Nuclear weapons are a menace to everyone, wherever they live on the planet.
… The scenario predicts that the huge fires caused by nuclear explosions (particularly from burning urban areas) would lift massive amounts of dark smoke and aerosol particles from the fires into the upper troposphere/ stratosphere. At 10-15 kilometers (6–9 miles) above the Earth’s surface, the absorption of sunlight would further heat the smoke, lifting it into the stratosphere where the smoke would persist for years, with no rain to wash it out. This would block out much of the sun’s light from reaching the surface, causing surface temperatures to drop drastically.
As much as five million tons of soot could be released, which could produce a cooling of several degrees over large areas of North America and Eurasia, including most of the grain-growing regions. The cooling would last for years and could be “catastrophic” according to researchers.
Another global threat comes from the immediate pulse of ionising radiation from a nuclear explosion and the longer-term radio-active fallout
In 1996 Judge Bedjaoui told the International court of justice:
… nuclear weapons are explosive devices whose energy results from the fusion or fission of the atom. By its very nature, that process, in nuclear weapons as they exist today, releases not only immense quantities of heat and energy, but also powerful and prolonged radiation. … the phenomenon of radiation is said to be peculiar to nuclear weapons. These characteristics render the nuclear weapon potentially catastrophic. The destructive power of nuclear weapons cannot be contained in either space or time. They have the potential to destroy all civilization and the entire ecosystem of the planet.
The radiation released by a nuclear explosion would affect health, agriculture, natural resources and demography over a very wide area. Further, the use of nuclear weapons would be a serious danger to future generations. Ionizing radiation has the potential to damage the future environment, food and marine ecosystem, and to cause genetic defects and illness in future generations.
It is because radiation is a unique feature of nuclear weapons, coupled with ever-changing weather conditions make their effects quite unpredictable that no one could ever even begin to assess the legality of the use on any particular occasion.