Tatsat Chronicle Magazine

Climate warming is causing Earth’s brightness to dim

October 5, 2021

Warming oceans reduce the ability of brilliant clouds to reflect sunlight into space, allowing more energy to enter the climate system

According to a study, Earth is dimming as a result of climate change because waters are warming create fewer brilliant clouds to reflect sunlight into space, trapping more energy on our planet. The scientists from the New Jersey Institute of Technology used decades of studies of earthshine – the light reflected from Earth that illuminates the moon’s surface – to acquire a better understanding of the impact of climate change. They also used satellite data to reveal that the Earth’s reflectance, or albedo, has decreased significantly during the last two decades.

The Earth is now reflecting about half a watt less light per square metre than it was 20 years ago, according to the researchers. The team said that half the drop in light happened in the past three years, after 17 years of flat albedo, mainly due to fewer low-lying clouds over the Pacific Ocean. Scientists had hoped that a warmer Earth caused by climate change would create more clouds, and a higher albedo to moderate the warming, but the opposite appears to be happening, which could accelerate climate change. The Earth’s reflectance had declined by around 0.5 percent in the previous three years, with the planet now reflecting 29.5 percent of total sunlight. ‘After 17 years of practically flat albedo, the albedo decline was such a surprise to us when we analysed the past three years of data,’ said Philip Goode, lead author. He was referring to earthshine data collected by the Big Bear Solar Observatory in Southern California from 1998 to 2017. When the most recent data was compared to previous years, the researchers saw a diminishing tendency. The brightness of the Sun and the reflectivity of the globe have an impact on the net sunlight reaching the Earth.

The team went to NASA satellites while seeking for clear changes in other observations that could explain the change in albedo.