as potential negative emissions technology. The obtained constraints on these processes also provide end member parameters to improve the climate models used to predict future climate change and carbon drawdown scenarios.