by Ross McCluney, Ph. D.

20 September 1988 

I am an optical physicist, specializing in studies of light and other types of electromagnetic radiation. My Ph. D. dissertation focused on the propagation of light in the sea. I worked for NASA's Goddard Space Flight Center in Greenbelt, Maryland as an optical oceanographer from 1973 until the beginning of 1976. For part of this work, I studied the propagation of sunlight through the earth's atmosphere prior to entering the oceans and other bodies of water. 

I am currently a principal research scientist at the Florida Solar Energy Center (2). One of my main research projects is to measure the quantities of solar radiation and daylight emerging from the bottom of the atmosphere. 

A number of scientific studies were carried out from the beginning of this decade until recently, on the environmental consequences of nuclear war. The major physical effect of massive thermonuclear explosions, which leads to severe ecological and other environmental effects, is a lessening of the quantity of solar radiation reaching the earth's surface. Because of this fact, and my particular scientific background, I believe that I am well qualified to report on the results of the environmental consequence studies that have been carried out for the last several years. 

The studies that were performed were carried out by many scientists from many nations, working in a coordinated fashion to determine the most likely environmental consequences of a major nuclear war. The studies were coordinated by an international committee called the Scientific Committee on Problems of the Environment (SCOPE). The project itself was given the acronym ENUWAR, standing for the Environmental consequences of NUclear WAR. 

A comprehensive two-volume report was published in 1986.(3)  There have also been a number of articles published in Science, the journal of the American Association for the Advancement of Science, in Scientific American, and in several other periodicals. These update the findings published in 1986. 

The study was carried out by a number of cooperating scientists from many nations, and was reported periodically at meetings held in the following cities from 1983 until March of this year: Stockholm, New Delhi, Leningrad, Tallinn, Delft, Paris, Hiroshima, Essex, Toronto, Caracas, Melbourne, London, Essex, London, Bangkok, Geneva, and Moscow. 

Financial support for the work came from the University of Essex, the Royal Society of London, and from the National Scientific Academies of Sweden, India, Great Britain, the USSR, the Netherlands, France, Japan, Canada, Venezuela, and Australia. 

Donations were received from the Carnegie Corporation and other foundations. The U. S. National Academy of Science carried out its own study, as did the Congress' Office of Technology Assessment. 

The resulting reports have been detailed, and there has been vigorous discussion and examination of the reports by the world scientific community. Additional independent studies have been performed by reputable scientists using the latest computer tools and experimental results. The basic conclusions of the early (1983-1984) studies have been upheld. The severities of some predictions of temperature drops and losses of sunlight have been revised downward, but the overall consequences of a large, 5000 megaton exchange of nuclear weapons is still believed to be devastating to the human population of this planet, including huge numbers of people outside the borders of the warring nations. 

Here's how nuclear winter works: Multiple nuclear explosions throw large quantities of dust very high into the atmosphere. The blasts themselves kill people within a several mile radius instantly, kill more people outside this radius by burning them to death, by depriving them of a breathable atmosphere, and by numerous other processes, including nuclear radiation, fallout, and massive fires that break out nearly instantly around the blast areas. 

The blasts emit such strong rays of intense light that they raise the temperatures of combustible materials to their fire points for miles around the blast centers. In urban areas the quantities of combustible materials are so great that massive fire storms are generated. These carry much more smoke and other small particles very high into the atmosphere where they are heated further by absorbing solar radiation. The heated air surrounding these particles carries them still higher into the atmosphere. The small sizes of the particles carried to great heights ensures that they will remain in the atmosphere for very long periods of time. 

The fire storms produce intense heat and gale force winds sucking into the fires and preventing the escape of humans and other animals being drawn into the fires. 

Fine dust and smoke particle clouds produce immediate darkness on the earth's surface below. As the winds and general atmospheric circulation patterns carry these particles horizontally away from the blast zones, they thin out, letting more sunlight through, but covering vast areas of the globe. This process takes from a few days to weeks, depending upon the magnitudes and locations of the explosions. 

For the first 20 days or so, sunlight levels are only 5 percent to 25 percent as great as before. For 20 to 100 days they are 25 percent to 75 percent of natural levels over the regions most strongly affected. 

This deprivation of solar radiation produces significant and prolonged cooling of the earth's surface if the war occurs in warm weather months, but the cooling effects are less pronounced during winter months when the days are shorter and natural solar radiation quantities are reduced. 

Substantial reductions in rainfall amounts are also produced. Reductions as great as 75% are possible for latitudes from 30 to 70 degrees north. There are other significant effects: Nitrogen oxide gases are injected into the atmosphere in large quantities. This can add significantly to global climatic cooling effects and will substantially reduce atmospheric ozone concentrations, producing increases in ultraviolet (UV) radiation levels at the earth's surface. One study predicted a doubling of UV radiation, over the whole northern hemisphere for many months. 

In 1985 two Russian investigators wrote: (4)

The scale of the disturbances of the atmospheric chemical composition as a result of multiple nuclear explosions is so enormous that, undoubtedly, this will lead to strong global climate change and ecological catastrophe. It is highly probable, however, that the principal cause of the catastrophe is not just nuclear winter but an even more serious strong climatic instability. 

Crop losses would be catastrophic, not just due to the loss of rain and sunlight, but also due to the loss of energy-based fertilizers, pesticides, and transportation fuels. 

Studies of the biological consequences yield very depressing estimates of the expected impacts. Two SCOPE ENUWAR participants, in a June 1988 article, summarize it thusly: (5)

The potential indirect effects of a large-scale nuclear war could greatly exceed the direct effects, and the substantial majority of the human population would be at risk of global famine resulting from severe reductions in agricultural productivity throughout at least the Northern Hemisphere. Ecological effects would be unprecedented in intensity and scale, and disruptions in energy subsidies to agriculture, such as loss of fertilizers and pesticides could exacerbate the agricultural effects. 

In a June 1987 Science article, Colin Norman wrote: "A limited nuclear strike on the U. S. that used only 1% of the Soviet Union's current arsenal could cause an economic collapse from which recovery would take many decades.... As a result, a large fraction of the U. S. population would starve to death in the ensuing months -- far more than would be killed in the direct attack -- and the survivors would probably be reduced to near-medireview levels of existence for decades." 

When I first started studying this issue, I was concerned that the dire predictions for global environmental impact were based upon quite a high level of nuclear exchange, 5000 Megatons of nuclear explosives, a significant portion of the current world inventory of nuclear weaponry, delivered in as many as 10,000 separate blasts. At first this seemed to me to be an unrealistically severe scenario upon which to base the calculations. 

Upon further reflection, however, I realized that this level of exchange would not be that unrealistic in an era where the decisions to launch weapons will have to be made so fast that they may have to be pre-decided, and stored in computers, the latter actually carrying out the launch and targeting commands. 

Also, I asked myself the question: "Once a nation is receiving several (or several hundred) megatons of incoming nuclear missiles, would it or could it limit the response to significantly fewer megatons?" Even if a wartime self-limiting policy were to be possible, it is clear to me that the damaging effects of even a limited exchange would produce terrible consequences for nearby nations not initially at war. 

The scientists studying these effects have looked at the consequences of more limited nuclear wars and have found substantial adverse impacts to be predicted even in such cases.

1  Adapted from testimony prepared for the trial of Jim Welch on 8 September 1988 in Rockledge, Florida, but not permitted by Judge Harry Stein.

2  These are the views of the author only, not those of the Florida Solar Energy Center.

3  A. B. Pitlock, T. P. Ackerman, P. J. Crutzen, M. C. MacCracken, C. S. Shapiro, and R. P. Turco, Environmental Consequences of Nuclear War: Volume 1-Physical and Atmospheric Effects, and M. A. Harwell and T. C. Hutchinson, Volume 2--Ecological and Agricultural Effects, SCOPE 28 (Chichester and New York: John Wiley and Sons, 1986).

4  Kondratyev, Moskalenko, and Gusev, Optics News, November, 1985, p. 21.

5  M. A. Harwell and Ann C. Freeman, Environment, Vol 30, No. 5, June 1988, p. 25.