Summer ozone did not make autumn canopy senescence earlier at 95 US PhenoCam deciduous sites in 2008-2025 with site and year controls; this excludes the US slope implied by Yin et al. 2026

Yin et al. (2026) report from satellite phenology at ozone monitors that ozone (AOT40) makes the end of season (EOS) earlier, with a mean per-site temporal partial correlation of -0.14 for all sites and -0.06 for the USA. We tested this with ground cameras. We used 751 site-years of PhenoCam GCC90 autumn transition dates (EOS50) at 95 US deciduous broadleaf sites in 2008-2025. Ozone came from EPA AQS hourly monitors within 50 km, and weather came from Daymet. With site and year fixed effects, the EOS50 slope was +0.31 days per ppm h of June-August AOT40 (95% CI -0.21 to +0.83; standardised +0.04, CI -0.03 to +0.11). This interval excludes the slopes that the US and global correlations imply (-0.45 and -1.04). With site effects only, the slope was -0.08 (CI -0.53 to +0.37), which excludes only the global value. Results were the same for Sep-Nov and May-Sep ozone, daily MDA8 metrics, a 100 km radius, the nearest monitor, EOS25/EOS10, and 2017-2025. A next-year-ozone placebo gave a similar value (+0.44). Autumn temperature, as a positive control, delayed EOS50 by 0.9-1.5 days per degree C. Spring ozone was linked to earlier, not later, leaf-out with site effects only (r = -0.20); year effects removed this link. Per-site correlations at 49 sites had mean +0.03, and a year-block bootstrap gave a standard error 2.3 times the naive value. The released Yin et al. per-site file has 17,530 exact duplicates among 20,400 rows. The published means and errors match all rows, so the reported errors are about 2.8 times too small. Limitations: monitors are not canopy flux measurements, the sample is mostly eastern, and year effects remove network-wide ozone variation.