How Much Attention Should We Give to Overshoot Narratives?

As the global temperature approaches an average of 1.5°C above preindustrial levels - the most ambitious limit set in the 2015 Paris climate agreement - researchers and policymakers are increasingly considering overshoot pathways that aim to mitigate the impacts of transgressing these guardrails. Such overshoot narratives warrant cautious consideration:
Firstly, achieving net-zero goals is challenging as it is. But achieving large-scale net-negative CO2 emissions on a global scale to reverse a temperature or carbon budget transgression will be even more challenging, when considering context-specific feasibility and desirability constraints to the implementation of carbon dioxide removal (CDR) options (see e.g. Borchers et al., 2024).
Secondly, if we would achieve global net-negative CO2 emissions, detecting a temperature overshoots amidst internal climate variability will pose a considerable challenge, that would considerably complicate the monitoring and accordingly the management of such anthropogenic interventions into the climate system.
Thirdly, the financial, social, and governance frameworks required to incentivise, implement and sustain global net-negative CO2 emissions to manipulate the atmospheric CO2 concentration, similar to other forms of climate interventions, are likely unattainable.
Fourth, even if these barriers were overcome, the resulting post-overshoot climate would very likely differ from one where temperature stabilisation is maintained without overshoot (see e.g., Schleussner et al., 2024), with potentially irreversible impacts on ecosystems and climate systems.

Mitigation deterrence - reducing incentives for near-term emissions reductions - represents an considerable risk associated with CDR and overshoot narratives (Carton et al., 2023). It is therefore crucial to approach overshoot research and communication with care, prioritising immediate and effective mitigation strategies to minimise reliance on uncertain and potentially unfeasible overshoot pathways.

 

Borchers, M., Förster, J., Thrän, D., Beck, S., Thoni, T., Korte, K., et al. (2024). A comprehensive assessment of carbon dioxide removal options for Germany. Earth's Future, 12, e2023EF003986. https://doi.org/10.1029/2023EF003986 

Schleussner, CF., Ganti, G., Lejeune, Q. et al. Overconfidence in climate overshoot. Nature 634, 366–373 (2024). https://doi.org/10.1038/s41586-024-08020-9

Carton, W., Hougaard, I.-M., Markusson, N., & Lund, J. F. (2023). Is carbon removal delaying emission reductions? WIREs Climate Change, 14(4), e826. https://doi.org/10.1002/wcc.826