Why is the Earth going dark?

Planet Earth is slowly getting darker. It now reflects about half a watt less light per square meter than 20 years ago.

This is reflected in a study published in ‘Geophysical Research Letters’, in which they explain that the warming ocean waters has caused a decrease in brightness from the earth. Less and less clouds reflect sunlight into space and more energy is trapped in the planet’s climate system.

The data has yielded a “significant” decrease in albedo (the reflection of sunlight on Earth) of the planet in the last two decades, according to the New Jersey Institute of Technology (United States), which leads the research. In total, the reflectance of the Earth – which reflects about 30% of the sunlight that illuminates it – has fallen by 0.5%.

In this sense, it should be noted that the observed changes in albedo are not related to periodic changes in the brightness of the Sun, which means that the variations in reflectivity are caused by another reason.

The study indicates that, in recent years, there has been a reduction in bright, reflective low-lying clouds over the eastern Pacific Ocean, according to satellite measurements made for NASA’s Ceres project. That’s the same area, off the western coasts of North and South America, where there have been increases in sea surface temperatures.

The planetary scientist at the University of California Edward Schwieterman has warned that this “is quite worrying” and recalled that, for some time, many experts had expected that a warmer Earth would lead to more clouds and a greater albedo. This increase in albedo would help moderate warming and balance the climate system, but it has now been shown to do so.