These are the facts:

• The chemistry of the atmosphere is changing and a global warming is expected due to the increasing concentrations of greenhouse gases and altered amounts of clouds and particles in the atmosphere.

• The stratospheric ozone layer and, consequently, the surface solar flux of ultraviolet radiation, is being modified.

• The oxidation capacity of the atmosphere is changing.

• Trace gases, including those with significant greenhouse warming potential, are abundant.

And, to document and understand these global changes, global cooperation is essential.

The chemical composition of the atmosphere is changing, with far reaching implications for the health of the environment and our future. Carbon dioxide and other greenhouse gas concentrations are increasing. The stratospheric ozone layer is being depleted. There is more tropospheric ozone and higher levels of acidity in precipitation. The radiative balance of the Earth-atmosphere-energy system is changing.

All these reflect the increasing influence of human activity on the global atmosphere. And, the responsibility for the long-term monitoring of global atmospheric composition and its related physical characteristics rests with the World Meteorological Organization (WMO), an intergovernmental organization and a specialized agency of the United Nations, through its Global Atmosphere Watch (GAW), established in 1989, with a coordinated network of observing stations, associated facilities and infrastructure encompassing measurement and related scientific activities. These activities, some of which date back to the 1950s, integrate the efforts of several regional and global networks. WMO facilitates and coordinates the monitoring activities and scientific assessments, and oversees the operation of component networks on a continuing basis, rather than being involved in day-to-day network operations. These are the responsibility of the WMO member countries that operate the stations and provide the central facilities such as quality assurance/science activity centres, world calibration centres and world data centres.

This complex task is being tackled by WMO jointly with other international organizations and the scientific community. In collaboration with the United Nations Development Programme, WMO has recently established through the Global Environment Facility six new GAW stations of global importance at pristine locations in Algeria, Argentina, Brazil, China, Indonesia and Kenya. These fill major climatic and ecological gaps in world station coverage, and join the network of 14 similar stations and over 200 others taking less comprehensive measurements. GAW has also established close cooperation with the International Global Atmospheric Chemistry Programme, a core project of the International Geosphere-Biosphere Programme, and global alliances have been built with other internationally recognized institutes and bodies. The data obtained have already contributed substantially to the scientific evidence which suggests a discernible human influence on global climate.

Assessment of environmental problems, their impacts and the responses to them occupy a prominent position on the international agenda today. By working together, a scientifically effective and economically efficient solution to these problems, confronting all countries of the world, will eventually emerge. Considering this, GAW has matured and is contributing extensively to activities such as the implementation of the relevant parts of the Rio Declaration and its Agenda 21, especially Chapter 9 on "Protection of the Atmosphere". There is increasing recognition by Governments and the global scientific community at large that GAW is an essential tool not only for monitoring the evolution of atmospheric composition but also for improving our understanding of its interactions with all aspects of the environment. In fact, the current knowledge of atmospheric concentrations and trends of increasing emissions of most greenhouse gases are derived from GAW data.

Please use this version of the article for printing.

Next Page of this article

The Global Atmosphere Watch measurements will be essential to the understanding of:

The relationship between changing atmospheric composition and changes of global and regional climate; The impact of changes in climate and other aspects of the Earth system on the chemical composition of the atmosphere; The long-range atmospheric transport and deposition of potentially harmful substances; The natural cycling of chemical elements in the global atmosphere/ ocean/biosphere system, and anthropogenic impacts thereon.