Negative CO2 Emissions - An Analysis of the Retention Times Required with Respect to Possible Carbon Leakage

Paper in proceeding, 2018

With present emissions the global CO2 budget associated with a maximum temperature increase of about 1.5 to 2ºC will likely be spent in less than a few decades, Thus, it will be extremely difficult or perhaps even impossible to meet the climate targets agreed upon in Paris only by decreasing fossil CO2 emissions. Scenarios presented in the IPCC reports accommodate for this by introducing so-called negative emissions. The idea is that the budgets will be exceeded, but that massive negative emissions, especially during the latter part of the century, will remove the surplus of CO2 in the atmosphere. A number of different Negative Emissions Technologies (NETs) have been proposed, including BECCS, afforestation/reforestation, altered agricultural practices, biochar production, enhanced weathering and direct air captured. However, many of the options proposed could be associated with carbon leakage which could compromise the purpose of negative emissions, e.g. storage in of carbon in growing/dead biomass. Furthermore, it may be difficult to safely assess the long-term leakage rates. To reach the large negative emissions needed is expected to require a mix of technologies having different expected retention times, and different safety in the assessment of leakage rates. Could the concept of leakage mean that we are just delaying the problem and transferring the problem to coming generations? The short answer to this is that it all depends on the leakage rates. Different leakage rates and mixes of leakage rates are investigated in the paper.