Earth's "ozone hole," October, 2004. Image courtesy of NASA.
One of the greatest impediments to tackling far-reaching threats such as global climate change is our tendency to focus on the near-term costs of corrective action rather than the long-term costs of doing nothing.
At the root of the matter may be simple human nature. Nothing in our evolutionary development has prepared us to deal with long-term problems of our own making, simply because our ability to create such problems is fairly recent. So, too, is our ability to make empirically-based predictions of what is likely to occur at some later point in time.
Often, it is only when conditions become impossible to ignore — rivers so polluted that they catch fire, water and air so fouled that they threaten our health — that we are spurred to pay the price of acting.
The Montreal Protocol
One notable exception was the Montreal Protocol to ban ozone-depleting chemicals, signed in 1989, by 193 nations. At issue was the use of chlorofluorocarbons (CFCs) in refrigerants and as propellants for aerosol sprays. Released into the atmosphere, CFCs react with with ultraviolet light in the stratosphere to destroy the ozone layer that protects us from the sun’s DNA-altering ultraviolet radiation.
Able to survive in the upper atmosphere for decades, ozone-depleting chemicals contributed to the appearance of an “ozone-hole” over Antarctica in the late 1970s — an event that shocked scientists and political leaders to action, and opened the eyes of the world to the notion that human activity could effect the environment on a global scale.
Under the Montreal Protocol, CFC production was phased out over a period of years and banned entirely in 1996, leading to current expectations that Earth’s ozone layer should recover to 1974 levels sometime around 2050.
Earth’s Ozone Layer if CFCs Hadn’t Been Banned
NASA images courtesy of the Goddard Space Flight Center Scientific Visualization Studio.
Last month, NASA-led scientists released an analysis of what the world would have looked like if the international community had not agreed to ban CFCs. From the NASA Earth Observatory:
The series of images starts with 1974, before CFCs had begun to do significant damage to the ozone layer. Concentrations of ozone in the stratosphere over the United States and Canada are high. By 1994, the model predicts that ozone concentrations over the region have fallen from highs above 500 Dobson Units to about 400. By the simulated year 2009, the ozone layer over much of the United States has thinned to only 300 Dobson Units. (See footnote for an explanation of Dobson Units)
By 2020, the model predicts that an ozone “holeâ€â€”concentrations below 220 Dobson Units—forms over the Arctic as well as the Antarctic. By 2040, the ozone hole is global. The UV index in mid-latitude cities reaches 15 around noon on a clear summer day (10 is considered extreme today). By the end of the model run, global ozone drops to less than 110 Dobson Units, a 67 percent drop from the 1970s.
To put those numbers in perspective, think 5-minute sunburn in Washington, D.C., and the untold consequences from a 500 percent increase in DNA-mutating radiation.
Kofi Annan, former UN Secretary General, called the Montreal Protocol “perhaps the single most successful international agreement to date.”
We did it once, we should be able to do it again.
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* What is a Dobson Unit?
The “ozone layer” is something of a misnomer, in that ozone is dispersed
throughout the upper reaches of Earth’s atmosphere. The Dobson Unit describes how much ozone there would be if all the dispersed ozone were concentrated into a single layer. Although the amount of ozone in the atmosphere varies naturally, the average is about 300 Dobson Units, roughly equivalent to a layer 3mm thick, or twice the thickness of a penny. Where concentration drops to 100 Dobson Units, it would be roughly the thickness of a dime.
