The ozone layer is thin. Absurdly thin. If you compressed all the ozone in the atmosphere down to sea-level pressure, it would form a band roughly three millimetres thick. That's about two coins stacked on top of each other. This is the thing standing between you and the full force of the sun's ultraviolet radiation.
Now remove it.
The first hour
UV radiation exists on a spectrum. UV-A passes through the ozone layer already and gives you a tan. UV-B is partially blocked and causes sunburn. UV-C is almost entirely absorbed by ozone and never reaches the ground under normal conditions. It's the nasty one. It destroys DNA on contact.
With the ozone layer gone, UV-B radiation at the surface roughly doubles. UV-C, previously stopped cold at 30 kilometres altitude, arrives at ground level for the first time in the history of complex life on Earth.
If you're outside when this happens, you won't notice immediately. UV radiation is invisible. There's no flash, no heat change, no obvious signal. The sky looks the same. The sun feels the same. But the photons hitting your skin are now carrying enough energy to break the molecular bonds in your DNA, and they're doing it at a rate your cells cannot repair.
Sunburn would develop in under ten minutes for fair-skinned people. Not the pink, mildly-uncomfortable kind. The blistering, peeling, needs-medical-attention kind. Within an hour of unprotected exposure, you'd have second-degree burns on any exposed skin.
Eyes first
Your skin can at least partially protect itself. It has melanin, clothing, shade. Your eyes have none of that. The cornea absorbs UV-C radiation directly, and it takes very little to cause photokeratitis, which is essentially sunburn of the eyeball.
Snow blindness is the closest natural equivalent. Mountaineers at high altitude get it from UV-B reflected off snow. That's with the ozone layer intact. Without it, you'd get the same condition just by walking to the shops on a Tuesday morning. Pain, blurred vision, temporary blindness. Repeated exposure causes cataracts and permanent damage.
Within a week, anyone spending time outdoors without eye protection would be experiencing vision problems. Sunglasses become medical equipment overnight.
Skin cancer at industrial scale
The relationship between UV exposure and skin cancer is well-documented and dose-dependent. Australia, which sits beneath the annual ozone hole that forms over Antarctica, already has the highest rate of skin cancer in the world. About two in three Australians will be diagnosed with skin cancer by age 70.
Remove the ozone layer entirely and those numbers become global, then get worse. Melanoma typically takes years to develop from UV exposure, so the immediate cancer wave wouldn't hit for 12 to 18 months. But when it arrives, it arrives everywhere simultaneously. Dermatology departments would be overwhelmed within the first year. The backlog would never clear.
Non-melanoma skin cancers, which are less lethal but far more common, would appear even sooner. Basal cell carcinomas developing on exposed skin within months. The medical system would buckle not from a dramatic crisis but from a slow, grinding, ever-increasing caseload that never peaks because the UV exposure never stops.
Agriculture dies in the open
Plants need sunlight. They don't need UV-C. Most crops have essentially no defence against short-wavelength ultraviolet because they've never needed one. UV-C damages plant DNA just as effectively as human DNA. Leaves bleach, photosynthesis degrades, yields collapse.
Rice, wheat, and maize are particularly vulnerable. A 1992 study by the United Nations Environment Programme estimated that a sustained 10% reduction in ozone would reduce soybean yields by up to 25%. Complete removal of the ozone layer is not a 10% reduction. It's the entire shield gone. Crop losses of 50-90% within the first growing season are realistic.
Greenhouses help. UV-filtering glass blocks the worst of it. But you can't greenhouse the world's farmland. Global agriculture relies on hundreds of millions of hectares of open fields. Moving that indoors is a generation-long infrastructure project and the food supply collapses in year one.
The ocean surface becomes a dead zone
Phytoplankton produce roughly half the oxygen on Earth and form the base of the marine food chain. They live in the top few metres of the ocean where sunlight penetrates. They have no way to dive deeper to escape UV radiation, and they have no protective pigmentation worth mentioning.
UV-C radiation penetrating the ocean surface would devastate phytoplankton populations within weeks. This doesn't just mean fewer tiny organisms in the water. It means the collapse of the food chain that supports krill, which supports fish, which supports seabirds, seals, whales, and a billion-dollar global fishing industry.
It also means less oxygen production. Not an immediate crisis for breathing, since the atmosphere contains enough oxygen to last thousands of years even without replenishment. But it's the beginning of a very long, very slow decline in atmospheric oxygen that would become somebody's problem eventually.
How humans adapt
Humans are stubborn. We wouldn't go extinct. We'd go indoors.
The first adaptation is simple: stay inside during daylight. UV-C doesn't penetrate glass, ordinary window glass blocks most of it. Life reorganises around dawn and dusk, the brief windows when the sun is low enough that atmospheric scattering reduces UV to survivable levels. Midday becomes as dangerous as a blizzard. You simply don't go out in it.
Outdoor workers wear full-body UV-protective suits with filtered visors. Construction, farming, and transport become hazardous occupations requiring the same level of protective equipment as working with radioactive materials. The cost of food, housing, and infrastructure rises sharply because everything that used to be done in a T-shirt now requires specialist gear.
Architecture changes. Windows get smaller or gain UV-filtering film as standard. Covered walkways connect buildings. Underground spaces become premium real estate instead of car parks and storage. Cities start looking like they were designed for a different planet, because in a sense, they were.
The thing we almost tested
This isn't entirely hypothetical. In the 1970s, chlorofluorocarbons were chewing through the ozone layer at a rate that would have destroyed it within decades. The 1987 Montreal Protocol banned CFCs and the ozone layer is now slowly recovering, expected to return to 1980 levels by roughly 2066.
If that treaty hadn't happened, current atmospheric models suggest that by 2065, UV radiation at northern European latitudes would cause sunburn in approximately five minutes of summer exposure. That's not total ozone loss, just continued depletion at the pre-ban rate.
We came closer to this scenario than most people realise. The three-millimetre shield held, but only because 197 countries agreed to stop poking holes in it. It remains the only UN treaty ever ratified by every member state. Apparently the prospect of planetary sunburn was motivating enough to get everyone in the same room.