The dangers of chlorofluorocarbons have been widely publicized. These substances are thinning Earth's stratospheric ozone layer, allowing more of the sun's ultraviolet rays to come through and damage our skin and our crops. We're fighting skin cancer with sunscreen, and we're trying to find ways to protect food crops, especially the grains vital to our health.(1)
Researchers now recognize that too thick a stratospheric ozone layer would present problems just as severe. If too little ultraviolet radiation gets through to Earth's surface, plant growth is inhibited and certain vitamins will not form in certain animal species. In other words, unless the stratospheric ozone layer is just right, not too thin and not too thick, Earth's biomass, biodiversity, and biovitality will be impaired.
Recently researchers have discovered the delicacy of ozone quantities in all three atmospheric layers, including the troposphere (the first six miles above Earth's surface) and the mesosphere (from fifteen to fifty miles out). Though the stratosphere (between six and fifteen miles above Earth) contains the lion's share of Earth's ozone, the troposphere holds about 10% and in the mesosphere, about 1%.
Tropospheric ozone, rather than being depleted by human activity, is being augmented by it, and dangerously so. Fossil fuel burning and agricultural burning have produced vast ozone-enhanced regions over the north mid-latitudes and the continental tropics. The negative impact of all this extra tropospheric ozone is respiratory failure in humans and other large animals, reduced crop yields, and the destruction of ozone-sensitive species.(2)
Some ozone in the troposphere is necessary, however, to cleanse the atmosphere of certain biochemical and industrial pollutants.(3) Ozone may be considered the troposphere's detergent. As is the case in the stratosphere, the ozone quantity for the troposphere must be just right, not too great, not too small, to support and protect life.
Ozone in the mesosphere also has a vitally important role. It absorbs ultraviolet radiation, and this absorption process is the most significant factor governing the chemistry and circulation of gases in that layer.(4,5) Mesopheric chemistry and gas circulation largely determine which gases are retained and which are lost by Earth's atmosphere, a determination vitally important to life's long-term survival. Again, the ozone quantity must be carefully balanced between too much and too little.
Recently, atmospheric physicists discovered yet another delicate ozone balance: the rate of ozone transfer between the stratosphere and the troposphere. Measurements by specially equipped commercial airliners reveal that efficient ozone exchange really does occur.(6) Apparently deep convective systems near the equator can transport huge amounts of ozone from layer to layer. What a complication! Not only must the quantity of ozone in the three atmospheric layers be carefully fine-tuned for life's sake, but so must the efficiency and stability of interlayer ozone transport.
Suddenly King David's words, penned three thousand years ago, carry even greater depth of meaning: "The heavens declare the glory of God; the skies proclaim the work of His hands. Day after day they pour forth speech; night after night they display knowledge."(7)
References:
1. Hugh Ross, "Fears Rise as Ozone Levels Drop," Facts & Faith (v. 5, n. 4, 1991), p. 2.
2. W. L. Chameides, P. S. Kasibhatla, Yienger, and H. Levy II, "Growth of Continental-Scale Metro-Agro-Plexes, Regional Ozone Pollution, and World Food Production," Science, 264 (1994), pp. 74-77.
3. Paul Crutzen and Mark Lawrence, "Ozone Clouds Over the Atlantic," Nature, 388 (1997), pp. 625.
4. Paul Crutzen, "Mesospheric Mysteries," Science, 277 (1997), pp. 1951-1952.
5. M. E. Summers, et al, "Implications of Satellite OH Observations for Middle Atmospheric H2O and Ozone," Science, 277 (1997), pp. 1967-1970.
6. K. Suhre, et al, "Ozone-Rich Transients in the Upper Equatorial Atlantic Troposphere," Nature, 388 (1997). Pp. 661-663.
7. Psalms 19:1-2, Holy Bible, New International Version.