Ozone Loss Due to Geo: The Whole Story?

[Alvia Gaskill]

Comments on this in a subsequent posting. Give you time to put on
some sunscreen.

The media is in full runway foam mode about this, but these appear to
be the unique articles generated.

http://www.nsf.gov/news/news_summ.jsp?cntn_id=111467&org=NSF&from=news

Press Release 08-069
Injecting Sulfate Particles into Stratosphere Could Have Drastic
Impact on Earth's Ozone Layer

Much-discussed climate change mitigation strategy may do more harm
than good

Earth's ozone hole, shown in blue, could be exacerbated by some
efforts to mitigate climate change.
Credit and Larger Version

April 24, 2008

A much-discussed idea to offset global warming by injecting sulfate
particles into the stratosphere would have a drastic impact on Earth's
protective ozone layer, new research concludes.

The study, led by Simone Tilmes of the National Center for Atmospheric
Research (NCAR) in Boulder, Colo., warns that such an approach would
delay the recovery of the Antarctic ozone hole by decades and cause
significant ozone loss over the Arctic.

The study results are published today in the journal Science Express.
The research was funded by the National Science Foundation (NSF),
NCAR's principal sponsor, as well as by NASA and other agencies.

"Our research indicates that trying to artificially cool off the
planet may be a perilous endeavor," Tilmes says. "While climate change
is a major threat, this solution could create severe problems for
society."

"The challenges of global warming mitigation are extremely complex,"
said Cliff Jacobs, program director in NSF's Division of Atmospheric
Sciences. "Continued investment in basic research will allow the most
cost-effective solutions--and those of the most benefit to society--to
be found."

Climate scientists, concerned that society is not taking sufficient
action to prevent significant changes in climate, have studied various
"geoengineering" proposals to cool the planet and mitigate the most
severe impacts of global warming.

One of the most-discussed ideas is to regularly inject large amounts
of sun-blocking sulfate particles into the stratosphere. The goal
would be to cool the climate, much as sulfur particles from large
volcanic eruptions have cooling impacts.

Since volcanic eruptions temporarily thin the ozone layer in the
stratosphere, Tilmes and her colleagues looked into the potential
impact of geoengineering plans on ozone.

The new study concluded that, over the next few decades, artificial
injections of sulfates could destroy between one-fourth and three-
fourths of the ozone layer above the Arctic. This could affect a large
part of the Northern Hemisphere because of atmospheric circulation
patterns.

The sulfates would also delay the expected recovery of the ozone hole
over the Antarctic by about 30 to 70 years, or until at least the last
decade of the twentieth century, the authors warn. The ozone layer is
critical for life on Earth because it blocks dangerous ultraviolet
radiation from the Sun.

"This study highlights another connection between global warming and
ozone depletion, which had been thought of as separate problems but
are now increasingly recognized to be coupled in subtle, yet
profoundly important, ways," says Science Express paper co-author Ross
Salawitch of the University of Maryland.

To determine the relationship between sulfates and ozone loss, the
authors used a combination of measurements and computer simulations.

They then estimated future ozone loss by looking at two geoengineering
schemes--one that would use volcanic-sized sulfates, and a second that
would use much smaller injections.

The study found that injections of small particles over the next 20
years could reduce the ozone layer by 100 to 230 Dobson Units. The
average thickness of the ozone layer in the Northern Hemisphere is 300
Dobson Units. (A Dobson Unit is a common measure of ozone.)

For large particles, the loss would range from 70 to 150 Dobson Units.
The larger figure is correlated with colder winters.

In the Antarctic, the sulfate injections would not significantly
reduce the thickness of the already depleted ozone layer. Instead,
they would significantly delay the recovery of the ozone hole.

The authors caution that the actual impacts on ozone could be somewhat
different than estimated if atmospheric changes led to unusually warm
or cold polar winters. They also warn that a geoengineering project
could lead to even more severe ozone loss if a volcanic eruption took
place at the same time.

"Clearly much more research needs to be conducted to determine the
full implications of geoengineering before we may discuss seriously
the injection of sulfate aerosols into the stratosphere," says co-
author Rolf Müller of the Jülich Research Center in Germany.

-NSF-

Media Contacts
Cheryl Dybas, NSF (703) 292-7734 cdy...@nsf.gov
David Hosansky, NCAR (303) 497-8611 hosa...@ucar.edu

The National Science Foundation (NSF) is an independent federal agency
that supports fundamental research and education across all fields of
science and engineering, with an annual budget of $5.92 billion. NSF
funds reach all 50 states through grants to over 1,700 universities
and institutions. Each year, NSF receives about 42,000 competitive
requests for funding, and makes over 10,000 new funding awards. The
NSF also awards over $400 million in professional and service
contracts yearly.

http://environment.newscientist.com/article.ns?id=dn13773&print=true

'Planetary sunshade' could strip ozone layer by 76%
19:00 24 April 2008
NewScientist.com news service
Catherine Brahic
Advertisement
Planetary engineering projects to cool the planet could backfire quite
spectacularly: a new model shows that a "sulphate sunshade" would
punch huge holes through the ozone layer above the Arctic.

To make matters worse, it would also delay the full recovery of the
Antarctic ozone hole by up to 70 years.

Pumping tiny sulphate particles into the atmosphere to create a
sunshield that would keep the planet cool was first suggested as a
solution to global warming by Edward Teller, a physicist was best
known for his involvement in the development of the hydrogen bomb.

Simone Tilmes of the National Center for Atmospheric Research in
Colorado, US, used computer models to see how a sulphate sunshade
would affect the ozone layer, which protects us from harmful UV rays.
She says it could have "a drastic impact".

Tilmes modelled two different scenarios: one in which "large"
particles measuring 0.43 microns in diameter are used, and one where
the particles are two-and-a-half times smaller.

Cooling effect
Sulphate particles catalyse the breakdown of ozone molecules by
chlorine atoms. Western economies have almost entirely stopped using
chlorine-based coolants called CFCs, thanks to the Montreal Protocol.
However, such substances are increasingly being used in Asia and the
atmosphere is still full of CFCs emitted during the 20th century.

In January 2008, researchers described how much of each type of
sulphate particle would need to be injected into the stratosphere in
order to compensate for a doubling in atmospheric carbon dioxide
concentrations (Geophysical Research Letters, DOI:
10.1029/2007GL032179). Tilmes used these volumes in her computer
models.

She found that injections of small particles over the next 20 years
could thin the wintertime ozone layer over the Arctic by between 22
and 76%. Large particles, which would have less of a cooling effect,
according to previous research, would still reduce Arctic ozone by 15
to 50% during the winter.

In the Antarctic, the injections would delay the recovery of the
existing ozone hole by 30 to 70 years.

Cancer increase
A thinner ozone layer – popularly known as an ozone "hole" – lets more
UV rays through, which can cause an increase in the incidence of
various cancers. According to NASA, a 1% decrease in the ozone layer
can cause an estimated 2% increase in UV-B irradiation, leading to a
4% increase in basal carcinomas – the most common form of skin cancer.

In 2007, Ken Caldeira of the Carnegie Institution of Washington in the
US found that if a sulphate sunshield were deployed and then removed –
for instance because of a change in governments – the effects of
global warming after the removal would be far worse than before the
sunshield.

Caldeira has also found that a sunshade could cause severe drought.

Journal reference: Science (DOI: 10.1126/science.1153966)

Climate Change – Want to know more about global warming – the science,
impacts and political debate? Visit our continually updated special
report.

Related Articles
'Sunshade' for global warming could cause drought
http://environment.newscientist.com/article/dn12397
02 August 2007


http://www.examiner.com/a-1357988~Using_chemicals_to_cut_global_warming_may_damage_ozone_layer.html

Science
Using chemicals to cut global warming may damage ozone layer
By RANDOLPH E. SCHMID, The Associated Press
2008-04-24 18:01:39.0
Current rank: # 96 of 7,761

WASHINGTON -
The rule of unintended consequences threatens to strike again. Some
researchers have suggested that injecting sulfur compounds into the
atmosphere might help ease global warming by increasing clouds and
haze that would reflect sunlight.

After all, they reason, when volcanoes spew lots of sulfur, months or
more of cooling often follows.

But a new study warns that injecting enough sulfur to reduce warming
would wipe out the Arctic ozone layer and delay recovery of the
Antarctic ozone hole by as much as 70 years.

"Our research indicates that trying to artificially cool off the
planet could have perilous side effects," said Simone Tilmes of the
National Center for Atmospheric Research in Boulder, Colo.

"While climate change is a major threat, more research is required
before society attempts global geoengineering solutions," said Tilmes,
lead author of a paper appearing in Thursday's online edition of the
journal Science.

And while one study worries that fixing climate will destroy ozone,
another raises the possibility that recovery of the ozone hole over
Antarctica will worsen warming in that region.

A full recovery of the ozone hole could modify climate in the Southern
Hemisphere and even amplify Antarctic warming, scientists from the
University of Colorado at Boulder, the National Oceanic and
Atmospheric Administration and NASA report in a paper scheduled for
Geophysical Research Letters.

Although temperatures have been rising worldwide, there has been
cooling in the interior of Antarctica in summer, which researchers
attribute to the depletion of ozone overhead.

"If the successful control of ozone-depleting substances allows for a
full recovery of the ozone hole over Antarctica, we may finally see
the interior of Antarctica begin to warm with the rest of the world,"
said Judith Perlwitz of the Cooperative Institute for Research in
Environmental Sciences, a joint institute of CU-Boulder and NOAA.

The authors used a NASA supercomputer to model interactions between
the climate and stratospheric ozone chemistry. A return to pre-1969
ozone levels would mean atmospheric circulation patterns now shielding
the Antarctic interior from warmer air to the north will begin to
break down during the summer, they concluded.

The idea of reversing global warming by injecting sulfates into the
air was suggested by eruptions such as the 1991 blast by Mount
Pinatubo in the Philippines, which produced a brief cooling.

The massive 1815 eruption of Tambora in what is now Indonesia produced
such a strong cooling that 1816 became known as the "year without a
summer" in New England, where snow fell in every month of the year.

But Tilmes knew that volcanic eruptions also temporarily thin the
ozone layer, which protects people, plants and animals from the most
dangerous ultraviolet rays from the sun.

So she and colleagues calculated the effect of suggested sulfate
injections and concluded that the result, over the next few decades,
would be to destroy between one-fourth to three-fourths of the ozone
layer above the Arctic. This would affect a large part of the Northern
Hemisphere because of atmospheric circulation patterns.

The sulfates would also delay the expected recovery of the ozone hole
over the Antarctic by about 30 to 70 years, or until at least the last
decade of this century, they said.

The research was supported by the United Kingdom Meteorological
Office, University Corporation for Atmospheric Research and NASA.

The study comes just a day after the National Oceanic and Atmospheric
Administration reported that despite efforts to reduce greenhouse
gases, the rate of increase of carbon dioxide in the atmosphere is
accelerating.

Concern has grown in recent years about such gases, with most
atmospheric scientists concerned that the accumulation is causing
increases in the earth's temperature, potentially disrupting climate
and changing patterns of rainfall, drought and other storms.

The Intergovernmental Panel on Climate Change has worked to detail the
scientific bases of this problem and the Kyoto agreement sought to
encourage countries to take steps to reduce their greenhouse
emissions. Some countries, particularly in Europe, have taken steps to
reduce emissions.

But carbon dioxide emissions, primarily from burning fossil fuels such
as coal, oil and gas have continued to increase. Since 2000, annual
increases of two parts per million or more have been common, compared
with 1.5 ppm per year in the 1980s and less than one ppm per year
during the 1960s, NOAA's Earth System Research Laboratory said. Last
year the increase was 2.4 parts per million.

Meanwhile, in a separate paper in Science, researchers said human
activities are at least partly responsible for the Arctic having
become a wetter place over the last half century.

Seung-Ki Min of Environment Canada, and colleagues, studied rain and
snowfall patterns in the arctic and the factors affecting them.

They concluded that human-induced greenhouse gases have contributed to
the increased precipitation rates observed in the Arctic region over
the past 60 years.

They warned that this "Arctic moistening" could occur more quickly
than current climate simulations indicate.

Their work was supported by the U.S. Department of Energy and the
Canadian International Polar Year Program.

---

http://www.telegraph.co.uk/earth/main.jhtml?view=DETAILS&grid=&xml=/earth/2008/04/24/sciatmos124.xml

Global warming fix could damage ozone layer
By Roger Highfield, Science Editor
Last Updated: 7:01pm BST 24/04/2008

A climate "fix" to curb global warming would have a serious side
effect, damaging the Earth's protective ozone shield.

James Lovelock's plan to pump ocean water to stop climate change
A DIY guide to saving Planet Earth
Scientists have put forward several proposals to reduce the amount of
sunlight that reaches the planet's surface, including the use of light-
reflecting sulphate particles in the atmosphere and putting mirrors in
orbit around the planet.

Injecting polar stratospheric clouds with sulphate particles could
deplete ozone
But there have been warnings that using these radical "geoengineering"
techniques to cool our overheated planet could well present great
risks that could worsen global warming should they fail or be
discontinued.

These fears are borne out today by a study published in Science that
concludes that injecting sulphate particles into the stratosphere
would have a drastic impact on Earth's protective ozone layer.

Nobel laureate Paul Crutzen and other researchers have argued that
injecting large amounts of sun-blocking particles would have the same
effects as those caused by major volcanic eruptions in the past, such
as Mount Pinatubo, which have been observed to cut surface
temperatures.

But the new study, led by Dr Simone Tilmes of the National Centre for
Atmospheric Research in Boulder, Colorado warns that such an approach
might delay the recovery of the Antarctic ozone hole by decades and
cause significant ozone loss over the Arctic.

"Our research indicates that trying to artificially cool off the
planet could have perilous side effects," Dr Tilmes says. "While
climate change is a major threat, more research is required before
society attempts global geoengineering solutions. These would be in
addition to ambitious efforts to stop the increase of greenhouse
gases."

Since major volcanic eruptions temporarily thin the ozone layer in the
stratosphere, Dr Tilmes and her colleagues looked into the potential
impact of geoengineering plans on ozone over the poles.

advertisementSulphates from volcanoes provide a surface on which
chlorine gases in the cold polar lower stratosphere can become
activated and cause chemical reactions that intensify the destruction
of ozone molecules, although the sulphates themselves do not directly
destroy ozone.

The new study concluded that, over the next few decades, artificial
injections of sulphates could destroy between about one-quarter and
three-quarters of the ozone layer above the Arctic.

This could affect a large part of the Northern Hemisphere because of
atmospheric circulation patterns. The impacts would likely be somewhat
less during the second half of this century because of international
agreements that have essentially banned the production of ozone-
depleting chemicals.

The suphates would also delay the expected recovery of the ozone hole
over the Antarctic by about 30 to 70 years, or until at least the last
decade of this century, the authors conclude.

Recovery of the ozone hole has been a major goal of policymakers
worldwide, and nations agreed in 1987 to a landmark accord, known as
the Montreal protocol, to restrict the production of industrial
chemicals, known as CFCs (chlorofluorocarbons), that cause ozone-
destroying chemical reactions. The ozone layer is critical for life on
Earth because it blocks dangerous ultraviolet radiation from the Sun.

"This study highlights another connection between global warming and
ozone depletion," says co-author Dr Ross Salawitch of the University
of Maryland. "These traditionally had been thought of as separate
problems but are now increasingly recognised to be coupled in subtle,
yet profoundly important manners,"

"Much more research needs to be conducted to determine the full
implications of geoengineering" says co-author Dr Rolf Müller of the
Jülich Research Centre, Germany.

[Alvia Gaskill]

Here is the press release from the authors at NCAR. You will note
that the average ozone level in the NH is given as 300-450 DU, not 300
as in the news articles.

Also, although I haven't seen the paper itself, I've seen derivative
work and supplemental information included with the paper. The severe
ozone losses in the Arctic really only correspond to one part of the
Arctic, about one fourth of the area and only for a brief period of
time. Losses below the Arctic are also not any worse than what would
be considered normal for populated areas during the year. So, while
there is much to consider and take stock of in this work, I would
caveat that like much of what is reported about geoengineering, the
reality and the headlines seldom completely agree.

The work also fails (as do all of the articles we seem to discuss
here) to consider other possibilities than the scenarios considered,
namely that there might be ways to do the aerosol treatment that do
not lead to the types of ozone losses calculated. Considering other
scenarios is important if we are to find out what can be done. For
example, would offsetting 25-50% of AGW forcing cause the same types
of ozone losses?

http://www.sciencemag.org/cgi/content/abstract/1153966

http://www.sciencemag.org/cgi/content/full/sci;1153966/DC1

http://www.ucar.edu/news/releases/2008/ozone.jsp

Contacts for This Release
For Journalists
David Hosansky, Head of Media Relations
303-497-8611

Rachael Drummond, Media Relations
303-497-8604

Simone Tilmes, NCAR Scientist
303-497-1445

Rolf Müller, Jülich Research Center Scientist
49-2461-613828

Ross Salawitch, University of Maryland Professor
626-487-5643

Stratospheric Injections to Counter Global Warming Could Damage Ozone
Layer
April 24, 2008

BOULDER—A much-discussed idea to offset global warming by injecting

sulfate particles into the stratosphere would have a drastic impact on
Earth's protective ozone layer, new research concludes. The study, led
by Simone Tilmes of the National Center for Atmospheric Research

(NCAR), warns that such an approach might delay the recovery of the

Antarctic ozone hole by decades and cause significant ozone loss over
the Arctic.

Simone Tilmes. [ENLARGE] (Photo by Carlye Calvin, ©UCAR.) News media
terms of use*

The study will be published Thursday in Science Express. It was funded
by the National Science Foundation, which is NCAR's principal sponsor,
as well as by NASA and European funding agencies.

"Our research indicates that trying to artificially cool off the

planet could have perilous side effects," Tilmes says. "While climate

change is a major threat, more research is required before society
attempts global geoengineering solutions."

In recent years, climate scientists have studied "geoengineering"

proposals to cool the planet and mitigate the most severe impacts of

global warming. Such plans could be in addition to efforts to reduce
greenhouse gas emissions. One of the most- discussed ideas, analyzed
by Nobel laureate Paul Crutzen and other researchers, would be to
regularly inject large amounts of Sun-blocking sulfate particles into
the stratosphere. The goal would be to cool Earth's surface, much as
sulfur particles from major volcanic eruptions in the past have
resulted in reduced surface temperatures.

Sulfates and ozone

Since major volcanic eruptions temporarily thin the ozone layer in the

stratosphere, Tilmes and her colleagues looked into the potential
impact of geoengineering plans on ozone over the poles. Sulfates from

volcanoes provide a surface on which chlorine gases in the cold polar
lower stratosphere can become activated and cause chemical reactions
that intensify the destruction of ozone molecules, although the

sulfates themselves do not directly destroy ozone.

The new study concluded that, over the next few decades, hypothetical
artificial injections of sulfates likely would destroy between about

one-fourth to three-fourths of the ozone layer above the Arctic. This
would affect a large part of the Northern Hemisphere because of

atmospheric circulation patterns. The impacts would likely be somewhat
less during the second half of this century because of international
agreements that have essentially banned the production of ozone-
depleting chemicals.

The sulfates would also delay the expected recovery of the ozone hole
over the Antarctic by about 30 to 70 years, or until at least the last

decade of this century, the authors conclude.

Recovery of the ozone hole has been a major goal of policymakers

worldwide. Nations agreed in 1987 to a landmark accord, known as the

Montreal protocol, to restrict the production of industrial chemicals,
known as CFCs (chlorofluorocarbons), that cause ozone-destroying
chemical reactions. The ozone layer is critical for life on Earth
because it blocks dangerous ultraviolet radiation from the Sun.

"This study highlights another connection between global warming and

ozone depletion," says co-author Ross Salawitch of the University of

Maryland. "These traditionally had been thought of as separate

problems but are now increasingly recognized to be coupled in subtle,

yet profoundly important, manners."

This sunset over northern Sweden in winter 1992 has a red tinge due to
the presence of sulphate aerosol particles that were injected into the
stratosphere by Mt. Pinatubo in June 1991. Also visible are polar
stratospheric clouds, called mother-of-pearl, that consist of ice
particles. [ENLARGE] (Photo by Fred Podlak, ©1992.)

Ozone impacts

To determine the relationship between sulfates and ozone loss, the
authors used a combination of measurements and computer simulations.
They then estimated future ozone loss by looking at two geoengineering

schemes--one that would use volcanic- sized sulfates and a second that

would use much smaller injections.

The study found that injections of small particles, over the next 20
years, could reduce the ozone layer by 100 to 230 Dobson Units. This
would represent a significant loss of ozone because the average
thickness of the ozone layer in the Northern Hemisphere is 300 to 450
Dobson Units. (A Dobson Unit is equivalent to the number of ozone
molecules that would create a layer 0.01 millimeters thick under
conditions at Earth's surface).

With large particles, the Arctic loss would range from 70 to 150
Dobson Units. In each case, the larger figure is correlated with
colder winters.

The ozone loss would drop in the later part of the century to about 60
to 150 Dobson Units, depending on the size of the sulfates and the
severity of winters.

In the Antarctic, most of the ozone is already depleted and the

sulfate injections would not significantly reduce the thickness of the

ozone layer. Instead, they would significantly delay the recovery of
the ozone hole.

The authors caution that the actual impacts on ozone could be somewhat
different than estimated if atmospheric changes led to unusually warm
or cold polar winters. They also warn that a geoengineering project

could lead to even more severe ozone loss if a major volcanic eruption

took place at the same time.

"Clearly much more research needs to be conducted to determine the

full implications of geoengineering before we may seriously consider

the injection of sulfate aerosols into the stratosphere," says co-
author Rolf Müller of the Jülich Research Center in Germany.

About the article
Title: "The sensitivity of polar ozone depletion to proposed geo-
engineering schemes"

Authors: Simone Tilmes, Rolf Müller, and Ross Salawitch

Publication: Science Express, April 24, 2008

Contacts for This Release
For Journalists
David Hosansky, head of Media Relations
303-497-8611, hosa...@ucar.edu

Rachael Drummond, Media Relations
303-497-8604, rach...@ucar.edu

[Ken Caldeira]

I see in one of the stories:

"Caldeira has also found that a sunshade could cause severe drought."

I am not aware of every having found that.

--
===============================
Ken Caldeira
Department of Global Ecology
Carnegie Institution
260 Panama Street
Stanford, CA 94305 USA
+1 650 704 7212; fax: +1 650 462 5968

kcal...@stanford.edu

http://globalecology.stanford.edu/DGE/CIWDGE/home/main%20page/caldeira.php

[Alvia Gaskill]

She got you confused with Trenberth.  But she also wrote both articles for the New Scientist.  One of the downsides of being a famous geoengineer, I guess.  You get credit for everything.

[Alvia Gaskill]

Following up on the Tilmes et al. work, I think there is a mismatch in
the time scales and amount of precursor added. They assumed 2Tg of S
per year based on the Rasch et al. (2008) work in which the aerosol
formed would be similar sized to known volcanic produced aerosol (and
likely to that from a human aerosol program also, it appears from my
recent reading).

However, the 2Tg/yr loading would, after a few years result in a
stratospheric reservoir of nearly 6Tg, since the Rasch work also
assumed around a 3-year lifetime for the aerosol. The 6Tg would be
enough to balance out an effective doubling of CO2 from pre-industrial
or some other baseline, but this level of loading wouldn't be
necessary in 2020, the time period when the massive Arctic ozone
depletions were calculated.

In fact, the level of S needed to balance out all human GHG forcing
added by 2020 would be around 3.5Tg. The 6Tg level wouldn't be
reached until around 2050.

If the goal is simply to stabilize the forcing at the 2000 level (a
moving target that the emissions reduction people keep rationalizing
forward as the various schemes they keep proposing keep falling behind
schedule or apart altogether), then the 2Tg per year wouldn't reach
the 6Tg reservoir level until almost 2080, when the ozone depleting
chemicals are nearly all gone from the stratosphere. In fact, in
2020, you would only need a total reservoir of 2Tg to offset the
forcing added since 2000, about a third of what the ozone depletion
modeling appears to have used.

If my assumptions are correct, the ozone depletion forecasts made in
the Tilmes et al. work are excessive, since they are based on an
incorrect understanding of how much forcing offset is actually
required to stop global warming. Even if I am wrong, the authors need
to consider the various scenarios and what they would actually mean to
Arctic and northern midlatitude ozone depletion. This would provide a
more balanced view of the options available than the media fire drill
that occurred yesterday and continues today.