Novel quantification of regional fossil fuel CO2 reductions during COVID-19 lockdowns using atmospheric oxygen measurements.

It is not currently possible to quantify regional-scale fossil fuel carbon dioxide (ffCO2) emissions with high accuracy in near real time. Existing atmospheric methods for separating ffCO2 from large natural carbon dioxide variations are constrained by sampling limitations, so that estimates of regional changes in ffCO2 emissions, such as those occurring in response to coronavirus disease 2019 (COVID-19) lockdowns, rely on indirect activity data. We present a method for quantifying regional signals of ffCO2 based on continuous atmospheric measurements of oxygen and carbon dioxide combined into the tracer "atmospheric potential oxygen" (APO). We detect and quantify ffCO2 reductions during 2020-2021 caused by the two U.K. COVID-19 lockdowns individually using APO data from Weybourne Atmospheric Observatory in the United Kingdom and a machine learning algorithm. Our APO-based assessment has near-real-time potential and provides high-frequency information that is in good agreement with the spread of ffCO2 emissions reductions from three independent lower-frequency U.K. estimates.

Greenhouse gases in the Earth system: setting the agenda to 2030.

What do we need to know about greenhouse gases? Over the next 20 years, how should scientists study the role of greenhouse gases in the Earth system and the changes that are taking place? These questions were addressed at a Royal Society scientific Discussion Meeting in London on 22-23 February 2010, with over 300 participants.

The atmospheric signature of carbon capture and storage.

Compared with other industrial processes, carbon capture and storage (CCS) will have an unusual impact on atmospheric composition by reducing the CO(2) released from fossil-fuel combustion plants, but not reducing the associated O(2) loss. CO(2) that leaks into the air from below-ground CCS sites will also be unusual in lacking the O(2) deficit normally associated with typical land CO(2) sources, such as from combustion or ecosystem exchanges. CCS may also produce distinct isotopic changes in atmospheric CO(2). Using simple models and calculations, we estimate the impact of CCS or leakage on regional atmospheric composition. We also estimate the possible impact on global atmospheric composition, assuming that the technology is widely adopted. Because of its unique signature, CCS may be especially amenable to monitoring, both regionally and globally, using atmospheric observing systems. Measurements of the O(2)/N(2) ratio and the CO(2) concentration in the proximity of a CCS site may allow detection of point leaks of the order of 1000 ton CO(2) yr(-1) from a CCS reservoir up to 1 km from the source. Measurements of O(2)/N(2) and CO(2) in background air from a global network may allow quantification of global and hemispheric capture rates from CCS to the order of ±0.4 Pg C yr(-1).