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A visualization of the Antarctic ozone hole from 1991, two years after the Montreal Protocol went into effect. Credit: NASA/Goddard Space Flight Center Scientific Visualization Studio

A new study finds the 1987 Montreal Protocol, which was negotiated to stop ozone-depleting emissions, also prevented significant climate change.

Why it matters: Former UN Secretary-General Kofi Annan called the Montreal Protocol "perhaps the single most effective international agreement," and its success in both reversing ozone depletion and slowing warming shows why.

What's happening: In a study published in Nature this week, researchers simulated what would have happened to the world if the Montreal Protocol had never gone into effect.

  • The treaty phased out ozone-depleting chemicals like chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs).
  • Previous research has shown the Antarctic ozone hole would have been 40% bigger in the treaty's absence.
  • The new study, though, shows continued use of ozone-depleting chemicals in the absence of Montreal could have led to an additional 2.5 °C of warming by the end of the century.

How it works: Some of that climate change would have been triggered by direct warming caused by CFC and HCFC emissions, which act as a greenhouse gas.

  • But because a damaged ozone layer would let in more harmful UV radiation, plants would have had a reduced ability to store carbon, which would have further contributed to warming.

The big picture: The success of the Montreal Protocol has often been cited as proof the global community can successfully negotiate a solution to a global environmental challenge.

  • But carbon — and the fossil fuels that contain them — is far more central to the global economy than CFCs and HCFCs, which could be replaced with ozone-safer alternatives at a relatively low price.
  • The geopolitical realm is arguably much more complex now than it was in 1987, when large developing countries like India and China — which will be the source of the bulk of current and future carbon emissions — were much smaller and had less of a voice.

The bottom line: The world's governments were unusually far-sighted in negotiating the Montreal Protocol, but climate change won't be as easy.

Editor's Note: This story has been updated to reflect that the Montreal Protocol phased out hydrochlorofluorocarbons (HCFCs), not hydrofluorocarbons (HFCs).

Go deeper

Ben Geman, author of Generate
Sep 20, 2021 - Energy & Environment

More warning signs ahead of COP26

Expand chart
Data: OECD; Chart: Jared Whalen/Axios

Two new reports show the gap between multilateral climate goals and what's actually happening.

Driving the news: OECD data shows developed economies are falling short of a 2009 pledge to mobilize $100 billion annually by 2020 to help developing nations cut emissions and adapt to warming.

FBI director: Domestic terrorism cases have surged since 2020

Christopher Wray testifies before the Senate Homeland Security Committee on Sept. 21. Photo: Greg Nash/The Hill/Bloomberg via Getty Images

FBI Director Christopher Wray testified before a Senate committee Tuesday that the agency's domestic terrorism caseload has "exploded" in size since spring of 2020.

Why it matters: The Jan. 6 Capitol riot refocused attention on the issue of domestic terrorism and security, but Wray's testimony points to a trend that pre-dates the insurrection.

18 mins ago - World

UN: Taliban nominates new envoy, asks to speak at General Assembly meeting

Afghanistan's current UN ambassador Ghulam M. Isaczai. Photo: Timothy A. Clary/AFP via Getty Images

The United Nations said Tuesday that the Taliban has asked to speak at the United Nations General Assembly's meeting this week, AP reports.

Why it matters: The move marks a direct challenge to Afghanistan's currently accredited UN ambassador, Ghulam Isaczai, whom the Taliban says no longer represents Afghanistan.

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