Statistical characterization of urban CO2 emission signals observed by commercial airliner measurements

Taku Umezawa,Shamil Maksyutov,Yosuke Niwa,Tomohiro Oda,Kaz Higuchi,Toshinobu Machida,Yousuke Sawa,Hidekazu Matsueda

doi:10.1038/s41598-020-64769-9

Abstract

Cities are responsible for the largest anthropogenic CO2 emissions and are key to effective emission reduction strategies. Urban CO2 emissions estimated from vertical atmospheric measurements can contribute to an independent quantification of the reporting of national emissions and will thus have political implications. We analyzed vertical atmospheric CO2 mole fraction data obtained onboard commercial aircraft in proximity to 36 airports worldwide, as part of the Comprehensive Observation Network for Trace gases by Airliners (CONTRAIL) program. At many airports, we observed significant flight-to-flight variations of CO2 enhancements downwind of neighboring cities, providing advective fingerprints of city CO2 emissions. Observed CO2 variability increased with decreasing altitude, the magnitude of which varied from city to city. We found that the magnitude of CO2 variability near the ground (~1 km altitude) at an airport was correlated with the intensity of CO2 emissions from a nearby city. Our study has demonstrated the usefulness of commercial aircraft data for city-scale anthropogenic CO2 emission studies.

Highlights

Climate change is considered to be one of the consequences of increased emissions of anthropogenic greenhouse gases during the industrial era, and carbon dioxide (CO2) is the dominant contributor to the enhanced radiative forcing caused by anthropogenic long-lived greenhouse gases
About 70% of the current anthropogenic CO2 emissions is considered to come from urban areas that contain over 50% of the world population[10], and accurate quantification of CO2 emissions from urban areas is of particular importance
Given that major airports are often located reasonably close to large cities and airlines optimize their flight destinations with priority on connecting between large cities, data collected by commercial airliners might provide useful information that can contribute to better assessments of greenhouse gas emissions from cities, complementing ground and satellite measurements

Summary

Introduction

Climate change is considered to be one of the consequences of increased emissions of anthropogenic greenhouse gases during the industrial era, and carbon dioxide (CO2) is the dominant contributor to the enhanced radiative forcing caused by anthropogenic long-lived greenhouse gases. For effective mitigation actions against climate change, various independent approaches must be used to reduce the uncertainties associated with citywide greenhouse gas emissions estimates, and one of those approaches can be provided by atmospheric CO2 observations[12] For this purpose, atmospheric CO2 measurements focusing on urban areas have been examined in recent years by means of citywide in-situ ground measurement networks[13,14,15,16] or satellite measurements[17,18]. Given that major airports are often located reasonably close to large cities and airlines optimize their flight destinations with priority on connecting between large cities, data collected by commercial airliners might provide useful information that can contribute to better assessments of greenhouse gas emissions from cities, complementing ground and satellite measurements. We show that the magnitude of atmospheric CO2 variability increases with intensity of CO2 emissions from the neighboring cities, demonstrating the usefulness of commercial aircraft-based measurements for urban emission studies

Methods

Results

Conclusion