Effects of Constrained Enhanced Rock Weathering with Cropland on Climate Change and Ocean Acidification in an Earth System Model

Abstract:

Terrestrial enhanced rock weathering (ERW) is a negative emission technology (NET) that removes atmospheric carbon dioxide by accelerating rock chemical breakdown and locking the carbon in ocean sediments, with potential to help averting ocean acidification. However, prior analyses were derived under idealised assumptions ignoring real-world constraints. We quantify the effect of realistically achievable enhanced weathering application on croplands on meeting the Paris Agreement warming targets, lowering ocean acidification and increasing aragonite saturation state required for maintaining coral reef health. Three scenarios of ERW, carbon capture and storage (CCS) and co-deployment were modelled in the Earth system model GENIE, and the outcome was compared to a strong mitigation scenario, RCP2.6 as the baseline, between 2020 and 2100. The results of the GENIE simulations showed ERW and CCS scenarios have similar impacts on decarbonisation and temperature decrease, and therefore they reduce the probability of peak and 2100 warming exceeding the 1.5 degrees target. These effects are doubled in the co-deployment scenario, suggesting that no adverse interaction occurs in the co-deployment of these two NETs. Compared to CCS, ERW slows the process of ocean acidification more effectively by increasing the surface ocean pH during deployment. Moreover, it enhances the aragonite saturation state in most areas, especially south Asia, where tropical coral species are vulnerable to decalcification due to ocean acidification. The results suggest that under realistic assumptions, the co-benefits of ERW alongside its climate change mitigation via carbon dioxide drawdown strongly support rapid deployment of this NET.