As Derek Johnson, chief executive of the anti-nuclear group Global Zero, tweeted, “You won’t see the mushroom clouds, but you can look forward to years of climate disruption, drought, famine, and death.”

The estimates were based on the possibility that India could use 100 weapons and Pakistan could use 150; by 2025, the researchers expect the two countries to have between 400 to 500 nuclear weapons combined.

The prediction that nuclear war could kill 125 million people immediately could be applied to any region or country with densely-population urban areas.

PSR noted that the research was released months after U.S. President Donald Trump announced the development of a new so-called “low-yield” nuclear weapon.

“Not to be overlooked, at this moment, the United States wants to deploy so-called ‘low-yield’ nuclear weapons, which are touted as ‘more usable,'” PSR Iowa coordinator Maureen McCue said in a statement. “The world cannot afford the impacts on public health, the environment and our climate that would result from any use of nuclear weapons. They must be eliminated before they eliminate us.”

Warning that “the world can’t afford to ignore the disturbing findings of the study,” the group urged policymakers to work to end nuclear proliferation in the U.S. and elsewhere to avoid catastrophic, long-lasting damage.

“Nuclear weapons make us less, not more, safe, and as this study highlights, nuclear war poses one of the gravest threats to human health and survival,” said Jeff Carter, executive director of PSR. “Given the current climate of withdrawal from vital international arms agreements, increased tensions that heighten the risk of nuclear conflict, and the escalation of a new nuclear arms race, there is no better time for the UnitedStates to assert leadership among its fellow nuclear-armed states by establishing an official policy never to use nuclear weapons first and prohibit funding for so-called ‘low-yield’ nuclear weapons.”