8 of methods for carbon removal later in this century, few of the technologies are even as well developed as CCS. The methods of carbon removal that are best understood, such as reforestation, afforestation, and ecological restoration, cannot remove sufficient quantities of carbon dioxide. Unless carbon emissions rapidly reach net zero, the quantity of carbon removal that will be necessary in order to limit climate change will be possible only with some of the new technologies that remain to be fully developed and tested at scale. Consequently, no grounds exist for full confidence that carbon removal can eliminate sufficiently large quantities of additional carbon emissions. Second, the new technology most often assumed in the integrated assessment models, CCS combined with bio-energy [BECCS], confronts all the obstacles faced by CCS, plus all the additional obstacles faced by extensive bio-energy. Most importantly, the production of the feedstocks for bio-energy requires extensive land and water so that this production may compete with food production and thus with sustainable development and even subsistence.22 Seizure of land or water needed for subsistence would violate fundamental rights. Third, although an earlier “overshoot” in carbon emissions can in theory be reversed by later carbon removal, the effects on the climate produced by those excessive emissions cannot necessarily be reversed. It is entirely possible that a “temporary” overshoot will cause a permanent change in the climate. And there are good scientific grounds to worry that those changes will include the passing of tipping points, even tipping points that will generate a cascade of self-reinforcing positive feedbacks for more extreme climate change. 23 Capture now is far safer than hoped-for removal later, and it is the responsibility of the carbon majors to see that it happens if they wish to continue to sell fossil fuels. If they do not, they will be responsible for much greater harm than they have already inflicted. Henry Shue October 21, 2018 ———————————— Pete Smith, Steven J. Davis, Felix Creutzig, et al., ‘Biophysical and economic limits to negative CO2 emissions’, Nature Climate Change 6 (2016), 42 - 50. doi:10.1038/nclimate2870. Also see Jan C. Minx, William F. Lamb, Max W. Callaghan, et al., ‘Negative Emissions—Part 1: Research landscape ad synthesis’, Environmental Research Letters, published on-line, 22 May 2018 [open access]. doi:10.1088/1748-9326/aabf9b. 23Will Steffen, Johan Rockström, Katherine Richardson, et al., ‘Trajectories of the Earth System in the Anthropocene’, Proceedings of the National Academy of Sciences of the United States of America, published on-line [open access], 6 August 2018. doi:10.1073/pnas.1810141115. Also see Henry Shue, ‘Uncertainty as the Reason for Action: Last Opportunity and Future Climate Disaster’, Global Justice: Theory Practice Rhetoric, Special Issue on Global Justice and Climate Change, 9 (2016), 86-103 [on-line, open access]. https://www.theglobaljusticenetwork.org/global/index.php/gjn/article/view/89/65. 22