Fog, mist and haze have been declining in Europe for the past 30 years, a study online in Nature Geoscience shows. This clearing of the air could have contributed to the rapid rate of regional warming in Europe.

Robert Vautard and colleagues analysed horizontal visibility data from 342 meteorological stations across Europe and found that the frequency of low-visibility events has declined over the past three decades. Because the occurrence of fog, haze or mist reduces the solar radiation that reaches the Earth’s surface, the clearer air may have caused a rise in temperatures. Using statistical analysis, the authors estimate that the reduction in low-visibility phenomena could have contributed around 10?20% of the European warming trend.

The decline in European fog has slowed since 2000, and the authors suggest that the frequency of low-visibility phenomena is likely to be further stabilized given the improvements in air quality that have already been achieved.