How the Montreal Protocol Put the Stratospheric Ozone Layer on the Path to Recovery and Delayed Climate Tipping Points
16 September 2025 – Today, on the occasion of the United Nations International Day for the Preservation of the Ozone Layer, IGSD, in collaboration with the Planetary Guardians Initiative, Plus Wonder, and others, released a report describing how the stratospheric ozone layer recovered from the danger zone through swift action under the Montreal Protocol on Substances that Deplete the Ozone Layer. The paper, How the Montreal Protocol Put the Stratospheric Ozone Layer on the Path to Recovery and Delayed Climate Tipping Points That Would Have Forced Earth Further Beyond Planetary Boundaries, also documents how recovery of the ozone layer helps protect the climate, agricultural and natural ecosystems, plant and animal species, and the built environment.
The paper was co-authored by leaders from the Institute for Governance & Sustainable Development (IGSD), the Netherlands National Institute for Public Health and the Environment (RIVM), the Planetary Guardians Initiative, Plus Wonder, and other experts formerly with the Montreal Protocol Ozone Secretariat and the United Nations Development Programme.
In a parallel effort, also in celebration of the International Day for the Preservation of the Ozone Layer, the Planetary Guardians Initiative released two reels sharing the inspiring history of Ozone protection (see here and here).
Dr. Sylvia Alice Earle, marine biologist and oceanographer:
“The authors are among the architects and implementers of the Montreal Protocol and pioneers of the planetary boundaries framework for maintaining a "safe operating space for humanity.” Here, they convey a sense of hope but also of utmost urgency for action concerning the other features identified as planetary boundaries.”
Dr. Stephen O. Andersen, IGSD Director of Research and lead-author:
“This paper shows how, over its nearly 40-year history, the Montreal Protocol can rightly claim to be the most successful international treaties ever struck. It has fulfilled its original objective by putting the stratospheric ozone layer on the road to recovery. But its benefits have not stopped there: it has also done more than any other measure to combat climate change.”
Dr. Johan Rockström, founder of Planetary Guardians Initiative and Co-Director of the Potsdam Institute for Climate Impact Research (PIK):
"Boundaries are set to avoid tipping points, to have a high chance to keep the planet in a state as close as possible to the Holocene, that allows it to maintain its resilience, stability, and life support capabilities. Go beyond and we enter a danger zone… the uncertainty range of science."
Forthcoming from the Planetary Boundary Initiative is also the Planetary Health Check 2025 Report, which will include an extra special focus on the oceans. The launch of the report will be on 24 September 2025.
How the Montreal Protocol Put the Stratospheric Ozone Layer on the Path to Recovery and Delayed Climate Tipping Points That Would Have Forced Earth Further Beyond Planetary Boundaries is available here. Co-authored by Dr. Stephen O. Andersen and Durwood Zaelke (IGSD), Dr. Suely Carvalho (formerly UNDP), Marco González (formerly Montreal Protocol Ozone Secretariat), Jean Oelwang (Plus Wonder), Dr. Johan Rockström (Planetary Guardians), and Dr. Guus J. M. Velders (RIVM)
Constructive peer-review comments can be submitted to Dr. Andersen at sandersen@igsd.org.
