Impact of climate change mitigation on ocean acidification projections

Abstract

Impacts of anthropogenic carbon emissions on the chemical state of the ocean are quantified. Coupled climate-carbon models are applied for the range of recently published multi-gas climate change mitigation and baseline emissions scenarios from the integrated assessment modelling community as well as for idealized emissions and concentration pathways. Mitigation scenarios lead to lower atmospheric CO2, less climate change, and less ocean acidification than noclimate policy baseline scenarios. Employing some of the most stringent scenarios in the literature allows us to estimate ‘minimum warming’ and ‘minimum ocean acidification’ given inertia in both the climate and socio-economic system. Regionally, surface water in the Arctic is currently changing from over- to undersaturated conditions with respect to aragonite, a mineral form of CaCO3 secreted by marine organisms to build their shells and skeletons. 21 st century carbon emissions provide a long-term commitment to future Earth System changes: undersaturation in the Arctic remains widespread for centuries for noclimate policy baseline scenarios, even when carbon emissions are completely and unrealistically stopped in year 2100. For a high 21 st century emissions scenario with subsequent emissions stop, the volume of supersaturated water, providing habitat to aragonite producing organisms, decreases from 42 to 8%. Minimum extension is reached 200 years after emissions have been stopped. Carbon emissions have to be reduced close to zero if atmospheric CO2 is to be stabilized and thus climate change and ocean acidification to be limited.