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Atmospheric greenhouse gas concentrations

Indicator Assessment Erstellt 08.01.2013 Veröffentlicht 23.01.2013 Zuletzt geändert 03.09.2015 19:17
Indicator codes: CSI 013 , CLIM 052

Key messages

  • The global average concentrations of various greenhouse gases in the atmosphere have reached the highest levels ever recorded, and concentrations are increasing. The combustion of fossil fuels from human activities and land-use changes are largely responsible for this increase.
  • The concentration of all GHGs, including cooling aerosols that are relevant in the context of the 2oC temperature target, reached a value of 403 ppm CO2 equivalents in 2010, exceeding the 400 ppm for first time.
  • The concentration in 2010 of the six greenhouse gases (GHG) included in the Kyoto Protocol has reached 444 ppm CO2 equivalent, an increase of 165 ppm (around +60 %) compared to pre-industrial levels.
  • The concentration of CO2, the most important greenhouse gas, reached a level of 389 ppm by 2010, and further increased to 391 ppm in 2011. This is an increase of approximately 112 ppm (around +40 %) compared to pre-industrial levels. 

What is the trend of greenhouse gas concentrations in the atmosphere? Will they remain below 450 ppm CO2-equivalent to give a 50% probability that the global temperature rise will not exceed 2 degrees Celsius above pre-industrial levels?

Contribution of the different GHGs to the overall greenhouse gas concentration in 1950, 1990 and 2010

Note: Contribution of the different GHGs as included in the Kyoto and Montreal protocol to the overall greenhouse gas concentration in 1950, 1990 and 2010.

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Atmospheric concentration of Carbon Dioxide (ppm)

Note: The figure shows the global atmospheric concentration of carbon dioxide up to 2010. The value for 2011 is 390.9 ppm but is not included in the chart to ensure consistency with the other greenhouse gas figures.

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Atmospheric concentration of Methane (ppb)

Note: The figure shows the global atmospheric concentration of methane up to 2010.

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Atmospheric concentration of Nitrous Oxide (ppb)

Note: The figure shows the global atmospheric concentration of nitrous oxide up to 2010.

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The concentration of greenhouse gases (GHG) in the atmosphere has increased during the 20th century and first part of the 21st century, extremely likely[1] caused mainly by human activities related to the use of fossil fuels (e.g. for electric power generation), agricultural activities and land-use change (mainly deforestation) (IPCC, 2007, see also Carbon Budget at Global Carbon Project). The increase of all GHG gases has been particularly rapid since 1950. The first 50 ppm increase above the pre-industrial value of carbon dioxide (CO2), the most important human greenhouse gas,- was reached in the 1970s more than 200 years since pre-industrial times, whereas the second 50 ppm increase occurred after just approximately 30 years.

The various greenhouse gases (Text box 1) affect the climate system differently (see also ‘Justification for Indicator Selection’ section). To evaluate the GHG concentration in the atmosphere in relation to temperature change, it is important to consider all greenhouse gases, i.e. the long-living GHGs under the Kyoto Protocol, those under the Montreal Protocol (direct and indirect), as well as ozone, water vapour and aerosols (IPCC, 2007). Considering these gases, the total CO2-equivalent concentration reached a level of 403 ppm CO2 eq. in 2010[2], exceeding the 400 ppm for first year (Figure 1).  The annual concentration increase has accelerated to 3.2 ppm CO2 eq.yr-1 in 2010, but the rate of increase is still lower than in earlier years. 

The contribution of tropospheric (ground-level) ozone to the climate system is considered to be stable over the recent decades when comparing large annual and special variation (IPCC, 2007a). However, long-term data on tropospheric ozone are difficult to assess due to the scarcity of representative observing sites with long records and the large spatial heterogeneity (IPCC, 2007a).

Overall, assuming a concentration threshold of 450 ppm CO2 equivalents will result in a 2oC temperature change (see ‘Justification for Indicator Selection’ section), means GHG concentrations can only increase by a further 50 ppm before this threshold value is exceeded. Assuming the 2000-2010 trend of annual increase of total GHG concentrations will continue in the coming years, the threshold value may be exceeded in less than 25 years. The lower band of the uncertainty range has been exceeded already in 2010, whereas it may take more than 50 years before the upper uncertainty band is exceeded.

Text box 1: Greenhouse gases and their inclusion in international legislation
Greenhouse gases (GHG) can intercept solar radiation and thus affect the Earth's climate system. In order to control the anthropogenic emissions of such gases, many of them are included within different international agreements, including the UNEP Montreal Protocol on Substances that deplete the Ozone layer (1987) and the Kyoto Protocol to the UNFCCC which aims to limit global warming (1997).     

(1) GHG included in the Kyoto Protocol are: carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and three fluorinated gasses (HFC, PFC, SF6).
(2) GHGs in the Montreal Protocol include three other groups of fluorinated gases: CFCs, HCFCs and CH3CCl3.    
(3) In addition, GHGs exist that are not included in global treaties, here called non-protocol gases (NPG), including stratospheric and tropospheric ozone (O3), aerosols such as black carbon, and water vapour. 

Excluding water vapour, ozone and aerosols, the total concentration of the remaining, long-lived GHGs has increased from 278 in pre-industrial times to 466 ppm CO2 equivalents in 2010. This is about 188 ppm higher than pre-industrial levels. That this concentration is higher than when all gases are considered is caused by the overall cooling effect of aerosols - although certain aerosols act in an opposite manner by enhancing the warming. Overall, aerosols are compensating for around 45% of the current warming induced by the Kyoto and Montreal GHGs. Aerosols have a relatively short lifetime in the atmosphere. The Montreal Protocol gases contributed as a group about 10% to the current warming (Figure 3). The concentrations of these gases have peaked around the end of the last millennium and have now started to decline due to natural removal processes (IPCC, 2007a).

Six GHGs are included in the Kyoto Protocol. Their concentration in the atmosphere has reached 444 ppm CO2-equivalent in 2010, an increase of about 165 ppm compared to pre-industrial times (Figure 1). Changes in atmospheric CO2 contributed by far most of the increase (about 67% of the increase from pre-industrial period). When translating the overall 450 ppm CO2-equivalent limit into a limit just for the Kyoto gases (491 ppm), this means only an additional 47 ppm CO2-equivalent increase is possible (with an uncertainty range of  -2 – 97 ppm CO2-equivalent).

The concentrations of the individual GHGs under the Kyoto protocol have reached new levels in 2010 (Figures 4, 5 and 6):

  • The CO2 concentration reached a level of 389 ppm in that year, and increased further in 2011 to 391 ppm (Figure 4). This is an increase of about 112 ppm (+39%) compared to the pre-industrial levels (i.e. before 1750) (NOAA, 2012). The present CO2 concentration has not been exceeded during the past 420 000 years and possibly not even during the past 15 million years (Tripati et al., 2009). 
  • The concentration of methane (CH4) has increased to 1810 parts per billion (ppb) in 2010 (+159% from pre-industrial levels), a value which also has not been exceeded during the past 420 000 years (Figure 5). Atmospheric concentrations of CH4 have increased notably during the past couple of years. The reasons for this renewed growth are not yet fully understood, but human-induced sources such as growing industrialisation in Asia, increasing wetland emissions due to land-use changes, biomass burning, as well as increases from natural sources from northern latitudes and the tropics (e.g. CH4 releases from thawing permafrost) (Dlugokencky et al., 2009; Mascarelli, 2009; Shakhova et al, 2010) are considered potential causes (WMO, 2010). 
  • The nitrous oxide (N2O) concentration in 2010 was 323 ppb (Figure 6), 20% above the pre-industrial level. This concentration has not been exceeded during at least the past 1 000 years.  
  • The concentrations of the F-gases within the scope of the Kyoto Protocol (HFCs, PFCs and SF6) have increased by large factors (between 1.3 and 6.4, depending on the gas) between 1999 and 2010. These gases are very effective absorbers of radiation and even small amounts can significantly affect the climate system. Their contribution to the total climate forcing is rapidly increasing in the past years.

[1] Defined as >95% probability (IPCC, 2007).

[2] More recent data are not available for the annual-average concentration except for CO2, for which data for 2011 are available.

Indicator specification and metadata

Indicator definition

The indicator shows the observed trends of greenhouse gas concentrations. The various greenhouse gases have been grouped in three different ways (see 'Justification for Indicator Selection’ section above). Next to the concentration of individual GHGs, greenhouse gasses are grouped in two ways, using the CO2-equivalent concentration as a way to add the different gasses. The CO2-equivalent concentration of a gas is the CO2 concentration that would cause the same amount of radiative forcing as the mixture of all GHGs. Global annual averages are considered, because in general the gases mix quite well in the atmosphere. 

Units

Atmospheric concentration in parts per million in CO2-equivalent (ppm CO2-eq.).


Policy context and targets

Context description

GHG concentrations is a key indicator relevant to  international climate negotiations as the overall objective of the United Nations Framework Convention on Climate Change (UNFCCC), is ‘to stabilize atmospheric greenhouse gas concentrations at a level that would prevent dangerous anthropogenic interference with the climate system’ (UNFCCC, 1993). Both at the global (UNFCCC, 2009) and the EU level (October 2008 Environment Council conclusions) this ‘dangerous anthropogenic interference’ has been recognised by formulating the objective of keeping the long-term global average temperature rise below 2°C compared to pre-industrial times. Studies have assessed the probability of keeping the long-term temperature rise below this 2°C target in relation to different stabilization levels of GHGs in the atmosphere (Meinshausen, 2006; den Elzen et al., 2007; Van Vuuren et al., 2008). These studies showed that to have a 50% probability of limiting the global mean temperature increase to 2 °C (above pre-industrial levels), the concentration of all GHGs in the atmosphere would need to be stabilised below about 450 ppm CO2  equivalent (range 400-500 ppm CO2 eq.). This includes ozone, water vapour and aerosols. For CO2 only, the 50% probability concentration threshold is around 400 ppm, and for all Kyoto gases about 480 ppm CO2 equivalent (range 432 – 532 ppm CO2  eq. ). Note that the value for the Kyoto gases only, is higher than when considering all GHGs, due to the cooling affect of aerosols (currently about 1.2 W.m-2 or about 70 ppm CO2 eq.). According to the scientific literature the probability of staying below the 2oC becomes very low when stabilization at 550 ppm CO2 eq, ranging between 0% and 37%, considering all GHGs.

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 2oC 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 2oC 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).

The Copenhagen Accord (Dec. 2009) recognised the objective of keeping the maximum global average temperature rise below 2 °C, although without specifying the base year or period, and the need for a review in 2015 to consider a possible goal of limiting temperature rise to 1.5 °C using new scientific insights.

Related 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

Methodology for indicator calculation

For atmospheric CO2, the global average values are directly taken from NOAA (NOAA, 2011, see also www.esrl.noaa.gov/gmd/ccgg/trends/global.html). Global average concentration values for the other gases are mainly based on CDIAC numbers (2011) (see agage.eas.gatech.edu) . 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 (2007a), and according toWMO (2002) for other gases. The equations used to compute the contribution of the individual gases 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.

In order to calculate the concentration of all long-living Greenhouse Gases also the Montreal Gases (i.e. CFCs & HCFCs) need to be included. A similar approach is applied for these gases:

CFCs & HCFCs

change in F = alpha (X-X0)

 X and X0 are the current and pre-industrial concentrations (ppb) of gas X, respectively.

Values for alpha depending on molecule (see below), taken from WMO, 2002.

Overview of used alpha values for chlorine Kyoto and Montral Gases 

Kyoto gases

Montreal gases

HFC-23

0.16

CFC-11

0.25

HFC-134a

0.159

CFC-12

0.32

CF4

0.116

CFC-13

0.25

C2F6

0.26

CFC-113

0.3

SF6

0.52

CFC-114

0.31

CFC-115

0.18

 

 

HCFC-22

0.2

 

 

HCFC-141

0.14

 

 

HCFC-142

0.163

 

 

CCl

0.13

 

 

CH4CC

0.01

 

 

CH4CCl3

0.06

 

 

CH3Br

0.05

In calculating the radiative forcing (and accompanying concentration levels) of the Montreal Protocol gases, the effect of ozone depleting substances on the stratospheric ozone layer was also considered. Velders et al (2007) estimated that the observed changes in stratospheric ozone between 2000 and 2010 contributed a forcing of -0.06 W.m2 (or about 10 ppm ppm CO2 eq.). To quantify the concentration of all greenhouse gases, important in relation to the 2oC target, the forcing of ozone, water vapor in the atmosphere and aerosols have been added. Due to uncertainties in the measurements and the large inter-annual and seasonal variation, the forcing is kept constant over the years for ozone and water vapour (IPCC, 2007a). These values are 0.35 and 0.07 W.m-2 for ozone and water vapor, respectively (IPCC, 2007a, pg 204). For aerosols a constant value of -1.2 W.m2 was used back to 2000. Between 1990 and 2000 2% higher values were assumed, and between 1970 and 1990 10% higher values (back to 1.35 W.m2 in 1970) (Bollen et al, 2009). For all three representations of the GHG concentration (i.e. Kyoto gasses only, all long-living GHG and all Greenhouse gases including zone and aerosols), the following approach has been used, adding the different climate forcing:

 

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 available stations data. 

Methodology references

No methodology references available.

Uncertainties

Methodology uncertainty

Global average concentrations since approximately 1980 are determined by averaging measurements from several ground-station networks (SIO, NOAA/CMDL,ALE/GAGE/AGAGE), each consisting of several stations distributed across the globe.

Absolute accuracies of global annual average concentrations are of the order of 1 % for CO2, CH4 and N2O, and CFCs; for HFCs, PFCs, and SF6, absolute accuracies can be up to 10-20 %. However, the year-to- year variations are much more accurate. Radiative forcing calculations have an absolute accuracy of 10% (IPCC, 2001); trends in radiative forcing are much more accurate.

The dominant sources of error for radiative forcing are the uncertainties in modelling radiative transfer in the Earths atmosphere and in the spectroscopic parameters of the molecules involved. Radiative forcing is calculated using parameterisations that relate the measured concentrations of greenhouse gases to radiative forcing. The overall uncertainty in radiative forcing calculations (all species together) is estimated to be 10 % (IPCC, 2001). Radiative forcing is also expressed as CO2-equivalent concentration; both have the same uncertainty. The uncertainty in the trend in radiative forcing/CO2-equivalent concentration is determined by the precision of the method rather than the absolute uncertainty discussed above. The uncertainty in the trend is therefore much less than 10 %, and is determined by the precision of concentration measurements (0.1 %).

It is important to note that global warming potentials are not used to calculate radiative forcing. They are used only to compare the time-integrated climate effects of emissions of different greenhouse gases.

Data sets uncertainty

Direct measurements have good comparability. Although methods for calculating radiative forcing and CO2-equivalent are expected to improve further, any update of these methods will be applied to the complete dataset covering all years, so this will not affect the comparability of the indicator over time.

Rationale uncertainty

Atmospheric concentrations of greenhouse gases are a well-established indicator of changes in atmospheric composition, which causes changes of the global climate system. Here we only present observed trends, having lower uncertainties than model projections. 

Datenquellen

Generic metadata

Themen:

Klimawandel Klimawandel (Primary topic)

Tags:
greenhouse gases | climate change | csi | kyoto protocol
DPSIR: State
Typology: Descriptive indicator (Type A - What is happening to the environment and to humans?)
Indicator codes
  • CSI 013
  • CLIM 052
Dynamic
Temporal coverage:
1750-2010
Geographic coverage:
Albania, Andorra, Armenia, Austria, Azerbaijan, Belarus, Belgium, Bosnia and Herzegovina, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Earth, Estonia, Finland, France, Georgia, Germany, Greece, Hungary, Iceland, Ireland, Italy, Kazakhstan, Kosovo (UNSCR 1244/99), Latvia, Liechtenstein, Lithuania, Luxembourg, Macedonia (FYR), Malta, Moldova, Monaco, Montenegro, Netherlands, Norway, Poland, Portugal, Romania, Russia, San Marino, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey, Ukraine, United Kingdom

Contacts and ownership

EEA Contact Info

John Van Aardenne

Ownership

EUA Management-Plan

2012 2.4.1 (note: EEA internal system)

Dates

Frequency of updates

Updates are scheduled once per year
Europäische Umweltagentur (EUA)
Kongens Nytorv 6
1050 Kopenhagen K
Dänemark
Telefon: +45 3336 7100