Global warming.

Since its adoption five years ago at the Earth Summit in Rio de Janeiro, the United Nations Framework Convention on Climate Change has been the centrepiece of global efforts to combat global warming. It also has been one of the international community's most essential tools in the struggle to promote sustainable development. A great deal has been accomplished since Rio - but the most difficult decisions still lie ahead.

In 1898, Swedish scientist Svante Ahrrenius warned that carbon dioxide emissions could lead to global warming. It was not until the 1970s, however, that scientists' growing understanding of the Earth-atmosphere system brought this previously obscure field of science to wider attention.

In response to growing scientific understanding, a series of intergovernmental conferences focusing on climate change were held in the late 1980s and early 1990s. In 1990, the Second World Climate Conference called for a framework treaty on climate change. Sponsored by the World Meteorological Organization (WMO), the United Nations Development Programme (UNEP) and other international organizations, this conference featured negotiations and ministerial-level discussions among 137 States plus the European Community.

The final declaration, adopted after hard bargaining, did not specify any international targets for reducing emissions. However, it did support a number of principles later included in the Climate Change Convention. These were climate change as a "common concern of humankind", the importance of equity, the "common but differentiated responsibilities" of countries at different levels of development, sustainable development and the precautionary principle - where there are threats of serious or irreversible damage, a lack of scientific certainty should not be used as a reason for postponing cost-effective measures to prevent environmental degradation.

Meanwhile, the general public was starting to react. Although not directly attributable to climate change, a series of heat waves and unusually destructive storms in the United States and elsewhere led to a series of press reports about climate change and its expected impacts. The high tide of environmental sentiment, plus the 1985 discovery of the Antarctic ozone "hole" (also unrelated to climate change), further stoked the growing concern.

Then, in December 1990, the General Assembly approved the start of treaty negotiations. The Intergovernmental Negotiating Committee (INC) for a Framework Convention on Climate Change met for five sessions between February 1991 and May 1992. Facing a strict deadline - the United Nations Conference on Environment and Development, in Rio de Janeiro, Brazil, in June 1992 - negotiators from 150 countries finalized the Convention in just 15 months. It was adopted in New York on 9 May 1992 and opened for signature several weeks later in Rio.

The new Convention established a process for responding to climate change over the decades to come. In particular, it set up a system whereby Governments report information on their national greenhouse gas emissions and climate change strategies. This information is reviewed on a regular basis in order to track the Convention's progress. In addition, developed countries agreed to promote the transfer of funding and technology to help developing countries respond to climate change. They were also committed to taking measures aimed at returning their greenhouse gas emissions to 1990 levels by the year 2000. The Convention entered into force on 21 March 1994 and today boasts some 165 States Parties.

After the Convention was adopted in Rio, the INC that drafted it continued its preparatory work, meeting for another six sessions to discuss matters relating to commitments, arrangements for the financial mechanism, technical and financial support to developing countries, and procedural and institutional matters. The INC was dissolved after its eleventh and final session in February 1995, and the Conference of the Parties (COP) became the Conventions ultimate authority. The COP held its first session in Berlin from 28 March to 7 April 1995.

The Convention required COP-1 to review whether the commitment of developed countries to take measures aimed at returning their emissions to 1990 levels by 2000 was adequate for meeting the Convention's objective. The Parties agreed that new commitments were indeed needed for the post-2000 period. They established the Ad hoc Group on the Berlin Mandate to draft "a protocol or another legal instrument" for adoption at COP-3 in 1997.

The Berlin Mandate process is considering steps involving emissions of all greenhouse gases. It is also considering setting quantified objectives for limiting and reducing emissions within specified time-frames such as 2005, 2010 and 2020. It does not require introduction of any new commitments for developing countries.

The COP held its second session from 8 to 19 July 1996. Ministers released a declaration stressing the need to accelerate talks on how to strengthen the Climate Change Convention and endorsed the Second Assessment Report (see p. 14) "as currently the most comprehensive and authoritative assessment of the science of climate change, its impacts and response options now available". COP-3 will be held from 1 to 12 December 1997 in Kyoto, Japan. It is expected to adopt new commitments requiring developed countries to reduce their greenhouse gas emissions after 2000. If COP-3 is successful, it will help to generate the momentum needed to combat climate change in the twenty-first century.

The sharing of information by Governments is central to how the Climate Change Convention works. Parties must therefore submit "national communications" to the COP on a regular basis. This information about national greenhouse gas emissions, international cooperation and national activities is reviewed periodically so that the parties can track the Convention's effectiveness and draw lessons for future national and global action.

Developed countries are exploring a wide range of climate change policies and measures. The policies Governments choose are generally dictated by national circumstances such as political structure and the overall economic situation. Many are "no-regrets" measures that have environmental or economic benefits, irrespective of climate change concerns. In addition to regulatory and economic instruments, parties are promoting voluntary agreements with industry and public authorities. Other measures involve research and development, and information and education.

Specific measures are being used for most of the major economic sectors. Policies for the energy sector (the largest source of emissions for many countries) include switching to low- or no-carbon fuels, reforming market regulations to spur competition, and removing subsidies on coal. Industry-related policies include voluntary arrangements, standards, financial incentives and liberalized energy prices.

The focus in the residential, commercial and institutional sector is on energy-efficiency standards for new buildings, higher energy prices and public information campaigns. Agricultural measures include reducing herd sizes and fertilizer use and improving waste management. While most Governments project an expansion of the transportation sector, relatively few measures for controlling its emissions were reported.

As of December 1996, the Berlin Mandate talks on future developed country commitments were preparing to enter the final negotiating phase. An agreed text must be circulated to Governments for review by June 1997. This text will be the subject of continued intense negotiations at meetings to be held in Bonn in March, August and October. Some of the key issues now being debated are:

* Binding timetables and targets for emissions reductions. A number of Governments (including some EU members) are calling for 10 per cent reductions in C[O.sub.2] by 2005. Some, such as the low-lying island States, want an even more ambitious cut of 20 per cent by that date. Still others, including Australia, Canada, Japan and the United States, argue that a 2005 date is unrealistic and propose objectives for the 2010-2015 period.

* Coordinated vs. flexible policies. Some Governments, notably EU members, argue the need for internationally coordinated policies. Others say it would be more cost-efficient to allow each country to adopt the policies and measures best suited to its national circumstances.

* Common vs. differentiated commitments. There are differing points of view on whether all developed countries should have the same targets and timetable, or whether it would be fairer if different countries had different commitments based on various possible formulae (e.g. per capita targets). Critics of differentiation are concerned that it poses too many methodological and political problems.

* Implications for developing countries. The Berlin Mandate talks address new commitments for developed countries only (they also address how to advance the implementation of existing commitments by all parties). However, some developed countries have offered proposals that would allow other countries to adhere to any future agreement on a voluntary basis. Meanwhile, a number of developing countries want to address the agreement's possible impacts on their economies and trade.

The Convention is an ongoing process dealing with such vital issues as the submission of information about national actions and the transfer of financial support to developing countries. But clearly the centre of attention in 1997 will be the drafting of the Kyoto accord.

In the time remaining, it seems unlikely that all of the proposals now on the table can be worked out in detail. Some of the unfinished ideas about how to implement developed country commitments could form the basis for continuing negotiations after 1997. What is needed is an agreement that is strong and convincing enough to give investors and consumers the right economic signals. This would make the Berlin Mandate a success and open the way to further action in the years to come.

The 1996 review of national communications from developed countries (developing countries will start making their initial submissions in 1997) reveals that carbon dioxide emissions continue to rise in most of them. Comparing the data from 1990 inventories with projections for the year 2000 shows carbon dioxide emissions rising over the decade if additional measures are not adopted. The major exceptions are the countries with economies in transition. For methane, all but three parties project that their emissions will decline or stabilize over the decade. Nitrous oxide trends are not clear, although some countries project major decreases.

The data also show that carbon dioxide accounts for 80.5 per cent of total greenhouse gas emissions from developed countries. Fuel combustion is confirmed as the most important source of C[O.sub.2]. With the 33 countries included accounting for around 63 per cent of the global C[O.sub.2] emissions in 1990, this seems to confirm carbon dioxide as the most important greenhouse gas resulting from human activities.