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Oliver Geden welcomes an analysis of the political inertia impeding a global treaty to limit warming.

As global negotiations fail on emissions reductions, scientific advisers need to resist pressure to fit the facts to the failure, warns Oliver Geden.

Various methods of carbon dioxide removal (CDR) are being pursued in response to the climate crisis, but they are mostly not proven at scale. Climate experts are divided over whether CDR is a necessary requirement or a dangerous distraction from limiting emissions. In this Viewpoint, six experts offer their views on the CDR debate.

Climate policy has gained focus with the adoption of the 2 °C target, but action to avoid dangerous climate change has not occurred as expected. It is time to reconsider the target, and most importantly, the relationship between climate science and policy.

The Paris Agreement introduced three mitigation targets. In the future, the main focus should not be on temperature targets such as 2 or 1.5 °C, but on the target with the greatest potential to effectively guide policy: net zero emissions.

The Intergovernmental Panel on Climate Change is preparing a report on keeping global warming below 1.5 °C. How the panel chooses to deal with the option of solar geoengineering will test the integrity of scientific climate policy advice.

To limit warming, action plans from countries and companies must be fair, rigorous and transparent.

Upward estimates for carbon budgets are unlikely to lead to action-focused climate policy. Climate researchers need to understand processes and incentives in policymaking and politics to communicate effectively.

Meeting the Paris Agreement targets requires deep emissions reductions supported by a scale-up in carbon dioxide removal. However, current country-reported mitigation pledges are off track to meet carbon dioxide removal needs, unless countries dramatically reduce emissions consistent with low-energy-demand scenarios.

Most scenarios to meet the Paris Agreement require negative emissions technologies. The EU has assumed a global leadership role in mitigation action and low-carbon energy technology development and deployment, but carbon dioxide removal presents a serious challenge to its low-carbon policy paradigm and experience.

Temperature overshoot scenarios that make the 1.5 °C climate target feasible could turn into sources of political flexibility. Climate scientists must provide clear constraints on overshoot magnitude, duration and timing, to ensure accountability.

To enable net-negative CO₂ emissions, the repayment of previously accrued carbon debt by establishing the responsibility for the net removal of CO₂ by carbon-emitting parties through carbon removal obligations is necessary.

Carbon dioxide removals (CDR) have been integrated into country-submitted reports under the Paris Agreement. However, this Analysis finds a gap between levels of CDR in these national proposals and the scenarios limiting global warming to the 1.5 °C target.

The publication of the IPCC Special Report on global warming of 1.5 ^oC paved the way for the rise of the political rhetoric of setting a fixed deadline for decisive actions on climate change. However, the dangers of such deadline rhetoric suggest the need for the IPCC to take responsibility for its report and openly challenge the credibility of such a deadline.

Scientists and policymakers must acknowledge that carbon dioxide removal can be small in scale and still be relevant for climate policy, that it will primarily emerge ‘bottom up’, and that different methods have different governance needs.

Policymakers are beginning to understand the scale of carbon dioxide removal that is required to keep global warming “well below 2 °C”. This understanding must now be translated into policies that give business the incentive to research, develop and deploy the required technologies.

Carbon dioxide removal via afforestation and reforestation could be scaled up globally to account for ten percent of net greenhouse gas emission reductions required between 2020 and 2030, according to an analysis of land-based carbon removal deployed in the IPCC-assessed scenarios.

Environmental policy often delays addressing problems. This Perspective defines such ‘stopgap measures’, considers examples, and applies to solar geoengineering a new framework for assessing stopgaps.

Achieving the long-term temperature goal of the Paris Agreement relies on every actor maximising their effort to reduce emissions. Generic targets claiming a basis in science have been used to justify inequitable efforts that insufficiently stretch the ambition of the best-resourced countries and companies.

Carbon Dioxide Removal (CDR) is a key element of any mitigation strategy aiming to achieve the long-term temperature goal of the Paris Agreement, as well as national net-zero and net-negative greenhouse gas emissions targets. For robust CDR policy, the credibility of certification schemes is essential.

Responses to the COVID-19 emergency have exposed break-points at the interface of science, media, and policy. We summarize five lessons that should be heeded if climate change ever enters a state of emergency perceived to warrant stratospheric aerosol injection.