The unexpected, world-saving side effects of the Montreal Protocol

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).