Climate Effects of Nuclear Conflict Discussed

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Publication date: 
20 June 2008

Professors Brian Toon and Alan Robock of the University of Colorado and Rutgers University, recently presented their research on the potential climatic effects of a nuclear conflict to congressional staffers and interested parties.  The event, sponsored by the American Association for the Advancement of Science (AAAS), examined the environmental impact of a hypothetical nuclear war between India and Pakistan.

Toon prefaced his lecture, saying that his and Robock’s research is a continuation of nuclear winter research from the 1980s.  The term nuclear winter refers to significant widespread climate cooling caused by massive quantities of aerosol particles thrust into the atmosphere by the use of nuclear weapons.  Toon, and later Robock, emphasized that the concept of nuclear winter has not been discredited, as some believe.

Beginning with statistics on the world’s current nuclear arsenal, Toon explained that the total number is about halved from 1980s levels.  In 2002, the U.S. and Russia agreed to reduce their operationally deployed strategic warheads to between 1,700 and 2,200 by the end of 2012 through the Strategic Offensive Reductions Treaty (SORT).  While that number is heartening, there remain an estimated 27,000 nuclear weapons worldwide.  Moreover, 40 countries are believed to have fissionable material and, according to Toon, 200,000 nuclear weapons could be made out of what is “sitting around.”
After showing images from Hiroshima, Toon explained how “one nuclear explosion can cause orders of magnitude more fatalities than previous wars.”  According to Toon’s research, the advent of megacities, and developments in nuclear technology have dramatically raised potential fatality numbers even when far fewer weapons are used.  Toon estimates that 50, 15 kiloton nuclear weapons, strategically used against the U.S., could kill approximately 4 million.  A nuclear war between India and Pakistan could result in more than 20 million deaths.

The density of flammable material in megacities, and the strategic value of striking those cities in a nuclear conflict, means that huge amounts of aerosol particles would be introduced into the atmosphere in even a regional war.  For example, an India-Pakistan nuclear conflict could produce 7 million tons of smoke and dramatically reduce the average global temperature.  In a global conflict where the entire U.S. and Russian SORT arsenal was used, 180 million tons of smoke could plunge average global temperatures to ice age levels.

Robock followed with a discussion on the technical details of nuclear-induced climate change.  Advances in computing technology have allowed for more sophisticated climate models which have reaffirmed the threat of nuclear winter.  Toon and Robock have used the NASA GISS ModelE atmosphere-ocean general circulation model to test various nuclear scenarios.  Robock explained that a nuclear war would cause extraordinary damage to the ozone layer, and affect all latitudes.  Precipitation rates and growing seasons would also be change.

During a question and answer period, Toon and Robock were asked if they discovered a breaking point, or threshold for the number of nuclear weapons that would need to be used to create a nuclear winter situation.  Robock responded that there probably is, but that they did not know what that figure would be.  Toon added that funding could help them determine a number.

A final question prompted Toon and Robock to speak outside of their fields of expertise.  An audience member asked if they believed the U.S. should rely more on nuclear energy.  Toon said that it may seem like an immediate solution, but that his image of a future France- which relies heavily on nuclear energy- is of huge nuclear “tombstones” across the country side.  Robock suggested that the issue of nuclear proliferation would be another reason to avoid expanded nuclear energy investment, saying that nuclear waste could produce 20 plutonium bombs per year.

Toon and Robock’s research, which has been featured in ScienceDaily and at the 2006 annual meeting of the American Geophysical Union (AGU), is available at their website,