Researchers found that the Earth is getting dimmer, and it is due to climate change. As the oceans get hotter fewer, bright clouds are generated, which means less sunlight is reflected into space and warm up the planet. By observing the earthshine that illuminates the moon, the researchers measured the albedo or reflectance of the Earth. To inform the study results nearly 20 years of data, from 1998 to 2017.
The new study is published in the AGU journal Geophysical Research Letters. Compared to 1998, the Earth reflects about half a watt less light per square meter, as shown by the measurement. It is equivalent to a 0.5% decrease in the Earth’s reflectance. In total, the Earth reflects about 30% of the sunlight that reaches it.
According to Phillip Goode, theoretical physicist, “The albedo drop was such a surprise to us when we analyzed the last three years of data after 17 years of nearly flat albedo.”
The Earth’s brightness depends on the amount of sunlight reaching it and its reflectiveness. Especially in recent years, something on Earth is causing the dimming. The research team looked at the satellite measurements from NASA’s Clouds and the Earth’s Radiant Energy System project, which suggest that a reduction in bright, reflective, low-lying clouds over the eastern Pacific Ocean has been a significant contributor to the decrease in Earth’s brightness shown in the data.
This is likely because of climate change. Ocean surface temperatures are rising; bright clouds are thinning in the same area. These are likely caused by the reversal of a climatic condition called the Pacific Decadal Oscillation. An essential determinant of climate is the Earth’s albedo. The changes in the environment arise due to the Earth’s albedo and greenhouse insulation.
According to the study, parts of North America could be rapidly frozen by the ocean currents. In 1977, the Pacific Decadal Oscillation switched to its warmer temperature cycle. Since then, it has remained in that phase, which could be unusual because cycles typically last 20 to 30 years. The Earth absorbs more of the heat than reflecting it when the temperature rises.
The dimming of the Earth can also be seen in how the Earth’s climate system is capturing much more solar energy. In the Earth’s oceans and atmosphere, the additional solar power is there. This contributes to global warming because extra sunlight is the same magnitude as the total anthropogenic climate forcing over the last two decades.
According to scientists, the dimming of Earth is significant. It is unclear whether this dimming arises from the natural reflections of the climate system or is an unexpected result of human influences. In the upcoming decades, Earth’s dimming will become significant. It was predicted by the Internal Planet on climate change in 2013 report that the average global sea temperature will rise by as much as 7.2 degrees F by 2100.
From the Big Bear Solar Observatory, Earthshine readings were taken, which is located in California. In total, about 1500 nights of usable data were gathered. For almost 100 years, earthshine has been recorded on and off. Leonardo da Vinci 1st described it in the 16th century.