How a nuclear war in north hemisphere would affect the south hemisphere?

Question

I'm trying to figure out how a nuclear war in the north hemisphere would affect the south (specially South America, where my story is set).

I read about the nuclear fallout and nuclear winter consequences, but all I saw is that the southern hemisphere wouldn't suffer that much apart from minimal climate changes (and only for a few months - correct me if I'm wrong).

What I need is a event that would trigger nuclear winter in South America, but not killing people in mass in that area (in a practical way, anything can be devastated, except South America). Like I said, I was hoping that a nuclear war in the northern part of the world would give me this effect, but my research concluded that the damage would be medium to minimal, and just for a few months. Of course a full-scale nuclear war would lead to that, but it would mass-murder the entire world.

How a nuclear detonation/war could lead to winter in South America? How "big" or "exceptional" this event would need to be?

Thanks!

Answer 1

I would refer you to the 1957 post-apocalyptic novel On the Beach and its 1959 film version.

The novel details the experiences of a mixed group of people in Melbourne as they await the arrival of deadly radiation spreading towards them from the Northern Hemisphere following a nuclear war a year previously.

You have to consider, that we are an interconnected planet. Even isolated atomic accidents can reach other hemispheres. It is not only the wind, but consider propagation through water currents, rivers. Fauna that survives would probably migrate carrying the poison with them.

I do not know how to calculate the spread rate, nor the maximum damage to the north hemisphere to prevent damage to the south, but if your scenario depicts destroying the north by anything other than accident, you can expect there would also be plans to destroy potential supplies from the enemy, i.e., the south.

In any case, I would be interested in reading your story.

Good luck!

UPDATE: For a more scientific or precise description of the nuclear winter process and requirements, I would suggest the following article Nuclear winter.

Answer 2

If you think the nuclear winter is not enough to have a heavy impact on the south, why not have one nuke hit Yellowstone and trigger the volcano? Where a nuclear or a volcanic winter might be northern hemisphere only a combination of both should/ or at least could be big enough to cool down the south, too.

One important thing to remember is that even a "slight" cooling of only 1-2°C can disrupt crops not meant for this new climate. And in addition to that the weather could change if the temperatures drop.So not only do the crops get too little warmth, they get the wrong amount of water, too. Same for cattle, the change in temperature can cause them to become ill.

Answer 3

take a look here : http://science.howstuffworks.com/nuclear-winter2.htm

The article details six levels of nuclear winter: Minimal, Marginal, Nominal, Substantial, Severe and Extreme (in the final case everybody and everything dies). For most of these scenarios; the conclusion from their analysis is based on this fact:

Everything below the equator would remain mostly unaffected, given the hemispheric separation of air currents and the fact that most nuclear targets exist in the Northern Hemisphere.

The worst level for which humanity will likely survive is this:

Substantial nuclear winter: This scenario, following full-scale nuclear war, involves catastrophic consequences for the Northern Hemisphere: freezing temperatures, widespread fallout, pollution, ozone depletion and disrupted precipitation. Imagine a deeply overcast day -- now imagine those conditions persisting for years. Green plants would barely receive enough sunlight for photosynthesis. Crops would fail, billions of humans would die, species would go extinct and while humanity would likely survive, civilization as we know it might not. Damage to the Southern Hemisphere would depend on the number of detonations below the equator.

In other words, the most plausible outcome for full-scale nuclear war is a hellscape in the Northern Hemisphere (where nearly all the major cities are) and a lightly damaged Southern Hemisphere (South America, Australia, the southern third of Africa, New Zealand, many islands).

If the Southern Hemisphere does suffer Nuclear Winter, it would be one of the earlier levels: Marginal would be plausible. You can look at those to see how much damage would likely occur in South America (or the southern hemisphere in general). Perhaps any big cities or major population centers would be bombed in a full scale war (thousands of nuclear bombs).

I live in Argentina and I think all here in South America would have to accommodate many people, basically anybody that survived in the Northern Hemisphere. The current population is around 420 million, perhaps tens of millions more would be refugees. This could trigger revolutions and new political orders and alignments, which may or may not be good.

Answer 4

If a nuclear winter would hit the northern hemisphere only, then the survivors of the war would all head south. Lets say 50-100million north americans all walk into South America. That kind of migration will lead to mass riots, mass starvation and a complete breakdown of society as we know it. I think I'd prefer the winter..

Answer 5

http://www.uow.edu.au/~bmartin/pubs/82cab/

Talks about the impact of nuclear war on Australia