Interdecadal antiphase covariability between temperature and ozone over the mid–high latitudes of Eurasia in spring

Springtime ozone–temperature coupling in the mid-to-high latitudes of Eurasia has important implications for regional climate and ecosystems, yet its decadal evolution and driving mechanisms remain unclear. Analysis of multiple reanalysis datasets (ERA5, JRA-55, EAC4) for 1980–2022 reveals a robust interdecadal antiphase covariability between surface temperature and tropospheric column ozone across mid-to-high latitudes of Eurasia during March–April. This covariability is closely linked to variations in the Baikal High (BH). A weakened BH induces mid-tropospheric cyclonic anomalies that steer polar cold, ozone-rich air southward, producing concurrent surface cooling and ozone enhancement, whereas a strengthened BH generates the opposite pattern. Approximately half of CMIP6 models reproduce this anti-correlation. Several model–scenario combinations indicate that, under SSP1–2.6 and SSP2–4.5, this dynamically driven ozone–temperature antiphase covariability is projected to persist through the 21st century. These findings highlight the central role of regional circulation in coupling atmospheric composition with climate, providing an important reference for simulating and projecting environmental risks across Eurasia.