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Subject: Re: Ozone depletion (was Re: The Final {En
From: (FMims) 
Date: Sep 20 1995
Newsgroups: sci.environment

Jonathan Shanklin ( in Message-ID:
<43mtru$> writes:

>Data from the US NSF  Polar Ultraviolet Monitoring Network, combined
>with satellite and ground based ozone data clearly
>shows that when ozone goes down, uv at the surface goes up.  This has
>been published in peer reviewed journals - see the ozone FAQ.


It is important to qualify the general statement that "When ozone goes
down, uv at the surface goes up."

First, sun angle is vastly important. There is less ozone in the winter
than in the spring yet there is higher uv in the spring. Indeed, it can be
said that on an annual basis, ozone and UV are positively, not inversely,
correlated. Of course, for times when the sun angle is similar, ozone and
UV are usually inversely correlated.  

Second, aerosols in the form of haze can significantly reduce UV. I have
measured very substantial reductions of UV caused both by sulphate haze in
Texas and Maryland and smoke in Brazil. I also measured decreases in UV
caused by Pinatubo aerosols.

Finally, clouds can either reduce or increase UV without any change in the
ozone column. I have measured cloud-induced differences with model results
many times at many places and described enhancement of UV by cumulus
clouds in a paper (Nature, 22 Sep 94).

Forrest M. Mims III
Sun Photometer Atmospheric Network (SPAN)

Subject: Re: Ultra Violet (was sunscreen safety)
From: rparson@spot.Colorado.EDU (Robert Parson)
Date: Nov 18 1996

In article <>,
Paul Abraham  <> wrote:
>Dawn Birt wrote:
>> The only thing I can offer on this subject is this...  There are two
>> types of ultraviolet light, uvA and uvB. One, I can't remember which is
>> the harmful one that you hear so much abotu while the other does very
>> little harm.
>What actually is the difference?

 There is no sharp distinction, they are merely names for different
 regions of the UV spectrum. The wavelength range 400-320 nm is 
 called UV-A, 320-280 nm is UV-B, <280 nm is UV-C. (Sometimes the
 UV-A/UV-B boundary is given as 315 nm.) UV gets increasingly obnoxious
 as you go to shorter wavelengths; a 319 nm UV-B photon does not
 differ significantly from a 321 nm UV-A photon, but a 290 nm UV-B
 photon is a lot nastier than a 390nm UV-A.

 The A/B/C boundaries are set by the absorption spectrum of
 ozone. This starts at ~320 nm and rises to a peak at  ~260nm. 
 UV-A with wavelengths greater than 320 nm is not appreciably absorbed
 by ozone, while for wavelengths <280 nm (UV-C) the absorption is
 so strong that essentially every photon coming in from the sun is
 absorbed. It is the range 280-320 nm that is most affected by just
 how much ozone there is in the stratosphere.

 By a peculiar coincidence that presumably has some evolutionary 
 significance, DNA and some other biological molecules have a UV 
 absorption spectrum that resembles that of ozone, also turning on 
 at around 300 nm, which is why UV-B contributes to skin cancer and
 other nastinesses. Photon for photon, UV-B is more harmful than UV-A,
 but there's a lot less of it. Arguments over whether UV-A or UV-B
 is more harmful in some context hinge upon whether the larger number
 of UV-A photons arriving at the earth's surface offsets the greater
 harm that each UV-B photon can do. For sunburns, nonmelanoma skin
 cancer, and plant damage it is clear that UV-B is the primary culprit.
 For melanoma skin cancer the issue is unresolved.


From: (Robert Parson)
Subject: Re: [Q]UV, Ozone in the past
Date: 3 Dec 1997 22:35:05 GMT

[Newsgroups line trimmed].

In article <663so4$>,
Lloyd R. Parker <> wrote:
>Matthew Fain ( wrote:
>: Lloyd R. Parker wrote:

>: > If they developed on the surface (note that word) before there was an
>: > ozone layer, they would have been fried by uv radiation.
>: But that doesn't make David Green's original comment on the origin of
>: life only after the development of an ozone layer any less wrong!
>Nor does it make mine "life on earth's surface" wrong either, but
>apparently David (and others) just read some words and not all.

 Substitute "multicellular life on earth's surface" for "life on
 earth's surface"; some bacteria do just fine in a high UV environment.
 (Can't be that much worse than 400C hot springs, I suppose.)
 In particular, cyanobacteria are pretty UV-tolerant; this is
 interesting since it suggests that earth's first photosynthetic
 organisms were also. They had to be, to some extent - they had
 to get enough sunlight to photosynthesize, and this would expose them
 to _some_ UV. Seawater is more UV-transparent than most people think; see
 N.G. Jerlov, "Ultraviolet Radiation in the Sea",_Nature_ _166_, 112, 1950.
 In clear seawater UV at 315nm is attenuated by ~14% per meter.

 Life, oxygen, and the ozone layer all co-evolved. Oxygen started out
 as a waste product, and ozone as a secondary waste product. The
 obnoxious effects of UV on present-day life are due to a handful
 of photochemical reactions in biological molecules, most notably
 UV-induced pyrimidine dimers in DNA.


From: (Robert Parson)
Newsgroups: sci.chem,sci.geo.meteorology
Subject: Re: [Q]UV, Ozone in the past
Date: 3 Dec 1997 22:41:46 GMT

In article <>,
Larry Caldwell <> wrote:
>There has been substantial work done to calculate the effect of ozone
>depletion.  I forget the exact relationships, but UV shielding is also
>very dependent on altitude.  Going from sea level to 300 meters makes
>a significant difference in the amount of UV you are exposed to.

 Hmm, I don't know if 300 meters is significant, but a few km certainly
 is. About 10 percent of the ozone column is in the troposphere, and
 molecule-for-molecule tropospheric ozone is more effective (about
 twice, IIRC) at absorbing UV than stratospheric (because scattering
 by aerosols, etc. leads to a longer effective path length at low
 altitudes). You can get _very_ nasty sunburns climbing or skiing
 in the Colorado Rockies, but this is mostly due to the high
 UV reflectivity of snow and ice.


From: (Robert Parson)
Newsgroups: sci.chem
Subject: Re: Ozone Depletion
Date: 18 Jan 1998 20:59:54 GMT

In article <69pilc$>,
Mark Tarka <> wrote:
>Anyone with real numbers regarding the energy of solar radiation
>outside of the "atmosphere", compared to energy of radiation at the
>"ozone layer", and energy at the surface of the planet?

 See _Aeronomy of the Middle Atmosphere_, by Guy Brasseur and Susan
 Solomon, D. Reidel 1984 (1st edition) or 1986 (2nd Edition) and
 references therein for a thorough discussion; Chapter 3 of
 T. Graedel and P. Crutzen, _Atmospheric Change_, Freeman 1993 for
 an introduction. Quick summary:

 Wavelengths less than 100nm are absorbed at ~150km (thermosphere).

 100-200 nm are absorbed mostly by molecular oxygen, and penetrate
 to ~100 km (mesosphere) at 150 nm, to ~40 km (upper stratosphere)
 at 200 nm. This is how ozone is made.

 Wavelengths 200-280 nm are absorbed mostly by ozone (240-280 entirely
 by ozone) and penetrate to ~20km (mid-lower stratosphere).

 280-320 nm is the UV-B region, where the ozone cross section is falling
 off so that you start to get penetration to the surface. This is the
 spectral region where the ozone column thickness controls surface UV.
 Less than 280 nm (UV-C) it's all absorbed, greater than 320 nm (UV-A)
 it's essentially all transmitted.

 Add in scattering, reflection from the surface, etc.


Newsgroups: sci.environment,,sci.chem,,sci.physics
From: (Bruce Hamilton)
Subject: Re: Ozone depletion and biological effects
Date: Thu, 5 Feb 1998 14:44:52 +12

In article <6bb0hm$oop$4@nntp.Stanford.EDU>
jonathan@Kowhai.Stanford.EDU (Jonathan Stone) writes:

Kowhai is a beautiful NZ tree, so I suspect that Jonathan
knows somewhat more about NZ than his email address
might initially imply......

>In article <x4hg1lzbhvr.fsf@Steam.Stanford.EDU>,
>John McCarthy <jmc@Steam.Stanford.EDU> writes:
>|> I think there should be a study that studies effects of UV in high
>|> latitudes on people.... The govenments of Chile, Argentina,
>|> Australia and New Zealand shouldget together on a study.

>Some times, John, you really should stick to what you know...
>1) You're using the wrong tense.  UV effects are a highly visible
>   public issue in Australasia. I have yet to hear hourly announcements
>   of  burn-time on the radio in California, for example.
>   There are significant public-health campaigns to _change
>   behaviour_, to get people to wear sunhats, wear clothes in the sun,
>   and to use sunblock.

Yes, and I've previously posted some details of the fairly effective
" Slip, Slop, Slap " campaigns ( Slip on some clothes, slop on
sunscreen, and slap on a hat  - or some such ) that are widely
advertised by the health ministries of both countries. Note that these
programmes are in no way due to the Ozone hole, but because of
sun-worshipping lifestyles of fair-skinned peoplein areas of relatively-high
surface UV without the thermal discomfort of excessive exposure in
tropical climates.

>2) The New Zealand Government _used_ to fund an ongoing network
>   ground-level UV measurement with a long baseline.
>   Funding for that study was cut under a right-wing administration.
>   I belive, though I'm not certain, that Bruce Hamilton posted
>   a summary of this about 18 months ago. (Gosh, I do hope I'm not
>   confusing it with a ground-level CO2 monitoring program!)

No. The programme is still going, although funding was curtailed
from one science source, the health authorities have continued
funding some of the work. It wasn't "right-wing" adminstrators,
but just a perception that it was not a good research investment,
compared to other "science". The public health advantages seem
to wilt under science peer-review that looks for "relevance",
"scientific merit " and economic returns over the next few years.

Sadly, some of the problems may arise because the limited funds
available mean that the IRL programme, based in the major population
centres, was effectively competing with other UV monitoring programmes
using higher resolution spectrophotometers at remote locations with
clearer skies. Sometimes the simpler, well calibrated, systems lack the
scientific appeal of high tech systems. The current suggestion is that,
rather than measure the UV-B, and report it immediately to  radio stations
using telephone pager systems, as happens now,  the " UV Index "  or
the alternative " burn time " could just be predicted instead, based on the
date/time/cloud cover etc.

The " Public Good Science Fund " criteria apparently have problems
accepting the diligent science ( that is always being refined and
improved ) behind the programme should becontinued in the public good.
I haven't seen any comparison of the predicted v measured UV Index.

[ Disclaimer - I'm involved at the periphery of the IRL UV-B  programme, and
so may indicate some prejudices that certainly will not reflect the official
position of IRL. If you want the IRL position, ask the senior management. ]

>3) Finding volunteers to get sunburnt in the countries with the highest
>   incidence of melanoma in the world is likely to be bloody awkward.
>   I mean, you _are_ aware of the hypotheses that early childhood
>   exposure is  more important than adult exposure?
>   And of the difficulties of measuring exposure?

The hypotheses have been pretty much accepted here, as has the
sensitivity of people of European descent to the relatively high
UV-B here. It is accepted that sunburn as a  youth can result in
serious and fatal diseases several decades later. I've previously
posted the data that shows NZ and Queensland europeans have the
unenviable record for highest incidence and death rates due to
skin disease arising from solar UV exposure.

UV-B in Wellington NZ is 30% higher than the equivalent latitude in
Greece - apparently mainly due to the much clearer skies. Major
programmes have focussed on ensuring children are not exposed
to midday sun ( today is a glorious, clear blue sky, midsummer day
with a temperature in the mid 20s ( Celsius ), and a peak UV Index of
10.2 ), and some schools require children to wear protection before
being allowed in the playground during midday meal break.

         Bruce Hamilton

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