Everyone knew that nuclear war would be hideous, but no one expeaed this. arly in 1979, the Congressional Office of Technol- ogy Assessment (OTA) completed a 151-page re-- port called "The Effects of Nuclear War."The first finding, set off in boldface, was "The effects of a nuclear war that cannot be calculated are at Eleast as important as those for which calculations are at- tempted "That has proved to be an unusually apt caveat. Now, only a few years after the OTA report, and four de-- cades after the invention of nuclear weapons, the scientific and defense communities have suddenly learned of an as- pect of nuclear war, overlooked by OTA and almost every- one else who had studied the subject, that could prove to be more devastating than any of the other effects--includ- ing the blast and radiation. The forgotten factor? Smoke. Government scfendm had been studying the physical effects of nuclear aplo- sions for decades, had produced massive wlumiel ,. of detailed observations, had scrutinized &CCOUDII of lbe blasts at Hiroshima and Nagasaki, the lln!stonDs at 0... den, Hamburg and Tokyo. But no one bad calnaleled tbe! HARD climatological effects of the globe-&paoDJDg paD of smoke that could rise from tbe lbousaodl of files ........... by a nuclear war. Indeed. wltb the ezcepllon of "!0 FACTS glected reports produced for tbe U.S. government In 1960s, the word smoke is baldly meotloaed in lbe ldeodl- ABOUT ic literature. I A paper publlsbed In lbe Swedish 1982 thus came 11 a complete surprise. stunning NUCLEAR and defeDse alike wltb Its slmpJe. ominous WINTER sion. Paul Crutzen, a Dutch atmospbertc ldentlst. uct; BY ANDREW C. REVKIN s.n1tw,.,. Andrlw c RaJidn Is 1«11ur«1 on tlw ,._ NUCLEAR WINTER have a major Impact on climate- The biologists said that lthe manifested by significant surface darkening over many weeks, sub- possibility of the extinction of freezing land temperatures persisting for up to several months, large pertur- Homo sapiens cannot be excluded." bations in global circulation patterns and dramatic changes in local weath- er and precipitation rates-a harsh 'nuclear winter' in any season." The biologists also presented theh findings. Their sweeping, controver- sial conclusion, later published in the same issue of Science. was that such a climatic catastrophe could "cause the extinction of a major fraction of the plant and animal species on the Earth.... In that event. the of the extinction of Homo sapiens cannot be excluded." The press, fresh from reporting on The shock waw loYOUid exlfngulsh some of 1he ftres set by Che President Reagan's Star WatS defense initiative and the lUst's thermal pulSe, but It wouJd •rso start l'l'l)'l1ad sec:oncs.ry ftres by bt'U.kfng g.s lines, fuel atnla and the Uke. GM!n 1he antinuclear protests in Europe. gave the news wide cover- right amdlttons, the ftres CXKild merge Into il single lrRino. age. The public was already sensitized to the issue by ad· vertisements for the ABC special ''The Day After," whict. tary but convincing way that smoke from a nuclear war- was aired just three weeks later. several hundred million tons of it-"would strongly restrict To be sure, not everyone agreed. A small but powerfu. the penetration of sunlight to the Earth's surface and cadre of critics, led by Edward Teller, a chief architect o: change the physical properties of the Earth's atmosphere." the hydrogen bomb and an important force at Lawrence And theh calculations were based only on smoke from Uvermore National Laboratory, attacked the reports, argt!- burning forests. When another research team considered ing that the studies were inconclusive and politically motl- smoke from burning cities, the forgotten factor took on vated. "The only news," Teller says, "is that Sagan has even more significance. made a lot of propaganda about a very doubtful effect'' Richard Turco, an atmospheric scientist at R & D Asso- ciates, in Marina del Rey, California, had been working hree congressional hearings, dozens of scientific with three researchers at the NASA Ames Research Center, meetings, several international conferences anG two of whom were former students of Cornell astronomer at least four books later, nuclear winter has tak· Carl Sagan, on the atmospheric effects of dust raised by nu- en its place-somewhere between megaton ana clear explosions. When Turco read an advance copy of the ouerki/1-in the burgeoning lexicon of terms Ambio study, be hnmediately saw that smoke would be far Tspawned by the study of nuclear war. After more than a more important than dust year of scrutiny, the TTAPS study bas held up, at least as a Turco reworked the Ambio calculations, adding in the "first order" estimate. "Critics of the original paper proba- smoke from burning cities. Along with the NASA group- bly never read it," says Startey Thompson, an aunospheri.;; O. Brian Toon, Thomas Ackerman and James Pollack- scientist at the National Center for Atmospheric Research and Carl Sagan, he put together a comprehensive analysis, (NCAR), i.n Boulder, Colorado, who bas contributed to se-:- including computer models, of the "global consequences eral subsequent computer analyses of the concept "If of multiple nuclear explosions." The group, which soon had read it carefully they would realize it's not very O\'er- became known as TTAPS (an acronym based on last stated. It has lots of caveats in it What has probably been names), discovered that the smoke could have a devastat- overstated has been public discussion. When you put It a.. ing effect on the Earth's climate. together, it looks bad." The findings were so dramatic, in fact, that in late April Almost everyone agrees on one point the need 1983, more than 100 scientists were invited to a closed ses- more research. "It's been an instant field," says Bob Cess sion at the American Academy of Arts and Sciences, in a specialist in clhnate modeling at the State University o:: Cambridge, Massachusetts, to review the study. The physi- New York, Stony Brook, who is working on the problerr. cal scientists met first, testing the assumptions, dissecting with researchers at Lawrence Uvermore. "Never has sc the models, checking the data. Some adjustments and re- much been said about a field in which so little has be-er. finements were made, but the basic conclusions held. done." Then the biologists took a crack at it They extrapolated The only absolute quantity in the entire concept is the from the climatic effects to the impact on agriculture and fantastic power of the bomb. The uncertainties are mul:i- ecosystems. The destruction wrought by nuclear war, they fold and frustratingly complex. Many aspects of the micro- concluded, would be much greater and more long-lived physics of lire and smoke and the macropbysics of weat."l- than anyone had previously conceived. er and climate are still mysteries. in fact, S. Fred Singer c. The results were announced to a capacity crowd at a geophysicist at George Mason University in Fairfax, Virgm- conference in Washington, D.C., on Halloween 1983 and ia, and a consistent critic of the TTAPS work, has argued were published in the December 23 issue of Science. The both Nature and the Wall Street Journal that, given lt.e TTAPS group concluded that "a global nuclear war could right conditions, a nuclear war could produce a dark. h :1t 64 SCENCE OIGEST-MAACH 1985 ···nuclear summer." Moreover, the computer-generated its bottle since it was unleashed on Japan 40 years ago. If models being used to study nuclear winter are---<lespite nuclear winter is proved plausible, MAD may be replaced the advent of supercomputers and weather satellites--still by a simpler form of deterrence, assured self-destruction, patchwork attempts to simulate the global climate. which guarantees that a nation launching a nuclear attack The formula for nuclear winter is rife with variables as will in effect be committing suicide. well as uncertainties. What type of nuclear war might be According to Sagan and many others, nuclear winter is fought? How many warheads, of what megatonnage, thus an unexpected panacea. delivered in the nick of time, would be exploded? (One megaton is the explosive power that may make nuclear weapons "obsolete" by turning of one million tons of TNT-an amount of explosives that them against their users. But others, including Freeman would fill a freight train 300 miles long.) Are the targets Dyson, a physicist at the Institute for Advanced Study, in "bard" or "soft," silos or cities? Does the war last a day, a Princeton, and the author of Weapons and Hope, predict week, months? Does it take place in summer, in the middle that if the theory is confirmed, it could create a new, dan- of the growing season, or in the chill of winter, when a gerous arms race-a race among military planners to drop in temperature might do less damage? make nuclear war "safe" again. Yet another sticking point has been finding reasonable numbers to substitute for these variables. Most of them are pelled out, the theory of nuclear winter is as sim- secrets, embedded in the closely guarded targeting scenar- ple as the chill you feel when a cloud passes in ios and combat strategies of the United States and the Sovi- front of the sun, and it is as complex as the ever- et Union. changing patterns of wind and weather that swirl In December, the National Research Council published daily across the surface of the globe. an exhaustive review of "the effects on the atmosphere of SIt is based on phenomena as minute as the behavior of a major nuclear exchange." Their best estimate was that the individual particles within a cloud of smoke and on there is a "clear possibility'' that nuclear war would lead to events as massive as the explosion of a thermonuclear nuclear winter.