GC33B-12: 

Rapid Expansion of Nuclear Arsenals by Pakistan and India Threatens Regional and Global Catastrophes

AGU Fall Meeting, Washington, DC, 10 - 14 December 2018

12 December 2018, 15:30 - 15:40 

Owen B Toon (Univ Colorado Boulder), Charles Bardeen (National Center for Atmospheric Research), Alan Robock (Rutgers University)

India and Pakistan are rapidly increasing their nuclear arsenals. Both countries are vulnerable to increasing pressure from global change, and have histories of conflict. 

Based on numbers of nuclear delivery platforms each country 

• now has about 130 nuclear weapons, and 
• may have 250 weapons by 2025. 

Casualties

• 250, 15 kt explosions in urban centers in each country could kill 70 million people by blast, thermal radiation and prompt nuclear radiation. 
• With 250, 50kt explosions in each country almost 130 million could die, potentially marking the first time in human history that a war killed more people than died worldwide from natural causes in a year. 
• Even 100, 50 kt explosions in each country could kill 80 million people. 

Heat

• Nuclear explosions will start fires in urban areas releasing hundreds or thousands of times more energy than the bombs. 

Smoke

• 125, 15 kt explosions in each country, half the arsenals projected for 2025, would produce about 15 Tg (= 15 Mt) of upper tropospheric smoke, while 
• 125, 50kt explosions would yield about 25 Tg (= 25 Mt) of upper tropospheric smoke. 

• Smoke would rise into the stratosphere and within weeks spread over the Earth. The smoke would absorb sunlight and cool the surface by several degrees, while heating the stratosphere by more than 50 degrees C. 
• The lower surface temperatures would adversely impact agriculture globally, possibly leading to crop losses so severe that many would starve to death even far from Asia. 
• The higher stratospheric temperatures would destroy much of the ozone layer, which protects us from harmful ultraviolet radiation. We have no natural experiments to determine the environmental effects of large ozone loss, but they are likely serious. 

Increasing arsenals with more powerful and more numerous weapons increases the chances of a catastrophe. The largest uncertainties may be the numbers, yields and targets of nuclear weapons, and whether politicians will take action to reduce this threat to global civilization.

Version: 5 March 2019

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Joachim Gruber