One previously unforeseen consequence of an Indo-Pakistani nuclear war would be global climate change beyond anything "experienced in recorded history." Among other things, says a study led by Alan Robock of Rutgers University, there would be 10 per cent less rain around the world. One major victim: the monsoon.
Robock's team used climate change models but applied them to the giant smoke clouds that would be created by nuclear explosions on large cities. Assuming an exchange of 100 Hiroshima-sized atom bombs (each of them a relatively small 15 kilotons) in a subtropical climate, the study concluded the war would produce "large and long-lasting" climate change across the world.
The impact would be worsened by strong sun which heats the smoke and drives it higher into the atmosphere. Though the paper does not mention countries, Robock says his simulation assumed an Indo-Pakistan nuclear exchange in May. "The plume would be marginally less high if a war took place in the winter," he said.
Smoke and famine
* High smoke plumes can have remarkable global impacts. It has shown that a 1783 explosion by the Icelandic volcano Laki led to the collapse of the monsoon in India that year, as well as famine in Egypt and Japan.
Among the results:
1. The smoke cloud that would be produced would see surface global temperatures cool by -1.25 degrees Centigrade for several years. This would result in "large climatic effects" occurring "in regions far removed from the target areas." Places as far apart as central Africa, Australia, the Deccan and Canada could see even summer temperatures fall by 4 degrees C. "A severe disruption of global agricultural production would be inevitable," says Robock.
2. The cooling would "weaken" the global hydrological cycle. Rainfall, snow and other forms of precipitation would drop by about 10 per cent. This would include "large reductions of the Asian summer monsoon." Robock said, "More models would be needed, but the one that we did showed sharp drops in rain in Cambodia, Thailand as well as Pakistan." One beneficiary: the sahel region of Africa would get more rain.
Robock's team included two new observations into their calculations.
One was "fuel-loads." A lesson learnt from watching the effect of Canadian forest fires is that concentrations of flammable material result in far greater amounts of smoke and lofts them higher into the atmosphere. Large cities, like forests, have large amounts of material that burn well including fuel, plastic and wood. After a nuclear hit these would throw up huge amounts of smoke.
Robock said fuel-loads were calculated on the basis of various older studies on the flammable content of individual buildings. They cut these figures in half for developing world cities. "We used Google Earth to work out the density of big cities in India," he said.
The other new factor was the impact of subtropical temperature. Because the subcontinent is warm, the smoke clouds will be driven "high into the stratosphere" and persist in the atmosphere for years on end. They would remain particularly high for the first six years.
Robock's animation of a nuclear exchange shows a deep red smoke burst taking barely a week to spread from the subcontinent to cover almost the entire world in pink.
This disproves earlier assumptions that small regional nuclear wars would have a more localised impact than the massive nuclear exchanges once feared between the US and the Soviet Union. While it would be less than the "nuclear winter" that a superpower exchange would have caused, but the length of the impact because of "stratospheric plume rise" would equal that of a big nuclear war. Says Robock, "The impact would be more than was thought before and would last longer."
However, Robock cautioned, "This is just the first such study in 20 years, it should be tested with other models and scenarios."
The climate consequences of a nuclear war would be above and beyond the better-known large-scale casualties that would occur in India and Pakistan as direct fallout of the war.
Another team, led by Owen Brian Toon of the University of Colorado, calculated that an exchange of 50 Hiroshima bombs on each side would see between 9 and 12.5 million Indians and between 6.5 and 9 million Pakistanis killed. If the numbers included the injured, the figures would roughly double.