Nuclear winter is a theory about global climate change, which predicts the climate disaster that may be caused by large-scale nuclear war. According to the theory of nuclear winter, the massive use of nuclear weapons, especially for flammable targets such as cities, will allow a large amount of smoke and carbon black to enter the earth's atmosphere, which may lead to very cold weather.

The granular layer of smoke and carbon black entering the atmosphere can significantly reduce the total amount of sunlight reaching the ground, and this granular layer is likely to stay in the atmosphere for weeks or even years (smoke and carbon black produced by burning petroleum and plastic products can absorb sunlight more effectively than smoke produced by burning wood). The mid-latitude westerly belt will transport smoke and dust, forming an annular belt in the northern hemisphere from 30 degrees to 60 degrees north latitude. These thick dark clouds can block out most of the sunlight for weeks. This will cause the surface temperature to drop during this period. Depending on the model, the temperature drop can reach tens of degrees Celsius at most.

This dark and deadly frost, combined with the high dose radiation of radioactive dust, will seriously damage plants in this part of the earth. Severe cold, high-dose radiation, large-scale destruction of industrial, medical and transportation facilities, coupled with the shortage of food and crops, will lead to famine, radiation and disease causing large-scale human deaths. Scientists also believe that nitrogen oxides produced by the explosion will destroy the ozone layer. Scientists observed this unexpected effect in the thermonuclear explosion experiment. This effect will be weakened by the regeneration of the ozone layer. But the impact of all-out nuclear war will undoubtedly be greater. The secondary effect of ozone depletion (and the subsequent increase of ultraviolet radiation) should be very significant, which will affect many major crops of human beings and destroy the marine food chain by killing plankton.

There are many scientists trying to predict the climate effects of large-scale nuclear war, the most famous of which is the research results of "TTAPS" group in 1983 (acronyms of five scientists: Richard Turko, Brian Thun, Thomas Ackerman, James Pollack and carl sagan). The TTAPS team was inspired by the cooling effect of sandstorms on Mars. They used a two-dimensional simplified model of the earth's atmosphere to calculate the nuclear winter effect, and found that a full-scale nuclear war may cause the temperature in inland areas to drop to MINUS 40 degrees Celsius. This research result was published in the journal Science at the end of 1983.

In recent years, a theory about the extinction of dinosaurs also holds that 65 million years ago, a small celestial body with a diameter of several tens of kilometers hit the earth, and the dust raised by this explosion covered the sky, resulting in a drop in temperature and the inability of plants to carry out photosynthesis, thus making the dominant species dinosaur at that time decline.

After the publication of TTAPS' research results, some scientists questioned it, including edward tylor, the father of American hydrogen bomb. Taylor and Sagan had an argument on this issue, and he thought that the influence of nuclear winter could be ignored. Other scientists believe that the cooling effect caused by large-scale nuclear war is not as serious as that shown by TTAPS team, so "nuclear winter" should be renamed "nuclear autumn".

Since then, scientists have used improved models to make more accurate calculations. 1990, TTAPS published another paper in the journal Science, reviewing the research since 1983. They believe that the new calculation shows that the temperature drop in the mid-latitude area of the northern hemisphere is about 10 to 20 degrees Celsius, which can be reduced by 35 degrees Celsius in some areas; Although this shows that the consequences of a total nuclear war may be lighter than what they predicted in 1983, a nuclear winter is still possible on the whole.

Since TTAPS published this paper in Science 1990, there is no more detailed research to further explore the possibility of nuclear winter. In the same year, Sagan and Teko, another member of TTAPS, published a book about the nuclear winter, entitled The Road No One Imagined: The Nuclear Winter and the End of the Arms Race.

199 1 year, the Soviet union disintegrated and the cold war period of confrontation between two superpowers ended, greatly reducing the possibility of total nuclear war. However, local nuclear conflicts may still occur. The climate impact of these nuclear wars still needs in-depth study.