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Annex VI : Summary of the science symposium: challenges and perspectives - ozone layer protection

Prague, Czech Republic, 19 November 2004

Chaired by Professor Mario Molina[9]

Throughout the twentieth century, halocarbons – including chlorofluorocarbons (CFCs) and methyl bromide – were used in increasing quantities for many industrial, agricultural, and domestic uses. In 1974, Mario Molina and Sherwood Rowland hypothesized that CFC emissions would significantly deplete the stratospheric ozone layer. The ozone layer protects the earth from harmful ultraviolet radiation that causes skin cancer, cataracts, suppression of the human immune system, and damage to agricultural and natural ecosystems. In 1985, scientists reported that alarming ozone depletion had been occurring over Antarctica since the early 1980s; scientists later reported that ozone depletion was also occurring at other latitudes. In 1987, The world’s Governments addressed this global environmental challenge by signing the Montreal Protocol on Substances that Deplete the Ozone Layer. The Montreal Protocol has proven to be a remarkable model of the way to solve global environmental problems through its reliance on scientific and technical advice, time-bound control measures, universal membership, and assistance to developing countries through a multilateral fund.

The Protocol is working. The emissions of ozone-depleting substances (ODS) have been greatly reduced and the overall level of ODS in the atmosphere is now in decline. This is a clear manifestation of international cooperation reversing human-induced changes in the chemical composition of Earth’s atmosphere.

Mario Molina – who with Sherwood Rowland and Paul Crutzen was awarded the 1995 Nobel Prize in Chemistry for pioneering ozone depletion science – convened the Prague Science Symposium in November 2004, at this critical stage in the implementation of the Montreal Protocol. The participants in the Symposium highlighted the importance of both the achievements of the Protocol and international solidarity in completing the phase‑out of ODS. They further emphasized the importance of preserving the integrity of the Montreal Protocol process, which is a successful example of how sustainable development can be assured for all nations, rich and poor.

The Montreal Protocol is working, but leaves no room for complacency.

The ozone layer is expected to recover in coming decades, assuming the full implementation of the Montreal Protocol. However, much remains to be done to complete our scientific understanding and the implementation of the Protocol. The ozone layer remains vulnerable due to the large amount of ODS that will remain in the atmosphere for many years to come. Scientific and policy efforts need to be continued until the protection of the ozone layer is fully achieved. Implementation of the Protocol requires continued efforts to develop and deploy alternatives to all currently used ODS.

Ozone‑depletion science: achievements and challenges

Our scientific understanding of the ozone layer has grown substantially over the past decades and has provided essential guidance to the Parties to the Montreal Protocol. Scientific research has led to: discovery of the Antarctic ozone hole and ozone depletion at other latitudes, development and validation of the ozone depletion theory, deployment of the ozone and ODS‑monitoring networks, and estimation of benefits of phase‑out of ODS under the Montreal Protocol.

Early warning and periodic assessments by scientists of policy-relevant information allowed nations and multiple stakeholders to build consensus on actions to protect the ozone layer. Scientific findings guided Governments to design controls for ODS and incentives for alternatives; guided industry to develop alternatives with higher energy efficiency, greater reliability, and less manufacturing waste; and provided the information necessary to transform markets at a pace that protected existing investment.

Since the onset of ozone depletion in the 1980s, however, human activities have continued to alter atmospheric composition through the increased emissions of a variety of chemical species in addition to those containing chlorine and bromine. These other species have changed important conditions that directly or indirectly influence the transport and loss of stratospheric ozone. For example, water vapour has increased and temperatures have decreased in the ozone layer. It is important to be able to predict future ozone abundances in our chemically changing atmosphere.

Furthermore, climate change is expected from the continuing accumulation of greenhouse gases in the atmosphere. Because ozone, ODS, HFC and some other substitutes are greenhouse gases contributing to the radiative balance of the Earth’s atmosphere, climate change is influenced by the reduction and phase‑out of ODS. Ozone depletion, in turn, depends on climate change through changes in atmospheric composition and meteorology. As a consequence of the complex interrelationship between ozone depletion and climate change, there is a clear need for scientists to continue development of atmospheric models to predict with greater accuracy how the ozone layer will change in the future.

The protection from ultraviolet radiation provided by the ozone layer limits damage to phytoplankton that provide a carbon sink in oceans. Because the formation of skin cancer by ultraviolet radiation increases at higher temperatures, climate change will increase skin cancer incidence, compounding the effects of ozone depletion. Monitoring and assessment of the global atmosphere by a large international group of scientists using space-borne and ground-based instruments has successfully guided the Montreal Protocol and will be essential in the coming decades as the ozone layer recovers.

It is paramount to maintain and further strengthen the scientific basis of the Protocol, particularly in developing countries, by building expertise and institutions for addressing, in a sustainable manner, the depletion of the ozone layer and other adverse environmental changes. This strengthening requires financing of scientific activities by national governments, private organizations, and multilateral agencies such as the United nations Environment Programme (UNEP), World Meteorological Organization (WMO), the World Bank and United Nations Educational, Scientific and Cultural Organization (UNESCO).

Implementation of the Protocol: progress and opportunities

As the phase‑out of ODSs reaches the final stage, some users may attempt to justify, on the plea of insignificant impact, continued uses that could be granted under the terms of the Protocol. The Symposium Participants urged strong caution because the cumulative effect of many small continuing uses and emissions can add a significant amount of ozone-depleting chlorine and bromine to the atmosphere. Furthermore, Parties to the Protocol need to determine, with guidance of scientists, whether current emissions exempted from control under the Montreal Protocol, such as feedstocks, process agents, essential uses, critical uses, laboratory and analytical uses, and other inadvertent uses, are environmentally acceptable and prudent under terms of the Precautionary Principle. If the recovery of the ozone layer in the next few decades is to be achieved, there continues to be a strong scientific justification to eliminate production and consumption of ODSs as currently scheduled by the Protocol. Protection of the ozone layer can be further strengthened by eliminating emissions at an accelerated pace. This acceleration can be achieved by collecting and destroying CFCs and halons contained in equipment and foam products, by reduction in the use of the Quarantine and Pre-Shipment exemption, and by accelerating the phase‑out of HCFCs in all the countries. This acceleration can consider the implications for the accumulation of greenhouse gasses. For example, HCFC-123 could be allowed in specific air-conditioning applications where its use promotes superior energy efficiency and assures near-zero refrigerant emissions.

Today, the ozone layer is most vulnerable owing to the high abundances of chlorine and bromine. An outstanding success of the Montreal Protocol has been the immediate reduction in the atmospheric abundances of the short-lived gases, methyl chloroform and methyl bromide. Methyl chloroform was successfully phased out in 1996 in developed countries. Current use of methyl bromide, with its high ODP, depletes ozone on an immediate timescale. Therefore, ozone depletion due to methyl bromide would end almost as rapidly as its use is halted. In fact, recent studies show that about twenty percent of the observed decline in equivalent chlorine abundances can be attributed to the decline in methyl bromide emissions. There is a risk, however, that the gains achieved so far in the reduction of methyl bromide may be negated by increases in emissions from exempted uses including quarantine, pre-shipment and critical use.

By the end of 2004, developed countries will have phased out – with the exception of exempted categories such as quarantine and pre-shipment and essential and critical use exemptions – CFCs, halons, methyl bromide, carbon tetrachloride, methyl chloroform and 35 per cent of the consumption of HCFCs, In addition, developing countries will have made significant progress in their phase‑out. The remaining global consumption of ODS in developing countries, although constituting a small fraction of their respective baselines, is harder to phase out because of the uses in the service sector and by thousands of micro enterprises. Continued support of the Multilateral Fund is necessary to achieve a total phase‑out by developing countries.

While all the signs point to the high probability of near total ODS phase‑out by 2015 by all Parties, the ozone hole will be a permanent feature during the Antarctic spring for many years to come. Recovery of the ozone layer can occur only after human-made ODS are no longer significant in the atmosphere.

Concluding statement

The success of the Montreal Protocol transcends the immediate achievement of protecting the stratospheric ozone layer. The scientific, policy, industrial, and public response evoked by the Montreal Protocol is an achievement of all humanity, preventing a global disaster. The Protocol is also a very important precedent for solving global environmental problems and sustaining life on earth. It is imperative to preserve the integrity of the Protocol with continued stringent controls, financing, and enforcement, until its objectives are achieved.


[9] A group of scientists from Australia, Czech Republic, Egypt, Mexico, Netherlands, Togo, United Kingdom and the United States of America, met to discuss challenges and perspectives in protecting the stratospheric ozone layer. The symposium was chaired by Mario J. Molina, 1995 Nobel Prize Laureate for Chemistry. Presenters and commentators included Ayite-Lo Nohende Ajavon (Togo), Stephen O. Andersen (United States), Jonathan Banks (Australia), Martyn Chipperfield (United Kingdom), Omar El Arini (Egypt), David W. Fahey (United States), Paul J. Fraser (Australia), Mario Molina (Mexico and United States), Stephen A. Montzka (United States), and Jan van der Leun (Netherlands). The symposium panel included Libor Ambrozek, Minister of Environment for the Czech Republic, and was coordinated with the assistance of Jiř Hlavček, Czech Republic Ministry of Environment. Introductory remarks were provided by Shafqat Kakakhel, Deputy Executive Director of the United Nations Environment Programme, and by distinguished members from the Czech Republic: Tomas Hušk, Director General of the Ministry of Foreign Affairs, Tomš Novoty, Deputy Minister of the Environment, and Aleš Sulc, Head of the Prime Minister’s Office. Mexico was represented by Ambassador Federico Salas and by Ives Gomez, Agustin Sanchez, and Sergio Sanchez from the Secretariat of Environment and Natural Resources.