Combined 14 CO 2 and CO Observations: A key to high-resolution fossil fuel CO 2 records ? ! Ingeborg Levin 1 and Ute Karstens 2 1 Institut für Umweltphysik Universität Heidelberg 2 Max-Planck-Institut für Biogeochemie, Jena

Outline Importance of fossil fuel CO 2 emissions for the CO 2 mixing ratio over Europe Determination of atmospheric fossil fuel CO 2 by 14 CO 2 observations Correlation fossil fuel CO 2 with CO Assessment of a purely observation-based method to derive hourly atmospheric fossil fuel CO 2

Schauinsland station of the Umweltbundesamt in the Black Forst 1205 m a.s.l.

Comparison of REMO-simulated CO 2 mixing ratios at Schauinsland with observations February 2002 July 2002

How can we measure fossil fuel CO 2 in the atmosphere to validate these model results ?

Radiocarbon 14 C ( 14 C, radioactive lifetime  = 8300 years) Natural 14 C production by reactions of neutrons from cosmic radiation with atmospheric Nitrogen  natural atmospheric background level Artificial 14 C production via atmospheric nuclear weapon tests in the 1950s and 1960s „Negative 14 C source“ via burning of fossil fuels and cement production which are free of 14 C

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

The temporal resolution of 14 C-derived fossil fuel CO 2 is not sufficient to validate high-resolution model simulations

Heidelberg sampling site in the populated Rhine valley

How well do CO mixing ratios correlate with fossil fuel CO 2 ?

Use a combination of integrated 14 CO 2 and hourly CO measurements : Test this approach in the REMO model world : Assess the difference between original and re- calculated hourly  CO 2 (foss) -> RMS deviation

Test with REMO model run for Heidelberg Annual mean  CO 2 foss [ppm]RMS error [ppm]RMS error [%]: IER: EDGAR:

REMO-simulated fossil fuel CO 2 in Europe and RMS difference to CO-based approach (Feb. 2002) → In most of Europe the CO-based method has RMS errors below 30% Fossil fuel CO 2 RMS error

Can we validate our suggested method to derive fossil fuel CO 2 from integrated 14 CO 2 and hourly CO observations in the real world ?

Event samples collected in Heidelberg [data from Gamnitzer et al., 2006] RMS deviation: 34 % RMS deviation: 32 % RMS deviation: 23 % RMS deviation: 20 %

Summary : Fossil fuel CO 2 emissions in Europe contribute between 30% and 50% to the atmospheric short-term (diurnal) CO 2 signal and also to the monthly mean continental signal both, at urban and remote (mountain) sites CO is a good surrogate tracer for FFCO 2 if well calibrated with 14 CO 2 observations, and can thus provide FFCO 2 at high temporal resolution But: Calibration needs to be an ongoing exercise Combined weekly or two-weekly integrated 14 CO 2 and hourly CO observations allow to determine hourly fossil fuel CO in Europe with uncertainties between 15 and 40% (depending on the relative importance of the fossil fuel CO 2 component) Our proposed method is purely observation-based and until now much more accurate and precise than any model-simulated approach [see Poster No. 179 by Karstens et al. ]

Suggestion for CarboEurope stations : Establish high-precision integrated 14 CO 2 measurements at all stations where continuous CO measurements exist to “measure” hourly fossil fuel CO 2 mixing ratios.

Thank you !

Test with REMO model run for Lutjewad Annual mean  CO 2 foss [ppm]RMS error [ppm]RMS error [%]: IER: EDGAR:

Test with REMO model run for Schauinsland Annual mean  CO 2 foss [ppm]RMS error [ppm]RMS error [%]: IER: EDGAR:

Continuous CO 2 and CO mixing ratios in Heidelberg February 2002 July 2002

January 2002 CO 2 Fluxes Fossil fuel CO 2 (extrap.) (Scholz et al., IER 2005) Biome-BGC NEE (Churkina et al., 2003) in kg C m -2 s -1 IER: Inst. of Energy Economics and the Rational Use of Energy, Univ. Stuttgart, Germany

Calculation of the fossil fuel CO 2 component from  14 C observations