Nuclear winter
From Wikipedia, the free encyclopedia
Nuclear winter (also known as
atomic winter) is a hypothetical
climatic effect, most often considered a potential threat following a
countervalue, or city-targeted,
nuclear war.
Climate models suggest that the ignition of 100
firestorms that are comparable in intensity to that observed in
Hiroshima in 1945 would produce a small nuclear winter.
[1] The burning of these firestorms would result in the injection of
soot into the
Earth's
stratosphere, producing an
anti-greenhouse effect, that lowers the
Earth's surface temperature.
With the models concluding that the size of this effect, from the
cumulative products of 100 of these firestorms, would unmistakably cool
the
global climate by approximately 1 °C for two to three years; with which the authors speculate, but do not model, would have
global agricultural losses as a consequence.
[2]
Whereas a much larger number of firestorms,
[quantify] which are assumed to be the result of any city-targeted, US-Russia
total war,
is modeled to cause a much deeper nuclear winter, with catastrophic
summer cooling by about 20 °C in core agricultural regions of the US,
Europe and China, and by as much as 35 °C in Russia.
[3][unreliable source?]
On the fundamental level, it is known that firestorms can inject sooty
smoke into the stratosphere, as each natural occurrence of a
wildfire
firestorm has been found to "surprisingly frequently" produce minor
nuclear winter effects, with short-lived drops in surface temperatures,
confined to the global
hemisphere that they burned in.
[4][5][6][7] This is somewhat analogous to the frequent
volcanic eruptions that inject sulfates into the stratosphere and thereby produce minor
volcanic winter effects.
A suite of satellite- and aircraft-based firestorm-soot-monitoring
instruments are at the forefront of attempts to accurately determine the
lifespan, quantity, injection height, and
optical properties of this smoke.
[8][9][10][11][12]
Information regarding all of these properties is necessary to truly
ascertain the length and depth of the cooling effect of firestorms,
independent of the nuclear winter computer model projections.
Presently, from satellite tracking data, stratospheric smoke aerosols are removed in a time span under approximately two months,
[10] and the existence of any hint of a
tipping point into a new stratospheric condition where the aerosols would not be removed within this timeframe, remains to be determined.
[10]
Mechanism
Picture of a
pyrocumulonimbus cloud
taken from a commercial airliner cruising at about 10 km. In 2002
various sensing instruments detected 17 distinct pyrocumulonimbus cloud
events in North America alone.
[5]
The nuclear winter scenario assumes that 100 or more city
firestorms[13][14] are ignited by the
nuclear explosions of a
nuclear war,
[15] and the firestorms lift large enough amounts of
sooty smoke into the upper
troposphere and lower
stratosphere, soot lifted by the movement offered by the
pyrocumulonimbus clouds
that form during a firestorm. At 10–15 kilometres (6–9 miles) above the
Earth's surface, the absorption of sunlight could further heat the soot
in the smoke, lifting some or all of it into the stratosphere, where
the smoke could persist for years, if there is no rain to wash it out.
This
aerosol of particles could heat the stratosphere and block out a portion of the
sun's light from reaching the surface,
causing surface temperatures to drop drastically, and with that, it is
predicted surface air temperatures would be akin to, or colder than, a
given region's
winter for months to years on end.
The modeled stable
inversion layer of hot soot between the troposphere and high stratosphere that produces the
anti-greenhouse effect was dubbed the "Smokeosphere" by
Stephen Schneider et al. in their 1988 paper.
[16][17][18]
Although it is common in the climate models for the city firestorms
to be ignited by nuclear explosions, they need not be ignited by nuclear
devices;
[19]
more conventional ignition sources can instead be the spark of the
firestorms. As prior to the previously mentioned solar heating effect,
the soot's injection height is controlled by the
rate of energy release from the firestorm's fuel, not the size, or lack thereof, of an initial nuclear explosion.
[14] For example, the
mushroom cloud from the
bomb dropped on Hiroshima reached a height of six kilometers (
middle
troposphere) within a few minutes and then dissipated due to winds,
while the individual fires within the city took almost three hours to
form into a firestorm and produce a "
pyrocumulus" cloud, a cloud that is assumed to have reached
upper
tropospheric heights, as over its multiple hours of burning, the
firestorm released an estimated 1000 times the energy of the bomb.
[20]
While the
firestorm of Dresden and Hiroshima and the
mass fires of Tokyo and
Nagasaki occurred with mere months separating them in 1945, the more intense and
conventionally lit Hamburg firestorm
occurred in 1943. Despite this, these five fires potentially placed
five percent as much smoke into the stratosphere as the hypothetical 100
nuclear-ignited fires of modern models.
[21] While it is believed that the effects of the mass of soot emitted by 100 firestorms (one to five
teragrams)
would have been detectable with technical instruments in WWII, only
five percent of that would not have been possible to observe at that
time.
[21]
Aerosol removal timescale
The exact timescale for how long this
smoke
remains, and thus how severely this smoke affects the climate once it
reaches the stratosphere, is dependent on both chemical and physical
removal processes.
The most important physical removal mechanism is "rainout", both during the "fire-driven
convective column" phase—which produces "
black rain" near the fire site—and rainout after the convective
plume's dispersal, where the smoke is no longer concentrated and thus "wet removal" is believed to be "very efficient."
[22]
However these efficient removal mechanisms in the troposphere are
avoided in the Robock 2007 study, where solar heating is modeled to
quickly "loft" the soot into the stratosphere, "detraining" or
separating the darker soot particles from the fire clouds' whiter
water condensation.
[23]
Once in the stratosphere, the
physical removal mechanisms having an impact on the timescale of the soot particles' residence are how quickly the aerosol of soot
coagulates with other particles,
[24][25] and falls out of the atmosphere via gravity-driven
dry deposition,
[25] and, to a slower degree, the time it takes for solar
radiation pressure to force the particles to a lower level in the atmosphere.
[citation needed] Whether by coagulation or radiation pressure, once the
aerosol of smoke particles are at this lower atmospheric level,
cloud seeding can begin, permitting
precipitation to wash the smoke aerosol out of the atmosphere by the
wet deposition mechanism.
The
chemical processes that affect the removal are dependent on the ability of
atmospheric chemistry to
oxidize the
carbonaceous component of the smoke, via reactions with oxidative species such as
ozone and
nitrogen oxides, both of which are found at all levels of the atmosphere,
[26][27] and which also occur at greater concentrations when air is heated to high temperatures, which will be discussed later.
Historical data on residence times of aerosols, albeit a
different mixture of aerosols, in this case
stratospheric sulfur aerosols and
volcanic ash from
megavolcano eruptions, appear to be in the one-to-two-year time scale.
[28]
The satellite tracking of wildfire smoke aerosols from the 17 North
American pyrocumulonimbus-cloud-injection events in 2002, indicates that
the aerosols are removed in a time span under approximately two months,
[10] although the exact mechanisms by which they are removed, and the existence of any hint of a
tipping point
into a new stratospheric condition were the aerosols would not be
removed within this timeframe, remains to be experimentally determined.
[10]
Aerosol–atmosphere interactions are still poorly understood.
[29][30]
Soot properties
Sooty aerosols can have a wide range of properties, as well as
complex shapes, making it difficult to determine their evolving
atmospheric
Optical depth
value. The conditions present during the creation of the soot are
believed to be considerably important as to their final properties, with
soot generated on the more efficient spectrum of
burning efficiency considered almost "elemental
carbon black," while on the more inefficient end of the burning spectrum, greater quantities of
partially burnt/oxidized fuel are present. These partially burnt "
organics"
as they are known, often form "tar balls" and "brown carbon" during
common lower-intensity wildfires, and can also coat the purer carbon
black particles.
[31][32][33] However, as the soot of greatest importance is that which is injected to the highest altitudes by the pyroconvection of the
firestorm—a
fire being fed with storm-force winds of air—it is estimated that the
majority of the soot under these conditions is of the more oxidized
carbon black nature.
[34]
Consequences
Diagram obtained by the
CIA from the
international seminar on nuclear war in Italy 1984. It depicts the findings of
Soviet
3-D computer model research on nuclear winter from 1983, and although
containing similar errors as earlier Western models, it was the first
3-D model of nuclear winter. (The three dimensions in the model are
longitude, latitude and altitude.)
[35]
The diagram shows the models predictions of global temperature changes
after a global nuclear exchange. Top shows effects after 40 days, bottom
after 243 days. A co-author was nuclear winter pioneer
Vladimir Alexandrov.
[36][37]
Climatic effects
A study presented at the annual meeting of the
American Geophysical Union
in December 2006 found that even a small-scale, regional nuclear war
could disrupt the global climate for a decade or more. In a regional
nuclear conflict scenario where two opposing nations in the
subtropics would each use 50
Hiroshima-sized
nuclear weapons (about 15 kiloton each) on major populated centres, the
researchers estimated as much as five million tons of soot would be
released, which would produce a cooling of several degrees over large
areas of
North America and
Eurasia,
including most of the grain-growing regions. The cooling would last for
years, and according to the research could be "catastrophic".
[38][39]
Ozone depletion
A 2008 study by Michael J. Mills and coauthors, published in the
Proceedings of the National Academy of Science,
found that a nuclear weapons exchange between Pakistan and India using
their current arsenals could create a near-global ozone hole, triggering
human health problems and causing environmental damage for at least a
decade.
[40]
The computer-modeling study looked at a nuclear war between the two
countries involving 50 Hiroshima-sized nuclear devices on each side,
producing massive urban fires and lofting as much as five million metric
tons of soot about 50 miles (80 km) into the mesosphere. The soot would
absorb enough solar radiation to heat surrounding gases, accelerating
catalytic cycles that destroy the stratospheric ozone layer protecting
Earth from harmful ultraviolet radiation.
Nuclear summer
A "nuclear summer" is a hypothesized scenario in which, after a
nuclear winter has abated, a greenhouse effect then occurs due to CO
2 released by combustion and methane released from the
decay of the organic matter that froze during the nuclear winter.
[41][42] It is supported scientifically far less, than nuclear winter, as a risk.
History
Early work
In 1952, a few weeks prior to the
Ivy Mike(10.4
megaton) test on
Elugelab
island, there was a concern that the "small particles"/aerosols lifted
by the explosion might cool the Earth. Major Norair Lulejian,
USAF, and astronomer Natarajan Visvanathan, studied this possibility reporting their findings in
Effects of Superweapons Upon the Climate of the World. According to a document by the
Defense Threat Reduction Agency,
this report was the initial study of the "nuclear winter" concept that
was popularized by others decades later. It indicated no appreciable
chance of explosion-induced climate change.
[46]
Following numerous
surface bursts of high yield "
Hydrogen bomb" explosions on
Pacific Proving Ground islands such as those of
Ivy Mike in the year 1952 and
Castle Bravo(15 megaton) in 1954,
The Effects of Nuclear Weapons by
Samuel Glasstone
was published in 1957 which contained a section entitled "Nuclear Bombs
and the Weather" (pages 69–71), which states: "The dust raised in
severe
volcanic eruptions, such as that at
Krakatoa
in 1883, is known to cause a noticeable reduction in the sunlight
reaching the earth ... The amount of debris remaining in the atmosphere
after the explosion of even the largest nuclear weapons is probably not
more than about 1 percent or so of that raised by the Krakatoa eruption.
Further, solar radiation records reveal that none of the nuclear
explosions to date has resulted in any detectable change in the direct
sunlight recorded on the ground."
[47]
The potential cooling from soil dust was again looked at in 1992, in a US National Academy of Sciences (NAS)
[48] report on
geoengineering, which estimated that about 10
10 kg of stratospheric injected soil dust with
particulate grain dimensions of 0.1 to 1
micrometer would be required to mitigate the warming from a
doubling of atmospheric CO
2, that is, to produce ~ 2
degree celsius of cooling.
[49]
In 1969,
Paul Crutzen discovered that
NOx (
oxides of
nitrogen) could be an efficient catalyst for the destruction of the
ozone layer/
stratospheric ozone.
[50] With studies on the potential effects of
NOx generated by engine heat in stratosphere flying
Supersonic Transport(SST) airplanes in the 1970s serving as a backdrop,
[51][52] John Hampson in 1974 suggested in the journal
Nature that due to the
nuclear fireballs creation of atmospheric
NOx,
a full-scale nuclear exchange could result in depletion of the ozone
shield, possibly subjecting the earth to ultraviolet radiation for a
year or more.
[53][54] Hampson's hypothesis "led directly",
[55] in 1975, to the
United States National Research Council (NRC) reporting on the models of ozone depletion following nuclear war in the book
Long-Term Worldwide Effects of Multiple Nuclear-Weapons Detonations.
[53] In this 1975 book it states that a nuclear war involving 4000Mt (megaton) from
present arsenals
would probably deposit much less dust in the stratosphere than the
Krakatoa eruption, judging that the effect of dust and oxides of
nitrogen would probably be slight climatic cooling which "would probably
lie within normal global climatic variability, but the possibility of
climatic changes of a more dramatic nature cannot be ruled out".
[51][53][56]
A study published in 1976 on the experimental measurements of an earlier
atmospheric nuclear test
as it affected the ozone layer found that nuclear detonations are
tentatively exonerated in depleting ozone, after initially discouraging
model calculations.
[57] In total about 500 megatons were atmospherically detonated between 1945 and 1971,
[58] with a peak occurring in 1961-62, when 340 megatons were detonated in the atmosphere by the United States and
Soviet Union.
[59] During this 1-2 year peak, counting only the multi-megaton range detonations in the
two nations nuclear test series, a total yield estimated at 300 megatons of energy was released, due to this,
3 x 10^34 additional molecules of
nitric oxide(about 5000 tons per megaton
[60])
are believed to have entered the stratosphere, and while ozone
depletion of 2.2 percent was noted in 1963, the decline had started
prior to 1961 and is believed to have been caused by other
meteorological effects, thus the 1985 book
The Effects on the Atmosphere of a Major Nuclear Exchange states: "one can not draw definite conclusions about the effects of nuclear explosions on stratospheric ozone".
[61]
Science Fiction
The first published suggestion that a cooling of climate or winter
could be an effect of a nuclear war, appears to have been originally put
forth by
Poul Anderson and F.N Waldrop in their post war story
"Tomorrow's Children", which appeared in the March 1947 issue of the
Astounding Science Fiction magazine, the story which is primarily about a team of scientists hunting down
mutants,
[62] warns of a "
Fimbulwinter"
caused by dust that blocked sunlight after the recent fictitious
nuclear war and speculates that this may even trigger a new ice age.
[63][64] Anderson went on to publish a novel based partly on this story in 1961 titling it;
Twilight World.
[65]
1982
In 1981, William J. Moran began discussions and research in the NRC
on the dust effects of a large exchange of nuclear warheads. An NRC
study panel on the topic met in December 1981 and April 1982 in
preparation of the release of
The Effects on the Atmosphere of a Major Nuclear Exchange in 1985.
[53]
As part of a study on the creation of
oxidizing species such as
NOx and ozone in the troposphere after a nuclear war,
[66] launched in 1980 by
Ambio, a journal of the
Royal Swedish Academy of Sciences,
Paul Crutzen
and John Birks circulated a draft paper in early 1982 with the first
quantitative evidence of alterations in short-term climate after a
nuclear war.
[53] In 1982, a special issue of
Ambio devoted to the possible environmental consequences of nuclear war by Crutzen and Birks titled
"Twilight at Noon" anticipating the nuclear winter scenario.
[67] The paper which looked into fires and their climatic effect as "an afterthought"
[66] discussed
particulate matter
from large fires, nitrogen oxide, ozone depletion and the effect of
nuclear twilight on agriculture. Crutzen and Birks' calculations
suggested that smoke particulates injected into the atmosphere by fires
in cities, forests and petroleum reserves could prevent up to 99% of
sunlight from reaching the Earth's surface, with major climatic
consequences: "The normal dynamic and temperature structure of the
atmosphere would therefore change considerably over a large fraction of
the Northern Hemisphere, which will probably lead to important changes
in land surface temperatures and wind systems."
[67]
An important implication of their work was that a "first strike"
nuclear attack would have severe consequences for the perpetrator.
1983
Interest in nuclear war environmental effects also arose in the USSR. After becoming aware of the papers by N.P.Bochkov and
E.I.Chazov,
[68] Russian atmospheric scientist
Georgy Golitsyn applied his research on dust-storms to the situation following a large nuclear war.
[69] His suggestion that the atmosphere would be heated and that the surface of the planet would cool appeared in
The Herald of the Academy of Sciences in September 1983.
[70]
In 1982,
[citation needed] the so-called TTAPS team (
Richard P. Turco,
Owen Toon, Thomas P. Ackerman,
James B. Pollack and
Carl Sagan) undertook a computational modeling study of the atmospheric consequences of
nuclear war, publishing their results in
Science in December 1983.
[71] The phrase "nuclear winter" was coined by Turco just prior to publication.
[72]
In this early work, TTAPS carried out the first estimates of the total
smoke and dust emissions that would result from a major nuclear
exchange, and determined quantitatively the subsequent effects on the
atmospheric radiation balance and temperature structure. To compute dust
and smoke impacts, they employed a one-dimensional
microphysics/radiative-transfer model of the Earth's lower atmosphere
(to the mesopause), which defined only the vertical characteristics of
the global climate perturbation.
Upon learning of the TTAPS scenarios,
[citation needed] Vladimir Alexandrov
and G. I. Stenchikov also published a report in 1983 on the climatic
consequences of nuclear war based on simulations with a
three-dimensional global circulation model.
[37] Two years later
Vladimir Alexandrov
disappeared under mysterious circumstances. Richard Turco and Starley
L. Thompson were critical of the Soviet model, Turco claimed it was "a
primitive rendition of an obsolete US model".
[73]
1986
In 1984 the
WMO
commissioned Georgy Golitsyn and N. A. Phillips to review the state of
the science. They found that studies generally assumed a scenario that
half of the world's nuclear weapons would be used, ~5000
Mt, destroying approximately 1,000 cities, and creating large quantities of carbonaceous smoke - 1–
2×1014 g being mostly likely, with a range of 0.2–
6.4×1014 g (NAS; TTAPS assumed
2.25×1014).
The smoke resulting would be largely opaque to solar radiation but
transparent to infra-red, thus cooling by blocking sunlight but not
causing warming from enhancing the
greenhouse effect. The
optical depth
of the smoke can be much greater than unity. Forest fires resulting
from non-urban targets could increase aerosol production further. Dust
from near-surface explosions against hardened targets also contributes;
each Mt-equivalent of explosion could release up to 5 million
tons
of dust, but most would quickly fall out; high altitude dust is
estimated at 0.1-1 million tons per Mt-equivalent of explosion. Burning
of crude oil could also contribute substantially.
The 1-D radiative-convective models used in these studies produced a
range of results, with coolings up to 15–42 °C between 14 and 35 days
after the war, with a "baseline" of about 20 °C. Somewhat more
sophisticated calculations using 3-D
GCMs
(Alexandrov and Stenchikov (1983); Covey, Schneider and Thompson
(1984); produced similar results: temperature drops of between 20 and
40 °C, though with regional variations.
All calculations show large heating (up to 80 °C) at the top of the
smoke layer at about 10 km; this implies a substantial modification of
the circulation there and the possibility of advection of the cloud into
low latitudes and the southern hemisphere.
The report made no attempt to compare the likely human impacts of the post-war cooling to the direct deaths from explosions.
In 1987 P. M. Kelly of the
University of East Anglia Climatic Research Unit
stated that "although there are a handful of vociferous critics, the
atmospheric community is united in its conclusion that the threat of
nuclear winter is genuine".
[74]
1990
In 1990, in a paper entitled "Climate and Smoke: An Appraisal of
Nuclear Winter," TTAPS give a more detailed description of the short-
and long-term atmospheric effects of a nuclear war using a
three-dimensional model:
[75]
First 1 to 3 months:
- 10 to 25% of soot injected is immediately removed by precipitation, while the rest is transported over the globe in 1 to 2 weeks
- SCOPE figures for July smoke injection:
- 22 °C drop in mid-latitudes
- 10 °C drop in humid climates
- 75% decrease in rainfall in mid-latitudes
- Light level reduction of 0% in low latitudes to 90% in high smoke injection areas
- SCOPE figures for winter smoke injection:
- Temperature drops between 3 and 4 °C
Following 1 to 3 years:
- 25 to 40% of injected smoke is stabilised in atmosphere (NCAR). Smoke stabilised for approximately 1 year.
- Land temperatures of several degrees below normal
- Ocean surface temperature between 2 and 6 °C
- Ozone depletion of 50% leading to 200% increase in UV radiation incident on surface.
Kuwait wells in the first Gulf War
The
Kuwaiti oil fires were not just limited to
burning oil wells,
one of which is seen here in the background, but burning "oil lakes",
seen in the foreground, also contributed to the smoke plumes,
particularly the
sootiest/blackest of them.
[76]
Smoke plumes from a few of the
Kuwaiti Oil Fires
on April 7, 1991. The plume boundaries/the maximum assumed extent of
the combined plumes from over six hundred fires during the period of
February 15 - May 30, 1991, are available.
[76][77] Only about 10% of all the fires, mostly corresponding with those that originated from "oil lakes" produced pure black
soot
filled plumes, 25% of the fires emitted white to grey plumes, while the
remaining emitted plumes with colors between grey and black.
[76]
Following Iraq's
invasion of Kuwait and
Iraqi threats of igniting the country's
800 or so oil wells were made, speculation on the cumulative climatic effect of this, presented at the
World Climate Conference in Geneva that November in 1990, ranged from a nuclear winter type scenario, to heavy
acid rain and even short term immediate
global warming.
[78] As threatened, the wells were set ablaze by the retreating Iraqis by March 1991 and the 600 or so successfully set
Kuwaiti oil wells were not fully extinguished until November 6, 1991, eight months after the end of the war,
[79] and they consumed an estimated six million
barrels of oil daily at their peak intensity.
In articles printed in the
Wilmington morning star and the
Baltimore Sun newspapers of January 1991, prominent authors of nuclear winter papers -
Richard P. Turco, John W. Birks,
Carl Sagan,
Alan Robock and
Paul Crutzen
together collectively stated that they expected catastrophic nuclear
winter like effects with continental sized impacts of "sub-freezing"
temperatures as a result of if the Iraqis went through with their
threats of igniting 300 to 500 pressurized oil wells and they burned for
a few months.
[78][80][81]
Later when
Operation Desert Storm had begun in late January 1991, coinciding with the first few oil fires being lit, Dr.
S. Fred Singer and
Carl Sagan discussed the possible environmental impacts of the Kuwaiti petroleum fires on the
ABC News program
Nightline.
Sagan again argued that some of the effects of the smoke could be
similar to the effects of a nuclear winter, with smoke lofting into the
stratosphere, a region of the
atmosphere
beginning around 48,000 feet (15,000 m) above sea level at Kuwait,
resulting in global effects and that he believed the net effects would
be very similar to the explosion of the Indonesian volcano
Tambora in 1815, which resulted in the year 1816 being known as the
Year Without a Summer.
He reported on initial modeling estimates that forecast impacts
extending to south Asia, and perhaps to the northern hemisphere as well.
Sagan stressed this outcome was so likely that, "It should affect the
war plans."
[82]
Singer, on the other hand, said that his calculations showed that the
smoke would go to an altitude of about 3,000 feet (910 m) and then be
rained out after about three to five days and thus the lifetime of the
smoke would be limited. Both height estimates made by Singer and Sagan
turned out to be wrong, albeit with Singers narrative being closer to
what transpired, with the comparatively minimal atmospheric effects
remaining limited to the Persian Gulf region, with smoke plumes, in
general,
[76] lofting to about 10,000 feet (3,000 m) and a few times as high as 20,000 feet (6,100 m).
[83][84]
Sagan later conceded in his book
The Demon-Haunted World that his predictions obviously 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."
[85]
Sagan and his colleagues expected that a "self-lofting" of the sooty
smoke would occur when it absorbed the sun's heat radiation, with little
to no scavenging occurring, whereby the black particles of soot would
be heated by the sun and lifted/lofted higher and higher into the air,
thereby injecting the soot into the stratosphere, a position where they
argued it would take years for the sun blocking effect of this
aerosol
of soot to fall out of the air, and with that, catastrophic ground
level cooling and agricultural impacts in Asia and possibly the
Northern Hemisphere as a whole.
[86]
The Atmospheric scientist tasked with studying the atmospheric impact of the Kuwaiti fires by the
National Science Foundation,
Peter Hobbs,
stated that "the fires' modest impact suggested that "some numbers
[used to support the Nuclear Winter hypothesis]... were probably a
little overblown."
[87]
Hobbs found that at the peak of the fires, the smoke absorbed 75 to
80% of the sun’s radiation. The particles rose to a maximum of 20,000
feet (6,100 m), and when combined with scavenging by clouds the smoke
had a short residency time of a maximum of a few days in the atmosphere.
[88][89]
Pre-war claims of wide scale, long-lasting, and significant global
environmental impacts were thus not borne out, and found to be
significantly exaggerated by the media and speculators,
[90]
with climate models by those not supporting the nuclear winter
hypothesis at the time of the fires predicting only more localized
effects such as a daytime temperature drop of ~10 °C within ~200 km of
the source.
[91]
This satellite photo of the south of
Britain shows black smoke from the 2005
Buncefield fire, a series of fires and explosions involving approximately 250,000,000
litres
of fossil fuels. The plume is seen spreading in two main streams from
the explosion site at the apex of the inverted 'v'. By the time the fire
had been extinguished the smoke had reached the
English Channel.
The orange dot is a marker, not the actual fire. Although the smoke
plume was from a single source, and larger in size than the individual
oil well fire plumes in Kuwait 1991, the Buncefield smoke cloud remained out of the stratosphere.
The idea of oil well and
oil reserve
smoke pluming to the stratosphere serving as a main contributor to the
soot of a nuclear winter was a central tenet of the early climatology
papers on the hypothesis; they were considered more of a possible
contributor than smoke from cities, as the smoke from oil has a higher
ratio of black soot, thus absorbing more sunlight.
[67][71]
Hobbs compared the papers' assumed "emission factor" or soot generating
efficiency from ignited oil pools and found, upon comparing to measured
values from oil pools at Kuwait, which were the greatest soot
producers, the emissions of soot assumed in the nuclear winter
calculations are still "too high".
[89]
Following the results of the Kuwaiti oil fires being in disagreement
with the core nuclear winter promoting scientists, the 1990s nuclear
winter papers generally attempted to distance themselves from suggesting
oil well and reserve smoke will reach the stratosphere.
In 2007, a nuclear winter study, which will be discussed later, 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
[quantify] like some forest fires can lift smoke
[quantify] into the stratosphere, and this is supported by recent evidence that it occurs far more often than previously thought.
[92][93][94][95][96][97][98]
The study also suggested that the burning of the comparably smaller
cities, which would be expected to follow a nuclear strike, would also
loft significant amounts of smoke into the stratosphere:
Stenchikov et al. [2006b][99]
conducted detailed, high-resolution smoke plume simulations with the
RAMS regional climate model [e.g., Miguez-Macho et al., 2005][100]
and showed that individual plumes, such as those from the Kuwait oil
fires in 1991, would not be expected to loft into the upper atmosphere
or stratosphere, because they become diluted. However, much larger
plumes, such as would be generated by city fires, produce large,
undiluted mass motion that results in smoke lofting. New large eddy simulation
model results at much higher resolution also give similar lofting to
our results, and no small scale response that would inhibit the lofting
[Jensen, 2006].[101]
However the above simulation notably contained the assumption that no dry and wet deposition/rain would occur.
[102]
Recent modeling
Based on new work published in 2007 and 2008 by some of the authors of the original studies, several new
hypotheses have been put forth.
[103][104]
However far from being "new", the very same beginning to "significant"
nuclear winter effects, was in the mid 1980s models, similarly regarded
to have been a threat from a total of 100 or so city firestorms.
[105][106]
A minor nuclear war with each country using 50 Hiroshima-sized atom
bombs as airbursts on urban areas could produce climate change
unprecedented in recorded human history. A nuclear war between the
United States and Russia today could produce nuclear winter, with
temperatures plunging below freezing in the summer in major
agricultural
regions, threatening the food supply for most of the planet. The
climatic effects of the smoke from burning cities and industrial areas
would last for several years, much longer than previously thought. New
climate model simulations, which are said to have the capability of
including the entire atmosphere and
oceans, show that the smoke would be lofted by solar heating to the upper stratosphere, where it would remain for years.
Compared to climate change for the past millennium, even the smallest
exchange modeled would plunge the planet into temperatures colder than
the
Little Ice Age
(the period of history between approximately A.D. 1600 and A.D. 1850).
This would take effect instantly, and agriculture would be severely
threatened. Larger amounts of smoke would produce larger climate
changes, and for the 150
teragrams (Tg) case produce a true nuclear winter (1 Tg is 10
12 grams),
making agriculture impossible for years. In both cases, new climate
model simulations show that the effects would last for more than a
decade.
2007 study on global nuclear war
A study published in the
Journal of Geophysical Research in July 2007,
[107] "Nuclear winter revisited with a modern climate model and current nuclear arsenals: Still catastrophic consequences",
[108]
used current climate models to look at the consequences of a global
nuclear war involving most or all of the world's current nuclear
arsenals (which the authors judged to be one the size of the world's
arsenals twenty years earlier). The authors used a
global circulation model, ModelE from the
NASA Goddard Institute for Space Studies,
which they noted "has been tested extensively in global warming
experiments and to examine the effects of volcanic eruptions on
climate." The model was used to investigate the effects of a war
involving the entire current global nuclear arsenal, projected to
release about 150 Tg of smoke into the atmosphere, as well as a war
involving about one third of the current nuclear arsenal, projected to
release about 50 Tg of smoke. In the 150 Tg case they found that:
A global average surface cooling of –7 °C to –8 °C persists for
years, and after a decade the cooling is still –4 °C (Fig. 2).
Considering that the global average cooling at the depth of the last ice
age 18,000 yr ago was about –5 °C, this would be a climate change
unprecedented in speed and amplitude in the history of the human race.
The temperature changes are largest over land ... Cooling of more than
–20 °C occurs over large areas of North America and of more than –30 °C
over much of Eurasia, including all agricultural regions.
In addition, they found that this cooling caused a weakening of the global hydrological cycle, reducing global
precipitation
by about 45%. As for the 50 Tg case involving one third of current
nuclear arsenals, they said that the simulation "produced climate
responses very similar to those for the 150 Tg case, but with about half
the amplitude," but that "the time scale of response is about the
same." They did not discuss the implications for agriculture in depth,
but noted that a 1986 study which assumed no food production for a year
projected that "most of the people on the planet would run out of food
and starve to death by then" and commented that their own results show
that, "This period of no food production needs to be extended by many
years, making the impacts of nuclear winter even worse than previously
thought."
2014
In 2014, Michael J. Mills (at the US National Center for Atmospheric
Research, NCAR), Owen B. Toon (of the original TTAPS team), Julia
Lee-Taylor, and Alan Robock published "Multi-decadal global cooling and
unprecedented ozone loss following a regional nuclear conflict" in the
journal
Earth's Future.
[109]
The authors used computational models developed by NCAR to simulate the
climatic effects of a regional nuclear war in which 100 "small" (15 kt)
weapons are detonated over cities. They concluded, in part, that
global ozone losses of 20-50% over populated areas, levels
unprecedented in human history, would accompany the coldest average
surface temperatures in the last 1000 years. We calculate summer
enhancements in UV indices of 30-80% over Mid-Latitudes, suggesting
widespread damage to human health, agriculture, and terrestrial and
aquatic ecosystems. Killing frosts would reduce growing seasons by 10-40
days per year for 5 years. Surface temperatures would be reduced for
more than 25 years, due to thermal inertia and albedo effects in the
ocean and expanded sea ice. The combined cooling and enhanced UV would
put significant pressures on global food supplies and could trigger a
global nuclear famine.
Criticism and debate
The TTAPS study was widely reported and criticized in the media.
Later model runs in some cases predicted less severe effects, but
continued to support the overall conclusion of significant global
cooling.
[110][111]
Recent studies (2006) substantiate that smoke from urban firestorms in a
local nuclear war would lead to long lasting global cooling but in a
less dramatic manner than a global nuclear war,
[112][113]
while a 2007 study of the effects of global nuclear war supported the
conclusion that it would lead to full-scale nuclear winter.
[107][108]
The original work by Sagan and others was criticized as a "myth" and "discredited theory" in the 1987 book
Nuclear War Survival Skills, a
civil defense manual by
Cresson Kearny for the
Oak Ridge National Laboratory.
[114] Kearny said the amount of cooling would last only a few days.
[114]
Kearny, who was not a climate scientist himself, based his conclusions
almost entirely on the 1986 paper "Nuclear Winter Reappraised"
[115][116] by Starley Thompson and
Stephen Schneider. However, a 1988 article by Brian Martin in
Science and Public Policy[110]
states that although their paper concluded the effects would be less
severe than originally thought, with the authors describing these
effects as a "nuclear autumn", other statements by Thompson and
Schneider
[117][118]
show that they "resisted the interpretation that this means a rejection
of the basic points made about nuclear winter". In addition, the
authors of the
2007 study above
state that "because of the use of the term 'nuclear autumn' by Thompson
and Schneider [1986], even though the authors made clear that the
climatic consequences would be large, in policy circles the theory of
nuclear winter is considered by some to have been exaggerated and
disproved [e.g., Martin, 1988]."
[107][108] And in 2007 Schneider emphasized the danger of serious climate changes from a limited nuclear war of the kind analyzed in the
2006 study above,
saying "The sun is much stronger in the tropics than it is in
mid-latitudes. Therefore, a much more limited war [there] could have a
much larger effect, because you are putting the smoke in the worst
possible place."
[119]
John Maddox, editor of the journal
Nature, issued a series of skeptical comments about nuclear winter studies during his tenure,
[120][121] being a long-time critic of environmental doomsdayism.
[122] Similarly
S. Fred Singer was a long term vocal critic of the hypothesis in the journal and in televised debates with Carl Sagan.
[123][124]
Russell Seitz, Associate of the Harvard University Center for
International Affairs, argues that the models' assumptions give results
which the researchers want to achieve and is a case of "worst-case
analysis run amok".
[122]
Seitz's opposition caused the proponents of nuclear winter to issue
responses in the media, and while both sides made important points, they
were largely incapable of collaborating as the proponents believed it
was simply necessary to show only the possibility of climatic
catastrophe, often a worst-case scenario, while opponents insisted that
to be taken seriously, nuclear winter should be shown as likely under
"reasonable" scenarios.
[125] One of these areas of contention, as elucidated by Lynn R. Anspaugh, is upon the question of which
season should be used as the backdrop for the models, most models choose the
summer in the
Northern Hemisphere
as the start point to produce the maximum cooling effect, whereas it
has been pointed out that if the firestorms occurred in the winter
months, when there is much less intense sunlight to loft soot into a
stable region of the stratosphere, the magnitude of the cooling effect
from the same number of firestorms as ignited in the summer models,
would be zero according to a January model run by Covey et al.
[126]
Lynn R. Anspaugh also expressed frustration that although a managed
forest fire in Canada is said to have been lit by proponents of nuclear
winter, with the fire potentially serving as an opportunity to do some
basic measurements of the optical properties of the smoke and
smoke-to-fuel ratio, which would have helped refine the estimates of
these critical model inputs, the proponents did not indicate that any
such measurements were made.
[127]
In 1986, atmospheric scientist Joyce Penner from the
Lawrence Livermore National Laboratory published an article in
Nature
in which she focused on the specific variables of the smoke's optical
properties and the quantity of smoke remaining airborne after the city
fires and found that the published estimates of these variables varied
so widely that depending on which estimates were chosen the climate
effect could be negligible, minor or massive.
[128]
The assumed optical properties for black carbon in more recent nuclear
winter papers(2006) are still "based on those assumed in earlier nuclear
winter simulations".
[129]
William R. Cotton Professor of Atmospheric Science at Colorado State University, specialist in
cloud physics modeling and co-creator of the highly influential,
[130][131] and previously mentioned
RAMS atmosphere model, had in the 1980s modeled and supported the predictions made by earlier nuclear winter papers,
[132]
but has since reversed this position according to a book co-authored by
him in 2007, stating that, amongst other systematically examined
assumptions; far more rain out/
wet deposition of soot will occur than is assumed in modern papers on the subject and that "We must wait for a new generation of
GCMs to be implemented to examine potential consequences quantitatively".
[18][133]
The contribution of smoke from the ignition of live non-desert vegetation, living forests and so on near to many
missile silos, a source of smoke originally brought up in the initial
Twilight at Noon
paper, was found after examination by Bush and Small in 1987, that the
burning of live vegetation would contribute only slightly to the
estimated total "nonurban smoke production". With the vegetation likely
to only sustain burning if it is within a
radius or two from the surface of the
nuclear fireball, which is at a distance that would also experience extreme
blast winds that would influence any such fires.
[134] This conclusion is supported by the 1950-60s in-field examination of tropical forests after
Operation Castle,
[135] and
Operation Redwing.
[136]
In a paper by the
United States Department of Homeland Security
finalized in 2010, fire experts stated that due to the nature of modern
city design and construction, with the U.S. serving as an example, a
firestorm is unlikely after a nuclear detonation in a modern city.
[137]
This is not to say that fires won't occur over a large area after a
detonation, but that the fires would not coalesce and form the all
important stratosphere punching
firestorm plume that the nuclear winter papers require as a prerequisite assumption in their climate computer models. The nuclear
bombing of Nagasaki for example, did not produce a firestorm.
[138]
Policy implications
During the early 1980s,
Fidel Castro recommended to the
Kremlin
a harder line against Washington, even suggesting the possibility of
nuclear strikes. The pressure stopped after Soviet officials gave Castro
a briefing on the ecological impact on
Cuba of nuclear strikes on the United States.
[139] In 2010
Alan Robock,
a co-author of nuclear winter papers was summoned to Cuba to help
Castro promote his new view that nuclear war would bring about
Armageddon, Robock's 90 minute lecture was later aired on nationwide television in the country.
[140]
However, according to Robock, in so far as getting US government
attention and affecting nuclear policy, he has failed. In 2009, together
with
Owen Toon, he gave a talk to the
United States Congress but nothing transpired from it and the then presidential science adviser,
John Holdren, did not respond to their requests in 2009 or at the time of writing in 2011.
[140]
United States and Soviet Union/Russia nuclear stockpiles. The effects of
the belief in nuclear winter does not appear to have had any reducing
impact on either countries nuclear stockpiles in the 1980s,
[141] only the failing
Soviet economy and the
dissolution of the country between 1989-91 which marks the end of the
Cold War and with it the relaxation of the arms race, appears to have had an impact. The effects of the
Megatons to Megawatts
can also be seen in the mid 1990s, continuing Russia's reducing trend. A
similar chart focusing solely on quantity of warheads in the
multi-megaton range is also available.
[142] Moreover, total
deployed US & "Russian" strategic weapons increased steadily from 1983 until the Cold War ended.
[143]
In an interview in 2000,
Mikhail Gorbachev,
in response to the comment "In the 1980s, you warned about the
unprecedented dangers of nuclear weapons and took very daring steps to
reverse the arms race," said "Models made by Russian and American
scientists showed that a
nuclear war
would result in a nuclear winter that would be extremely destructive to
all life on Earth; the knowledge of that was a great stimulus to us, to
people of honor and morality, to act in that situation."
[144]
However a 1984 US
Interagency Intelligence Assessment
expresses a far more skeptical and cautious approach by stating that as
the hypothesis is not convincing scientifically, they predicted that
Soviet
nuclear policy would be to maintain their strategic nuclear posture, such as their fielding of the high
throw-weight SS-18
missile and they would merely attempt to exploit the hypothesis for
propaganda purposes, such as directing scrutiny on the US portion of the
nuclear arms race.
Moreover, it goes on to express the belief that if Soviet officials did
begin to take nuclear winter seriously, it would probably make them
demand exceptionally high standards of scientific proof for the
hypothesis, as the implications of it would undermine their
military doctrine—a level of scientific proof which perhaps could not be met without field experimentation.
[145] The un-
redacted portion of the document ends with the suggestion that substantial increases in Soviet
Civil defense food stockpiles might be an early indicator that Nuclear Winter was beginning to influence Soviet upper
echelon thinking.
[146]
In 1985
Time magazine noted "the suspicions of some Western scientists that the nuclear winter hypothesis was promoted by
Moscow to give
anti-nuclear groups in the U.S. and Europe some fresh ammunition against America's arms buildup."
[147]
In 1986, the
Defense Nuclear Agency document
An update of Soviet research on and exploitation of Nuclear winter 1984-1986 charted the minimal research contribution on, and Soviet
propaganda usage of, the nuclear winter phenomenon.
[148]
Dr. Vitalii Nikolaevich Tsygichko, a Senior Analyst at the
Soviet Academy of Sciences, author of the study,
Mathematical Model of Soviet Strategic Operations on the Continental Theater,
and a former member of the General Staff, has said that Soviet military
analysts discussed the idea of a "nuclear winter" (although they did
not use that exact term) years before U.S. scientists wrote about it in
the 1980s.
[149] Starley L. Thompson, of the
National Center for Atmospheric Research,
Boulder, Colorado, says that Soviet research into nuclear winter in
1983 used US computer models that had been developed in the early 1970s.
[73] Soviet intelligence officer
Sergei Tretyakov, who defected in 1990, maintained that "the
KGB was responsible for creating the entire nuclear winter story to stop the
Pershing II missiles".
[150]
The 1951
Shot Uncle of Operation Buster-Jangle, had a yield about a tenth of the 13 to 16 kt
Hiroshima bomb. 1.2 kilotons,
[151] and was detonated 5.2 m (17 ft) beneath ground level.
[152] The explosion resulted in a cloud that rose to 3.5 km "11,500 ft".
[153] The resulting crater was 260 feet wide and 53 feet deep.
[154] The yield is similar to that of an
Atomic Demolition Munition.
Altfeld & Cimbala argue that true belief in nuclear winter might
lead nations towards building greater arsenals of weapons of this type.
[155] However, despite being complicated due to the advent of
Dial-a-yield technology,
data on these low yield nuclear weapons suggests that they now make up
no less than a tenth of the arsenal of the US and Russia, and the
fraction of the stockpile that they occupy has diminished since the
1970-90s, not grown.
[156]
In 1989 Carl Sagan and colleague Richard Turco wrote a policy implications paper that appeared in
Ambio
that suggests that as nuclear winter is a "well-established prospect",
both superpowers should jointly reduce their nuclear arsenals to "
Canonical Deterrent Force"
levels of 100-300 individual warheads each, such that in "the event of
nuclear war [this] would minimize the likelihood of nuclear winter."
[157]
As the implications of nuclear winter began to be taken seriously in the late 1980s,
[citation needed] military analysts turned to reinforce "
existing trends" in
warhead miniaturization, of higher accuracy and lower yield nuclear warheads.
[146] This trend, enabled by
GPS navigation etc., was motivated by the desire to still destroy the target but while reducing the severity of fallout
collateral damage
depositing on neighboring, and potentially friendly, countries. As it
relates to the likelihood of nuclear winter, the hazard from
thermal radiation ignited fires would also be reduced. While the TTAPS paper had described a 3000
Mt counterforce attack on
ICBM sites; Michael Altfeld of
Michigan State University and
political scientist Stephen Cimbala of
Pennsylvania State University argued that smaller, more accurate warheads and
lower detonation heights could produce the same counterforce strike with only 3 Mt and produce less climatic effects, even if cities were targeted, as
lower fuzing heights, such as
surface bursts, would limit the range of the burning
thermal rays due to terrain masking and shadows cast by buildings,
[158] while also temporarily lofting far more
radioactive soil into the atmosphere. This logic is similarly reflected in the 1984
Interagency Intelligence assessment, which suggests that targeting planners would simply have to consider target combustibility along with yield,
height of burst, timing and other factors to reduce the amount of smoke to safeguard against the potentiality of a nuclear winter.
[146]
Therefore, as a consequence of attempting to limit the target fire
hazard by reducing the range of thermal radiation with fuzing for
surface and
sub-surface bursts, this will result in a scenario where the far more concentrated, and therefore deadlier,
local fallout that is generated following a
surface burst forms, as opposed to the comparatively dilute
global fallout created when nuclear weapons are fuzed in
air burst mode.
[158][159]
Altfeld and Cimbala also argued that belief in the possibility of
nuclear winter would actually make nuclear war more likely, contrary to
the views of Sagan and others, because it would inspire the
development of more accurate, and lower explosive yield, nuclear weapons.
[160] As it suggests that the replacement of the then Cold War viewed
strategic nuclear weapons in the multi-megaton yield range, with weapons of explosive yields closer to
tactical nuclear weapons, such as the
Robust Nuclear Earth Penetrator,
would safeguard against the nuclear winter potential. Tactical nuclear
weapons, on the low end of the scale have yields that overlap with large
conventional weapons,
and are therefore often viewed "as blurring the distinction between
conventional and nuclear weapons", making the prospect of using them
"easier" in a conflict.
[161][162]
Mitigation techniques
A number of solutions have been proposed to mitigate the potential
harm of a nuclear winter if one appears inevitable; with the problem
being attacked at both ends, from those focusing on preventing the
growth of fires and therefore limiting the amount of smoke that reaches
the stratosphere in the first place, to food production under dimmed
skies with the assumption that the very worst-case analysis results of
the nuclear winter models prove accurate and no other mitigation
strategies are fielded.
Fire control
In a report from 1967, techniques included various methods of
applying liquid nitrogen, dry ice, and water to nuclear-caused fires.
[163] The report considered attempting to stop the spread of fires by creating
firebreaks by blasting combustible material out of an area, possibly even with nuclear weapons, along with the use of preventative
Hazard reduction burns. According to the report, one of the most promising techniques investigated was
initiation of rain from seeding of mass-fire thunderheads and other clouds passing over the developing, and then steady-state, firestorm.
Producing food without sunlight
David Denkenberger and
Joshua Pearce have proposed in
Feeding Everyone No Matter What a variety of alternate foods which convert
fossil fuels or
biomass into food without sunlight to address nuclear winter.
[164] The solution using a fossil fuel energy source is natural-gas-digesting bacteria.
[165] One example of a biomass alternate food is that
mushrooms can grow directly on wood without sunlight.
[166] Another example is that
cellulosic biofuel production typically already creates
sugar as an intermediate product.
[167]
Large-scale food stockpiling
The minimum annual global wheat storage is approximately 2 months.
[168] To feed everyone despite nuclear winter, years of
food storage prior to the event has been proposed.
[169] While the suggested masses of
preserved food
would likely never get used as a nuclear winter is comparatively
unlikely to occur, the stockpiling of food would have the positive
result of ameliorating the impact of the far more frequent distruptions
to regional food supplies caused by
lower-level conflicts and
droughts. There is however the danger that if a sudden rush to food stockpiling occurs without the
buffering effect offered by
Victory gardens etc., it may exacerbate current
food security problems by elevating present
food prices.
Climate engineering
Despite the name "nuclear winter", nuclear events are not necessary to produce the modeled climatic effect.
[14][170] In an effort to find a quick and cheap solution to the
global warming projection of
at least two degrees of surface warming as a result of the doubling in CO2 levels within the atmosphere, through
solar radiation management(a form of
climate engineering)
the underlying nuclear winter effect has been looked at as perhaps
holding potential. Besides the more common suggestion to inject
sulfur compounds into the stratosphere to approximate the effects of a
volcanic winter, the injection of other chemical species such as the release of a particular type of
soot particle, to create minor "nuclear winter" conditions, has also been proposed by Paul Crutzen and others.
[171][172] According to the threshold/minor "nuclear winter" computer models,
[173][174] if one to five
teragrams of
firestorm-generated soot
[175] is injected into the low stratosphere, it is modeled, through the
anti-greenhouse effect,
to heat the stratosphere but cool the lower troposphere and produce
1.25 °C cooling for two to three years; after 10 years, average global
temperatures would still be 0.5 °C lower than before the soot injection.
[2]
Potential climatic precedence
An animation depicting a massive asteroid–Earth impact and subsequent
impact crater formation. The asteroid connected with the extinction of the Dinosaurs/
Cretaceous–Paleogene extinction event released an estimated energy of 100
teratonnes of TNT (420
ZJ).
[176] corresponding to 100,000,000
Mt of energy, roughly 10,000 times the maximum combined arsenals of the US and Soviet Union in the Cold War.
[177] This is hypothesized to have produced sufficient ground-energy coupling to have caused severe
mantle plume (volcanism) at the
antipodal point (the opposite side of the world).
[178]
Similar climatic effects to "nuclear winter" followed historical
supervolcano eruptions, which plumed
sulfate aerosols high into the stratosphere, with this being known as a
volcanic winter.
[179]
Similarly, extinction-level
comet and asteroid impacts are also believed to have generated
impact winters by the
pulverization of massive amounts of fine rock dust. This pulverized rock can also produce "volcanic winter" effects, if
sulfate-bearing rock is hit in the impact and lofted high into the air,
[180] and "nuclear winter" effects, with the heat of the heavier rock
ejecta igniting regional and possibly even global forest firestorms.
[181][182]
This global "impact firestorms" hypothesis, initially supported by
Wolbach, Melosh and veteran nuclear winter modeler Owen Toon, suggests
that as a result of massive
impact events, the small
sand-grain-sized ejecta fragments created can
meteorically re-enter the atmosphere forming a hot blanket of global debris high in the air, potentially turning the entire sky
red-hot for minutes to hours, and with that, burning the complete global inventory of above-ground
carbonaceous material, including
rain forests.
[183][184] This hypothesis is suggested as a means to explain the severity of the
Cretaceous–Paleogene extinction event, as the
earth impact of an asteroid about 10 km wide
which precipitated the extinction is not regarded as sufficiently
energetic to have caused the level of extinction from the initial
impact's energy release alone.
The global "impact firestorms"/firestorm winter, however, has been
questioned in more recent years (2003-2013) by Claire Belcher,
[183][185][186] Tamara Goldin
[187][188][189] and H. Jay Melosh,
[190][191] with this re-evaluation being dubbed the "Cretaceous-Palaeogene firestorm debate" by Belcher.
[183]
Depending on the size of the meteor, it will either burn up high in the atmosphere or reach lower levels and explode in an
air burst akin to the
Chelyabinsk meteor of 2013, which approximated the thermal effects of a nuclear explosion.
The issues raised by these scientists in the debate are the perceived
low quantity of soot in the sediment beside the fine-grained
iridium-rich asteroid dust layer,
if the quantity of re-entering ejecta was perfectly global in
blanketing the atmosphere, and if so, the duration and profile of the
re-entry heating, whether it was a high
thermal pulse of heat or the more prolonged and therefore more incendiary "
oven" heating, and finally, how much the "self-shielding effect" from the first wave of now-cooled meteors in
dark flight contributed to diminishing the total heat experienced on the ground from later waves of meteors, in part due to the
Cretaceous period being a high-
atmospheric-oxygen era, with concentrations above that of the present day.
[192] In 2013, Owen Toon et al. were critical of the re-evaluations the hypothesis is undergoing.
[184] It will be difficult to successfully tease out the percentage contribution of the soot in this period's
geological sediment record from living plants and
fossil fuels present at the time,
[193]
in much the same manner that the fraction of the material ignited by
the meteor's heating effects will be difficult to determine, as other
ignition sources that were also present at, or soon after, the impact
such as mantle
lava flows complicate the matter.
[178]
See also
- Doomsday device
- Younger Dryas impact hypothesis, a similarly controversial hypothesis that an impact event & fires triggered the last ice age.
- Younger Dryas, most recent ice age, ended approximately 10,000 BC, the event may be linked with the birth of agriculture.
- Impact event
- Impact winter
- Volcanic winter
- Krakatoa, 1883 eruption, which caused approximately 1 kelvin of global cooling for 2 years due to sulfate emissions.
- Year Without a Summer, 1815, created by a volcanic eruption in Tambora.
- Laki, 1783 eruption of an Icelandic volcano which produced continentally localized cooling for 1–2 years.
- Toba catastrophe theory, a controversial hypothesis that a volcanic winter produced by the eruption of a volcano in Toba, Indonesia, created a human population bottleneck approx 80,000 years ago.
- List of states with nuclear weapons
- Global dimming, global reduction in ground insolation, due to the atmospheric injection of aerosols from various sources.
- Nuclear darkness, hypothetical global nuclear war induced deep, and prolonged, dimming of daylight during the nuclear winter.
- Nuclear summer, hypothetical prediction of a prolonged increase in global temperatures following the end of a nuclear war.
- List of wildfires
- List of historic fires
Documentaries
- On the 8th Day - Nuclear winter documentary (1984) filmed by the BBC
and available on Internet video hosting websites; chronicles the rise
of the hypothesis, with lengthy interviews of the prominent scientists
who published the nascent papers on the subject.[194]
Media
External links
References
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