Yu, X., Fiore, A. M., Santer, B. D., Correa, G. P., Lamarque, J.-F., Ziemke, J. R., Eastham, S. D., & Zhu, Q. (2024). Anthropogenic fingerprint detectable in upper tropospheric ozone trends retrieved from satellite. Environmental Science & Technology. https://doi.org/10.1021/acs.est.4c01289

Tropospheric ozone is a strong greenhouse gas, particularly in the upper troposphere. Limited observations point to a continuous increase in upper tropospheric ozone in recent decades, but the attribution is complicated by large internal climate variability. Here we derive a time-invariant fingerprint of human-caused upper tropospheric ozone changes from a 16-member initial-condition ensemble performed with a chemistry-climate model (CESM2-WACCM6). We then search for this pattern in a product obtained from the OMI and MLS satellite instruments. Although the satellite retrieved upper tropospheric ozone record began in 2005 and is only 17 years in length, we found that the model-simulated fingerprint is detectable  with high statistical confidence after only 13 years of monitoring, revealing a unique pattern of human influence on Earth’s atmospheric chemistry in the upper troposphere.