Greenhouse gases

About greenhouse gases and climate change

The greenhouse gases reported under the Climate Convention are:

  • Carbon dioxide, CO2
  • Methane, CH4
  • Nitrous Oxide, N2O
  • Hydrofluorocarbons, HFCs
  • Perfluorocarbons, PFCs
  • Sulphur hexafluoride, SF6

The main greenhouse gas responsible for the anthropogenic influence on the heat balance is CO2. The atmospheric concentration of CO2 has increased from a pre-industrial value of about 280 ppm to 379 ppm in 2005 (an increase of about 35 %), and exceeds now the natural range of 180-300 ppm over the last 650 000 years as determined by ice cores (IPCC, Fourth Assessment Report, 2007). The main cause for the increase in CO2 is the use of fossil fuels, but changing land use, including forest clearance, has also been a significant factor. The greenhouse gases CH4 and N2O are very much linked to agricultural production; CH4 has increased from a pre-industrial atmospheric concentration of about 715 ppb to 1774 ppb in 2005 (an increase of about 140 %) and N2O has increased from a pre-industrial atmospheric concentration of about 270 ppb to 319 ppb in 2005 (an increase of about 18 %) (IPCC, Fourth Assessment Report, 2007). Changes in the concentrations of greenhouse gases are not related in simple terms to the effect on the heat balance, however. The various gases absorb radiation at different wavelengths and with different efficiency. This must be considered in assessing the effects of changes in the concentrations of various gases. Furthermore, the lifetime of the gases in the atmosphere needs to be taken into account – the longer they remain in the atmosphere, the greater the overall effect. The global warming potential (GWP) for various gases has been defined as the warming effect over a given time of a given weight of a specific substance relative to the same weight of CO2. The purpose of this measure is to be able to compare and integrate the effects of individual substances on the global climate. Typical lifetimes in the atmosphere of substances are very different, e.g. 12 and 120 years approximately for CH4 and N2O, respectively. So the time perspective clearly plays a decisive role. The time frame chosen is typically 100 years. The effect of the various greenhouse gases can, then, be converted into the equivalent quantity of CO2, i.e. the quantity of CO2 giving the same effect in absorbing solar radiation. According to the IPCC and their Fourth Assessment Report, which UNFCCC has decided to use as reference for reporting, the global warming potentials for a 100-year time horizon are:

  • Carbon dioxide (CO2):      1
  • Methane (CH4):                25
  • Nitrous oxide (N2O):         298
  • Sulphur hexafluride (SF6): 22800

Based on weight and a 100-year period, methane is thus 25 times more powerful a greenhouse gas than CO2, N2O is 298 times more powerful and SF6 is 22800 times more powerful. For HFCs and PFCs, the GWP depends on the specific compound and varies from 12 to >17000 for substances included in the inventories. 

The Climate Convention and the Kyoto Protocol

At the United Nations Conference on Environment and Development in Rio de Janeiro in June 1992, more than 150 countries signed the UNFCCC (the Climate Convention). On the 21st of December 1993, the Climate Convention was ratified by a sufficient number of countries, including Denmark, for it to enter into force on the 21st of March 1994. One of the provisions of the treaty was to stabilise the greenhouse gas emissions from the industrialised nations by the end of 2000. At the first conference under the UN Climate Convention in March 1995, it was decided that the stabilisation goal was inadequate. At the third conference in December 1997 in Kyoto in Japan, a legally binding agreement was reached committing the industrialised countries to reduce the six greenhouse gases by 5.2 % by 2008-2012 compared with the base year. For F-gases, the countries can choose freely between 1990 and 1995 as the base year. On May 16, 2002, the Danish parliament voted for the Danish ratification of the Kyoto Protocol. Denmark (including Greenland and excluding the Faroe Islands) is, thus, under a legal commitment to meet the requirements of the Kyoto Protocol, when it came into force on the 16th of February 2005. Hence, Denmark (including Greenland) is committed to reduce greenhouse gases with 8 %. The European Union is under the KP committed to reduce emissions of greenhouse gases by 8 %. However, within the EU member states have made a political agreement – the Burden Sharing Agreement – on the contributions to be made by each member state to the overall EU reduction level of 8 %.

Under the Burden Sharing Agreement, Denmark (excluding Greenland and the Faroe Islands) must reduce emissions by an average of 21 % in the period 2008-2012 compared with the base year emission level.

In accordance with the Kyoto Protocol, Denmark’s base year emissions include the emissions of CO2, CH4 and N2O in 1990 in CO2 equivalents and Denmark has chosen 1995 as the base year for the emissions of HFCs, PFCs and SF6.

The role of the European Union

The European Union (EU) is a party to the UNFCCC and the Kyoto Protocol. Therefore, the EU has to submit similar datasets and reports for the collective 15 EU Member States under the burden sharing. The EU imposes some additional guidelines and obligations to these EU Member States through Decision No. 280/2004/EC concerning a mechanism for monitoring community greenhouse gas emissions and for implementing the Kyoto Protocol (EU monitoring mechanism).

Danish greenhouse gas emissions

The greenhouse gas emissions are estimated according to the IPCC guidelines and are aggregated into six main sectors. The greenhouse gases include CO2, CH4, N2O, HFCs, PFCs and SF6. The figures below show the allocation of CO2 equivalent emissions in 2015 in the different sectors and the estimated total greenhouse gas emissions in CO2 equivalents from 1990 to 2015. The emissions are not corrected for electricity trade or temperature variations. CO2 is the most important greenhouse gas contributing in 2015 to the national total in CO2 equivalents excluding LULUCF (Land Use and Land Use Change and Forestry) with 73.2 % followed by CH4 with 14.3 %, N2O with 11.0 % and F-gases (HFCs, PFCs and SF6) with 1.5 %. Seen over the time-series from 1990 to 2015 these percentages have been increasing for CH4 and F-gases, and decreasing for N2O. The percentages for CO2 show larger fluctuations during the time series. Stationary combustion plants, Transport and Agriculture represent the largest contributing categories to emissions of greenhouse gases, followed by Industrial processes and product use, Waste and Fugitive emissions, see the figure below. The net CO2 uptake by LULUCF in 2015 is 7.3 % of the total emission in CO2 equivalents excl. LULUCF, the uptake lies in both forest land and harvested wood products. The national total greenhouse gas emission in CO2 equivalents excluding LULUCF has decreased by 30.6 % from 1990 to 2015 and decreased 29.3 % including LULUCF. From 2014 to 2015 the total greenhouse gas emission excluding LULUCF decreased by 4.8 %. The decrease is mainly caused by decreasing emissions from the energy sector due to increasing production of wind power and other renewable energy.

CO2-equivalent emission, 2015

Danish greenhouse gas emission, latest emission year

 

Danish greenhouse gas emission, time series

(Click the chart to view the background data)

Illustrations: Greenhouse gas emissions in CO2-equivalents distributed on main sectors and for the time-series.

 

Read more about the greenhouse gasses: