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per gram of air.

Most of the moisture measurements made between the tropo


pause and 30 lom the limit of balloon sounding are in the range 1-4 micro


grans per gran (1). The stratosphere is kept dry by this natural freeze-out mechanism and the total moisture content above 16 km is about 2015


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The flux of moisture into the stratosphere based upon current estimates


of the mean vertical velocity at the tropopause (2, 3) is between 7 and

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the stratosphere from methane and hydrogen passing up from the troposphere

and oxygen already in the stratosphere (4). This possibility contributes

to the uncertainty in the flux figure.

For flux values of 7 and 10 million


grams per second the mean residence times (content derived, by flux) are

4.5 and 3.2 years respectively. Recent estimates of the mean residence

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times of carbon 14 and tritium are 3.3 years and 3.5 years respectively

(5, 6).

These residence times for gases are of course longer than those

for particles which are usually taken to be about 1 1/2 to 2 years in the


region below 25 km.

The water vapor observations fit together well, with perhaps the main


uncertainty being the methane contribution, and the natural flux is brac

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500 planes will contribute about 2 million grams per second the main


difference being that this water vapor is added above the cold trap.

the long run then the stratospheric water vapor content will go up by 20

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= mean flux times residence time). Locally in regions of

high travel density there will of course be regions of much higher concen


Patches of air with radioactivity concentrations well above the

global mean persist for many months after nuclear tests and radioactive

tungsten from the 1958 Pacific shots was seen to have higher concentrations

in the tropical stratosphere than in the high latitude stratosphere for

more than two years.

Water vapor enters the stratosphere at low latitudes in the rising

motion region of the lladley cell circulation (see figures in my Scientific

American article attached). There are no major middle lacitude sources;


if there were there would be a much higher mean concentration observed in

the stratosphere for the temperatures are much higher, at middle latitudes.

Much has been said in the press concerning thunderstorms as a source of

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of the mean Hadley cell circulation at low latitudes but they cannot

Introduce more than the number quoted above of 7-10 million grams per


If they did the stratosphere would very soon show evidence of

increasing water vapor concentrations.

The hypothesis in these letters

to the press that one thunderstorm introduces as much as 2 million grams

per second and that thousands are penetrating to 70000ft. at any one time

implies rapid flooding of the stratosphere.

It is clearly an incorrect

hypothesis and it is significant to me that it has not been offered

seriously in the scientific literature; I cannot even trace its originator!

There are three consequences of this additional water vapor:

it will

change the radiative cooling in the stratosphere; it will interact with

ozone to reduce the ozone concentration; and it may give rise to additional


The change in radiative cooling due to the presence of the vapor

alone is expected to be small (7). Basically this is because water vapor

plays a subsidiary role to ozone and carbon dioxide in the stratosphere.

The problems of computing the ozone concentration in an atmosphere

containing water vapor have been studied by a number of people in the

past few years. (8-13). Ozone (03) 1s formed when atomic oxygen (0) originating from molecular oxygen (O2) by the absorption of short wavelength radiation, combines with molecular oxygen (O2). The studies show an expected decrease of ozone; for example Harrison of the Boeing Company

predicts a decrease in ozone of about 4% from the additional SST water

vapor. Basically the decrease occurs because the hydrogen from the water

vapor acts as a catalyst to change ozone back to molecular oxygen.


reactions that take place at these high altitudes are not known with


it is quite possible that hydrogen introduced from the fuel

in forms other than water vapor would act in the same way to further

deplete the ozone.

Professor MacDonald has raised the possibility that


the decrease in ozone will permit more ultraviolet to reach the surface

and that this in turn will increase the incidence of skin cancer.

It is

straightforward to estimate the magnitudes involved in the first part of

his hypothesis. For example at the latitude of Miami in summer ultraviolet at 30008 wavelength would increase by 11% if ozone decreased by 4%, assuming

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the biological effects of ultraviolet light (e.g. 14, 15) and it is not

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I discussed the possibility of cloud formation one year ago and there have been no scientific rebuttals in the literature since. It is also


discussed in the M.I.T. Study of Critical Environmental Problems (16).

Clouds form in air which is saturated with water vapor; the air can


hold less water vapor at low temperatures and in the stratosphere rising

motion and adiabatic expansion coupled with radiative processes produce

the low temperatures.

Clouds occur naturally in the 22-27 km height range

at high latitudes in winter.

These mother-of-pearl clouds are often

reported as patches over Norway but as continuous sheets over the Antarctic

where temperatures are lower.

The region of cloud formation would be

expected to grow in extent as the water vapor concentration Increases.

The feedback of the clouds on the temperature distribution cannot properly

be assessed without a comprehensive dynamical model and this is not yet


The region of increased cloudiness will correspond fairly

closely with the region of lowest temperatures at 25 kom. In January this

region is over Norway, Greenland and Iceland and sometimes moves over


(see two examples in Figure 1). Temperatures are normally too

high for additional clouds to form in the summer season near 25 km.

Clouds form near 80 km in summer at high latitudes; again they occur

In regions of low temperatures and rising motions.

These noctilucent

clouds are often obsrved over Norway and Sweden. Again increased water

vapor would be expected to result in increased clouds.

I note here that changes in other gaseous constituents such as the oxides

of nitrogen and hydrogen as mentioned earlier, can alter ozone amounts. Few

computations have been performed (11).

All the estimates of the influence on the real atmosphere require a full

dynamical model simulation before they can be properly assessed; this applies

to the photochemical computations which need to have the effects of atmospheric

motions included (after all they are dominant in the lower stratosphere) as well

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as the discussion of clouds.

In addition a careful study of all other

possible reactions is needed.

Measurements are required of all the gaseous

and particulate components of the stratosphere and for a full understanding

these should be on a global basis.


The SST fleet will introduce small particles directly into the stra

tosphere and as there are no processes acting to wash them out their resi

dence time is long, typically 2 years.

This hold-up of particulate debris

was quite evident in the nuclear test observations and contrasts sharply

to the case of the troposphere where most of the muclear debris was removed

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within 30 days (much by rainfall). The amounts of aerosols that might be

lavolved are discussed in the M.I.T. Summer-Study book (16) and I will

Qot repeat the discussion here.

Not discussed at length there is the

possibility of smog formation from the gases introduced by the sst. Large

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quantities of oxides of nitrogen are expected, together with traces of

hydrocarbons and these seem to be the necessary ingredients of smog.


short-wave flux favorable to smog formation is stronger in the stratosphere

than at the surface and there is of course ozone in abundance,

The whole

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topic of particle formation in the stratosphere is at a very rudimentary

stage and needs much more work. In fact the joint Interaction between
ozone, water vapor and oxides of nitrogen 18 another area where much remains

to be done.

Parenthetically suppose that you had been told in 1920 that the emissions

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from autos in California would build up to the point where in 50 years

time school-children would be kept indoors and told not to excercise


would have been the response? We now have the smog and are taking plece

meal actions aimed at ensuring that it does not get too much worse but

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there is little serious hope of major improvement. If the SST fleet does

produce stratospheric smog in 1990 what hopes would there be for a rever

sal then? By then so many jobs will be involved that the arguments will

be the same as those used to justify the condition of Los Angeles now.



We do know that when particles appear in the stratosphere they absorb

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sunlight and lead to higher temperatures. After the Mt. Agung, Bali

eruption in 1963 temperatures in the lower stratosphere increased by 5-8°C

over equatorial regions (18). We do not know whether the volcano Intro

duced particles directly or whether it introduced gases (sulphur dioxide

and water vapor) which contributed to particle growth.


The small particles introduced by the volcano absorbed sunlight and

this caused a rise in temperature of the lower tropical stratosphere. In

turn this higher temperature permits more water vapor to enter the

scratosphere (as the cold trap is heated) and there has been some evidence from noctilucent cloud occurrence that volcanoes are associated with the clouds. My point here is that if the SST's introduce substances from

which particles can form then nature can augment the additional water

vapor introduced by the planes by its own water vapor from the troposphere

passing upwards through the cold trap.


500 SST's flying 7 hours/day and using 28000 lbs of fuel per hour per

engine will require about 340 million barrels of fuel per year. This

about 200

should be compared with the present jet fuel production rate
million barrels per year (19). The future sst requirements will exceed all

present jet uses.

If we assume that 100 barrels of crude oil give 44 barrels of jet fuel

the total crude oil necessary will be about 775 million barrels per year

or in round figures 2 million barrels per day. As can be seen in the

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