ETH scientists show that sunlight at the earth surface – after decades of decrease (“global dimming”) – has recovered since the mid 1990s. This significantly affects Earth’s climate.
Zurich – Sunlight reaching the Earth surface is the primary energy source for life on our planet and a key element of climate change.
Several studies showed that sunlight at the Earth surface has been reduced significantly since the 1960s when worldwide measurements of this quantity started (“global dimming”).
These studies were based on observations stored in two databases located at ETH Zurich, which compile the worldwide measurements of sunlight at the surface.
New studies carried out at the Institute for Atmospheric and Climate Science ETH show, that the dimming of sunlight faded in the mid 1980s and did not continue during the 1990s. Rather, a widespread tendency towards brightening has been noted.
This trend reversal is reconcilable with changes in cloudiness and air pollution, the principal responsibles for variations of sunlight at the earth surface.
Whereas the solar dimming could have partially counterbalanced the increasing greenhouse effect prior to the 1980s, this masking of the greenhouse effect and related impacts may have no longer been effective thereafter, enabling the greenhouse signals to become more evident during the 1990s.
