The act could even reveal how to look for life on alien planets.
Despite mostly positive changes, a scientific assessment of the Montreal Protocol shows how we still need to do better.
And we should take what it's taught us into future fights.
CFC-11 isn't leaving the atmosphere as quickly as it should.
Agreeing to ban ozone depleting chemicals is paying off.
The ozone layer is no longer thinning, but we need to keep an eye on it
Some answers from an atmospheric scientist
On the 40th anniversary of Earth Day, we take a look back at where it all began
The 20th century's biggest environmental success may exacerbate the 21st century's biggest environmental crisis
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