Long-term response of oceans to CO2 removal from the atmosphere

Abstract

Carbon dioxide removal (CDR) from the atmosphere has been proposed as a measure for mitigating global warming and ocean acidification. To assess the extent to which CDR might eliminate the long-term consequences of anthropogenic CO 2 emissions in the marine environment, we simulate the e ect of two massive CDR interventions with CO 2 extraction rates of 5 GtC yr −1 and 25 GtC yr −1 , respectively, while CO 2 emissions follow the extended RCP8.5 pathway. We falsify two hypotheses: the first being that CDR can restore pre-industrial conditions in the ocean by reducing the atmospheric CO 2 concentration back to its pre-industrial level, and the second being that high CO 2 emissions rates (RCP8.5) followed by CDR have long-term oceanic consequences that are similar to those of low emissions rates (RCP2.6). Focusing on pH, temperature and dissolved oxygen, we find that even after several centuries of CDR deployment, past CO 2 emissions would leave a substantial legacy in the marine environment.

Assessing carbon dioxide removal through global and regional ocean alkalinization under high and low emission pathways

“…By 2100, despite the return to 2020 values of atmospheric CO 2 concentration under RCP2.6 (Fig. 2), neither pH nor aragonite saturation state return to 2020 values, consistent with Mathesius et al (2015).…”

The Carbon Dioxide Removal Model Intercomparison Project (CDRMIP): rationale and experimental protocol for CMIP6

“…To date, modeling studies of CDR focusing on the carbon cycle and climatic responses have been undertaken with only a few Earth system models (Arora and Boer, 2014;Boucher et al, 2012;Cao and Caldeira, 2010;Gasser et al, 2015;Jones et al, 2016a;Keller et al, 2014;MacDougall, 2013;Mathesius et al, 2015;Tokarska and Zickfeld, 2015;Zickfeld et al, 2016). However, as these studies all use different experimental designs, their results are not directly comparable, and consequently building a consensus on responses is challenging.…”

Hazards of decreasing marine oxygen: the near-term and millennial-scale benefits of meeting the Paris climate targets

“…A range of multi-millennial projections available so far have focused primarily on the evolution of surface air temperature (SAT), atmospheric CO 2 , oceanic pH, sea level and the Atlantic Meridional Overturning Circulation (AMOC) (Plattner et al, 2008;Eby et al, 2009;Zickfeld et al, 2013;Golledge et al, 2015;Winkelmann et al, 2015;Clark et al, 2016;Zickfeld et al, 2017;Pfister and Stocker, 2016;Lord et al, 2016;Ehlert and Zickfeld, 2017). Fewer long-term model simulations have focused on oceanic oxygen (Yamamoto et al,15 2015; Matear and Hirst, 2003;Schmittner et al, 2008;Mathesius et al, 2015). We show that the oceanic oxygen equilibration timescale is considerably longer than its thermal equilibration timescale and that oceanic oxygen changes are dominated by changes in Atlantic and Indo-Pacific overturning, predictive variables to be considered in future multi-millennial projections with General Circulation Models (GCMs).…”