Enhancing scientific transparency in national CO2 emissions reports via satellite-based a posteriori estimates

Biennial Update Reports (BURs) are essential requirements from the United Nations Framework Convention on Climate Change (UNFCCC). However, many non-Annex I countries have not submitted these reports due to difficulties in compiling the inventories. We developed a satellite-based method for the top-down inverse estimation of CO2 emissions using partial-column data in the lower troposphere obtained by the Greenhouse Gases Observing Satellite, adopted to validate the Mongolian 2nd BUR (BUR2) for the energy sector in 2018. The estimated CO2 emissions were only 1.5% higher than those reported in the BUR2; these were also very close (4.2% smaller) to estimates from the Emission Database for Global Atmospheric Research. Mongolia is the first country to introduce an independent inverse estimate in its BUR, thereby increasing scientific transparency. Our method could be applied into other countries and could be incorporated into UNFCCC reporting guidelines, significantly improving global CO2 emission estimates.

Important evidence of constant low CO2 windows and impacts on the non-closure of the greenhouse effect

The CO₂ distribution in the atmosphere remains unclear for the complexity of the long-range vertical transport process and other influencing factors. In this work, regression analysis was used to verify the accuracy of CO₂ concentrations datasets. Geostatistical analyses were used to investigate the spatiotemporal distributions of CO₂ at 7 levels from near the surface to the mid-troposphere (0~5 km). Spatial correlation and time series analyses were used to further determine the diffusion characteristics of the CO₂ concentration based on the horizontal wind (NCEP R2), which is one of the main driving factors. The results showed that the horizontal, not vertical, diffusion of CO₂ becomes increasingly more prominent with the decrease in atmospheric pressure to the mid-troposphere, whereas many regions, such as the Rocky Mountains and Qinghai-Tibet Plateau, have constant low values throughout the year due to the influence of high topography (up to 10.756 ppmv lower than that near the surface). These areas form low CO₂ concentration 'windows' keeping letting thermal infrared energy out into space. This study is the first to question the existing view of the closure of the 'greenhouse effect'. Future research studies should more precisely determine the closure threshold and the uncertainties about the surface fluxes.

Variability in AIRS CO2 during active and break phases of Indian summer monsoon

Due to human activities, the atmospheric concentration of Carbon Dioxide (CO2) has been rising extensively since the Industrial Revolution. Indian summer monsoon (ISM) has a dominant westerly component from ocean to land with a strong tendency to ascend and hence may have role in CO2 distribution in lower and middle troposphere over Indian sub-continent. A substantial component of ISM variability arises from the fluctuations on the intra-seasonal scale between active and break phases which correspond to strong and weak monsoon circulation. In view of the above, an attempt is made in this study to examine the AIRS/AQUA satellite retrieved CO2 distribution in response to atmospheric circulation with focus on active and break phase. Correlation analysis indicates the increase in AIRS CO2 linked with strong monsoon circulation. Study also reveals that anomalous circulation pattern during active and break phase show resemblance with high and low values of AIRS CO2. Homogeneous monsoon regions of India show substantial increase in CO2 levels during active phase. Hilly regions of India show strong contrast in CO2 and vertical velocity during active and break phases.