 The damage caused by international nuclear exchange is not necessarily limited to the participating countries, as the hypothesized rapid climate change associated with even small-scale regional nuclear war could threaten food production worldwide—a scenario known as nuclear famine.Despite a reduction in global nuclear tensions and major nuclear arms reductions after the end of the Cold War (in 1989), estimated nuclear warhead stockpiles total roughly 15,000 worldwide, with the United States and Russia holding 90% of the total.Though exact details on many nuclear close calls are hard to come by, the analysis of particular cases has highlighted the importance of a variety of factors in preventing accidents.