Europe — Europe has become less foggy over the past three decades, according to scientists who have examined weather records across the continent. Fog, mist and haze have become less frequent and have contributed, they calculate, to between 10% and 20% of the warming trend during that period. The change is down to reduced air pollution, the scientists think.
Robert Vautard at the Atomic Energy Commission in Gif sur Yvette, France, and colleagues, looked at the number of “low-visibility” events, where visibility fell to under 8km. They found a 50% drop since the 1970s, which they call a “massive decline”.
Fog, mist and haze block sunlight, and the team reckons the clearing of the air could have contributed around 10-20% of the European warming trend over the period. Europe has warmed by 0.5C a decade more than predicted by climate change models.
Writing in the journal Nature Geoscience, the scientists describe how they analysed data from 342 weather stations, and found “a massive decline of low-visibility occurrence throughout Europe”, which they say “represents a real change”. They link the decrease to lower sulphur dioxide pollution that has come about through efforts in Europe to curb air pollution.
Dave Britton of the UK Met Office said. “That makes sense. Clouds form around particles and dust in the air, so cleaner air brings clearer skies.” Fog, mist and haze are essentially clouds that form at ground level, he said. “Go back to the 1950s and the big pea-soupers in London came from the amount of crap that people were putting out of their chimneys from coal fires.”
The decline in low-visibility events has slowed since 2000, the research shows.
The discovery highlights a trend that scientists call “global brightening”, which reverses an earlier phenomena known asglobal dimming. Observations across the world showed that the amount of sunlight reaching the Earth’s surface dipped from the 1950s-1990s because of sulphur air pollution. This led to a decline in temperatures despite increasing CO2 emissions. The effect has faded along with the fall in sulphur emissions with regulation and the collapse of polluting heavy industry in the former Soviet Union.
Some climate experts have suggested that the cooling effect of global dimming could have concealed the true extent of global warming, and that temperatures could increase sharply as skies clear. Others question the size of the effect, because the dimming seems to have been confined to some regions of the world.