Shifts in atmospheric circulation can explain anomalous trends in surface ozone levels over Hawaii since the 1980s, reports a study published online this week in Nature Geoscience. The findings suggest that decadal variability in climate should be taken into account when interpreting trends in ozone levels in the lower atmosphere.

Meiyun Lin and colleagues examined the link between decadal variations in climate and Hawaiian ozone levels over the past three decades, using a suite of climate model simulations. They find that the flow of ozone-rich air from Eurasia to Hawaii weakened during spring in the 2000s, lowering springtime ozone levels. In contrast, the flow of ozone-rich air to Hawaii strengthened in autumn from the mid-1990s onwards, raising autumnal ozone levels in the region.

In an accompanying News and Views, Guang Zeng writes that the authors show that “shifts in atmospheric circulation have helped shape season-specific trends in surface ozone levels in Hawaii since the 1990s.”