Nuclear mattersThe global consequence of a regional nuclear war

The terrorist attacks in Mumbai, and the slow disintegration of Pakistan, highlight the danger of a nuclear confrontation between India and Pakistan. Lawrence Krauss writes in New Scientist that you would not know it from recent U.S. policy. Two examples:

• The Bush administration turned a blind eye to an ongoing Pakistani project to build a plutonium reactor which would be capable of making enough fuel each year for up to fifty nuclear weapons.
• In 2006 Congress approved a nuclear cooperation pact with India that would help promote that country’s bomb-making capacity.

Neither India nor Pakistan has signed the Nuclear Nonproliferation treaty NPT. Krauss urges the new administration to defuse the situation on the subcontinent by encouraging disarmament in this region, not proliferation.

The United States — and, indeed, the whole world — have an immediate interest in this issue. Aside from the direct sociopolitical and economic consequences of a regional nuclear war, it is now clear that the longer-term impact of even a localized nuclear conflict between Pakistan and India would be more severe than previously estimated. A study published last year shows that global temperatures and growing seasons could decline significantly following as few as 50 15-kiloton explosions, as might result from such a regional war (see Toon et al. Physics Today article, cited below).

Here are some of the consequences of a regional India-Pakistan nuclear exchange:

• One billion people to starve to death around the world, and hundreds of millions more to die from disease and conflicts over food.
• Such a conflict would throw five million tonnes of black soot into the atmosphere, triggering a reduction of 1.25°C in the average temperature at the earth’s surface for several years. As a result, the annual growing season in the world’s most important grain-producing areas would shrink by between 10 and 20 days.
• Since global grain stocks stand at 49 days, lower than at any point in the past five decades, they would not provide any significant reserve in the event of a sharp decline in production. We would see hoarding on a global scale.
• Countries which import more than half of their grain, such as Malaysia, South Korea, and Taiwan, would be particularly vulnerable. So, too, would 150 million people in north Africa, which imports 45 percent of its food. Many of the 800 million around the world who are already officially malnourished would also suffer.
• Large-scale impacts on food supplies from global cooling are credible because they have happened before. The eruption of the Indonesian volcano Tambora in 1815 produced the “year without a summer” in 1816, causing one of the worst famines of the nineteenth century.
• The global death toll from a nuclear war in Asia could exceed one billion from starvation alone. Food shortages could also trigger epidemics of cholera, typhus, and other diseases, as well as armed conflicts, which together could kill hundreds of millions.
• Smoke unleashed by 100, small, 15-kiloton nuclear warheads could destroy 30-40 percent of the world’s ozone layer. This would kill off some food crops.
• The smoke would warm the stratosphere by up to 50°C, accelerating the natural reactions that attack ozone. There is a potential here for mass starvation.

-read more in Own B. Toon, Alan Robock, and Richard P. Torco, “Environmental Consequences of Nuclear War,” Physics Today (December 2008): 37-42