The Global Atmosphere Watch (GAW) Programme of WMO focuses on building a single coordinated global understanding of atmospheric composition, its change, and helps to improve the understanding of interactions between the atmosphere, the oceans and the biosphere. It coordinates high-quality atmospheric composition observations across global to local scales to drive high-quality and impact science while co-producing a new generation of research enabled products and services. About 100 countries are participating in the GAW Programme. Some components of the GAW observational network are recognized as comprehensive and baseline networks of the Global Climate Observing System (GCOS). The GAW Programme operates according to the GAW Implementation Plan 2024-2027.

One major aspect of the GAW mission is to organize, participate in and coordinate assessments of the chemical composition of the atmosphere on a global scale. In this way, GAW provides reliable scientific information for policymakers, supports international conventions and contributes to improve the understanding of climate change and long-range transboundary air pollution.

Background and History

Monitoring of trace atmospheric constituents was originally driven by scientific curiosity. It was not long, however, before questions were raised as to what the consequences would be for humanity should the observed increases in certain trace chemicals continue unabated. The development of major international activities concerned with protection of the environment started in earnest during 1968 when the United Nations was called upon to organise a world conference on internationally significant problems related to the human environment. The conference took place in Stockholm in 1972 and successfully drew world-wide attention to environmental problems, including changes in the atmosphere due to rapid industrialisation.

During the 1970s three important atmospheric issues were addressed:

1. the threat of CFC's to the ozone layer,
2. 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,
3. potential 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 WMO's atmospheric composition monitoring programme.

In the 1950s, the WMO formally embarked on the development of a programme for atmospheric chemistry and the meteorological aspects of air pollution. This included assuming responsibility for standard procedures for uniform ozone observations and establishing the Global Ozone Observing System (GO3OS) during the 1957 International Geophysical Year. In the late 1960s, the Background Air Pollution Monitoring Network was established which was subsequently consolidated with the Global Ozone Observing System into the current WMO Global Atmosphere Watch (GAW) in 1989. The GAW monitoring programme comprises a coordinated global network of observing stations along with supporting facilities. GAW provides data for scientific assessments and early warnings for changes in the chemical composition and related physical characteristics of the atmosphere that may have adverse affects upon our environment. Monitoring priorities have been given to greenhouse gases for possible climate change, ozone and ultraviolet radiation for both climate and biological concerns, and certain reactive gases and the chemistry of precipitation for a multitude of roles in pollution chemistry.

The GAW programme has matured considerably during the last few years, and presently consists of many coordinated components that have been designed to provide accessible, high quality atmospheric data to the scientific community. These components include: (a) measurement stations, (b) calibration and data quality centres, (c) data centres and, (d) external scientific groups for programme guidance. Support for these components is provided, in large part, by individual WMO Member countries that directly participate in the GAW programme, augmented by some outside international funding, and the WMO Secretariat's internal budget.

The GAW programme is guided by a plan that is detailed in the WMO/GAW Report #228: WMO Global Atmosphere Watch (GAW) Implementation Plan: 2016-2023 released in 2017. This report focuses on expanding and improving 7 key areas:

Over the lifetime of this Strategic Plan, human activities will continue to change the composition of the atmosphere, although efforts will be made to control them. The WMO GAW network of stations must continue to monitor the critical atmospheric parameters and provide scientific data needed to understand and ultimately predict environmental changes on both regional and global scales.