CSI 013 Specification - Atmospheric greenhouse gas concentrations

Rationale

Justification for indicator selection

Greenhouse gasses (GHG) have the ability to affect the radiation balance on earth and are crucial for the climate on earth. Without these gasses the global average temperature would be about 32^oC lower than it is now (i.e. -18^oC instead of the current +14^oC global mean temperature average), too cold to support contemporary life and especially the modern human society. The most important GHG is carbon dioxide (CO₂).
The GHG equivalent concentration is defined as the concentration of CO₂ that would cause the same amount of radiative forcing as the mixture of CO₂ and other GHGs. CO₂-equivalent concentrations rather than radiative forcings are presented here, because they are more easily understandable by the general public. There are, in general, three main ways the GHG equivalent concentration can be calculated. Firstly, an approach often used is to group together the forcing of the six Kyoto Greenhouse Gasses (i.e. CO₂, CH₄, N₂O, HFCs, PFCs & SF₆). A second approach is to group all long-living greenhouse gasses (i.e. Kyoto gasses plus the Montreal Gasses CFCs, HCFCs & CH₃CCl₃). Finally in a third approach, ozone, aerosols, black carbon are also included, providing a considerable lower concentration value compared to the other two approaches due to the cooling effect of aerosols. For the current period (e.g. in 2008), the three approaches lead to quite different concentration levels, but for the long-term the three approaches should converge. This is due to the fact that Montreal Protocol gases are beginning to decline (IPCC, 2007a) and sulphur and aerosols emissions are likely to be reduced due to non-climate related policies.
Although the emissions of most GHGs occur in the northern hemisphere, the use of global average values is justified because the atmospheric lifetime of GHGs is long compared with the timescales of global atmospheric mixing. This leads to a rather uniform mixing around the globe. Exceptions are ozone, sulfur and aerosols. But as mentioned, these gasses are less relevant over the long-term.
The GHG concentration is a key indicator used for international climate negotiations because of the overall objective of the United Nations Framework Convention on Climate Change (UNFCCC), i.e. 'to stabilize atmospheric greenhouse gas concentrations at a level that would prevent dangerous anthropogenic interference with the climate system' (UNFCCC, 1993). The EU has interpreted this 'dangerous anthropogenic interference' by setting a long-term target to limit global temperature increase to below 2°C above preindustrial levels (Decision No 1600/2002/EC of the European Parliament and of the Council of 22 July 2002, laying down the sixth Community environment action programme, confirmed by the Environment Council conclusions of March 2005 and subsequent Environment Council conclusions). Various studies have assessed the probability of keeping the long-term temperature rise below this target in relation to different stabilization levels of GHGs in the atmosphere (Fig. 2, Meinshausen, 2006; IPCC, 2007b). These studies showed that there is an about 50% probability that the temperature rise would remain below the 2^oC increase if the GHG concentration would be stabilized in the long-term at 450 ppm CO₂-eq. At 550 ppm CO₂-eq. stabilization the probability of staying below the 2^oC is very low, ranging between 1% and 37% (Meinhausen, 2006; IPCC, 2007b).

• Rationale references

  See references section

Indicator definition

Targets

The ultimate objective of the United Nations Framework Convention on Climate Change (UNFCCC) is to achieve 'stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system. Such a level should be achieved within a time-frame sufficient to allow ecosystems to adapt naturally to climate change, to ensure that food production is not threatened and to enable economic development to proceed in a sustainable manner'.

To reach the UNFCCC objective, the EU has specified more quantitative targets in its 6th environmental action programme (6th EAP) which mentions a long-term EU climate change objective of limiting global temperature rise to a maximum of 2^oC compared with pre-industrial levels. This target was confirmed by the Environment Councils of 20 December 2004 and 22-23 March 2005. Scientific insight shows that in order to have a high chance of meeting the EU policy target of limiting global temperature rise to 2^oC above pre-industrial levels, global GHG concentrations may need to be stabilised at much lower levels, e.g. 450 ppm CO₂-equivalent. Stabilisation of concentrations at well below 550 ppm CO₂-equivalent may be needed and global GHG emissions would have to peak within two decades, followed by substantial reductions by 2050 compared with 1990 levels.

The EU Environment Council (October 2008) adopted the conclusion that to achieve stabilisation in an equitable manner, developed countries should reduce emissions by about 15-30% by 2020 and 80-95% by 2050, below the base year levels (1990).

• Policy documents references

  See references section

Policy questions and graphics

Key policy question: What is the trend in greenhouse gas concentration in the atmosphere? Will it remain below 450 ppm CO2-equivalent giving a 50% probability that the global temperature rise will not exceed 2 degrees Celsius above pre-industrial levels?

The assessment should answer to this policy question and be supported by the following graphics.

• Example (at European level)

  Measured and projected concentrations of 'Kyoto' greenhouse gases

• Graphic example for countries benchmarking has not been specified for this policy question.

Methodology

Methodology for indicator calculation

Global average concentration values are calculated from measurements at individual stations representative for different latitude bands. The average trend of these stations present is then used as global trend. Radiative forcings are calculated with approximate equation according to (IPCC, 2001; IPCC, 2007a), based on the observed atmospheric concentrations and using radiative efficiencies for CO₂, CH₄, and N₂O based on IPCC (2001), and according to WMO (2002) for the other gases. The equations used to compute the contribution of the individual gasses are presented below:

 

Trace gas	Parameterisation, Radiative forcing, change in F (Wm-2)	Constants
CO2	change in F = alpha ln (C/C0) C and C0 are the current and pre-industrial concentrations (ppm) of CO2, respectively	alpha = 5.35
CH4	change in F = alpha (sq. root of M - sq. root of M0 ) - (f (M,N0) - f (M0,N0)) where  f (M,N)= 0.47 ln [1+2.01*10-5 (MN)0.75 + 5.31*10-15 M(MN)1.52] M and M0 are the current and pre-industrial concentrations (ppb) of CH4, respectively; N and N0 are the current and pre-industrial concentrations (ppb) of N2O, respectively.	alpha  = 0.036
N2O	change in F = alpha (sq. root of N - sq. root of N0 ) - (f (M0,N) - f (M0,N0)) where  f (M,N)= 0.47 ln [1+2.01*10-5 (MN)0.75 + 5.31*10-15 M(MN)1.52] M and M0 are the current and pre-industrial concentrations of CH4, respectively; N and N0 are the current and pre-industrial concentrations of N2O, respectively.	alpha  = 0.12
HFC, PFC & SF6	change in F = alpha (X-X0)  X and X0 are the current and pre-industrial concentrations (ppb) of gas X, respectively.	Values for alpha depend on molecule, and are taken from WMO, 2002.
	Calculation of CO2-equivalent concentration, Ceq (ppm)
	Ceq = C0 exp ((SUM change in F) / alpha) Ceq is the current CO2-equivalent concentration; C is the pre-industrial CO2 concentration. Summation is over radiative forcings of all greenhouse gases considered.	alpha  = 5.35

 

Methodology for gap filling

If measurements from a station are missing for a certain year, the global trend is derived from the stations that are present.

Methodology references

See references section

Data sets

Data set title	Source	Reporting obligations (ROD)
CH4 and N2O concentrations	Advanced Global Atmospheric Gases Experiment	No ROD info available for this data set.
CO2 concentrations	Scripps Institution of Oceanography	No ROD info available for this data set.
Climate Change 2001 - The Scientific Basis	Intergovernmental Panel on Climate Change (IPCC)	No ROD info available for this data set.
HFC-134a and SF6 concentrations	NOAA's National Geophysical Data Center (NGDC)	No ROD info available for this data set.

General metadata

Identification CSI code 013 IMS internal code ISpecification20041007131717 Creation date Oct 2004 Publish date 20 Apr 2005

Ownership DG ENV EEA Eurostat Status in CSI Status Endorsed by management board

References

Scientific references:

IPCC (2001) Climate Change 2001 (link not available)

IPCC (2001) Climate Change 2001: The Physical Science Basis. (eds.) J. T. Houghton, Y. Ding, D.J. Griggs, M. Noguer, P. J. van der Linden and D. Xiaosu. Working Group 1 Contribution to the Third Assessment Report of the Intergovernmental Panel on Climate Change (IPCC). Appendix II.3.11 on GHG forcing)

IPCC (2007a) Climate Change 2007 (link not available)

IPCC (2007a) Climate Change 2007: The Physical Science Basis. (eds.) Solomon S, Qin D, Manning M, Chen Z, Marquis M, Averyt K, Tignor MMB & Miller HL,. Working Group 1 Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC). Technical Summary and Chapter 10 (Global Climate Projections)

IPCC (2007b) Climate Change 2007 (link not available)

IPCC (2007b) Climate Change 2007: Mitigation. Eds. B. Metz, O. R. Davidson, P. R. Bosch, R. Dave, L. A. Meyer, Working Group III contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC), Technical Summary, chapters 3 (Issues related to mitigation in the long term context) and 11 (Mitigation from a cross sectoral perspective)

Meinshausen M (2006) (link not available)

Meinshausen M (2006) What Does a 2°C Target Mean for Greenhouse Gas Concentrations. In: Avoiding Dangerous Climate Change (eds. Schellnhuber HJ, Cramer W, Nakicenovic N, Wigley T & Yohe G), pp. 265-280. Cambridge University Press, Exeter.

UNFCCC (1993) (link not available)

UNFCCC (1993) The United Framework Convention on Climate Change. United Nations.

WMO Greenhouse Gas Bulletin (2007)

The Environment Division of WMO's Atmospheric Research and Environment Programme has recently published the second of a series of WMO-GAW Annual Greenhouse Gas Bulletins. Each year, these bulletins will report the latest trends and atmospheric burdens of the most influential, long-lived greenhouse gases.

Policy documents:

Council Decision (2002/358/EC) of 25 April 2002

Council Decision (2002/358/EC) of 25 April 2002 concerning the approval, on behalf of the European Community, of the Kyoto Protocol to the United Nations Framework Convention on Climate Change and the joint fulfilment of commitments thereunder.

Greenhouse gas monitoring mechanism

Decision No 280/2004/EC of the European Parliament and of the Council of 11 February 2004 concerning a mechanism for monitoring Community greenhouse gas emissions and for implementing the Kyoto Protocol

Methodology references:

No methodology references available.