The sun rises each day, but the amount of sunlight reaching Earth’s surface is not as constant as we might think. A new study published in Advances in Atmospheric Science reveals significant fluctuations in the amount of solar radiation reaching the planet, a phenomenon tied to decades of pollution and clean energy efforts. This research highlights two major phases—“dimming” and “brightening”—which have had profound effects on solar energy availability worldwide.
How Pollution Affects Solar Radiation
The study, led by Professor Martin Wild of the Swiss Federal Institute of Technology (ETH Zurich), highlights how the amount of solar energy reaching Earth’s surface is far from stable.
As Wild explains, “The amount of sunlight—which is solar radiative energy—we receive at Earth’s surface is not necessarily stable over the years but can undergo substantial decadal variations.”
These variations are particularly marked in the “global dimming” phase, which lasted from the 1950s to the 1980s. During this time, solar radiation decreased significantly due to the growing use of fossil fuels, which produced large amounts of air pollution, blocking solar energy from reaching the surface.
The Brightening Phase: A Gradual Recovery
After the dimming phase, the study finds signs of recovery, particularly from the 2000s onward, in what is known as the “brightening” phase. This shift has been attributed to effective air pollution control measures and the growing adoption of cleaner energy practices.
“These indicate declining solar radiative energy in large parts of the world from the 1950s to the 1980s—known as global dimming—and a partial recovery thereafter, known as brightening, at many observation sites.” says Wild. This recovery has led to more sunlight reaching Earth’s surface.
A Focus on China’s Solar Energy Variations
One of the most notable aspects of the study is its focus on China, a region that has become a key area of research on solar radiation. China’s long-term, well-organized observation network has made it an ideal location to study how aerosol pollution impacts solar energy.
“China provides a conducive environment for understanding aerosol radiative effects—or how air pollutants impact the amount of solar radiative energy reaching Earth’s surface,” notes Wild.
Data collected from China show that solar energy decreased significantly from the 1960s to the 1990s, but the trend began to reverse in the 2000s, largely due to successful pollution reduction efforts. This shift is a sign of hope for regions looking to reduce pollution and increase solar radiation.
What This Means for Solar Power Production
The implications of these findings for solar energy are clear: countries that have reduced pollution are seeing a rise in available solar energy, and this trend could continue as air quality improves.
“If China fully recovers from the dimming phase and reverts to the clean atmosphere levels of the 1960s, the country could make substantial gains in solar power production,” says Wild.
This observation suggests that global efforts to clean the air can have significant benefits for solar power generation, driving the expansion of renewable energy sources in regions that have struggled with pollution.
