[ Clearly you’d want to move to Australia or New Zealand or stockpile 5 years of food.  Related posts:

• Nuclear winter: World-wide ozone loss from small nuclear war = 1 billion + deaths
• The EMP Commission estimates a nationwide blackout lasting one year could kill up to 9 of 10 Americans through starvation, disease, and societal collapse

Alice Friedemann   www.energyskeptic.com  author of “When Trucks Stop Running: Energy and the Future of Transportation”, 2015, Springer and “Crunch! Whole Grain Artisan Chips and Crackers”. Podcasts: Practical Prepping, KunstlerCast 253, KunstlerCast278, Peak Prosperity , XX2 report ]

Extracts from: Robock, A. 2010. Nuclear winter.  Climate change 1418-1427.

Survivors face not only radiation but high levels of toxic chemicals from plastics, asphalt, oil refineries, forests, and so on.

The global average cooling, of about 1.25 C, would last for several years, and even after 10 years the temperature would still be 0.5 C colder than normal.

These numbers might not seem like much, but even during the Little Ice Age, global temperatures were only about 0.5 C below normal. Every once in a while large volcanic eruptions produce temporary cooling for a year or two. The largest of the past 500 years, the 1815 Tambora eruption in Indonesia, produced global cooling of about 0.5 C for a year.

Year 1816 became known as the ‘Year Without a Summer’ or ‘18 hundred and froze to death’.  There were crop-killing frosts every month of the summer in New England. The price of grain skyrocketed, the price of livestock plummeted as farmers sold the animals they could not feed, and a mass migration westward from the US East Coast across the Appalachians to the Midwest began. In Europe, widespread famines occurred and the weather was so cold, dark, and gloomy that Mary Shelley was inspired to write Frankenstein in 1816. A nuclear war could trigger declines in yield nearly everywhere at once, with strong impacts on the global agricultural trading system.

The most important consequence of nuclear winter for humans is the disruption of food supplies. 8 This comes from environmental disruptions that reduce or completely wipe out agricultural production and the disruption of the distribution mechanisms.

Not only would it be virtually impossible to grow food for 4–5 years after a 150-Mt nuclear holocaust, but it would also be impossible to obtain food from other countries. In addition to the disruption of food, there would be many other stresses for any surviving people. These would include the lack of medical supplies and personnel, high levels of pollution and radioactivity, psychological stress, rampant diseases and epidemics, and enhanced UV-B.

There  are many  ways  that  agriculture  is vulnerable to nuclear winter. The cold and the dark alone are sufficient to kill many crops. Superimposed on the average cooling would be large variations. During the summer of 1816 in New England, there were killing frosts in each summer month.  Only  1 day with the temperatures below freezing is enough to kill rice crops. Colder temperatures mean shorter growing seasons, and also slower maturation of crops; the combination results in much lower yields. Most of the grains that are grown in mid-latitudes, such as corn, are actually of tropical origin, and will only grow in summer-like conditions. For example, a study done in Canada shows that with summer temperatures only 3 C below normal, spring wheat production would halt. Insufficient precipitation would also make agriculture difficult.

The tremendous productivity  of  the  grain belt of the US and Canada feeds not only those countries but also many in the rest of the world where normal climate variability often results in reduced harvests. This productivity is the result of modern farming techniques that allow a tiny percentage of the population to produce more than enough for the rest. To do this, tremendous energy subsidies are needed. Farmers depend on fuel for their machinery, fertilizer, and pesticides, none of which would be available or distributed in the aftermath of a war.

Furthermore, insects have a higher tolerance for radiation and the stresses that would follow than do their predators, such as birds. Whatever might grow would be eaten by pests, already a significant problem in today’s production.

Also, the seeds that are in use were designed to yield high productivity assuming the current climate and inputs of chemicals and energy as discussed above. These seeds would not grow well in a radically altered growing environment.

Our dependence on technology is such that if every human in the US went out to the fields to try to raise crops with manual labor, and if they knew what they were doing, and if they had enough food to eat, and if they were healthy, they still could not produce what is produced today.

Thus, most of the world’s people are threatened with starvation following a full-scale nuclear war. The number that would survive depends on how much food is in storage and how much could be produced locally. Earlier studies of various countries around the world conclude that even with extremely optimistic assumptions of perfect distribution systems within countries, 8 that each person who will survive becomes a vegetarian and eats the minimum needed for survival, and the others waste none of the food, that nations in Asia, Africa and South America could only last 1–2 months. In many nations, people would be reduced to a hunter/gatherer existence with nothing to hunt and precious little to gather.

The effects on health would add to the misery. Immune deficiencies can be produced by any of the following: burns and trauma, radioactivity, malnutrition, psychological stress, and UV-B radiation. All of these would be present for the survivors in the target nations.

Pollution from dioxins, PCBs, asbestos, and other chemicals will make the air unhealthy to breath. Severe psychological stress will prevent the survivors from making the efforts to continue to exist.

One might think that the ocean shore would be a good place to survive because the temperatures would not fall as much, and there would be plenty of food to catch. Although the ocean would not cool very fast, the darkness would decimate the phytoplankton, which are at the base of the oceanic food chain. That, combined with toxic and radioactive pollution, would severely limit the food sources in the oceans. Furthermore, the large temperature contrasts between the oceans and the land would produce strong storms that would make fishing difficult at best.

Citizens in Australia and New Zealand have the best chance to survive.

The good news: Earth will not be plunged into an ice age. Ice sheets, which covered North America and Europe only 18,000 years ago and were more than 3-km thick, take many thousands of years to build up from annual snow layers, and the climatic disruptions would not last long enough to produce them. The oxygen consumption by the fires would be inconsequential, as would the effect on the atmospheric greenhouse by carbon dioxide production.