Tuesday, January 25, 2022

Just Hear Me Out: "Would Nuclear Winter Cancel Out Global Warming?"

 From Hackaday, January 25:

Nuclear war was very much a front-of-mind issue during the fraught political climate of the Cold War era. Since then, atomic sabre rattling has been less frequent, though has never quite disappeared entirely.

Outside of the direct annihilation caused by nuclear war, however, is the threat of nuclear winter. The basic concept is simple: in the aftermath of a major nuclear war, the resulting atmospheric effects could lead to a rapid cooling in global temperatures.

Some say it couldn’t ever happen, while others – including Futurama – suggest with varying degrees of humor that it could help cancel out the effects of global warming. But what is the truth?

Hard data is isn’t really available, as thus far there have been  no large-scale nuclear wars for scientists to measure. Several studies have explored the concept of nuclear winter, however, and explored its potential effects.

How Does It Work, Anyway?

Hundreds of large firestorms triggered by nuclear weapons could loft soot into the upper atmosphere, serving as the causative mechanism of the “nuclear winter” theory. The nuclear aspect is only as an ignition source; any other cause of widespread firestorms could do the same. Image Credit: Public Domain, Jim Peaco

The basic concept of nuclear winter is simple. In a large nuclear conflict, where nuclear weapons are used in strategic strikes against urban and industrial areas, large-scale fires would rage out of control. These fires would then loft large amounts of black carbon soot into the upper reaches of the atmosphere. Once there, the smoke particles might then be lofted further up into the stratosphere as they absorb heat from the sun, up to a point where the particles are too high to be quickly “rained out” of the air by precipitation. These particles would then essentially shade the surface, creating a cooling effect.

Papers published as recently as 2007 suggests that a full-scale nuclear war between superpowers could cause a drop in global average temperatures by as much as 8 °C . If that doesn’t sound dramatic, to put it into perspective the average temperature was 5 °C lower during the last ice age 18,000 years ago.

Modelling from researchers on the topic suggests that the major knock on effect on agriculture would be crippling to humanity around the globe. Temperatures in critical growing regions in Ukraine and Iowa, for example, could see daily minimum temperatures reach below freezing for several years, making growing food crops near-impossible. Global famine would be the result.

This photo is often mistaken for being a shot of the mushroom cloud created by the nuclear bomb dropped on Hiroshima in 1945. However, it is in fact an image of the pyrocumulus cloud created in the firestorm that happened in the aftermath of the attack. Image credit: Public domain, US Military

Running simulations with newer climate models has continued to turn up similar results, even in recent studies. Those studies are run with similar base numbers that suggest an all-out nuclear war using up most of the stockpiles of major superpowers would loft around 150 teragrams of soot into the atmopshere. However, that value remains an assumption that has drawn criticism from some sectors.....