• Introduction
• Greenhouse Gases
• Air Pollution
• Aerosols
• Ozone Layer
• Data integration

Greenhouse gases are trace gases present in the atmosphere which absorb and emit radiation within the thermal infrared range. This process is called the greenhouse effect. The main greenhouse gases in the Earth's atmosphere are water vapour, carbon dioxide, methane, nitrous oxide, and ozone.

The greenhouse effect is a natural phenomenon which warms up the Earth to an average global temperature of 15°C. Without it, the average temperature on Earth would be around -18°C making life very difficult to sustain.

Although greenhouse gases account for a tiny proportion of the gases present in the atmosphere (less than 0.05%) small changes in their abundance can have a huge impact on our climate. In particular more greenhouse gases means that more of the infrared heat re-emitted by the Earth is prevented from escaping through the atmosphere than would otherwise be the case.

Click here to see the oldest direct measurement of greenhouse gas in the world.

The amount of greenhouse gases (GHG) in the air is rising around the world

Below, you can see differences in concentrations measured at various stations of GEOmon due to their location: the impact of the seasonal vegetation cycle is observed in the Northern Hemisphere stations. Plants absorb carbon in spring/summer and, due to decomposition, emit carbon in autumn/winter. In the Southern Hemisphere, as the proportion of land area is smaller, the influence of vegetation is lower.
The CO₂ spikes superposed on the seasonal cycle reflect the variability of CO₂ emissions at local to regional level and their dilution in the planetary boundary layer (PBL).

The planetary boundary layer (PBL) is the lowest layer of the earth’s atmosphere where wind is influenced by friction on the surface. The thickness of this layer is not constant. The height of the PBL depends on wind speed and temperature. At night and in the cold season the PBL tends to be lower than in the day and in the warm season because cold air is denser than warm air. High wind speeds allow for more convective mixing, which will cause the PBL to expand. At night, the PBL contracts due to a reduction of rising thermals from the surface.

Why does GEOmon measure greenhouse gases ?

1. To work out the greenhouse gas budgets. GEOmon will help us work out both the natural carbon gas cycles and human additions. We need to know where emissions are occurring, their extent and how carbon sinks operate. Nowadays, meteorologists understand wind circulation patterns around the Earth much better. Soon we may be able to tell how carbon gases are carried by  winds, and how much is produced or taken up in each location.
   
   For example, by collecting methane (CH₄) measurements from a wide range of stations around the planet, and by using known winds patterns we can work out where methane is being emitted.  Moreover, because the methane from different sources (e.g. gas leaks, livestock) contains different types of carbon (different carbon isotope ratios), we can work out what sources are producing the methane, and when, at which time of the year.
   
   The CO₂ budget is somewhat more complex as the sinks (e.g. plant uptake, ocean uptake) are more varied and more biological than the sources, but in principle it should be possible to develop a detailed daily understanding of global CO₂ emissions. From our understanding of Atlantic and European measurements, we should be able to determine how much  specific regions emit and remove – for example, US emissions, or French forest uptake. Longer term we should be able to tell how much the burning of African biomass produces,  or Chinese  emissions. Locally in Europe, we should be able to assess emissions from 'hotspots' like London or Paris.
   
   
2. To verify compliance with international treaties on greenhouse gas emissions. The UN Framework Convention on Climate Change obliges nations (including the US and EU) to assess their emissions. Those nations that signed the Kyoto Treaty have committed to control emissions. Carbon trading places a monetary value on emissions. Currently all emissions data are self-declared by the emitting countries. The auditing process checks the validity of the paperwork behind declarations, but there is no independent checking system. Atmospheric monitoring 'sniffs' the air and offers a wholly independent method of verifying emissions. The work is still in its infancy, but as carbon trading develops it will become essential.
   
   Only with rigorous independent verification can carbon trading succeed. GEOmon will help provide data that make verification possible.

   How GEOmon improves knowledge on Climate Change?

International climate and environmental policy

The Kyoto Protocol, an international and legally binding agreement to reduce greenhouse gases emissions world wide, entered into force on 16 February 2005. This international agreement, which builds on the United Nations Framework Convention on Climate Change, sets legally binding targets and timetables for cutting the greenhouse-gas emissions of industrialised countries. Goto the UNFCCC web site to learn more.