Research highlights dangerous over-reliance on future CO₂ removal

Governments and businesses are counting on dangerous amounts of future carbon dioxide (CO) removal₂) of the atmosphere, instead of reducing emissions more quickly and phasing out fossil fuels. This problem is partly due to an incomplete picture of the harmful consequences of carbon dioxide removal on populations, food security and natural ecosystems, according to a new study published in Science.

The paper reveals that the carbon dioxide removal potential currently reported by the United Nations’ climate science assessment body, the Intergovernmental Panel on Climate Change (IPCC), significantly overestimates the heavy amount carbon dioxide removal, particularly bioenergy with carbon capture and storage, and tree removal. planting, can do so safely in pursuit of climate goals.

The IPCC works by synthesizing the best literature available at the time of writing and publishing its reports.

Scientific understanding of how to slow and stop global warming has become more sophisticated in recent years, now allowing researchers to map carbon dioxide removal options against sustainability risks, to see what would meet the objectives of climate policy without presenting unacceptable dangers.

Lead author Alexandra Deprez, IDDRI-Sciences Po, said: “Governments and industries are banking on future large-scale carbon dioxide removal deployments to meet the Paris Agreement climate goals, but the proposed scale threatens food security, human rights, poses serious damage to natural resources. ecosystems and risks crossing multiple planetary boundaries in a potentially irreversible manner. »

The researchers examined the climate science publications that inspired the most recent IPCC reports, as well as the pathways limiting warming to 1.5°C.

They found that sustainable thresholds for removing land-based carbon dioxide using bioenergy crops, forestry and ecosystem restoration were significantly lower than the deployment expectations conveyed by most of the pathways presented in the reports. of the IPCC, once the risks linked to biodiversity and human livelihoods are applied to the different scenarios.

Co-author Professor Paul Leadley, from the University of Paris-Saclay, said: “Levels of carbon dioxide removal that are considered achievable at reasonable cost by the IPCC create high risks for the agriculture, livelihoods and the environment. There isn’t enough land on our planet to remove huge amounts of carbon dioxide – something else has to give. Biodiversity, freshwater use and food security should be the issues that guide the limits of carbon dioxide removal rather than current estimates of technical and economic potentials.

The latest IPCC report on mitigation (AR6 WGIII) addresses the issue of meeting the ambitious climate goals of the Paris Agreement, in part by identifying the technical and economic limits of carbon dioxide removal options.

The upper end of the proposed cap for bioenergy with carbon capture and storage and afforestation/reforestation (maintenance, improvement or planting of new forests), when considered land area, could require conversion of up to 29 million km.² of land – more than three times the size of the United States – to bioenergy crops or trees. This could potentially push more than 300 million people into food insecurity, almost equal to the entire U.S. population.

Analysis of existing climate commitments reveals that by the end of this decade, countries collectively plan to produce twice as much fossil fuels as recommended in the trajectories aligned by the IPCC in Paris with little or no overshoot beyond 1.5°C, and to use 12 million by 2060. kilometers² for land-based carbon removal, an area close to the total area of ​​global cropland currently available.

Co-author Dr Kate Dooley, from the University of Melbourne, said: “Removal of carbon dioxide from land and forests cannot legitimately be used to offset ongoing fossil fuel emissions. Government climate plans should set distinct and transparent targets for emission reductions and removals, which limit dependency. on the latter, and respect commitments on climate and biodiversity through the restoration and maintenance of natural ecosystems.

The document makes three recommendations to policymakers and scientists:

1. Estimate a sustainable carbon dioxide removal (CDR) budget, based on a socio-ecological limit
2. Identify viable 1.5°C trajectories that do not exceed the CDR sustainability thresholds, with a focus on short-term national climate plans (NDCs) expected in 2025 under the UNFCCC process.
3. CDR governance should allocate limited sustainable supply to most legitimate uses

The document also calls on the scientific community to inform the next cycle of IPCC reports, which will take place in the second half of this crucial decade for climate action. Identifying scenarios aligned with the Paris Agreement that do not exceed sustainability limits should be a key priority of the IPCC’s seventh round of assessment reporting (AR7).

Alexandra Deprez added: “The climate and biodiversity crises are two sides of the same coin, and large-scale elimination of carbon dioxide will not solve either problem. Carbon removal must be carefully deployed on a much smaller scale than current climate plans and most climate scenarios suggest, and alongside a rapid, fair and orderly phase-out of fossil fuels, if we are to achieve our climate goals . »