Urban and non-urban trends for 4MDA8 (ppb/yr) for the 15-year period 2000–2014. Each panel shows trends for North America (top); Europe (bottom left) and East Asia (bottom right). The direction of arrows indicates the magnitude of the trend (see inset). Red and orange colours indicate increasing ozone levels and blue colours indicate decreasing ozone levels over time. Trends with: a p-value < 0.05 are coloured dark red (increase) and dark blue (decrease). Results with a p-value = 0.05–0.1 are coloured dark orange (increase) and blue (decrease); a p-value = 0.1–0.34 are coloured light orange (increase) and light blue (decrease); a p-value >= 0.34 is coloured green. DOI: https://doi.org/10.1525/elementa.273.f8a