Nuclear Winter and City Firestorms

Robin Hanson at Overcoming Bias looks at nuclear winter again

Robin looks at the Scientific American article that attempts to make the case that a regional nuclear war in India and Pakistan would be sufficient to trigger a nuclear winter

Nuclear bombs dropped on cities and industrial areas in a fight between India and Pakistan would start firestorms that would put massive amounts of smoke into the upper atmosphere.

The nuclear winter case is predicated on getting 150 million tons (150 teragram case) of soot, smoke into the stratosphere and having it stay there The assumption seems to be that the cities will be targeted and the cities will burn in massive firestorms.

The burning characteristics of forest fires may not be a perfect analog for cities, but firestorms with injection of smoke into the upper atmosphere were observed in previous cases of burning cities, after the earthquake-induced fire in San Francisco in 1906 [London, 1906] and the firebombing of Dresden in 1945 [Vonnegut, 1969].

Note: The pro-nuclear winter need to mention this because there have been massive forest fires that have not produced the claimed effects.

The Steps needed to prove nuclear winter:
1. Prove that enough cities will have firestorms (the claim here is that does not happen)
2. Prove that when enough cities in a sufficient area have firestorms that enough smoke and soot gets into the stratosphere (trouble with this claim because of the Kuwait fires)
3. Prove that condition persists and effects climate as per models (others have questioned that but this issue is not addressed here

Nuclear war is definitely to be avoided but we can be precise about effects for proper planning, policy and civil defence.

Nextbigfuture has looked at Nuclear war effects before.

Here we look at some more information on city firestorms.

This Glasstone Blogpost with a lot of links to the effect of fires and thermal radiation Basically there would need to be an analysis of the building density and composition and loading in cities in Pakistan and India. Plus there would need to be an analysis of likely war targeting. Would it be cities or military installations ? After the discussion of firestorm pre-requisitites, I look at the composition of cities in India and Pakistan and do not see a correlation for a firestorm.

If there are not multiple citywide firestorms then there is no trigger for nuclear winter even if the later modeling (which is still uncertain) would even need to be considered. It also shows that civil defense that reduces the likelihood of fires and firestorms is relevant and useful.

Firestorms have always required at least 50% of buildings to be ignited. A 71 pages long report by Robert M. Rodden, Floyd I. John, and Richard Laurino, Exploratory Analysis of Fire Storms, Stanford Research Institute, California, report AD616638, May 1965, identified the following parameters required by all firestorms:

(1) More than 8 pounds of fuel per square foot (40 kg per square metre) of ground area. Hence firestorms occurred in wooden buildings, like Hiroshima or the medieval part of Hamburg. The combustible fuel load in London is just 24 kg/m2, whereas in the firestorm area of Hamburg in 1943 it was 156 kg/m2. The real reason for all the historical fire conflagrations was only exposed in 1989 by the analysis of L. E. Frost and E.L. Jones, ‘The Fire Gap and the Greater Durability of Nineteenth-Century Cities’ (Planning Perspectives, vol.4, pp. 333-47). Each medieval city was built cheaply from inflammable ‘tinderbox’ wooden houses, using trees from the surrounding countryside. By 1800, Britain had cut down most of its forests to build wood houses and to burn for heating, so the price of wood rapidly increased (due to the expense of transporting trees long distances), until it finally exceeded the originally higher price of brick and stone; so from then on all new buildings were built of brick when wooden ones decayed. This rapidly reduced the fire risk. Also, in 1932, British Standard 476 was issued, which specified the fire resistance of building materials. In addition, new cities were built with wider streets and rubbish disposal to prevent tinder accumulation in alleys, which created more effective fire breaks.

(2) More than 50% of structures ignited initially.

(3) Initial surface winds of less than 8 miles per hour.

(4) Initial ignition area exceeding 0.5 square mile.

The fuel loading per unit ground area is equal to fuel loading per unit area of a building, multiplied by the builtupness fraction of the area. E.g., Hamburg had a 45% builtupness (45% of the ground area was actually covered by buildings), and the buildings were multistorey medieval wooden constructions containing 70 pounds of fuel per square foot. Hence, in Hamburg the fuel loading of ground area was 0.45*70 = 32 pounds per square foot, which was enough for a firestorm.

By contrast, modern cities have a builtupness of only 10-25% in most residential areas and 40% in commercial and downtown areas. Modern wooden American houses have a fuel loading of 20 pounds per square foot of building area with a builtupness below 25%, so the fuel loading per square foot of ground is below 20*0.25 = 5 pounds per square foot, and would not produce a firestorm. Brick and concrete buildings contain on the average about 3.5 pounds per square foot of floor area, so they can’t produce firestorms either, even if they are all ignited

Theodore Poston in his ignorant paper ‘Possible Fatalities from Superfires following Nuclear Attacks in or Near Urban Areas’, in the 1986 U.S. National Academy of Sciences book The Medical Implications of Nuclear War, assumes falsely that brick and concrete cities can burn like the small areas of medieval German cities and like Brode and Small, he simply ignores the mechanism for the firestorm in Hiroshima which had nothing to do with thermal radiation but was just due to overturned breakfast charcoal braziers. Theodore Poston also falsely complains that wooden houses exposed to nuclear tests didn’t burn because they had white paint on them and shutters over the windows. That discredits Theodore Poston’s whole anti-civil defence
countermeasure tirade by actually PROVING the value of simple civil defense; but actually if you open your eyes, you find that most wooden houses are painted white, and in a real city – unlike the empty Nevada desert – few windows will have a line of sight to the fireball anyway.

The Material of the Houses in India and Pakistan do not Appear to be Right for Firestorms

India Housing census of 2001

Material of Roofs in India

Concrete 19.8%
Tiles 32.6%
Grass, thatch,bamboo, wood, mud 21.9%
Other 25.7%

Material of Walls in India

Burnt Brick 43.7%
Mud, Unburnt Brick 32.2%
Grass, thatch, bamboo, Wood, etc. 10.2%
Other 13.9%

Material Used in Houses in India : Floors

Mosaic, Floor tiles 7.3%
Cement 26.5%
Mud 57.1%
Other 9.1%

Kerosene was used in 43% of homes for lighting. Kerosene is flammable but how much kersone per home ? How much more electrification has occurred.

Fuel was used for cooking. However, natural gas is often used in developed countries. So the cooking fuel would burn but how much per house ?

Pakistan also has a lot of mud and brick homes

Kuwait Oil Fires

The Kuwaiti oil fires were a result of the scorched earth policy of
Iraqi military forces retreating from Kuwait in 1991 after conquering
the country but being driven out by Coalition military forces ….
during the Persian Gulf War, the First Gulf War,or often as the Second Gulf War and by Iraqi leader Saddam Hussein as The Mother of all Battles, or commonly as Desert Storm, for the military response… showed the effects of vast emissions of particulate matter into the atmosphere in a geographically limited area; directly underneath the smoke plume constrained model calculations suggested that daytime temperature may have dropped by ~10°C within ~200 km of the source.

Carl Sagan of the TTAPS study warned in January 1991 that so much smoke from the fires “might get so high as to disrupt agriculture in much of South Asia….” Sagan later conceded in his book The Demon-Haunted World: Science as a Candle in the Dark is a book by astrophysicist Carl Sagan, which was first published in 1995.The book is intended to explain the scientific method to laypeople, and to encourage people to learn critical or skeptical thinking…that this prediction did not turn out to be correct: “it was pitch black at noon and temperatures dropped 4°-6°C over the Persian Gulf, but not much smoke reached stratospheric altitudes and Asia was spared.”

The 2007 study discussed above noted that modern computer models have been applied to the Kuwait oil fires, finding that individual smoke plumes are not able to loft smoke into the stratosphere, but that smoke from fires covering a large area, like some forest fires or the burning of cities that would be expected to follow a nuclear strike, would loft significant amounts of smoke into the stratosphere

Older Analysis

Nuclear winter reappraised (1986 Foreign Affairs)

Nuclear war survival skills book from 1987

° Myth: Because some modern H-bombs are over 1000 times as powerful as the A-bomb that destroyed most of Hiroshima, these H-bombs are 1000 times as deadly and destructive.

° Facts: A nuclear weapon 1000 times as powerful as the one that blasted Hiroshima, if exploded under comparable conditions, produces equally serious blast damage to wood-frame houses over an area up to about 130 times as large, not 1000 times as large.

° Myth: A Russian nuclear attack on the United States would completely destroy all American cities.

° Facts: As long as Soviet leaders are rational they will continue to give first priority to knocking out our weapons and other military assets that can damage Russia and kill Russians. To explode enough nuclear weapons of any size to completely destroy American cities would be an irrational waste of warheads. The Soviets can make much better use of most of the warheads that would be required to completely destroy American cities; the majority of those warheads probably already are targeted to knock out our retaliatory missiles by being surface burst or near-surface burst on their hardened silos, located far from most cities and densely populated areas.

Unfortunately, many militarily significant targets – including naval vessels in port and port facilities, bombers and fighters on the ground, air base and airport facilities that can be used by bombers, Army installations, and key defense factories – are in or close to American cities. In the event of an all-out Soviet attack, most of these ‘”soft” targets would be destroyed by air bursts. Air bursting (see Fig. 1.4) a given weapon subjects about twice as large an area to blast effects severe enough to destroy “soft” targets as does surface bursting (see Fig. 1.1) the same weapon. Fortunately for Americans living outside blast and fire areas, air bursts produce only very tiny particles. Most of these extremely small radioactive particles remain airborne for so long that their radioactive decay and wide dispersal before reaching the ground make them much less life- endangering than the promptly deposited larger fallout particles from surface and near-surface bursts. However, if you are a survival minded American you should prepare to survive heavy fallout wherever you are. Unpredictable winds may bring fallout from unexpected directions. Or your area may be in a “hot spot” of life-endangering fallout caused by a rain-out or snow-out of both small and tiny particles from distant explosions. Or the enemy may use surface or near-surface bursts in your part of the country to crater long runways or otherwise disrupt U.S. retaliatory actions by producing heavy local fallout.

Today few if any of Russia’s largest intercontinental ballistic missiles (ICBMs) are armed with a 20-megaton warhead. A huge Russian ICBM, the SS-18, typically carries 10 warheads each having a yield of 500 kilotons, each programmed to hit a separate target. See “Jane’s Weapon Systems. 1987-1988.” However, in March 1990 CIA Director William Webster told the U.S. Senate Armed Services Committee that “…. The USSR’s strategic modernization program continues unabated,” and that the SS-18 Mod 5 can carry 14 to 20 nuclear warheads. The warheads are generally assumed to be smaller than those of the older SS-18s.

° Myth: A heavy nuclear attack would set practically everything on fire, causing “firestorms” in cities that would exhaust the oxygen in the air. All shelter occupants would be killed by the intense heat.

° Facts: On aclear day, thermal pulses (heat radiation that travels at the speed of light) from an air burst can set fire to easily ignitable materials (such as window curtains, upholstery, dry newspaper, and dry grass) over about as large an area as is damaged by the blast. It can cause second-degree skin burns to exposed people who are as far as ten miles from a one-megaton (1 MT) explosion. (See Fig. 1.4.) (A 1-MT nuclear explosion is one that produces the same amount of energy as does one million tons of TNT.) If the weather is very clear and dry, the area of fire danger could be considerably larger. On a cloudy or smoggy day, however, particles in the air would absorb and scatter much of the heat radiation, and the area endangered by heat radiation from the fireball would be less than the area of severe blast damage.

“Firestorms” could occur only when the concentration of combustible structures is very high, as in the very dense centers of a few old American cities. At rural and suburban building densities, most people in earth- covered fallout shelters would not have their lives endangered by fires.



A fire storm is characterized by strong to gale force winds blowing toward the fire everywhere around the fire perimeter and results from the rising column of hot gases over an intense, mass fire drawing in the cool air from the periphery. These winds blow the fire brands into the burning area and tend to cool the unignited fuel outside so that ignition by radiated heat is more difficult, thus limiting fire spread. The conditions which give rise to a fire storm appear to be low natural wind velocity, flat terrain and a uniform distribution of high-surface density, highly combustible fuels which burn rapidly, coalescing individual fires into one burning mass within the fire perimeter.

Such fire storms have been observed in forest fires and were frequently experienced in the mass incendiary air raids in Europe and Japan during World War II. In fact, such fire storms were the most frequent type observed in Japan during mass raids.P )It was typical in such cases that the fire was mainly confined to the areas initially seeded with incendiary bombs but within these areas fire destruction was virtually complete. In Hiroshima, hundreds of fires were burning throughout the area ultimately burned over within ten minutes after the bomb exploded. Each of these spread rapidly to adjacent structures during the first half hour, by which time the fire storm was well developed. Practically all fire spread had ceased after two hours at which time the fire storm was approaching its peak intensity, with centrally directed winds of 30-40 mi/hr.

In Nagasaki, in spite of the similar yield, altitude of burst and weather conditions, a fire storm did not develop, probably because of the uneven terrain, the irregular layout of the city and the location of ground zero. In a long relatively narrow river valley north of the center of the city. Here, such spread of the fire beyond the area of initial IcItioon as vas observed, was to the southeast against the wind direction at the time of the explosion. Because the rate of spread was slower, the fire burned longer. Here also, the combination of terrain, city layout, position of ground zero and wind direction limited the spread of fire primarily areas seriously damaged by blast.

Civil defense document from 1973 (74 pages)

India’s nuclear arsenal

Though India has not made any official statements about the size of it nuclear arsenal, the NRDC estimates that India has a stockpile of approximately 30-35 nuclear warheads and claims that India is producing additional nuclear materials. Joseph Cirincione at the Carnegie Endowment for International Peace estimates that India has produced enough weapons-grade plutonium for 50-90 nuclear weapons and a smaller but unknown quantity of weapons-grade uranium. Weapons-grade plutonium production takes place at the Bhabha Atomic Research Center, which is home to the Cirus reactor acquired from Canada, to the indigenous Dhruva reactor, and to a plutonium separation facility.

Shakti 1 claimed yield 43-60 kiloton, yield reported 12-25 kiloton
Shakti 2 Fission device, claimed yield 12 kiloton

Wikipedia lists the current indian nuclear weapons as 40-80 bombs

Pakistan has weapons of comparable yield

boosted device 1998 claimed 25-36 kiloton, reported 9-12 kiloton

Wikipedia indicates that Pakistan has 70-90 nuclear weapons From these tests Pakistan can be estimated to have developed operational warheads of 20 to 25kt and 150kt in the shape of low weight compact designs and may have 300–500kt large-size warheads

Analysts assume Pakistan could have developed operational ‘tactical’ warheads of 20 to 25 kt and 150 kilotons as well as heavy warheads with a yield of 300–500 kt. The low-yield weapons are probably designed to be carried by fighter bombers, such as Pakistan’s F-16 Fighting Falcon or French Mirage 5 aircraft. Furthermore, these warheads are presumably fitted to Pakistan’s short-range ballistic missiles. The higher-yield warheads are probably fitted to the Shaheen and Ghauri ballistic missiles.

Indian and Pakistan nuclear weapons appear to be mostly in the 20-25 kiloton range with a few larger ones. If Pakistan has a few larger nuclear weapons in the 150-500kt range then India probably does as well.

Nuclear proliferation analysis report from 2001


Simple and affordable defences against nuclear bombs and hurricanes

Further improvement of buildings for more resistance to nuclear bomb effects

Not included was white paint helps to reduce thermal effects. Reflects heat away.

Re-inventing civil defense with zero soft targets