Towards CO2 emission monitoring from space using FOCAL XCO2 retrievals of OCO-3 satellite measurements

Anthropogenic emissions of carbon dioxide (CO2) are the main driver of the change in climate since the industrial revolution. Policy mitigation strategies include reduction of these emissions. The Paris Agreement from 2015 requires the states to report their greenhouse gas emissions on a regular basis. Space-borne remote-sensing measurements of CO2 are considered potentially of great value  to monitor CO2 emissions, due to their better coverage in comparison to in-situ instruments. Measuring CO2  from space of an adequate quality is a challenge because of the stringent requirements related to the accuracy and precision of the data products and thus the instruments. In this study, we use the Fast atmospheric traCe gAs retrievaL (FOCAL) algorithm to retrieve maps of the column-averaged dry-air CO2 mole fraction (XCO2) with the goal of quantifying CO2 emissions for specific emission targets using Orbiting Carbon Observatory 3 (OCO-3) snapshot area maps. This data product is planned to  be used in the German national Integrated Greenhouse Gas Monitoring System (ITMS), for which an operational data assimilation system for greenhouse gases is being set up for Germany.