Ozone Depletion: The Story of a Successful Environmental Agreement and Some Linkages

and Parallels to Climate Change Susan Solomon

1. Antarctic ozone depletion: discovery of the ozone hole, ozone hole chemistry

2. Arctic versus Antarctic

3. How Montreal helped Kyoto (a lot)

4. Looking back: Antarctic history

5. Looking ahead

Ozone And You, and Your World

What ozone does: The ozone layer protects life on the ground from DNA-damaging UV light.

What ozone depletion doesn’t do: ozone depletion doesn’t warm up the planet.

But chlorofluorocarbons are greenhouse gases….

An ozone surprise!!

Once used in:

Spray cansInsulating foamsRefrigerationACSolventsAnd more…..

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We have identified one factor that has substantially strengthened the stratospheric vortex: less ozone makes it colder, and this is well documented and understood.

Antarctica really is thecoldest place on Earth.

Clouds that form in the cold Antarcticstratosphere allow surface(heterogeneous) chemistry to take place,enhancing ozone destruction bymanmade chlorine.

Key reaction isHCl + ClONO2 -> Cl2 + HNO3

(Solomon et al., Nature, 1986).

"The light was especially good today; the sunwas directly reflected by a single twistediridescent cloud in the north, a brilliant andmost beautiful object."

(Robert Falcon Scott,Diary entry for August 1, 1911)

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ClONO2Cl2

Polar cloud surfaces lead to muchmore ozone destruction, in the heart of the layer

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Amount of ozone

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ReservoirsActivatedfor ozone lossSun+Cold: Both Needed

David Hofmann and colleagues

Fingerprint in time and space:

Normal ozone in August

Dropping in September….

Dropping more…..

Fingerprint in altitude: Enhanced ClO from 12-24 km

1000 pptv ClO destroys about 2-3% of the ozone per day based on known chemistry…so ozone all gone in about 5-7 weeks….

Enhanced by 100x

AAOE mission in August-September 1987:

observations inside the polar vortex show high ClO is related to a strong decrease of ozone over the course of the Antarctic spring, as sunlight returns to the polar cap

Fingerprint in latitude

Ground-based and airborne expeditions measured a host of important chemicals….ClO, OClO, NO, NO2, HCl…..

-> Massive perturbations to Antarctic chlorine chemistry on PSCs, capable of depleting the ozone layer very effectively.

Poles Apart: Arctic and Antarctic

Solomon, Portmann and Thompson, PNAS, 2007

Records in the Antarctic are more systematic and complete than in the Arctic - a legacy of the Antarctic treaty that has benefitted global environmental decision-making.

Red - balloon sondes

Black - total column

Antarctic and Arctic Total Column Ozone Changes

Larger total column changes in colder Antarctic. Continuous records since 1957 in Antarctica at 4 sites, only 1 in the Arctic

From a science perspective:

-Evidence for understanding the ‘fingerprint’ of ozone depletion as a function of latitude, altitude, and season.

-Well understood chemistry. Active chlorine directly destroys ozone. Feedbacks are small, and chlorine is well-measured along with many other chemicals.

-Linkages between the ozone hole and CFCs can be established in just one season of observations.

From a practical perspective:

-Danger of cancer is personal, substitutes for the CFCs available, and chemical industry/safety issues have broad public understanding.

Concern about ozone depletion led the nations of the world to agree to a Montreal Protocol to freeze and then phaseout CFC emissions.

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Quotations About Ozone Negotiations, From A Book By A Participant

“Skepticism about the …..theory and minimizing of possible

harmful effects marked the official XXXX position.”

“The YYYY government based its position and tactics largely on the self-serving data and contentions of….big companies.”

“The ZZZZ government and its allies introduced a resolution…..for arriving at a legally binding control protocol.”

Quotations About Ozone Negotiations, From A Book By A Participant

“Skepticism about the….theory and minimizing of possible

harmful effects marked the official UK position.”

“The European Commission government based its position and tactics largely on the self-serving data and contentions of….big companies.”

“The US government and its allies introduced a resolution…..for arriving at a legally binding control protocol.”

Benedick, Ozone Diplomacy

The United States was the world leader on the Montreal Protocol to protect the ozone layer (in 1987).

US, Canada, Sweden and Norway ban CFCs in sprays (only)

Many Different Sectors Used Ozone Depleting Substances

+ small use in medical applications such as asthma inhalers, specialty electronics etching, etc.

CFCs -> deplete ozone, are potent greenhouse gases.

HCFCs and HFCs substitutes -> less or no ozone loss, but also greenhouse gases

Benefits of Montreal Protocol for Climate

World avoided by the Montreal Protocol?

Reduction Montreal Protocol of ~11 GtCO2-eq/yr

5-6 times global Kyoto target

New issue now under consideration: how to reduce emissions of HFC substitutes too.

CO2 emissions

Velders et al., PNAS, 2007

Ozone and Climate in the VortexA fundamental aspect of temperature, wind, and climate variability in the polar regions

Gillett and Thompson

Circulation trends in SH linked mainly to ozone depletion, with secondary effects of GHGs; see also Arblaster/Meehl, Miller, Cai/Cowan…

Ozone depletion made the vortex ‘tighter’, i.e.strengthened the westerlies around Antarctica and enhanced warming in Peninsula region

March 3: “What poet has ever sung of the splendour of the polar world…we were held spellbound by this spectacle…..a dazzling dreamscape….”

Captain Adrien de Gerlache de Gomery,

Age 29

The Belgian Antarctic Expedition 1898

An international crew November 12, 1897 (Montevideo) “The women here are unforgettable. I have never seen so many beautiful women in one place at the same time.”

February 23, 1898 “Unfortunately the scientists are very frightened….why did they come here then? Wasn’t it to discover unknown territory?”

July 10, 1898 “The state of health of those on board is not too good”

July 8, 1898 “Everyone has an irregular heartbeat.”

Roald Amundsen, Norwegian

An international crew

“depression…heart action is failing…difficulty in respiration….headaches… insomnia…. gastric disorder”

“diet of canned food [leads to] something in the human system which makes it refuse to utilize the elements of nutrition.”

As doctor, Cook ordered restriction of food to fresh meat. His finest hour?

Frederick Cook, American

June 6: “In the obscurity of the midday twilight we carried Lieutenant Danco's body to a hole which had been cut in the ice, and committed it to the deep. A bitter wind was blowing as, with bared heads, each of us silent, we left him there...And the floe drifted on...”

July 10: “The observations during the night wore me out very quickly….my greatest desire is for fresh meat, eggs, and milk…”

Arctowski was Polish, and returned there after the expedition. In 1939 he was at a scientific meeting on climate in Washington DC when war began. He stayed in the US and continued to work as a scientist…. at the Smithsonian.

Arctowski made hourly met obs together with Lt. Danco

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Variability of Peninsula Climate

Day of Year

Temperature (°C)

Belgica, 1898-1899

“The notable drop in temperature during the first 15 days of September is probably quite unusual….the wind direction has a preponderant influence….” - Arctowski

Stronger westerlies, fewer cold excursions, warmer Peninsula climate now due to ozone depletion. See Zazulie, Rusticucci, and Solomon, J. Clim., Jan., 2010

Arctowski; August 5, 1898: at 8 am the sky was beautiful….the clouds themselves refracted and decomposed the light of the dawning day….one could see….prismatic colors produced by the iridescent clouds…” (published in Ciel et Terre, 1902).

Probably the first observation of an Antarctic polar stratospheric cloud (PSC).

Photo by Seth White

PSCs: a beautiful curiousity…..until they teamed up with increasing CFCs due to people to cause the ozone hole in the early 1980s….

Antarctic ozone science: Antarctic ozone science: a tool for diplomacya tool for diplomacyan enduring source of policy issues (even now, an enduring source of policy issues (even now,

with HFCs)with HFCs)an enduring source of new paradigms (ozone, an enduring source of new paradigms (ozone,

winds….)winds….)a confidence-building activitya confidence-building activitya source of design advice in policya source of design advice in policya place to monitor, verifya place to monitor, verifyan early warningan early warninga source of insights into effectiveness of regimesa source of insights into effectiveness of regimesan example of science as a force for changean example of science as a force for change

AndAndscience that connects us toscience that connects us toour choices, our world, and Antarctica’s historyour choices, our world, and Antarctica’s history