Anthropogenic fingerprint detectable in Upper Tropospheric ozone trends retrieved from satellite

Limited observations point to a continuous increase in UT O3 in recent decades, but the attribution of UT O3 changes is complicated by large internal climate variability. We show that the anthropogenic signal ("fingerprint") in the patterns of UT O-3 increases is distinguishable from the background noise of internal variability.

The time-invariant fingerprint of human-caused UT O-3 changes is derived from a 16-member initial-condition ensemble performed with a chemistry-climate model (CESM2-WACCM6). The fingerprint is largest between 30 degrees S and 40 degrees N, especially near 30 degrees N. In contrast, the noise pattern in UT O-3 is mainly associated with the El Nino-Southern Oscillation (ENSO). The UT O-3 fingerprint pattern can be discerned with high confidence within only 13 years of the 2005 start of the OMI/MLS satellite record.