Nuclear Darkness

Deadly global climate change from nuclear war

Nuclear war would devastate the environment, climate,  ecosystems and inhabitants of Earth.

A "regional" nuclear war, fought between emerging nuclear weapon states with relatively primitive nuclear weapons, would create a Nuclear Haze which would quickly lead to deadly global climate change. A large nuclear war, fought with thousands of modern thermonuclear weapons, would create either Nuclear Twilight or Nuclear Darkness.  Extreme Ice Age weather conditions would result, and would trigger a mass extinction event that would extinguish most complex forms of life on Earth, including human life.

The darkness and global cooling predicted to result from nuclear war (along with massive radioactive fallout, pyrotoxins, and ozone depletion) was first described in 1983 as "nuclear winter".  These initial studies estimated the smoke from nuclear firestorms would stay in the stratosphere for about a year. However in 2006, researchers using modern computer models found the smoke would form a global stratospheric smoke layer that would last for ten years.

 The longevity of such a smoke layer would allow much smaller quantities of smoke than first predicted in the 1980’s to have a great impact upon both global climate and atmospheric ozone which blocks ultraviolet (UV) light. Thus scientists predict that even a "regional" nuclear conflict could produce enough smoke to significantly cool average global surface temperatures, reduce precipitation, and vastly increase the amount of dangerous UV light reaching the surface of Earth.

A nuclear war fought between India and Pakistan would produce enough smoke to make the blue skies of Earth appear grey. Although the amount of sunlight blocked by this Nuclear Haze would not produce the profound darkening of the Earth predicted in a nuclear winter (after a nuclear war fought with thousands of strategic nuclear weapons), the deadly climate change created by a regional conflict would likely have devastating global effects upon all human populations, through its shortening of growing seasons and corresponding negative effects upon global agriculture.

In 2006, U.S. researchers used a NASA computer model (Model 1E, also used for the Intergovernmental Panel on Climate Change) to evaluate the effects of a regional nuclear war fought in the sub-tropics.  50 Hiroshima-size nuclear weapons (15 kilotons per weapon) were detonated in the largest cities of each combatant nation (100 total detonations).

The studies predicted the nuclear explosions would kill 20 million people in the war zone, the equivalent to half of all the people who died during World War II. The conflict would also significantly disrupt global climate. Up to 5 million tons of smoke from burning cities would quickly rise above cloud level into the stratosphere, and within 2 weeks would form a global stratospheric smoke layer which would remain in place for about 10 years.

The computer models estimated this smoke layer would block 7–10% of warming sunlight from reaching the surface of the Earth. Average surface temperatures beneath the smoke would become colder than any experienced during the last 1000 years. There would be a corresponding shortening of growing seasons by up to 30 days and significant reductions in average rainfall in many areas, with a 40% decrease of precipitation in the Asian monsoon region.

Such rapid and drastic climate change would have major impacts on global grain reserves, which already are at 50 year lows.  Grain exports would likely cease for several years from large exporting nations like Canada.  The 700 million people now living on the edge of starvation, along with those populations heavily dependent upon grain imports, would face mass starvation as grain reserves disappeared, prices skyrocketed and hoarding occurred. Global nuclear famine is the predicted result of this scenario. As many as one billion people could die during the years subsequent to the deadly climate change created by this level of nuclear conflict.

A stratospheric smoke layer would also cause massive destruction of the protective ozone layer. Studies in 2008 predicted smoke from a regional nuclear conflict (as described above) would create ozone losses of 25-45% above mid latitudes, and 50-70% above northern high latitudes persisting for 5 years, with substantial losses continuing for 5 additional years. Severe ozone depletion would allow intense levels of harmful ultraviolet light (UV-B) to reach the surface of the Earth – even with the stratospheric smoke layer in place.

Global stratospheric ozone levels would fall to near those now seen only over Antarctica during the formation of the "ozone hole". The UV index in the mid-latitudes would increase by 42–108%, which would cause fair skinned people to suffer sunburn in as little as 7 minutes. In the high northerly latitudes, the UV index would increase by 130–290%, shortening the time required for fair skinned people to sunburn from 32–43 minutes to 8–19 minutes.

Massive increases of UV-B light would clearly have negative impacts upon marine and terrestrial ecosystems, yet no research has been done to investigate the consequences of such a scenario. Likewise, no studies using modern climate models have yet been done to assess ozone depletion following larger nuclear conflicts fought with high-yield strategic nuclear weapons.

The United States and Russia have more than 7000 operational high-yield nuclear weapons which are ready for immediate use. These weapons have a combined explosive power 500 to 1000 times greater than the explosive power contained within 100 Hiroshima-size weapons. Virtually all their land-based intercontinental ballistic missiles are operating under the policy of Launch-On-Warning.

In 2008, scientists predicted the detonation of 4400 strategic nuclear weapons in large cities could cause 770 million prompt fatalities and produce up to 180 million tons of thick, black smoke. Ten days after detonation, the smoke would form a dense global stratospheric smoke layer which would block about 70% of warming sunlight from reaching the surface of the Northern Hemisphere and 35% of sunlight from reaching the Southern Hemisphere.

The resulting nuclear darkness would cause rapid cooling of more than 20º C (36º F) over large areas of North America and of more than 30º C (54º F) over much of Eurasia. Daily minimum temperatures would fall below freezing in the largest agricultural areas of the Northern Hemisphere for a period of between one to three years.  Average global surface temperatures would become colder than those experienced 18,000 years ago at the height of the last Ice Age.

The cooling of the Earth’s surface would weaken the global hydrological cycle and the Northern Hemisphere summer monsoon circulations would collapse because the temperature differences that drive them would not develop. As a result, average global precipitation is predicted to decrease by 45%.

The cumulative effects of deadly climate change and ozone destruction would eliminate growing seasons for more than a decade. Catastrophic climatic effects lasting for many years would occur in regions far removed from the target areas or the countries involved in the conflict.  Under such conditions, it is likely that most humans and large animal populations would die of starvation.

Nuclear arsenals must be eliminated, because if they are left intact, they will eventually be used. Nuclear weapons must be outlawed, dismantled and abolished. A draft treaty, or Model Nuclear Weapons Convention, has been prepared by civil society organizations and submitted to the United Nations.  Nuclear weapon states are obligated (under the terms of the Nuclear Non-Proliferation Treaty) to negotiate in good faith to achieve such a treaty to eliminate their nuclear arsenals.

For other online versions of this article,

see (the website of the Nuclear Peace Age Foundation)

the Strategic Arms Reduction website of the Moscow Institute of Physics and Technology Center for Arms Control, Energy and Environmental Studies at