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Climate Effects of Worldwide Fires/Smoke

cameron_chapman

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I have a question about smoke volume from fires worldwide and what effect it would likely have on climate.

So, in my story, there's a worldwide plague that causes people to die a nice, painless—though relatively quick—death. Not everyone is affected by the plague, but let's say a good 80% of the population ends up dead. The worst part about this is that after the bodies have sat for more than a day or two, the insides liquefy. When the bodies are moved, even just a little, they have a tendency to burst.

As you can imagine, the survivors aren't too keen on having a bunch of on-the-verge-of-bursting bodies of their loved ones lying around. So, since they can't move the bodies, they opt to burn them in place. This results in entire towns and cities being burned around the world. Probably something like 90% of the populated areas would end up with some fires, though whether they'd be destroyed completely isn't determined yet.

Now, if a majority of the villages, towns, and cities are burned, and let's assume that some of the surrounding countryside gets burned, too (not to the extent of The Road or anything), a lot of smoke and ash is going to be released.

My question is: would the amount of smoke released be enough to cause any significant climate change? I'm thinking along the lines of the Little Ice Age in the 16th-19th centuries (though probably not as long?) or at least like 1816 (better known as Eighteen Hundred and Froze to Death), when there was no summer in a lot of regions after the eruption of Mount Tambora. I know volcanoes can often effect climate for a couple of years after an eruption, but they tend to send ash really high into the atmosphere. Could a lot of big ground fires do something similar? How severe would it be?

If not, what effects would the fires likely have? I'm guessing falling ash would blanket large regions and effect crops and water supplies. What else?

The story itself happens a few decades after this event, but I need to get the backstory straight in my head before I can write what happens after. Thanks in advance for any assistance!
 

Chris P

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I doubt it. Figure 80% of seven billion, that's 5.6 billion funeral pyres. Now, say it takes 100 pounds (45 kg) of wood to burn one body (rough guess). That's 252 billion kg (252 million metric tons) of wood to burn all the dead (I'm using metric for a reason; bear with me).

Now, the 1980 eruption of Mt. St. Helens ejected about 540 million metric tons of ash, or twice the amount of wood burned. Wikipedia doesn't note any climate effects, but the MUCH larger eruption of Mt. Pinatubo in 1991 temporarily lowered global temperatures by 0.5 C (0.9 F). Therefore, burning your dead in wood fires isn't likely to do much, especially not decades later.
 

cameron_chapman

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Even with burning entire towns/cities? Since the bodies wouldn't be moved out of wherever they died.

What other effects might there be, then? I'm thinking surface water would be contaminated and made acidic from the ash, and that there would be changes in the mineral composition of the ground from ash falling on top, but is that all? And how long would those effects last? Would there be an effect on groundwater?
 

Chris P

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Well, you could also look at studies of the effects of forest fires on soil minerology and surface water. I'm not sure how an ash layer affects soil pH, etc; that's not so much my area. In general, ground water quality suffers from the increased sediment load caused by erosion after the loss of ground vegetation. There might also be a drop in dissolved oxygen (and therefore fish kills) if a lot of organic matter or nutrients enter the water. The effects tend to be short lived, and herbaceous vegetation returns within days or weeks and stabilizes the soil, followed by a return of woody species. A Google Scholar search will get you the latest scientific info. It might be more detailed than you need, though.

Being a novel, you can fudge some of the details and effects. In reality, I think most bodies would simply be left in place to decompose over the couple weeks it would take rather than people burning every single body (unless there was a reason the bodies HAD to be burned, such as a virus). Modern cities are designed so they don't burn, so I think you would have difficulty digging a fire break around Pittsburgh and setting it to the torch. Napalming it from the air, however...hmm. Sorry, just thinking out loud (and nothing against Pittsburgh). If every city in the world was napalmed within a week, then I would certainly buy the idea of climate effects. Having enough people left able to fly the airplanes and make enough napalm would be a challenge, as 80% of those currently trained to do this would have been killed.

Bah! I'm overthinking this now. It's fiction. If you keep it somewhat general I don't think you'll have too much of a problem. Most readers want a good story and won't care if you exaggerate the pH of the river.
 

NoGuessing

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Wouldn't affect global climate, but volcanic ash is fantastic soil for pasture and so are decaying fauna. It's 2:30am though so typically I have no idea what forest fires would do to local soil fertility.

Rivers would likely be polluted and surviving humans and animals would suffer lung damage from smoke inhalation.
 

Amadan

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I think you've got some major plot holes here, besides the climate effects.

So, in my story, there's a worldwide plague that causes people to die a nice, painless—though relatively quick—death. Not everyone is affected by the plague, but let's say a good 80% of the population ends up dead. The worst part about this is that after the bodies have sat for more than a day or two, the insides liquefy. When the bodies are moved, even just a little, they have a tendency to burst.

You'll want to do some research on epidemiology. It's actually quite hard for a disease with a high, fast fatality rate to spread far, because it kills off the host population too quickly. Depending on how much realism you want in this novel, maybe you can fudge it, but a global plague that kills off 80% of the population would have to have a pretty long incubation and infectious period -- long enough to spread worldwide before people start dying off.

As you can imagine, the survivors aren't too keen on having a bunch of on-the-verge-of-bursting bodies of their loved ones lying around. So, since they can't move the bodies, they opt to burn them in place. This results in entire towns and cities being burned around the world. Probably something like 90% of the populated areas would end up with some fires, though whether they'd be destroyed completely isn't determined yet.

As Chris P said, most modern cities aren't just going to burn down, even if you set entire neighborhoods ablaze. I don't know how the 20% of the surviving population would manage to set all the world's towns and cities on fire. And a large percentage of the population (varying by country) still doesn't live in cities.

Now, if a majority of the villages, towns, and cities are burned, and let's assume that some of the surrounding countryside gets burned, too (not to the extent of The Road or anything), a lot of smoke and ash is going to be released.

That's a large assumption. Some regions (with lots of wood and brush) would burn, but most cities aren't surrounded by combustible countryside.

My question is: would the amount of smoke released be enough to cause any significant climate change? I'm thinking along the lines of the Little Ice Age in the 16th-19th centuries (though probably not as long?) or at least like 1816 (better known as Eighteen Hundred and Froze to Death), when there was no summer in a lot of regions after the eruption of Mount Tambora. I know volcanoes can often effect climate for a couple of years after an eruption, but they tend to send ash really high into the atmosphere. Could a lot of big ground fires do something similar? How severe would it be?

Short answer: no. Chris P explained why. You'd have to pretty much block out the sun to actually lower global temperatures, and the amount of actual burning material you'd get even with millions of people making a concerted effort to burn down cities wouldn't match one volcano.

If not, what effects would the fires likely have? I'm guessing falling ash would blanket large regions and effect crops and water supplies. What else?

Burning cities wouldn't create that much ash. The only effects would be on the cities themselves, and maybe some blackened trees in the countryside for a while. Some wildlife might be killed, but it won't blanket the area in ashes.

The story itself happens a few decades after this event, but I need to get the backstory straight in my head before I can write what happens after. Thanks in advance for any assistance!

If your plot requires climate changes as a result of the plague and subsequent destruction of cities, you'll need some other cause. Perhaps the survivors unleashed nukes? Of course, that would be a whole different set of climate changes. But short of a doomsday weapon causing multiple volcanoes to erupt, or an orbital heat ray that sets the Amazon ablaze, or releasing millions of tons of gas directly into the atmosphere, I can't think of a manmade source for instantaneous global climate change.
 

cameron_chapman

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Luckily it's not really necessary for the plot. The only thing really necessary would be the abandonment and/or destruction of at least some cities/towns. The death from the plague is relatively quick and painless, but the infection and incubation period can easily be longer. I'm also thinking it might be a disease that might have carriers that are infectious but aren't affected by the illness (whether those carriers will be people or animals I haven't decided yet).

Thanks for the further insight. This is a story I've been kicking around in my head for about a year now, and not something I've done a whole lot of planning or research on, but I'm feeling like this fall might be the time to write it.