Global Atmosphere Watch Programme

The Global Atmosphere Watch (GAW) Programme provides information and services on atmospheric composition to the public and to decision-makers relating to:

• the steadily increasing amounts of greenhouse gases, especially carbon dioxide, are impacting the climate
• the depletion of the protective stratospheric ozone layer has increased ultraviolet radiation, which can lead to more incidences of skin cancer and other diseases
• urban air pollution, especially fine particles, which is affecting human health

The Global Atmosphere Watch Programme monitors and studies the variability and trends in the composition of the global atmosphere and the related physical parameters and assesses their consequences. The foremost challenges for the Global Atmosphere Watch include gaining understanding of:

• stratospheric ozone depletion and the increase of ultraviolet (UV) radiation;
• the changes in the weather and climate due to the impact of human activities on atmospheric composition, especially on greenhouse gas, ozone and aerosol levels, and
• the risks of air pollution on human health and other issues related to atmospheric deposition and the long-range transport of air pollution, and how to reduce these.

The Programme increasingly focuses on service delivery in application areas where Global Atmosphere Watch data can provide added value. 

The Global Atmosphere Watch (GAW) Programme is a partnership – between the Members of WMO, contributing networks and collaborating organizations – that provides reliable scientific data on the chemical composition of the atmosphere. The WMO Commission for Atmospheric Sciences (CAS) and its Environmental Pollution and Atmospheric Chemistry Scientific Steering Committee govern the Programme. There is a Scientific Advisory Group (SAG) for each group of variables measured in the Global Atmosphere Watch:

• Aerosols;
• GAW Urban Research Meteorology and Environment (GURME);
• Greenhouse gases;
• Ozone and Ultraviolet Solar Radiation;
• Reactive Gases;
• Total atmospheric deposition; 

In addition, there is a Scientific Advisory Group for near-real-time modelling applications.

The Global Atmosphere Watch (GAW) Programme provides globally-harmonized, quality-assured data on variables of importance to atmospheric composition. A network of observational stations constitutes the core of the Programme. The Global Atmosphere Watch includes a comprehensive quality assurance and data archiving system, supported through a set of Member-hosted Central Facilities for the various categories of variables. Scientific Advisory Groups and Expert Teams, consisting of leading scientists in their fields, provide guidance to the programme when it comes to data quality, utilization of data for environmental assessments and development of products based on Global Atmosphere Watch data.

In the 1950s, WMO launched a programme on atmospheric chemistry and the meteorological aspects of air pollution that transformed early sporadic measurements into regular observations. The new programme determined that adequate gathering of such data – and analysis of its anthropogenic impact on a global scale – would require that all measurements be expressed in the same units and on the same scale, so that measurements performed by different countries could be comparable.

The first steps towards reaching this objective were made during the 1957 International Geophysical Year. The WMO began developing standard procedures for uniform ozone observations and established the Global Ozone Observing System (GO3OS), which involved ozonesonde intercomparisons, preparation of the ozone bulletins and ozone assessments, and support of the Ozone Data Centre in Toronto, Canada (later to become the World Ozone and Ultraviolet Radiation Data Centre). The Organization also coordinated the Dobson, and later Brewer, spectrophotometer network to measure total atmospheric ozone.

In the late 1960s, the Background Air Pollution Monitoring Network (BAPMoN) was established, focusing on precipitation chemistry, aerosol and carbon dioxide measurements. The Network included regional and background stations and a WMO World Data Centre in the United States of America.

During the 1970s, three important atmospheric issues were addressed: (i) the threat of chlorouorocarbons (CFCs) to the ozone layer, (ii) the acidification of lakes and forests in large parts of North America and Europe, caused principally by the conversion of sulphur dioxide into sulphuric acid by precipitation processes in the atmosphere, and (iii) global warming caused by the build-up of greenhouse gases in the atmosphere. Each of these issues is now the subject of international treaties or conventions. The initial development of these agreements and the subsequent assessments of the mitigation measures they contain rely heavily on the information derived from the WMO atmospheric composition observations and analysis programme.

In 1989, the two observing networks, BAPMoN and GO3OS, were consolidated into the current WMO Global Atmosphere Watch (GAW) Programme. As the networks evolved and grew, so did the community involved in atmospheric composition observations and analysis.