Excerpt from the movie «The Road»
We may have mentioned the term "nuclear winter" at some point in the aftermath of a serious meteorological event or phenomenon. For example, what is anticipated could happen if the Campi Flegrei supervolcano. That sudden cooling that the planet would suffer would have great similarities to a nuclear winter. But what is it really?
This type of winter is the concept that includes the resulting climatic period that would remain after a nuclear war. The consequences would be so dramatic that a phenomenon called a "bottleneck" would arise. Roughly it is the rapid disappearance of total or partial parts of a species or population. This event results in what is called "genetic drift" which also, counterintuitively, encourages the evolution of species. It is an outcome as a chain reaction from which no species would be saved, and which even humans have had to go through in their history.
The consequences of the nuclear winter
In short, a nuclear winter is the climatic phenomenon resulting from the indiscriminate use of nuclear bombs. That global cooling would come from the enormous clouds of dust that would rise to the stratosphere. This area, located between 10 and 50 km high, would fill up with the material that would prevent the passage of sunlight. Not only in a war with atomic bombs, it follows that a supervolcano would also have the same effect due to the enormous columns of material emitted towards the high altitudes. An example of this could be the impact on the climate that a potentially dangerous asteroid, such as the one described in our article, would have. guide to asteroids.
Unlike the normal winter we know, this one would cause a reduction in sunlight. For living beings that carry out photosynthesis, such as plants, it would mean the total or partial death of species. Another thing that could not be anticipated is that, although we know its effects would be devastating, this cloud of dust could stay in heaven for many months, similar to the conditions of other extreme weather events. The more of them, the more damage to ecosystems. Starting with the death of plants, would come, a wave of extinction following the food chain. After the plants, herbivores would come, and then carnivores. It's possible that, depending on the magnitude and location, the unbreathable air itself caused animals to die instantly in some regions. According to some theories, this phenomenon has also been used to explain the extinction of the dinosaurs due to a meteorite that caused similar effects.
How does a bottleneck occur?
The "bottleneck" is a term used in biology to refer to past times where, from a series of events, the populations of species have been greatly reduced in number and even reaching extinction. The reasons have tended to be almost always accompanied by great cataclysms, similar to the effects of a nuclear winter. So, whereas we previously had a large population with great genetic variability, we now have a small population with little variability. In this sense, the drastic population reduction can be linked to extreme weather events, to which we can also add the impact of dangerous asteroids and their consequences on the genetic diversity of species.
All this leads to the deduction that the least variability leads to a genetic drift, due to speciation and adaptive evolution. This has been the case in every recorded era. Survivors of these cataclysms, such as nuclear winters, accelerate their genetic drift and evolution, thus producing new species. The majority (or strongest) genetic traits tend to stabilize and persist, while the weaker or minority traits tend to become extinct.
When did humans experience it?
75.000 years ago. Known as the Toba catastropheThis supervolcano in Indonesia erupted. It's now a lake due to its large crater. It's estimated that the human species was reduced to a few thousand individuals. This same period also saw a variable decline in other species, reflecting the devastating effects of a global cooling similar to a nuclear winter, caused by a massive natural phenomenon.
Although we've talked about volcanoes, due to their relationship with nuclear winters, bottlenecks are very different. That is, they could range not only from climatic effects, but also from plagues or epidemics. An example is the Black Death experienced in Central Europe. Or more, as an eruption, more famine and disease, as occurred in Iceland with the Lake eruption in 1783.
