In 1986 and ’87, expeditions to Antarctica confirmed a development that left the world on edge: chemicals called chlorofluorocarbons (CFCs), found in many personal hygiene products, had caused a hole in the ozone layer that was only getting bigger.

The news was dramatic enough to spur the signing of the Montreal Protocol by the end of 1987, kicking off the phaseout of CFCs. This month, the European Union’s Copernicus Atmospheric Monitoring Service reports that the area of the Antarctic ozone hole could be the smallest recorded since the mid-1980s.

Scientist Susan Solomon led those Antarctic expeditions. In 2008, TIME named her one of the world’s 100 most influential people, for co-chairing one of the working groups that produced the landmark 2007 Intergovernmental Panel on Climate Change (IPCC) report, which stated for the first time in the group’s history that climate change is “unequivocal,” and that hotter temperatures are “very likely” caused by human activity. The organization shared the 2007 Nobel Peace Prize with Al Gore.

These days, the panel is known for its report, out last year, laying out the stakes of climate change if it is not stopped from surpassing a 1.5°C increase. That report helped motivate a year of increased activism on the subject, leading up to a day of global protest last Friday. On Monday, world leaders gather at the United Nations’ 2019 Climate Action Summit, as activists wait to see whether the warnings of scientists will translate into international action, the way it did three decades ago.

Solomon, now a Professor in the Earth, Atmospheric, and Planetary Sciences department at the Massachusetts Institute of Technology (MIT), spoke to TIME about how that moment compares to now.

TIME: How is today’s climate movement similar to or different from the movement to address the ozone hole?

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