Negative Emissions: A new phase of climate policy to reduce global warming to 1 °C above pre-industrial levels.

Summary: The Intergovernmental Panel on Climate Change's new synthesis report projects that it is unlikely that it will be possible to limit global warming to 1.5 °C. The latest scientific findings on tipping points also show that irreversible changes to the Earth system are highly likely to occur if the atmospheric CO₂ content already reached today is not reduced to a lower level. In terms of quantity, a reduction in the atmospheric CO₂ concentration from today's around 424 ppm to 350 ppm is necessary. The value of 350 ppm would correspond to a warming of around 1 °C compared to the pre-industrial value of 280 ppm.

Politically determined targets should be adapted to the progress of scientific knowledge. In­ternational determinations and concrete steps towards this 1 °C target should be taken an­nually. This would be a new phase in climate policy in which, in addition to the primary goal of avoiding all greenhouse gas emissions, the secondary goal of quickly achieving nega­tive emissions before 2050 would be added as a second branch of the global climate strat­egy. This secondary goal must under no circumstances – including from a financial perspec­tive – affect the efforts to reduce emissions which need to be reinforced. While the state must set the framework conditions, non-state actors also have an important role to play in financing negative emissions.

Scaling up the CO₂ extraction and storage (sequestration) approaches to the necessary scale in the near future is an ambitious but not utopian goal. Plant-based CO₂ extractions will play an important role but cannot handle the volume required. The inexpensive availa­bility of renewable energies in many places around the world increasingly enables the use of tech­nological approaches despite their high energy requirements. In addition to climate-ethical aspects (with consequences for the financial viability of this approach), the physical and technical feasibility are discussed in this article. The permanent storage of CO₂ in the geo­logical subsoil is considered comparatively safe and there is sufficient capacity, e. g. in po­rous formations. The safest option is to store it in the formations in which the CO₂ miner­ali­zes. Technologies for capturing the gas include especially direct air capture (DAC) and – with limitations – bioenergy carbon capture and sequestration (BECCS). In addition, accel­erated weathering and afforestation (even without BECCS) and carbon accumulation in soils or moors could make substantial contributions. The biodiversity crisis also requires large areas for species protection that can also be used for biological CO₂ removal. The German Carbon Dioxide Storage Act is no longer up to date in this new phase of climate policy because it prohibits the transport and storage of CO₂.

Suggested citation: Tremmel, J., Steinberger, B., Linow, S., Breyer, C., Gerhards, C., Vollmer, D., Zens, J., Fichter, C., Masurenko, C. (2024). Negative Emissions: A new phase of climate policy to reduce global warm­ing to 1 °C above pre-industrial levels. Diskussionsbeiträge der Scientists for Future, 16, 1–39. doi: 10.5281/zenodo.11493905