The transition from sodium to LED exterior lighting over recent years appears to have made global light pollution worse not better, scientists have reported.
A team of researchers who studied NASA images say that in the last four years the illuminated area of the earth grew by 2 per cent. The growth was most pronounced in developing nations.
While increasing prosperity accounted for part of that increase, the scientists believe LEDs are partly to blame.
Lead researcher Christopher Kyba from the German Research Centre for Geoscience in Potsdam told the BBC that the introduction of artificial light was ‘one of the most dramatic physical changes human beings have made to our environment’.
The team had anticipated a decrease in brightness in developed and industrial areas as orange sodium were replaced with LEDs, but in fact the reverse happened.
‘I expected that in wealthy countries – like the US, UK, and Germany – we'd see overall decreases in light, especially in brightly lit areas,’ he told BBC News. ‘Instead we see countries like the US staying the same and the UK and Germany becoming increasingly bright.’
To make matters worse, the light sensor on the satellite – a radiometer – is not able to measure the bluer part of the spectrum of light that LEDs emit, meaning that visible light pollution is even worse than that measured.
‘Because there is more blue light in LEDs than in sodium, it’s more liable to be scattered due to the Rayleigh effect,’ said Lux technical editor Alan Tulla. ‘An additional factor would be the combination of increased prosperity in developing nations and the falling prices of LED luminaires globally.’
The findings are certain to increase the pressure on the lighting industry to take light pollution seriously and improve the optics and upward light control.
The researchers published the findings in the journal Science Advances.