Contributor to the recent and first version of recommendation for measurement on regional scale and urban environments. The key difference to background observations are:

- less strict requirements for instrument precision and accuracy, due to larger concentration enhancement found in the atmosphere

- larger calibration span needed for most GHG, as the maximum of our well defined WMO scales are often surpassed

- finding suitable instruments that have a linear response on a large concentration range

- the issue of the representativeness of a site and local influences are more important for this type of observations


Besides this the on-going work on carbon isotopes has contributed to the chapter on the recommendation for Radiocarbon measurements in CO2 at GGMT-17 in Beijing (together with J. Turnbull and others). For this tracer the sample preparation and measurement techniques in different labs could cause systematic biases, which forces us to setup inter-comparison programs. The first comparison activity for Δ14C in CO2 was initiated at the 13th WMO/IAEA Meeting of CO2 Experts in Boulder, Colorado, and is on-going about once per year (Miller et al., 2013). Laboratories participated by sending flasks to NOAA/ESRL to be filled with air from two whole-air reference cylinders for CO2 extraction, target preparation and 14C AMS analysis. Plans for future atmospheric 14C comparison exercises are laid out in the report of the atmospheric 14CO2 workshop at the 21th International Radiocarbon Conference (Turnbull et al., 2013; Lehman et al., 2013). Other comparison exercises have been performed on an ad hoc basis: the full Δ14C of CO2 measurement process from sampling method to AMS measurement (Graven et al., 2013); comparison of AMS and conventional measurements (Vogel et al., 2011).