What is a nuclear winter

What would happen in a global nuclear war

It has been some time since thoughts of nuclear war were quite easy to ignore. But the end of the Washington Treaty on Intermediate Range Nuclear Systems earlier this month and recent tests on both the Russian and US sides remind us that there are around 15,000 nuclear warheads in the world - and around 7,000 each from Russia and the US -American presidents can be activated.

The fact that Donald Trump does not fundamentally rule out the use of nuclear weapons and that two nuclear powers, India and Pakistan, are in a potentially explosive dispute over Kashmir do not help to calm the situation.

We stop at two to twelve

For these reasons, too, the doomsday clock in the magazine "Bulletin of the Atomic Scientists" is currently at two to twelve. This sets the value that prevailed between 1953 and 1960, when the superpowers of the time tested atomic and hydrogen bombs very intensively and the Cold War actually threatened to get hot.

But what happens if the nuclear arsenals are actually used? From a scientific point of view, atmospheric researchers have primarily dealt with this. One of the first works comes from the later Nobel Prize winner Paul J. Crutzen, the co-discoverer of the ozone hole and the inventor of the term Anthropocene. In 1982 he and a colleague came to the conclusion that after an atomic exchange of blows, there would be enormous fires and, as a result, a fatal release of nitrogen oxides and oxygen radicals. That in turn would lead to a cooling of the earth for several years and to a collapse of food production in the northern hemisphere.

"Nuclear winter"

A year later, the climate researcher Richard Turco and his colleagues presented a groundbreaking model calculation in the journal "Science", which also became conceptual: At that time, Turco and his colleagues coined the term "nuclear winter" for a radical cooling of the earth to temperatures from minus 15 to minus 25 degrees Celsius. This so-called TTAPS study has been slightly modified in the model calculations since then, but largely confirmed - for example in a report by the Goddard Institute for Space Research at NASA in 2007.

The latest model calculation comes from a group led by Joshua Coupe (Rutgers University), who also limit themselves entirely to the climate impacts of a nuclear war. (If a little more than half of the atomic bombs detonated in large cities, around three billion people would be killed instantly.)

According to the simulations by Coupe and his colleagues, which essentially confirm the older model calculations, the nuclear detonations would blow around 147 million tons of soot into the atmosphere - so high that they would spread in the stratosphere and darken the sun. There is also a clear video:

Seven years of darkness

As the researchers write in the latest issue of the journal "Journal of Geophysical Research: Atmospheres", global temperatures would drop by seven degrees Celsius in the first year after the catastrophe and then drop by another nine degrees in permanent darkness. In addition, a reduction in precipitation would make food production more difficult in the long term. Only after about seven years would the soot and with it the nuclear winter, to some extent, disappear again.

Please also bring the authors' résumé to the attention of the two presidents mentioned at the beginning: A nuclear attack and the resulting environmental catastrophe would in any case be suicidal for the country that launched it. (tasch, 23.8.2019)