Lecture Slides on Nuclear Winter - Nuclear Warfare | PHYS 20061, Papers of Physics

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Nuclear WinterNuclear Winter

What is Nuclear Winter?

Prediction by some scientiststhat smoke and debris risingfrom massive fires of anuclear war could blocksunlight for weeks ormonths, cooling the earth'ssurface and producingclimate changes that could,for example, negativelyaffect world agricultural andweather patterns. (EPA)

Carl Sagan and others conductedCarl Sagan and others conductedadditional studies and found that sootadditional studies and found that sootfrom cities and dust from the explosionsfrom cities and dust from the explosionsthemselves were also climaticallythemselves were also climaticallysignificant and could cool the surface ofsignificant and could cool the surface of

the earththe earth

In 1983, R.P. Turco, O.B. Toon, T.P. Ackerman, J.B. Pollack, andCarl Sagan (referred to as TTAPS) published a paper entitled" Global Atmospheric Consequences of Nuclear War

" which is the

foundation that the nuclear winter theory is based on.The theory states thatnuclear explosions willset off firestorms in thecities and surroundingforest areas. The smallparticles of soot arecarried high into theatmosphere. The smokewill block the sun'slight for weeks or months.The land temperatureswould fall below freezing.This^ combination

of^ reduced^ temperatures

and^ reduced^

light

levels^ would^

have^ catastrophic

ecological^ consequences. Average light levels would be below the minimum required forphotosynthesis during the first 30-40 days after the explosion andmost fresh water would be frozen. The TTAPS study concluded:"...the possibility of the extinction of Homo Sapiens cannot beexcluded." This effect is similar to what may have killed thedinosaurs.

Natural Disasters Nuclear winter theory is supported by observationalevidence from natural catastrophic events: ‰ Volcano eruptions ‰ Asteroid impact ‰ Bushfires

Krakatau^1883 >130 active volcanoes in Indonesia, Krakatau eruptions: 535 AD, 1883 AD, 200X Considerable impact onglobal temperatureswas recorded for bothvolcano events!

Effects on Sunset

Spectacular sunrise andsunset colors from sulfuricparticles and dust:Painting by William AshcroftNovember 1883

The vivid red sky inEdvard Munch’s painting“The Scream” wasinspired by the twilightsin Norway

Scattering effects of photons onsub-micron sized particles in thedusty stratosphere & troposphere

Krakatau’s impact on art!

Sulfur and Aerosol Effects Conversion of ejected gaseous SO

2

into H^ SOwithin six months^24 Increase of stratosphere temperature by ~

o^ , decrease of temperature in hemisphere by ~0.

OHSOH o. OHOH SO^

(^242) 2 2

2 3

+⇒ ++

Asteroids^ Relatively frequentevents over the age ofthe earth, 47 arerecorded on NorthAmerican continent Artist’s conception & computer simulation^ same conclusion:^ ⇒^ BIG SPLASH!

Geological Time-scales Catastrophic^ events

are^ often associated with drastic geologicalchanges.^ The

best^ known example^ is^ correlated

with^ the end^ of^ the^ Cretaceous

period. This^ change^ is

correlated^ with the^ sudden^ extinction

of^ the Dinosaurs^ as^

well^ as^ with^ the disappearance of 60-80% of theexisting marine species.^ FREQUENCY OF IMPACTORS:^ Pea-size meteoroids - 10 per hour^ Walnut-size - 1 per hour^ Grapefruit-size - 1 every 10 hours^ Basketball-size - 1 per month^ 50-m rock that would destroy an area the size of New Jersey - 1 per 100 years^ 1-km asteroid - 1 per 100,000 years^ 2-km asteroid - 1 per 500,000 years^ A "nemesis" parabolic comet impactor would give us only a 6-month warning.

Common explanation, impact of alarge asteroid which caused dusteruption and long term decrease ofglobal temperatures.

Iridium rich layer

Impact energy

The impact energy deposited = the

kinetic energy^ ( KE

) of incoming object, where ν^ is large! Orbital velocity ~ 30 km/sec = 66,000 mphMass is large!^

where^ d^ is the diameter of the object.

For rocks, Density ~ 5 gr/cc ===> Mass ~ 2.

3 d tons, with^ d^ in meters

Converting to equivalent explosive energy in units of tons of TNT. 1 ton TNT = 4 x 10

16 ergs.

===> Impact energy = 250

3 d equivalent tons of TNT.

An object with^ d

=4 meters packs the explosive power of the Hiroshima bomb (20,000 tons).

If^ d =200 meters, a common size of asteroid, energy =

1 2 vM 2 2 billion tons of TNT=2000 Megatons!

KE^ ⋅=^6

3 dV

M^

π=ρρ

Further consequences of^ smaller asteroid impact:^ Spreading of wild fires

Observational evidence in soot layersassociated with Iridium enrichment

Dire Consequences

The Chicxulup event corresponds to 70 Million Megaton TNT~ 7000 times the maximum arsenal of US and Soviet Union!