Basing a future carbon budget on warming targets is subject to uncertainty due to uncertainty in the relationship between carbon emissions and warming, and may not prevent dangerous change throughout the entire climate system. Here, we use a climate emulator to constrain a future carbon budget that is more representative by using a combination of both warming and ocean acidification targets. The warming targets considered are the Paris Agreement targets of 1.5 and 2°C; the acidification targets are -0.17 and -0.21 pH units informed by aragonite saturation states. Considering acidification targets in conjunction with warming targets is found to narrow the uncertainty in the future carbon budget, especially in situations where the acidification target is more stringent than, or of similar stringency to, the warming target. Considering a strict combination of the two more stringent targets (both targets of 1.5°C warming and -0.17 acidification must be met), the carbon budget ranges from -74.0 to 129.8PgC. This reduces uncertainty in the carbon budget from 286.2PgC to 203.8PgC (29%). Assuming an emissions rate held constant since 2021 (which is a conservative assumption), the budget towards both targets was either spent by 2019, or will be spent by 2026.
Avrutin S., Goodwin P. & Ezard T. H. G., 2022. Assessing the future carbon budget through the lens of policy-driven acidification and temperature targets. Research Square. Article.
