The amount of sunlight that reaches the Earth’s surface has varied for decades and a new study supports the idea that human activity is to blame.
In the late 1980s, researchers first noticed a steady decline or “attenuation” of the Earth’s brightness in various parts of the world, including a 30% drop in sunlight since the 1950s. a specific region of the Soviet Union.
A few decades later, after the ban on the most harmful aerosols and the dissolution of the Soviet Union, the trend suddenly changed from a “global attenuation” effect to a brighter one.
For a long time it is suspected that fine particles, such as sulfated aerosols, create a mist in the atmosphere that prevents sunlight from entering. Tests have shown that this type of pollution reflects almost all the radiation found in the atmosphere, while reflecting or absorbing light.
Whether or not these particles are responsible for decades of global darkening remains controversial and some argue that natural variability, such as the absorption of clouds from sunlight, is a greater factor than the pollution of the amount of light that reaches the Earth.
This new study attempted to account for variations in sunlight in clear, cloudy conditions and found that human-caused pollution is, in fact, one of the main culprits for darkening.
Wild and his colleagues used historical data collected between 1947 and 2017 by the Potsdam solar radiation registry. The Potsdam record is considered one of the longest and best-maintained continuous measurements of solar radiation on the Earth’s surface.
Even when the skies are clear of clouds, the analysis reveals that there may be strong tendencies of darkening and light, similar to cloudy skies.
“Our analyzes show that strong decennial variations (attenuation and clarity) not only appear when clouds are considered, but also remain evident in cloud-free conditions when cloud effects are removed,” the authors write in their published article.
With the clouds discarded, the authors argue that aerosol variations must be a substantial modifier of overall darkening and lighting.
“Even though we had already assumed it, so far we had not been able to prove it directly,” says Martin Wild, a climate scientist and lead author of the study.
It would be nice to think that global blackout is no longer a problem, but just because the world is happy doesn’t mean it is.
Recently, some internationally banned aerosols have begun to mysteriously rise, and even if we get scientists under control, scientists are worried that the historic decline has already helped mask some of the effects of global warming.
They warn that more sunlight being shed on the planet is not necessarily good. it could make the future “greenhouse land” even hotter.
That’s why, in part, some experts are researching ways to induce global darkening through solar geoengineering, while others think it’s too risky.
Recently, for example, a study in the Arctic linked heavy mining practices to regional darkening, and was found to reduce tree growth since the 1970s.
Forests are one of the most important carbon sinks on Earth, and if tree growth slows with less sunlight to such an extent, we could be seriously shooting ourselves in the foot.
Clearly, there is no easy solution, but this new research suggests that we have posed the problem.
The study was published in Geophysical research letters.