This study presents a new approach to quantify anthropogenic terpene emissions by measuring VOCs during winter, when biogenic emissions are negligible. Measurements in Helsinki showed that although anthropogenic terpenes accounted for less than 1 % of VOC mass, they made a disproportionately large contribution to atmospheric reactivity. The findings highlight the importance of including anthropogenic terpene emissions in urban air quality studies and atmospheric chemistry models.

We investigate low-frequency Northern Hemisphere stratospheric variability using reanalysis and three multi-century climate model simulations. We identify an intermittent oscillation with a period of about 15 years. This signal is closely connected to the surface North Atlantic Oscillation and tends to precede it, whereas its link to North Pacific circulation is weaker. These results help improve our understanding of stratosphere-surface coupling on multi-year to multi-decadal timescales.