Atmospheric greenhouse gas concentrations (CSI 013/CLIM 052) - Assessment published Feb 2014
Climate change (Primary topic)
Typology: Descriptive indicator (Type A - What is happening to the environment and to humans?)
- CSI 013
- CLIM 052
Key policy question: Will the atmospheric concentration of all greenhouse gases 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 global average concentrations of various greenhouse gases in the atmosphere remains 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 416 ppm CO2 equivalents in 2011
- The concentration in 2011 of the six greenhouse gases (GHG) included in the Kyoto Protocol has reached 446 ppm CO2 equivalent, an increase of 168 ppm (around +60%) compared to pre-industrial levels.
- The concentration of CO2, the most important greenhouse gas, reached a level of 391 ppm by 2011, and further increased to 393 ppm in 2012. This is an increase of approximately 115 ppm (around +40%) compared to pre-industrial levels.
The concentration of greenhouse gases (GHG) in the atmosphere has increased during the 20th century and first part of the 21st century, extremely likelycaused 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, 2013, See also Carbon Budget at Global Carbon Project, www.globalcarbonproject.org/carbonbudget/index.htm). The increase of all GHGs 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) each affect the climate system differently (see rationale). 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, 2013). Considering these gases, the total CO2-equivalent concentration reached a level of 416 ppm CO2 eq. in 2011, again exceeding the 400 ppm (Figure 2). The annual concentration increase is 2.5 eq.yr-1 in 2011, somewhat smaller than annual increase in earlier years. This due to the economic situation in the world, leading to less emissions.
The contribution of tropospheric ozone to the climate system is considered to be stable in the recent decades when comparing large annual and special variation (IPCC, 2007a, IPCC, 20133). Long-term data on tropospheric ozone are difficult to develop due to the scarcity of representative observing sites with long records and the large spatial heterogeneity (IPCC, 2013). Overall, assuming a concentration threshold of 450 ppm CO2 equivalents will result in a 2oC temperature change (see rationale), means concentrations can only increase by a further about 45 ppm before this threshold value is exceeded. Assuming the 2000-2011 trend of annual increase of total GHG concentrations will also 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 in such a way affect the climate system. In order to control the 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).
- GHG in the Kyoto Protocol are: Carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and three fluorinated gasses (Hydrofluorocarbons (HFC), PerfluorocarbonsPFC, Sulphur Hexafluoride (SF6))
- GHG in the Montreal Protocol are three other groups of fluorinated gases: CFCs, HCFCs and CH3CCl3
- 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 468 ppm CO2 equivalents in 2011. This is about 190 ppm higher than pre-industrial levels. That this concentration is higher than when considering all gases 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. The Montreal Protocol gases contributed as a group about 10% to the current warming (Figure 3). The concentrations of these gases has peaked around the millennium change and 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 446 ppm CO2-equivalent in 2011, an increase of nearly 170 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 45 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 remain increasing (Figure 4). Overall, the concentrations in the atmosphere of CO2, CH4 and N2O exceeded the range of concentrations recorded in ice cores during the past 800,000 years (IPCC, 2013).
The CO2 concentration reached a level of 391 ppm in 2011, and increased further up 393 ppm in 2012 (Figure 4, Carbon Dioxide). This is an increase of about 115 ppm (+41%) compared to the pre-industrial levels (i.e. before 1750) (NOAA, 2012).
The concentration of methane (CH4) has increased to 1804 parts per billion (ppb) in 2011, which is an increase by a factor of about 2.5 from pre-industrial levels (Figure 4, Methane). The growth of the CH4 concentration in the atmosphere has been variable in recent decades. But since 2007 it is steadily growing again. The exact drivers of this (renewed) growth are still debated (Dlugokencky et al., 2009) IPCC, 2013). Anthropogenic CH4 sources play a dominant role in the increase, while fluctuations in natural sources are most likely causing the global inter-annual variability of CH4 emissions (high confidence), with a smaller contribution from biomass burning emissions during high fire years.
The nitrous oxide (N2O) concentration in 2011 was 324 ppb (Figure 4, Nitrous Oxide), about 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 (i.e. HFCs, PFCs and SF6) have increased by factors 1.2 to 38 (depending on the gas) between 1995 (reference year under Kyoto Protocol) and 2011. 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. Defined as >95% probability (IPCC, 2007)
More recent data are not available for the annual-average concentration except for CO2, for which data for 2012 are available
 Note that the value is higher than reported in 2012. This due to updated values for the radiative forcing of tropospheric ozone (0.4 instead of 0.35). This based on recent IPCC information (IPCC, 2013)
provided by Scripps Institution of Oceanography
National Geophysical Data Center (NGDC)
provided by National oceanic and atmospheric administration (NOAA)
HFC-134a and SF6 concentrations
provided by National oceanic and atmospheric administration (NOAA)
Climate Change 2001 - The Scientific Basis
provided by Intergovernmental Panel on Climate Change (IPCC)
CH4 and N2O concentrations
provided by Advanced Global Atmospheric Gases Experiment (AGAGE)
More information about this indicator
See this indicator specification for more details.
Contacts and ownership
EEA Contact Info
- National oceanic and atmospheric administration (NOAA)
- European Environment Agency (EEA)
- Oak Ridge National Laboratory (ORNL)
EEA Management Plan2013 2.4.1 (note: EEA internal system)
Frequency of updates
For references, please go to www.eea.europa.eu/soer or scan the QR code.
This briefing is part of the EEA's report The European Environment - State and Outlook 2015. The EEA is an official agency of the EU, tasked with providing information on Europe’s environment.
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