A Hole That Was a Design Decision: NASA's Antarctic Ozone Images

The discovery arrived as a table of numbers. In May 1985, three British Antarctic Survey scientists, Joseph Farman, Brian Gardiner and Jonathan Shanklin, published a short paper in Nature reporting that springtime ozone over Halley Bay had fallen catastrophically since the late 1970s. The measurements came from a Dobson spectrophotometer that had been operating at the station since 1956, an instrument so unglamorous that the finding was initially hard to credit. NASA had a satellite, Nimbus-7, carrying the Total Ozone Mapping Spectrometer, and it had been recording the same collapse for years. Nobody at NASA had noticed, because values that low had been flagged by the processing software as probable instrument error. The threshold had been set to catch broken hardware, not a broken atmosphere.

Once the British paper forced a reexamination of the satellite record, the pictures followed quickly. In August 1985, at a meeting in Prague, the atmospheric scientist Pawan Bhartia presented the first space-based view of the phenomenon, and by late that year NASA's false-color maps were circulating through newspapers and television. Everyone reading this has seen the form they take: the polar cap rendered as a disc, ozone concentrations in Dobson units mapped onto a spectrum from warm to cool, and at the center a spreading blot of blue and violet and black. It reads instantly as damage. It reads as a wound in something that is supposed to be continuous.

It is worth being precise about what those images are, because they are not photographs in any ordinary sense. Nothing in the stratosphere is purple. The instrument measures backscattered ultraviolet radiation, from which a column ozone amount is calculated for each grid cell, and a human being then decides which numbers get which colors and where the boundaries between them fall. Move the color ramp and the hole grows, shrinks, or dissolves into a gradient. Even the word is a choice; ozone over Antarctica was depleted, not absent, and the term "hole" is generally credited to the chemist Sherwood Rowland before the press adopted it. The most consequential environmental image of the 1980s was, in the strict sense, a designed object built on top of a measurement.

That is not a debunking. It is the point. Historians of science who have studied the Montreal Protocol negotiations argue that these visualizations functioned as instruments of diplomacy, circulating far beyond the scientific literature and shaping what negotiators believed was at stake. The chronology supports them. The chemistry was still contested in 1987; competing explanations involving atmospheric dynamics and the solar cycle remained live, and the definitive attribution to chlorofluorocarbons came only afterward, with the Antarctic airborne expeditions. The main CFC-producing and CFC-consuming nations signed the Montreal Protocol in September 1987 anyway, before the mechanism was settled. What they had, and what publics had, was the picture.

This makes the ozone hole an unusual and useful case for anyone thinking about environmental communication, because it is the one where the images and the policy both worked. The Montreal Protocol became the most successful environmental treaty ever concluded, ratified universally, tightened repeatedly, and effective. The Antarctic ozone layer is now on a projected path back to its 1980 state somewhere around the middle of this century. The counterfactual, an unregulated world of accelerating CFC use, is genuinely frightening, and it did not happen. When people ask whether any of this ever accomplishes anything, this is the answer available.

Two lessons compete for the moral, and both belong in the record. The optimistic one is that a designed image can carry an invisible problem into political reality fast enough to matter, and that visualization is not decoration but infrastructure. The cautionary one is that the ozone case was unusually easy. A small number of chemicals, a manageable number of producers, viable substitutes already in development, a clearly bounded harm with a familiar name attached to it, and a single spatial image that made the problem look like an object with edges. Carbon dioxide has none of those properties, which is one reason the warming stripes and the hockey stick have had to work so much harder for so much less.

Still, there is a reason to keep the ozone maps in a series otherwise composed of loss. Every other image in this category asks the viewer to grieve something. This one asks them to remember that the alternative outcome exists, that within a couple of years of a graph appearing in Nature the world's governments moved, and that the thing which moved them was a picture assembled by scientists who had to decide, quite deliberately, what an absence should look like.