Sagan discusses nuclear winter with Trudeau, MPs

Roy McFarlane — July 1984

OTTAWA – Dr. Carl Sagan, the award-winning astronomer from Cornell University, spent two days in Ottawa, June 3 and 4, addressing physicians, civil servants, Prime Minister Trudeau, Members of Parliament, and others on I the post-nuclear war scenario known as nuclear winter.

The two days were organized by the Ottawa Chapter of Physicians for Social Reponsibility (PSR), along with Science for Peace, Lawyers for Social Responsibility and Nurses for World Peace.

On Sunday, June 3, Sagan explained nuclear winter to a dinner attended by 300 people, including doctors,. nurses, lawyers, engineers, peace activists and interested members of the public.

Sagan told them that. the probability of nuclear winter fIrst came to the attention of astronomers during the Mariner 9 space mission to Mars. “The original path by which we got into the discovery of nuclear winter was by studying, of an things, dust storms on the planet Mars in December of 1971. “ In these studies, scientists discovered surface temperatures which were much colder than they usually are on ordinarily chilly Mars, because of a dust storm. The observation of the cooling effect of the Martian dust storm on that planet’s. surface led him and.others to postulate nuclear winter.

Sagan explained nuclear winter as follows: “If you put a number of fIne particles up in the atmosphere, especially particles that absorb visible light but are transparent to the infra-red radiation that the Earth radiates away to space, you will cool the surface of the Earth. You will prevent sunlight from getting down to the Earth, and you will not impede the thermal radiation of the Earth escaping back into space. And it turns out that the fIne particles of dust raised by high-yield (nuclear) ground bursts can do that to some extent, but that soot, from the burning of cities, is enormously powerful in creating such an effect. “

Sagan explained that there are two reasons that nuclear war will produce this cooling effect. “First of all,” he said, “soot is very dark in the visible part of the spectrum where sunlight is, but quite transparent in the infra-red part of the spectrum, where the Earth likes to radiate into space. Secondly, human beings have cleverly concentrated burnable materials, in large quantities, in a few locations and then have targetted nuclear weapons -on those locations. This clever arrangement guarantees that in the case of nuclear war. we produce huge quantities of soot.”

Sagan also observed that in a nuclear exchange, the fine particles in the air would be carried first across the northern hemisphere, since the nations presently armed with nuclear weapons – the Soviet Union, the United States, Britain, France and China – are all in the northern hemisphere.

Sagan added, however, that it now appears that the fine particles put into the lower stratosphere and upper troposphere, in a nuclear war, will also transport themselves into the southern hemisphere, embracing the entire planet in the consequence of nuclear war.”

After outlining the well-known effects of nuclear war – blast, immediate radiation, heat, immediate fallout, radiation that is carried downwind, the deaths of millions of human beings – Sagan detailed the added results of nuclear winter.

“What nuclear winter suggests,” he continued, “is that the remainder of the population of the planet appears to be at risk. The temperature declines are (measured in) tens of degrees centigrade, which means, independent of the season of the war, there will be subfreezing temperatures all over the northern hemisphere. As you go further south the effects should not be as severe, but it is important to remember that tropical plants, animals and humans have very few defences against even small temperature drops.”

As well, Sagan explained, the chain of ecological devastation leads to dire consequences. The blocking out of sunlight would not allow for plant photosynthesis. Birds, which are especially vulnerable to cold, dark and radiation, would die in huge numbers. Insects, on the other hand, he said, which are more resistant to these effects, would freeze temporarily, would later thaw out, and would then crawl or flyaway into a world where birds – their principal natural predators – are gone. There would then be a proliferation of insects, many of which would be disease carriers.

Sagan carried the scenario a step further. “We have to remember that the surviving humans will have been subjected to radiation doses which compromise their immune systems, and we also have to remember that this will be at a time when there will be essentially no medical care, and certainly no disease vaccines available. Put all that together and you have…a net consequence…much worse than the sum of the individual components.”

These nuclear winter effects were examined by a number of biologists, notably Paul Ehrlich and others. They concluded, according to Sagan, that nuclear war will produce “very dire consequences not just for humans, but for plants, animals and micro-organisms. They concluded that the effects in the tropics may even be worse than in the north. For the northern hemisphere they predict massive extinctions, including, they say, the possibility of the extinction of all northern hemisphere vertibrates. And they imagine rather small pockets of human beings (in the southern hemisphere) that would survive such a nuclear war in the short term, but in the long term, they argue that the extinction of the human species cannot be excluded.”

On Monday, June 4, Sagan repeated his message to senior federal civil servants from various departments including External Affairs, National Defence, Emergency Planning Canada and the Department of Health.

In a later interview, Bill Snarr, Head of Emergency Planning, discussed the effect Sagan’s talk would have on his department. He said that Sagan’s predictions “go so far as suggesting that one could come very close to the possibility of extinction of very large numbers of species of plants and animals on earth, and perhaps even the human species could be destroyed. Now, obviously, there is no amount of planning or preparation that could overcome that prospect.”

Snarr said he asked Sagan at the Monday meeting if he was “sufficiently confident in his prediction that we should make some substantial change in the rather modest civil defence planning and preparation that we are making in Canada. .. The bottom line was that he was not prepared to say that, on the basis of the current state of his theories, we should make any change in our civil defence preparations.”

Snarr added that Sagan’s nuclear winter predictions had been studied prior to his visit and that the Canadian government “instituted additional studies in Canada to add to the work that is going on throughout the world in an effort to gain more knowledge about these possibilities and to determine what degree of certainty one can put in them.”

Snarr concluded that “the message that is of greatest importance, and the one that Dr. Sagan emphasized, was that the risk… is so horrendous, so devastating, that it warrants redoubled efforts aimed at reducing the inordinate number of nuclear weapons that now exist on both sides of the East-West balance.”

The Sagan visit was wrapped up with a lunch with Prime Minister Trudeau, and an open forum with Members of Parliament. According to Ed Ragan, chairman of PSR Ottawa, Sagan found Trudeau to be well informed on the issues related to nuclear weapons, and the two men did not veer off the topic.

“They didn’t talk about interplanetary exploration, or anything like that; they stayed on the issue of nuclear winter, the number of weapons that exist on the planet, and what’s going on from a scientific point of view” Sagan said.

At the final session, Sagan addressed two dozen Members of Parliament. Despite the low turnout of MPs, both Sagan and Ragan considered the two days of meetings a success in getting across the concept of what is being called the ultimate doomsday scenario: nuclear winter.

The Peace Calendar

Canadian Disarmament Information Service, 1983-1984

Sagan discusses nuclear winter with Trudeau, MPs