The total number of nuclear weapons is estimated over 15,349 (early-2016). Being that Russia and U.S. are under hair-trigger alert, even today, makes nuclear war risk still high among the serious problems in modern world, that could endanger the survival of mankind.
The estimates seem to indicate that a major war would result in over a 10-year old nuclear winter, making most of mankind starve to death, and even a limited war with 50 "small" (15 kt) detonations (e.g., a war between India and Pakistan) over cities would cause global temperatures plunge below the lowest in the last 1000 years, and have effects on ozone layer, too.
In the FLI/nuclear section, there is a statement: “we should take our nuclear weapons off hair-trigger alert” because “keeping nuclear weapons ready to launch on a moment’s notice is a dangerous relic of the Cold War. Such policies increase the risk of catastrophic accidents or miscalculation.”
Please, write ideas of what needs to be done to reduce the risk of nuclear wars, and prevent them from ever happening.