Offsetting unabated agricultural emissions with CO2 removal to achieve ambitious climate targets

Abstract

The Representative Concentration Pathway 2.6 (RCP2.6), which is broadly compatible with the Paris Agreement’s temperature goal by 1.5–2°C, contains substantial reductions in agricultural non-CO2 emissions besides the deployment of Carbon Dioxide Removal (CDR). Failing to mitigate agricultural methane and nitrous oxide emissions could contribute to an overshoot of the RCP2.6 warming by about 0.4°C. We explore using additional CDR to offset alternative agricultural non-CO2 emission pathways in which emissions either remain constant or rise. We assess the effects on the climate of calculating CDR rates to offset agricultural emission under two different approaches: relying on the 100-year global warming potential conversion metric (GWP100) and maintaining effective radiative forcing levels at exactly those of RCP2.6. Using a reduced-complexity climate model, we find that the conversion metric leads to a systematic underestimation of needed CDR, reaching only around 50% of the temperature mitigation needed to remain on the RCP2.6 track. This is mostly because the metric underestimates, in the near term, forcing from short-lived climate pollutants such as methane. We test whether alternative conversion metrics, the GWP20 and GWP*, are more suitable for offsetting purposes, and found that they both lead to an overestimation of the CDR requirements. Under alternative agricultural emissions pathways, holding to RCP2.6 total radiative forcing requires up to twice the amount of CDR that is already included in the RCP2.6. We examine the costs of this additional CDR, and the effects of internalizing these in several agricultural commodities. Assuming an average CDR cost by $150/tCO2, we find increases in prices of up to 41% for beef, 14% for rice, and 40% for milk in the United States relative to current retail prices. These figures are significantly higher (for beef and rice) under a global scenario, potentially threatening food security and welfare. Although the policy delivers a mechanism to finance the early deployment of CDR, using CDR to offset remaining high emissions may well hit other non-financial constraints and can thus only support, and not substitute, emission reductions.

Definitions and implications of climate-neutral aviation

“…Where the amount of ERF that needs to be offset via CO 2 removal is denoted as ERF CDR (t). Theoretically, the rates of CO 2 removal can be explicitly calculated from ERF CDR (t), for example, following the approach by Jenkins et al 56 or Brazzola et al 25 . Yet this sort of computation is time and skills intensive and thus not in line with current practices under international treaties (for example, the United Nations Framework Convention on Climate Change, UNFCCC).…”

“…Thus a definition of climate neutrality requires setting the baseline relative to which net emissions are neutral 19,24 . First attempts to investigate the implications of climate neutrality and the related issue of offsetting non-CO 2 forcing with CO 2 removal exist for some sectors dominated by short-lived greenhouse gases, such as agriculture 23,25,26 . There has been no such analysis of the aviation sector, which has far more complex climatic effects.…”

Consistent Greenhouse Accounting Identifies Forests and Land Use as Crucial Determinants of Climate

“…100-year Global Warming Potentials (GWPs) are the IPCC convention choice for comparison, but recent advances in determining emissions-based Effective Radiative Forcing (ERF) and derived Global Surface Air Temperature (GSAT), as defined in the IPCC's AR6 Supplementary Material 6.SM.1 [29], present a less contested means of comparing sector contributions. ERF is also believed to produce more accurate estimates of agriculture's climate impact than other commonly used climate metrics [34]. This does require, however, accurate proportioning of emission species to each sector, but once the proportion is defined, the ERF and GSAT attribution to sectors is trivial.…”

ZnIn2S4‐Based Nanostructures in Artificial Photosynthesis: Insights into Photocatalytic Reduction toward Sustainable Energy Production

“…It is predicted that the annual average CO 2 concentration for 2021 is 416.3 ppm (±0.6), which is the first year on record that sees CO 2 levels of more than 50% above preindustrial levels, indicating the urgency of the global environmental burdens. [ 1 ] Since the pioneering utilizing n‐type TiO 2 electrode to produce H 2 via photoelectrochemical water splitting by Fujishima and Honda in 1972, semiconductor photocatalysis technology is considered as one of the fascinating technologies to alleviate energy problems. [ 2 ] With the development of research in recent years, photocatalytic reduction reaction (such as photocatalytic water splitting, CO 2 reduction, and nitrogen fixation) has been paid more and more attention to solve the critical issues related to energy and the environment.…”