How an India-Pakistan nuclear war could start—and have global consequences

Available here till January 2020.

Key point:

A nuclear winter would halt agriculture around the world and produce famine for billions of people. Though not of the scale of the US-Russia nuclear war referenced earlier, all of the three scenarios described in the hypothetical India-Pakistan nuclear war just described would produce severe effects for periods of years. We have calculated how food production would change in China (Xia and Robock 2013; Xia et al. 2015) and the United States (Özdoğan et al., 2013) for specific crops for a case of 5 teragrams of smoke – that is, a case involving significantly less smoke than any of the three India-Pakistan scenarios described here. We are now using detailed calculations of how specific food crops globally would respond to the resulting temperature, precipitation, and sunlight reductions for various smaller amounts of smoke. Also, ozone would be destroyed as the rising smoke absorbs sunlight and heats the stratosphere (Mills et al. 2014), allowing more ultraviolet light to reach the ground and creating negative effects that we have yet to study.

While we wait for agricultural simulations to be completed, our climate model can calculate a more general measure of environmental health, net primary productivity – a measure of how much carbon dioxide is converted to organic plant matter through photosynthesis after accounting for plant respiration. Net primary productivity is therefore a proxy for how much food could be grown on land and how much food would grow in the oceans for fish. (See Figure 4.) Based on these results, any of the India-Pakistan nuclear cases we posit clearly would cause large reductions in agriculture and food shortages. Depending on whether people hoard food or share, there could be famine for millions or billions of people – even for the smaller amounts of smoke in the scenarios presented here.

Always best to face reality.