While the absolute number of nuclear warheads fell from 22,600 to 15,850 between 2010 and 2015, according to Stockholm International Peace Research Institute's annual disarmament report, countries continue to upgrade and improve their nuclear weapons arsenals.
The institute pointed to “extensive and expensive long-term modernization programmes” in the world’s two largest nuclear powers, The United States and Russia, which account for 90 percent of the weapons.
“Despite renewed international interest in prioritizing nuclear disarmament, the modernization programs under way in the nuclear weapon-possessing states suggests that none of them will give up their nuclear arsenals in the foreseeable future,” SIPRI researcher Shannon Kile said.
The other three nuclear armed states legally recognized by the 1968 Nuclear Non- Proliferation Treaty - China (260 warheads), France (300 warheads) and Britain (215 warheads) - are “either developing or deploying new nuclear weapon systems or have announced their intention to do so” according to the researchers.
China was the lone state among the five global nuclear powers to have just a “modest” increase in the size of its arsenal.
India (90 to 100 warheads), Pakistan (100 to 120 warheads) and Israel (80 warheads), which do not have legally recognized nuclear programs, continue to increase their arsenals while Israel has tested long-range ballistic missiles.
North Korea is believed to be working on an arsenal of six to eight warheads but SIPRI said “technical progress” was difficult for the team to assess. Questions remain about the size of their nuclear devices, as weapons that are suitable for a missile must be small in size and weight, an added technical challenge.
Trustworthy information on each country's nuclear program varied greatly between states, with the United States getting top marks for transparency in the report, and Russia and Israel divulging nothing officially.