This paper describes the statistical analysis of annual trends in long term datasets of greenhouse gas measurements taken over ten or more years. The analysis technique employs a bootstrap resampling method to determine both the long-term and intra-annual variability of the datasets, together with the uncertainties on the trend values. The method has been applied to data from a European network of ground-based solar FTIR instruments to determine the trends in the tropospheric, stratospheric and total columns of ozone, nitrous oxide, carbon monoxide, methane, ethane and HCFC-22. The suitability of the method has been demonstrated through statistical validation of the technique, and comparison with ground-based in-situ measurements and 3-D atmospheric models.

Methane is one of the most important gaseous hydrocarbon species for both industrial and environmental reasons. Understanding and quantifying methane emissions to atmosphere is therefore an important element of climate change research. Range-resolved infrared differential absorption Lidar (DIAL) measurements provide the means to map and quantify a wide range of different methane sources. This paper describes the DIAL measurement technique and reports the application of an infrared DIAL system to field measurements of methane emissions from active and closed landfill sites. This paper shows how the capability of the DIAL to measure the spatial distribution of methane plumes enables DIAL vertical scans to spatially separate and independently quantify emissions from different sources. It also allows DIAL horizontal scans carried out above the surface to identify emission hot-spots. An overview of the landfill emission surveys carried out over the last decade by the National Physical Laboratory (NPL) DIAL system is presented. These surveys were part of research projects and commercial works aimed to validate the method and to provide reliable information on the methane emissions measuring the total site and area-specific emissions from active areas, capped areas, and gas engine stacks. This work showed that methane emissions are significantly higher for active sites than closed sites due to the methane emitted directly to air from the uncapped active areas. On active sites, the operational tipping areas generally have higher emission levels than the capped areas, although there is considerably variation in the emission from different capped areas. The information obtained with DIAL measurements allow site operators to identify significant fugitive emission sources and validate emissions estimates, and they allow the regulators to revise and update the emission inventories. Operators’ remediation actions driven by DIAL measurements have also been shown to considerably decreased total site methane emission.

Area sources are a key contributor to overall greenhouse gas emissions but present a particular challenge to emission measurement techniques due to the heterogeneous nature of the sources. A new Controlled Release Facility (CRF) has been developed that is able to recreate in the field both the distribution and rate of emissions seen in actual industrial applications. The results of a series of field validation experiments involving this facility and an infrared differential absorption Lidar (DIAL) facility are presented, which have demonstrated the capability of the CRF to generate controlled methane emissions from 1.8 kg/h to 11 kg/h with a typical expanded (k = 2) uncertainty of ~0.3 kg/h, and established that any underlying systematic uncertainty in the DIAL measurements across this range of methane emissions is less than 4% (or 0.2 kg/h).

Impurities in carbon dioxide can affect several aspects of the carbon capture and storage process, including storage capacity, rock erosion, accuracy of flow meters, and toxicity of potential leaks. There is an industry need for guidance on performing purity analysis before carbon dioxide is transported and stored. This paper reviews selected reports that specifically provide threshold amount fraction limits for impurities in carbon dioxide for the purpose of transport and storage, with rationales for these limits. A carbon dioxide purity specification is provided (including threshold amount fractions of impurities) on the basis of the findings, as well as recommendations on further work required to develop a suitable gas metrology infrastructure to support these measurements including primary reference materials, sampling methods, and instruments for performing purity analysis. These recommendations provide important guidance to operators and gas analysis laboratories for performing quality assurance.

Differential absorption lidar (DIAL) has been shown to be a very effective technique for the location and quantification of emissions of pollutants and greenhouse gases at industrial facilities. Several field trials have demonstrated the DIAL system performances and contributed to the development of the DIAL methodology, which is the basis of the protocols described in the European Standard EN 17628. While numerous papers have focused on different aspects of DIAL uncertainties, a rigorous propagation of the uncertainties in the DIAL equation has not been found. In this study, all the uncertainty sources contributing to a DIAL concentration measurement are assessed and the impact they have on the calculation of the mass emission rate. We derive the equations for both a DIAL system path-concentration integral and concentration uncertainties. The results from a methane measurement are presented, showing that for a signal to noise ratio on the backscattered lidar signals of 500, the path-concentration integral standard uncertainty is 2.3 ppb km and the concentration standard uncertainty is 92 ppb over a sampling spacing of 45 m. An equation is also presented enabling calculation of the contribution of the concentration uncertainty to the mass emission rate uncertainty.

Solar-pointing Fourier transform infrared (FTIR) spectroscopy offers the capability to measure both the fine scale and broadband spectral structure of atmospheric transmission simultaneously across wide spectral regions. It is therefore suited to the study of both water vapour monomer and continuum absorption behaviours. However, in order to properly address this issue, it is necessary to radiatively calibrate the FTIR instrument response. A solar-pointing high-resolution FTIR spectrometer was deployed as part of the ‘Continuum Absorption by Visible and Infrared radiation and its Atmospheric Relevance’ (CAVIAR) consortium project. This paper describes the radiative calibration process using an ultra-high-temperature blackbody and the consideration of the related influence factors. The result is a radiatively calibrated measurement of the solar irradiation at the ground across the IR region from 2000 to 10 000 cm ⁻¹ with an uncertainty of between 3.3 and 5.9 per cent. This measurement is shown to be in good general agreement with a radiative-transfer model. The results from the CAVIAR field measurements are being used in ongoing studies of atmospheric absorbers, in particular the water vapour continuum.