Hypothetical Nuclear War: Fire and Smoke

Hello readers! Today we’re returning to a previous topic; a hypothetical nuclear war! While the last post on this topic looked at the overall effects from 50 Hiroshima-sized bombs being launched between India and Pakistan, today’s article works with the same scenario, but focuses on the effects of the resultant widespread fires and the aerosols (teeny tiny atmospheric particles) they would send into the atmosphere.
This article, Climate effects of a hypothetical regional nuclear war: Sensitivity to emission duration and particle composition, written by  Francesco S.R.Pausata, Jenny Lindvall, Annica M. L. Ekman, and Gunilla Svensson, was published in 2016 in the American Geophysical Union journal Earth’s Future. The article points out that previous studies only looked at the aerosol known as ‘black carbon’ (BC). However, the fires that were triggered from the detonations would also produce organic carbon (OC) which would be created by forest fires, for example. Another term you’ll be seeing is POM, the particulate organic matter, which is the sum of organic carbon and chemicals that go with it. The nuclear bombs could cause the ignition of organic matter in and near the cities creating a mix of the previously studied BC, with the addition of POM. This mix does not behave the same as black carbon on its own. 
The authors used a general circulation model to simulate the behavior of the aerosols, oceans, and atmosphere for several different scenarios; some had only BC (to compare to previous studies), and others with a mixture of BC and POM. These were 5 Tg of BC with either 15 or 45 Tg of POM. The ‘Tg’ stands for teragram;  one teragram is 1012 grams, or a million metric tons, or around 1.1 million US tons.
Smoke from fires in Africa. Depending on what is burning, different amounts of black carbon is produced. Image credit: Jeff Schmaltz, LANCE/EOSDIS Rapid Response/NASA Earth Observatory.
Smoke from fires in Africa. Depending on what is burning, different amounts of black carbon is produced. Image credit: Jeff Schmaltz, LANCE/EOSDIS Rapid Response/NASA Earth Observatory.
Also noted was that previous studies modeled all of the BC being put into the atmosphere in only one day. Most likely, a war would last longer than that; also included were scenarios where it took one week or one month to put all of the aerosols into the atmosphere. This study used January 1st, 1986 as its start date for the hypothetical war; using a known date, we can put actual data into the model instead of having that as another variable. Additionally, this year did not have an El Nino or La Nina effect ongoing, keeping the simulation neutral in this regard.
The aforementioned previous studies created colder, drier conditions for years following the war, destruction of the ozone layer, the global average temperature cooling, and agriculture worldwide being devastated. So, what about the new results?
The first thing to mention is that the longer the length of time, the lower in the atmosphere the aerosols reached, and the less the BC mixed with the POM, which called for different warming effects within the atmosphere. After one month, all scenarios showed about the same amount of BC remaining in the atmosphere; after one year, there was less BC in the tests where the aerosols were put into the atmosphere over one month compared to one day or one week. Since the longer term scenario meant the aerosols did not get as high in the atmosphere, it meant they were removed sooner. The one month scenarios had less impact on global temperature, but a larger impact on global average precipitation; up to fifty percent less precipitation.
For a closer look, the authors chose the intermediate scenario of 5 Tg of BC and 15 Tg POM put into the atmosphere over a course of one week. This resulted in 1 degree Celsius (1. Fahrenheit) in cooling averaged around the world, peaking in the third year. The first year had already seem the worst decrease in global precipitation, though this beings to recover in the fourth year. Overall the growing season was shortened by 20 to 60 days (more days for locations close to the detonations). The worst effects were found in the third year, when there is the most cooling.
For comparison, in an oft-referenced previous study, the 5 Tg of BC in one day scenario made for the fifth year after the detonations with a 2 Celsius (3.6 Fahrenheit) drop in global temperature (still 0.4 C (.72 F) after twenty years)) and precipitation that took much longer to recover.
As always after something is finished, scientists ask themselves what could have been done differently. The authors note multiple things that could be improved in a future study; for one, their model only looked at part of the atmosphere, so this may have underestimated the cooling effects. Also, this did not include the interaction with the ozone layer. Estimates of BC/POM ratios in the areas in question would also make for improvements. However, it does appear that the changes could recover faster than they would with only BC. Hopefully, this remains fully a simulation; actual nuclear war would create severe worldwide problems, as has been made quite clear through studies and history.

 

Bibliography

Pausata, F. S. R., J. Lindvall, A. M. L. Ekman, and G. Svensson (2016), Climate effects of a hypothetical regional nuclear war: Sensitivity to emission duration and particle composition, Earth’s Future, 4doi:10.1002/2016EF000415
Today’s main article.
United States Environmental Protection Agency. “Black Carbon Research.” EPA. N.p., 23 Sept. 2016. Web.
A page about the basics of black carbon.
Voiland, Adam. Aerosols: Tiny Particles, Big Impact. National Aeronautics and Space Administration, Earth Observatory. 2 Nov. 2010. Web.
A long but informative page on aerosols.
Voiland, Adam. A Band of Fire in Sub-Saharan Africa. National Aeronautics and Space Administration, Earth Observatory. 30 Jan. 2016. Web.
The source for the image in today’s post.
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