Expert scientists have revealed the devastating impact of nuclear war between Russia and the US in bombshell new research.
Predictions say that a global famine would be caused and around five billion people would be killed.
Lead author Professor Lili Xia, of Rutgers University in New Jersey, studied the disastrous consequences by using simulations.
He said: "The data tell us one thing. We must prevent a nuclear war from ever happening."
The prospect of nuclear war remains unlikely, but continued muscle-flexing from Russia and the likes of China and North Korea sets alarm bells ringing.
Russia is now set to give out to the likes of North Korea and Iran "the most modern types of weapons, from small arms to armoured vehicles and artillery to combat aviation and unmanned aerial vehicles," according to Vladimir Putin.
Nuclear weapons were not specified, but the strengthening of the military capabilities of rogue states does little to calm people in Washington DC, London and the rest of the West.
Research said in the event of nuclear war, firestorms would be so severe they would block out the sun and result in global crop failure.
Calculations were based on the size of Russia's and the US' nuclear arsenals.
Nine countries have a total of 13,000 nuclear weapons and the research comes amid increasing tensions between the US and Russia over the Ukraine war.
Other scenarios were based on a possible war between India and Pakistan, who have a combined warhead total of just under 300 each according to some estimates.
Prof Xia said: "Future work will bring even more granularity to the crop models.
"For instance, the ozone layer would be destroyed by the heating of the stratosphere, producing more ultraviolet radiation at the surface, and we need to understand that impact on food supplies."
Climate scientists at Colorado University are creating detailed soot models for specific cities - such as Washington DC.
Inventories of every building will provide a more accurate picture of how much smoke would be produced.
Co-author Prof Alan Robock, also from Rutgers, said researchers already have more than enough information to know a nuclear war of any size would obliterate global food systems - killing billions of people in the process.
He said: "If nuclear weapons exist, they can be used, and the world has come close to nuclear war several times.
"Banning nuclear weapons is the only long-term solution.
"The five-year-old UN Treaty on the Prohibition of Nuclear Weapons has been ratified by 66 nations, but none of the nine nuclear states.
"Our work makes clear that it is time for those nine states to listen to science and the rest of the world and sign this treaty."
