Evaluation of CO and SF 6 as quantitative tracers for fossil fuel CO 2 : The Experimentalists’ view Ingeborg Levin 1, Ute Karstens 2, Ulrike Gamnitzer 1, Christoph Schönherr 1, Bernd Kromer 1 and Samuel Hammer 1 1 Institut für Umweltphysik Universität Heidelberg 2 Max-Planck-Institut für Biogeochemie, Jena

February CO 2 Fluxes Fossil fuel CO 2 (EDGAR V3.2 FT, Olivier et al., 2005) Biome-BGC NEE (Churkina et al., 2003) kg C m -2 s

Heidelberg: February 2002 (REgional MOdel)

Heidelberg: June 2002 (REgional MOdel)

Schauinsland: February 2002 (REgional MOdel)

Can we validate these model results ? … measure total CO 2 and fossil fuel CO 2

—› measure Radiocarbon ( 14 C) in atmospheric CO 2 … … because fossil fuel CO 2 contains no 14 C and dilutes atmospheric 14 CO 2

Long-term 14 CO 2 background observations in Europe „clean“  14 CO 2 background level in the Alps Reference:  Atmosphere in 1890

Long-term 14 CO 2 observations in Europe „clean“  14 CO 2 background level in the Alps Depletion of the  14 CO 2 level close to fossil fuel sources

Monthly mean fossil fuel CO 2 at Schauinsland station and in Heidelberg mean fossil fuel CO 2 offset: Schauinsland: ca. 1.4 ppm Heidelberg: ca. 10 ppm

… but the temporal resolution of our 14 C measurements is poor: weekly means … and the sensitivity is quite low: minimum uncertainty ≈ ±2.5 ‰ of 370 ppm ≥ ±1 ppm

—› proxies/surrogates needed to substitute 14 CO 2 observations Carbon Monoxide (CO) Sulfur Hexafluoride (SF 6 )

Continuous trace gas observations in Heidelberg in October 2004 CO 2 CO SF 6 CO: Mainly anthropogenic sources (fossil fuel burning) and oxidation of hydrocarbons chemical life time ca. 2 months SF 6 : Only anthropogenic sources roughly distributed according to population density chemically inert

14 CO 2, fossil fuel CO 2 and CO offset in Heidelberg

How well can we quantitatively use CO as a fossil fuel CO 2 surrogate ?

Weighted mean ratio [ppb/ppm]: Observations: 12.2±0.4 Fossil fuel CO 2 and CO offset and their ratio

Weighted mean ratios [ppb/ppm]: Observations: 12.2±0.4 Emissions Inventories (incl. soils, etc.) Edgar: 14.7 Fossil fuel CO 2 and CO offset and their ratio in comparison with emissions inventories

Weighted mean ratios [ppb/ppm]: Observations: 12.2±0.4 Emissions Inventories (incl. soils, etc.) IER: 18.0 Edgar: 14.7 Fossil fuel CO 2 and CO offset and their ratio in comparison with emissions inventories IER: Institute of Energy Economics and Rational Use of Energy, Stuttgart

Conclusions (I): Fossil fuel CO 2 (FFCO 2 ) emissions in Europe contribute almost half to the continental CO 2 signal Monthly mean fossil fuel CO 2 levels at urban sites can be determined by high precision 14 CO 2 measurements to better than ±10% in winter and about ±30% in summer. At remote sites, the mean FFCO 2 signal is small (1-5 ppm) and can be determined by 14 CO 2 measurements only to about 30%. Higher temporal resolution of 14 CO 2 measurements is required here to achieve better precision.

Conclusions (II): CO is a potentially applicable surrogate tracer for FFCO 2, however, Emissions inventories of CO (and FFCO 2 ) are yet not accurate enough to apply it quantitatively, CO has sources other than from fossil fuel burning (soils !!) which also need to be known accurately The catchment area and relative mix of emissions needs to be known accurately, this requires modelling  See REMO results from Karstens et al., Poster FF-134

Thank you !

Comparison of measured and REMO- modelled CO and FFCO 2 mixing ratios

Comparison of measured and REMO- modelled CO/FFCO 2 ratios See also Poster by Ute Karstens et al. No. FF-134 Mean ratios [ppb/ppm]: Observations: 13.5±0.6 REMO & EDGAR: 12.7±0.1 REMO & IER: 11.0±0.2

CO/CO 2 fossil fuel emission ratios 2000 IER mean 2000 (Scholz et al., IER 2005) EDGAR V3.2 FT 2000 (Olivier et al., 2005) in mmol / mol