Concentration of greenhouse gases, 1980-2002

The global concentration of carbon dioxide (CO₂) continued to rise in 2002, as did that of nitrous oxide (N₂O) and various gases containing fluorine. The concentration of methane (CH₄) has stabilised in recent years.

Concentrations of carbon dioxide and nitrous oxide continue to increase

The global average CO₂ concentration in 2002 was 372.3 ppm ¹⁾. This was therefore up 0.5% on 2001. The global average N₂O (nitrous oxide or laughing gas) concentration was 317.1 ppb ²⁾, 0.2% higher than in 2001. The current concentrations of CO₂ and N₂O are therefore 34% and 17% respectively above the average preindustrial level of more than a century ago.
The increase in the concentrations is caused by emissions generated by human activities. A major source of CO₂ emissions is the use of fossil fuels and the conversion of forests into agricultural land. Agricultural activities, that include the use of chemical fertilisers, are the main source of N₂O emissions.

1) ppm=parts per million: number (volume) of parts of the gas in question per million parts of dry air.
2) ppb=parts per billion: number (volume) of parts of the gas in question per billion parts of dry air.

Methane concentration stabilizing

The global average concentration of methane (CH₄) has been stable for the last four years at 1772 ppb. It is striking that the concentration has not increased further in recent years and that it has actually fallen in some places. As yet, this is not fully understood. The probable cause is a stabilisation of the emissions generated by human activity. It is also possible that a faster breakdown of methane in air plays a role. The methane concentrations are still more than 21/2 times higher than the average preindustrial concentration of approximately 700 ppb. The main source of methane emissions is agriculture (paddy fields) and livestock raising, energy production, and landfill.
The highest concentrations of greenhouse gases are found where emissions from human activities are highest. For most gases, this is the Northern Hemisphere (see the lines on the graphs for Alaska, Hawaii, Ireland and Oregon/California). The long residence time of greenhouse gases in the atmosphere - generally decades or longer - mean that greenhouse gases spread throughout the world. Methane has a relative short life of approximately 10 years and, as a result, larger North/South differences are found than for other greenhouse gases.

Concentrations of greenhouse gases containing fluorine increasing sharply

The concentrations of various new greenhouse gases containing fluorine are rising.

• The sharpest increase was for HFC-134a; approximately 20% a year in 2001. HFCs are partially halogenated CFCs;
• The concentrations of HFC-23, SF₅CF₃, and the perfluorocarbons (PFCs) CF₄ and C₂F₆ have increased in recent years by approximately 5%, 3%, 1% and 3% a year respectively. Recent measurements for these latter gases are not available.
• The concentration of SF₆ (sulphur hexafluoride) rose in 2001 by approximately 4% a year.

HFCs, PFCs and SF₆ are powerful greenhouse gases that can be released from industrial products and production processes, for example during production and use as coolants. HFC-134a is mainly used as a coolant in air conditioning systems in cars. SF₆ is mainly used for electric insulation in electricity power lines.
Of the global greenhouse gases, the greenhouse gases containing fluorine account for approximately 0.7% of the current enhanced greenhouse effect. The sharp increase in concentrations means that these substances will become more important in the future.

Climate treaty and Kyoto Protocol

The objective of the UN Climate Treaty (UNFCCC, 1992; Rio de Janeiro) is to stabilise the concentrations of greenhouse gases in the atmosphere at a level that will not result in a dangerous human influence on the climate. This means that, in time, the emissions of greenhouse gases must be reduced by approximately 70% compared to 1990. However, the Climate Treaty does not contain quantitative agreements about emission reductions.
In 1997, the Climate Treaty was extended to include the Kyoto Protocol (UNFCCC, 1997; Kyoto). The Kyoto Protocol contains agreements about reducing emissions of greenhouse gases. The objective is an average reduction in emissions of greenhouse gases by industrialised countries of 5.2% over the period 2008-2012 compared to 1990. The reduction objective is 8% for the EU as a whole and 6% for the Netherlands. The Kyoto Protocol can be thought of as a first modest step towards stabilising greenhouse gas concentrations. It covers the gases CO₂, CH₄, N₂O, HFCs, PFCs and SF₆.

• Climate change: policy

Greenhouse effect

Of the greenhouse effect caused by the global greenhouse gases, 61% is now accounted for by CO₂, 19% by CH₄, 6% by N₂O, and 0.7% by the new greenhouse gases (HKFs, PFCs, and SF₆). The remaining 13% are accounted for by hydrocarbons containing chlorine and bromine, that are also responsible for the breakdown of ozone in the stratosphere. This group of greenhouse gases is already covered by the Montreal Protocol (UNEP, 1987-2000) and have therefore not been included in the Kyoto Protocol.
Alongside the global greenhouse gases looked at here, ozone is also an important greenhouse gas. Ozone is formed in the atmosphere and anthropogenic emissions of various substances affect ozone concentrations. As a result of human activities, the ozone concentration in the lower atmosphere has increased in recent centuries. However, in the higher atmosphere (the stratosphere), ozone levels have actually fallen since 1980. On balance, the changes in ozone concentrations result in an enhancement of the greenhouse effect caused by the global greenhouse gases.

• Concentration of ozone-depleting substances, 1980-2002

Concentration measurement methods

The concentrations of greenhouse gases have been measured at a limited number of background sites at various geographical latitudes. This sites are selected in such a way that they are far away from the sources. This makes them representative for large areas. The global average is calculated as the average for these sites.

References

• Keeling, C.D. and T.P. Whorf (2002). Atmospheric CO₂ records from sites in the SIO air sampling network. In Trends: A Compendium of Data on Global Change. CDIAC, Oak Ridge National Laboratory, U.S. DoE, Oak Ridge, Tenn., U.S.A.
• UNEP (1987 - 2000). The Montreal Protocol on substances that deplete the ozone layer (with amendments).
• UNFCCC (1992). United Nations Framework Convention on Climate Change Rio de Janeiro, 1992.
• UNFCCC (1997). Kyoto Protocol to the United Nations Framework Convention on Climate Change. Kyoto, 11 December 1997. Link naar PDF-file. Link naar HTML-versie.

Relevant sections and indicators in the Environmental Data Compendium

• Environmental pressure, theme of Climate change: introduction and Climate change: policy
• See the 'Environmental pressure, theme of Climate change (greenhouse effect)' guide for the emissions of substances that affect the climate.
• Greenhouse effect, 1950-2002

Relevant information outside of the Environmental Data Compendium

• Information about the Climate Treaty and the Kyoto Protocol can be found on the website of the United Nations Framework Convention on Climate Change (UNFCCC).
• Information about Dutch climate policy can be found on the website of the Ministry of Housing, Spatial Planning and the Environment.
• More information about the effects of climate change on the weather can be found on the website of the Royal Netherlands Meteorological Institute.
• More information about climate change and concentrations of greenhouse gases can be found on the websites of the IPCC (Intergovernmental Panel on Climate Change) and ETC/ACC (European Topic Center on Air and Climate Change).
• Information about current and future developments for the Kyoto Protocol can be found in Environmental Balance 2003 and National Environmental Outlook 2000-2030, both of which are RIVM publications.