All life depends on a healthy planet, but the interwoven systems of atmosphere, oceans, watercourses, land, ice cover and biosphere, which form the natural environment, are threatened by human activities. The Global Atmosphere Watch (GAW) programme provides reliable scientific data and information on aerosols, greenhouse gases, selected reactive gases, ozone, ultraviolet radiation and precipitation chemistry (or atmospheric deposition). 

The natural environment suffers, for example, from lack of precipitation for extended periods and uncontrolled land use, leading to desertification. It is estimated that one-third of the Earth’s surface and one-fifth of the world’s population are threatened by desertification. WMO, therefore, directs its attention to the aspects of climate variability and change that impact the environment. The observational data of weather, climate and the atmosphere that are collected through the WMO networks of observing, data-transmitting and forecasting systems keep policy-makers informed of the state of the environment so that they are in a better position to prevent its further degradation and are used by used by the Intergovernmental Panel on Climate Change (IPCC) in its assessments of climate climate change, its potential impacts and options for adaptation and mitigation. 

WMO is the recognized, comprehensive source of unique global systematic observations on the state of a wide variety of geophysical phenomena, datasets and long-term archives, and scientific and technical expertise in support of policy advice on various critical environmental issues.

Biodiversity (the variety of life on Earth and the natural patterns it forms) helps keep the global environment working. Polluted air, depleted or contaminated water, degraded soil and urban growth are all threats to biodiversity. Rising ocean temperatures are responsible for the widespread bleaching of coral reefs that support vast populations of marine life and are also important tourist attractions. Ecosystems such as wetlands, forests and lakes are an important part of the natural regime of a river. They are a buffer between river and terrestrial ecosystems and play an important role in storing or attenuating floodwaters. Stratospheric ozone protects plants, marine life, animals and people from solar ultraviolet radiation, which is harmful for life on Earth. Chlorofluorocarbons and other anthropogenic chemicals are responsible for the destruction of ozone. It is necessary, therefore, to ensure that all these Earth systems remain healthy. 

An essential activity of National Meteorological and Hydrological Services is to monitor long-term changes in atmospheric greenhouse gases, ultraviolet radiation, aerosols and ozone, and to assess their consequent effects on people, climate, air and water quality and marine and terrestrial ecosystems. Another important activity is monitoring the atmospheric and water transport of dangerous particles in the wake of a volcanic explosion or an industrial accident.

The Global Atmosphere Watch (GAW) programme provides reliable scientific data and information on aerosols, greenhouse gases, selected reactive gases, ozone, ultraviolet radiation and precipitation chemistry (or atmospheric deposition). The GAW Urban Research Meteorology and Environment (GURME) project works together with the Group of Experts on Scientific Aspects of Marine Environmental Protection (GESAMP) as well as provides Sand and Dust Storms Warning (SDS-WAS). GAW recently initiated the Integrated Global Greenhouse Gas Information System (IG3S) that will use observations of greenhouse gases and inverse modelling techniques to support climate mitigations efforts. This new approach (explained in the animations below) supports of the UN Framework Convention on Climate Change (UNFCCC) and its Paris Agreement by providing an additional way of identifying and estimating urban and national emissions. It seeks to empower policymakers to take more effective action on mitigation.










The Global Atmosphere Watch monitors:

Air Quality

Ongoing climate change, caused by the accumulation of greenhouse gases in the atmosphere, is happening on a timescale of decades to centuries and is driving environmental changes worldwide. In contrast, the air pollution that occurs near the Earth’s surface happens on a timescale of days to weeks, and across spatial scales that range from local (for example, urban centres) to regional (such as the eastern United States of America, northern India or the Amazon).

Sand and Dust Storms

Sand and dust storms are common meteorological hazards in arid and semi-arid regions.


Ozone is a form of oxygen with molecules carrying three atoms instead of two. Ozone is found both in the troposphere, the lower 10 km of the atmosphere, and in the stratosphere, 10 to 50 km above the ground. Ozone acts as a shield protecting us against harmful ultraviolet radiation from the Sun. 

Atmospheric composition forecast and assessments

CAMS forecasts charts demonstration provided to WMO by Copernicus Atmosphere Monitoring Service implemented by ECMWF on behalf of European Commission.

Greenhouse gases

The Earth has a natural greenhouse effect due to trace amounts of water vapour (H2O), carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) in the atmosphere. These gases let the solar radiation reach the Earth’s surface, but they absorb infrared radiation emitted by the Earth and thereby lead to the heating of the surface of the planet. One needs to distinguish between the natural greenhouse effect and the enhanced greenhouse effect. The natural greenhouse effect is caused by the natural amounts of greenhouse gases, and is vital to life.


The impact of aerosols on the atmosphere is widely acknowledged as one of the most significant and uncertain aspects of climate change projections. The observed global warming trend is considerably less than expected from the increase in greenhouse gases, and much of the difference can be explained by aerosol effects. Aerosols impact climate through direct scattering and absorption of incoming solar radiation and trapping of outgoing long-wave radiation as well as through alteration of cloud optical properties and the formation of clouds and precipitation.

Atmospheric Deposition

Atmospheric constituents such as ozone, nitrogen- and sulphur-containing compounds and particulate matter can find their way into soil, marine and fresh water bodies and plant and animal tissue through the naturally occurring processes of dry and wet deposition. Dry deposition is the free fall to Earth directly from the atmosphere of atmospheric trace gases and particulate matter. Wet deposition is the process whereby atmospheric gases mix with suspended water in the atmosphere and are then washed out through rain, snow or fog. Acid rain is an example of wet deposition that damages forests,