Cleaner air brings better views, more sunshine and warmer summer days in the Netherlands

Introduction. In the late 1980s Atsumu Ohmura and several others (e.g. Ohmura and Lang, 1989) discovered that the amount of solar radiation reaching the surface had decreased at many radiation measurement sites between 1960 and 1990. Near densely-populated areas and industries, 30% less solar radiation was reaching the ground in the 1980s than a few decades earlier (Wild, 2009). However, since the mid 1980s a significant increase in visibility has been noted in western Europe (e.g. Doyle and Dorling, 2002), and there are strong indications that a reduction in aerosol load from anthropogenic emissions (in other words, air pollution) has been the dominant contributor to this effect, which is also referred to as ‘brightening’. In the Netherlands visibility, sunshine duration, surface global short-wave radiation and temperature have shown a significant rise during this period, consistent with direct and indirect aerosol effects, implying large regional aerosol effects on climate. The brightening has been stronger during continental windflow than during maritime episodes. This article discusses the evidence for brightening in the Netherlands and its possible connection to the accelerated warming since 1985.