Quantifying greenhouse-gas emissions from atmospheric measurements: a critical reality check for climate legislation

Abstract

Emissions reduction legislation relies upon 'bottom-up' accounting of industrial and biogenic greenhouse-gas (GHG) emissions at their sources. Yet, even for relatively wellconstrained industrial GHGs, global emissions based on 'top-down' methods that use atmospheric measurements often agree poorly with the reported bottom-up emissions. For emissions reduction legislation to be effective, it is essential that these discrepancies be resolved. Because emissions are regulated nationally or regionally, not globally, topdown estimates must also be determined at these scales. High-frequency atmospheric GHG measurements at well-chosen station locations record 'pollution events' above the background values that result from regional emissions. By combining such measurements with inverse methods and atmospheric transport and chemistry models, it is possible to map and quantify regional emissions. Even with the sparse current network of measurement stations and current inverse-modelling techniques, it is possible to rival the accuracies of regional 'bottom-up' emission estimates for some GHGs. But meeting the verification goals of emissions reduction legislation will require major increases in the density and types of atmospheric observations, as well as expanded inversemodelling capabilities. The cost of this effort would be minor when compared with current investments in carbon-equivalent trading, and would reduce the volatility of that market and increase investment in emissions reduction.

Compositions and greenhouse gas emission factors of flared and vented gas in the Western Canadian Sedimentary Basin

“…Although the uncertainty inherent in this type of gross estimate should not be understated, GHG emissions of this magnitude would represent significant source globally ($5% of the world total of 38.75 Gt in 2005) (Climate Analysis Indicators Tool; World Resources Institute, 2011). Uncertainties in sources of this potential magnitude highlight the need for closer analyses of industry-reported data and ultimately for better direct flow and composition monitoring of flared and vented gas streams globally, and are a further example of the challenges faced in reconciling bottomup global GHG reporting with top-down estimates derived from atmospheric measurements (Weiss and Prinn, 2011).…”

Impacts of updated spectroscopy on thermal infrared retrievals of methane evaluated with HIPPO data

“…Quantifying the anthropogenic and natural emissions of CH 4 is thus essential to determining CH 4 emission reduction targets and verifying that these targets have been met. Atmospheric observations can provide "top-down" constraints to improve the bottom-up CH 4 emission inventories (Weiss and Prinn, 2011). Satellite observations can provide global, spatially and temporally dense data covering many years, and are therefore extremely valuable to these topdown studies.…”

Inverse modelling of European CH<sub>4</sub> emissions during 2006–2012 using different inverse models and reassessed atmospheric observations

“…abandoned coal mines or landfill sites), which, if not properly accounted for, may result in incorrect inventories. Independent verification using atmospheric measurements and inverse modelling is therefore considered essential to ensuring the environmental integrity of reported emissions (Levin et al, 2011;National Academy of Science, 2010;Nisbet and Weiss, 2010;Weiss and Prinn, 2011) and has been suggested to be used for the envisaged transparency framework under the Paris agreement (WMO, 2016a).…”