Every spring a hole tears open in the ozone layer over Antarctica. We saw it, named the cause, signed a treaty, and watched it begin to heal — one of the only times humanity reversed a planetary-scale problem on purpose. Here is the whole story in two numbers per year.
The dataset: NASA Ozone Watch — annual Antarctic ozone-hole metrics derived from satellite instruments (TOMS, OMI, OMPS), 1979 to 2023. Each year reports the maximum hole area (millions of km², measured each spring) and the minimum ozone concentration (in Dobson Units; lower = more depleted).
Why this one: Most "interesting datasets" are static snapshots of people. This is a 45-year measurement of an entire planet's chemistry — and unlike climate doomscrolls, it has a hopeful arc. The 1987 Montreal Protocol banning CFCs is visible *in the data*: depletion stops getting worse and the hole begins, slowly, to shrink. You can literally see a global policy decision in a time series.
Scrub through 45 years
Drag the slider or hit play. The blue disc is Antarctica seen from above; the dark patch is the ozone hole scaled to that year's measured area. Antarctica itself is ~14 million km².
1979spring of
1.1
Max hole area (M km²)
194
Min ozone (Dobson Units)
The full timeline
Hole area over time (bars). Hover any year. The treaty line marks 1989, when the Montreal Protocol entered force — note how the relentless growth flattens after it.
Ozone hole area (M km²)Selected yearMontreal Protocol in force (1989)
Depletion vs. recovery
Minimum ozone concentration (Dobson Units) — the depth of the hole. Lower means more depleted. The dotted line at 220 DU is the threshold scientists use to define "hole" conditions. Watch it crash through the 1980s–90s, then crawl back up.