Rapidly expanding nuclear arsenals in Pakistan and India portend regional and global catastrophe.

Toon, Owen B; Bardeen, Charles G; Robock, Alan; Xia, Lili; Kristensen, Hans; McKinzie, Matthew; Peterson, R J; Harrison, Cheryl S et al. · Sci Adv · 2019

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Abstract

Pakistan and India may have 400 to 500 nuclear weapons by 2025 with yields from tested 12- to 45-kt values to a few hundred kilotons. If India uses 100 strategic weapons to attack urban centers and Pakistan uses 150, fatalities could reach 50 to 125 million people, and nuclear-ignited fires could release 16 to 36 Tg of black carbon in smoke, depending on yield. The smoke will rise into the upper troposphere, be self-lofted into the stratosphere, and spread globally within weeks. Surface sunlight will decline by 20 to 35%, cooling the global surface by 2° to 5°C and reducing precipitation by 15 to 30%, with larger regional impacts. Recovery takes more than 10 years. Net primary productivity declines 15 to 30% on land and 5 to 15% in oceans threatening mass starvation and additional worldwide collateral fatalities.