The front page of the Toronto Star on May 27, 1992, was deeply of the decade. Premiere Bob Rae’s face scowled above the fold, and the Blue Jays beat the Milwaukee Brewers 5 to 4, adding to their scorching, World-Series calibre record.

A short story announced a change to the weather report. Environment Canada would begin publishing forecasts of the intensity of ultraviolet radiation from the sun.

It was information they hoped Canadians would use to avoid sunburns and the attendant risk of skin cancer.

Today is the 25th birthday of the UV index. The scale was invented by three Toronto-based Environment Canada scientists.

It has since been adopted around the world.

When forecasters issue a UV index of six in Brussels or 22 in the Andes, they are comparing local ultraviolet radiation to a sunny summer day at Dufferin and Steeles.

It confirms that Toronto is, in fact, the centre of the universe — at least when it comes to calibrating sunburn risk.

The story of the UV index is one of Canadian leadership in atmospheric science, technology transfer and public communication.

“In a sense, we managed to put a hat on everybody in the world,” says Tom McElroy, one of the UV index’s inventors. McElroy is now a professor at York University’s Department of Earth and Space Science and Engineering.

The story shows, some say, how far Canada has shifted from its world-leading position in this field; measuring ultraviolet radiation is inextricably linked to measuring variations in the ozone layer.

But the program at Environment Canada was diminished by the Stephen Harper government.

“I think it’s going to take a lot of effort to get the place back on its feet again,” says Thomas Duck, a professor in physics and atmospheric science at Dalhousie University, about Environment Canada and its ozone research.

“We’ve got a lot to be proud of, and I think it should be a continuing source of pride.”

Scientists had been measuring ozone for half a century.

Then alarm bells began ringing.

Ozone, a molecule that exists in trace amounts throughout the atmosphere, is concentrated in a band centred about 25 kilometres above Earth’s surface.

The ozone layer absorbs almost all the intense ultraviolet light emitted by the sun, protecting organisms on the Earth’s surface from damaging high-energy rays.

An Oxford University physicist, G.M.B. Dobson, created an instrument in the 1920s that compared how much of two different UV wavelengths were reaching land, allowing him to infer total ozone amounts in the air column above. A small network of Dobson devices sat across the globe.

In the 1970s, two disturbing facts emerged. A Dutch chemist, Paul Crutzen, realized that nitrogen oxides destroys ozone. Proposed fleets of supersonic aircraft would emit nitrogen oxides as they flew very close to the ozone layer. And two American chemists, Mario Molina and Sherwood Roland, discovered that the chlorofluorocarbons used in spray bottles and refrigerators also destroy ozone, and predicted this would have harmful effects. In 1995, all three would win the Nobel Prize in Chemistry.

At the time, scientists were concerned yet uncertain.

Was ozone depletion a trivial problem?

Or was it an existential one?

“There seemed to be a growing need for monitoring,” says Jim Kerr, another co-inventor of the UV index, who is now retired.

The Dobson instrument, though capable, was from another era. “There were no automation capabilities. Every day you had to walk up to it and read dials and fire it up and write down numbers. It was just not the way things were heading.”

Kerr, McElroy, and another atmospheric physicist named David Wardle had all been graduate students or postdoctoral fellows at the University of Toronto in the 1960s. They worked with a professor and former colleague of G.M.B. Dobson, Alan Brewer, to develop a prototype for a more modern ozone instrument. The team of three moved to what was then called the Atmospheric Environment Service, now called Environment and Climate Change Canada, in the early 1970s.

There, they collaborated with industry to commercialize the technology and mass produce a new instrument, the Brewer Ozone Spectrophotometer.

Aside from being a more modern, automated device, the Brewer could also measure ultraviolet directly and in detail.

“It did fill quite a need at that time,” says Kerr.

Alarm intensified with the 1985 discovery of a gaping ozone hole over Antarctica.

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Canada was at the forefront of combating this threat: Canadian-made Brewers spread around the world, creating a robust monitoring network. Environment Canada operated the World Meteorological Organization’s global data centre for ozone in Toronto. World leaders met in Montreal in 1987 and agreed to phase out ozone-depleting substances.

Even after the Montreal Protocol, it was not clear how the ozone layer would recover, and the trio at Environment Canada recognized a need for better public communication.

“(There was a) need to get the message across to the public that we should be worried about ozone going down. One of the best ways to do that is to say, how does that affect people?” says McElroy. “If ozone goes down, your possibility of skin cancer is going to go up.

“That’s a very simple message.”

The team had been recording Brewer measurements at Environment Canada’s Downsview office for several years. They took the peak ultraviolet intensity from the sunniest day in July and divided it by an arbitrary number to create a nice, round maximum of 10.

The UV index was born.

Ottawa unveiled the index on May 27, 1992. The UV that day registered a moderate-to-high 6.7 on the scale, the Star reported.

Two years later, the World Health Organization and the United Nations Environment Program adopted the UV index internationally. (They decided to allow values to rise above 10 so that a 10 means the same thing in Canada and the Tropics.) The highest UV index ever recorded was 43.3 on top of a volcano in Bolivia.

McElroy, Kerr, and Wardle were given an innovator’s award from the United Nations Environment Programme on the 20th anniversary of the Montreal Protocol. Brewers are still operating in more than 45 countries in the world, from the Antarctic to the high Arctic and in between.

The trio of scientists and the government are still receiving royalty cheques for newly-fabricated Brewers.

“One of the satisfying aspects about the introduction of the UV index was seeing parents of children . . . . They were always covering their children up and putting sunscreen on their children.

“That, to me, was satisfying, that something was being done,” says Kerr. “If you’re a government worker, public service is your bottom line.

“We’re scientists. We’re interested in the science, but we’re also interested in our responsibilities.”

Scientists worldwide were dismayed by changes to Environment Canada’s ozone program under the government of former Prime Minister Stephen Harper. In 2011, a large part of the ozone-monitoring program was cut, changes the government described as “consolidation and streamlining.” The Environment Canada scientist in charge of the WMO’s ozone and ultraviolet data centre was reassigned and replaced with a data manager, Nature reported in 2012. Since then, data logged by the centre has dropped precipitously; the last reported data from Environment Canada was in 2014.

“I would suggest this tells you that there is a continuing shortfall in ozone staffing at Environment Canada,” says Dalhousie’s Thomas Duck.

A request for comment from Environment and Climate Change Canada, as it was renamed by Prime Minister Justin Trudeau, was not returned by press time.

The ozone layer is recovering, but threats continue. In 2011, an unprecedented ozone hole appeared in the Arctic.

“Without the ozone layer, this planet is, for the most part, uninhabitable,” says Duck.

As for Canada, “we’re going to have to put in some effort to maintain that leadership role.”

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