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| Titel |
Long-term observations of 14C-based atmospheric fossil fuel CO2 (FFCO2) and the CO/FFCO2 ratio in the Heidelberg urban environment |
| VerfasserIn |
Ingeborg Levin, Samuel Hammer, Bernd Kromer |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250073712
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| Zusammenfassung |
| Urban environments are large emitters of fossil fuel CO2 and of combustion-related
pollutants, such as carbon monoxide (CO). While huge efforts are currently undertaken to
agree on commitments to reduce fossil fuel CO2 emissions, these have not really
been successful yet, and the global atmospheric CO2 abundance is still increasing.
However, the implementation of emission controls on pollutants, e.g. from traffic,
seem to have been more efficient, based on recent emission inventory data (e.g.
http://www.statistik.baden-wuerttemberg.de). In order to verify this bottom-up information
we present here ten years of quasi-continuous atmospheric observations of CO2, fossil fuel
CO2 (FFCO2) and CO in Heidelberg. The fossil fuel CO2 component is determined from
integrated radiocarbon (14CO2) measurements, exploiting the fact that fossil fuel CO2 lacks
14C (e.g. Levin et al., Geophys. Res. Lett. 30, 2003).
Our measurements show that the fossil fuel CO2 level in the Heidelberg suburbs has not
significantly changed (i.e. decreased) in the last decade. Observed inter-annual variations are
rather due to inter-annual changes of atmospheric transport, as was already reported by
Levin and Rödenbeck (Naturwissenschaften 95, 2008). However, we find a ca. 25%
change in the CO/FFCO2 ratio of the regional concentration offsets compared to
background levels from about 14.5 ppb/ppm in 2002 to about 11 ppb/ppm in 2009. This
observation is in very good agreement with the emission statistic for the closer catchment
area of our measurement site. The Statistische Landesamt, Baden-Württemberg
(http://www.statistik.baden-wuerttemberg.de) reported a change in the CO to FFCO2
emission ratio for the city area of Heidelberg from 13.8 ppb/ppm in 2000 to 10.5 ppb/ppm in
2007. A more than 20% decrease of the CO/FFCO2 emission ratio is also reported
for the whole state of Baden-Württemberg (south-west Germany), but note that
these ratios are generally smaller, between 11.5 and 9 ppb/ppm, due to a smaller
contribution of traffic to the emissions. Our results clearly show that statistical
emissions inventories, or at least the ratios of emissions and their changes, can be
reliably verified on the local to regional scale by careful long term atmospheric
observations.
A temporal change of the CO/FFCO2 emission ratio has, however, also implications for
the use of CO as surrogate tracer for high-resolution fossil fuel CO2 estimates (e.g. Levin &
Karstens, Tellus 59B, 2007): Without ongoing 14C calibration of the CO/FFCO2 ratio,
decadal trends in CO-based fossil fuel CO2 estimates can be largely biased by up to
20-30%.
The research leading to these results has received funding from the European Community’s
Sixth and Seventh Framework Programs in the CarboEurope-IP (GOCE-CT-2003-505572)
and ICOS Preparatory Phase (211574) projects. |
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