CO2 induced droughts are only partly irreversible with CDR

[Tom Goreau]

To reduce long-term CO2 climate feedbacks, it is essential to stop fossil fuel emissions and increase carbon sinks, whether or not SRM can save us by preventing peak climate overshoot.

• Article
• Open access

• Published: 10 September 2025

Hysteresis and reversibility of agroecological droughts in response to carbon dioxide removal

• Laibao Liu, 
• Mathias Hauser, 
• Michael Windisch & 
• Sonia I. Seneviratne 

Nature Water volume 3, pages1017–1024 (2025)

Abstract

Agroecological droughts are expected to increase with climate change, becoming one of the greatest threats to ecosystems and human society. To mitigate climate change and the growing risk of agroecological droughts, carbon dioxide removal (CDR) is increasingly recognized as unavoidable. However, it remains unclear whether the increase of agroecological drought due to atmospheric CO₂ emissions will be symmetrically reversed by an equivalent atmospheric CDR. Here we investigate this question by utilizing an idealized atmospheric CO₂ emission and removal experiment from the CDR Model Intercomparison Project, involving eight Earth system models, and develop a new methodology to quantify climate hysteresis and reversibility. We find that drought increases in hotspot regions cannot be symmetrically reversed by an equivalent CDR: drought severity under the CDR pathway is 65% ± 30% greater than under the emission pathway; drought frequency increases are only partially reversed by 73% ± 18% when CO₂ emissions are balanced by equivalent CDR. Drought hysteresis and irreversibility are most pronounced in the Mediterranean, northern Central America, west and east southern Africa and southern Australia. Our findings imply irreversible drought impacts associated with CDR, highlighting the need for planning long-term drought adaptations.

 

[Bruce Melton -- Austin, Texas]

Liu 2025 – Asymetrical drought recovery with CDR, Tipping, feedbacks, and the point of no return… This is an important lesson in tipping and publications that appear to offer definitive results. The abstract and content of this article are misleading unless read fully. The modeling experiment increased CO2 from pre-industrial to 4x pre-industrial at 1 percent per year, (148 years total, about 100 years above 425 ppm CO2), then reversed with CDR at an equal rate back to pre-industrial. At a quadrupling of 280 ppm CO2, irreversible tipping of most Earth systems is projected to be foregone by the tipping literature, meaning the systems are destroyed, not to return in time frames that matter. This does not mean that Earth systems will not self-restore before warming is reversed back to pre-industrial before the irreversible tipping point of no return. The experiment did not test this scenario.

The concept presented though, does offer insight into reversing earth system degradation. Their findings that self-restoration proceeds at a slower pace than degradation confirms that self-restoration is affected by feedbacks, most notably in this experiment but not mentioned, would be the drought feedback where the more extreme the drought, the greater is the warming feedback. This means that the longer we wait, the slower will be self-restoration, until the point of no return not modeled in this experiment.

Liu et al., Hysteresis and reversibility of agroecological droughts in response to carbon dioxide removal, Nature Water, September 10, 2025.
https://www.nature.com/articles/s44221-025-00487-8 

Bruce Melton PE
Director, Climate Change Now Initiative, 501c3
President, Melton Engineering Services Austin
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[rob...@rtulip.net]

Hello Tom, thank you, I agree with you on sinks and on cutting long-term feedbacks.  My view on the best way to manage emissions is by obliging coal and gas operators to turn CO₂ into feedstock for large-scale ocean biomanufacturing.  I wrote a paper discussing this, and have generated the attached commentary, with AI assistance.  It rambles a bit but has some interest I hope.  You referenced my 2014 work on ocean CDR in your book Geotherapy.

 

Regards

 

Robert Tulip

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