Trends in tropospheric ozone, an important air pollutant and short-lived; climate forcer (SLCF), are estimated using available surface and; ozonesonde profile data for 1993-2019. Using a coherent methodology,; observed trends are compared to modeled trends (1995-2015) from the; Arctic Monitoring Assessment Programme SLCF 2021 assessment.; Statistically significant increases in observed surface ozone at Arctic; coastal sites, notably during winter, and concurrent decreasing trends; in surface carbon monoxide, are generally captured by multi-model median; (MMM) trends. Wintertime increases are also estimated in the free; troposphere at most Arctic sites, but tend to be overestimated by the; MMMs. Springtime surface ozone increases in northern coastal Alaska are; not simulated while negative springtime trends in northern Scandinavia; are not always reproduced. Possible reasons for observed changes and; model behavior are discussed, including decreasing precursor emissions,; changing ozone sinks, and variability in large-scale meteorology.
