If you have ever wondered how the Earth looks like when seen from distant planets, you may have deduced that, just as we observe glowing stars twinkling in the sky, our planet looks like any other bright star in space. The proof of this is the pale blue dot that Carl Sagan once made famous after observing the Earth from the Voyager II probe near Saturn. However, our once bright planet is losing its shine. As climate change advances imminently, the Earth is dimming, new research claims.
How is Earth’s luminous puzzle related to climate?
It’s a beautiful phenomenon that connects climate to Earth’s brightness; the key is clouds. Clouds are a critical piece when it comes to reflecting sunlight. And with advancing climate change, cloud formation is changing as well. Research from the Big Bear Solar Observatory in Southern California reveals that the Earth is darkening as climate change progresses. They drew this conclusion from two decades of observations on the Earth’s brightness that occurs when the planet reflects light from the Sun.
The reflectivity of light on Earth
The reflectivity of sunlight is a phenomenon that physicists call albedo. Thus, the different characteristics of the Earth cause the albedo to be higher or lower. Some elements reflect more light than others; the Earth’s surface, for example, has a lower albedo (more reflected light) if its surface is covered with vibrantly colored flowers. Icebergs and snow have a very low albedo, which means they reflect most of the light they receive. Clouds are also important; they return about half of the light that hits them back to space.
Scientists have been keeping an eye on the fluctuation in our planet’s light reflectivity since 1998. They discovered that, in the last three years, there was a drop in Earth’s light. This came as a surprise to the researchers because, after 17 years of a nearly flat albedo, the Earth experienced significant changes.
On average, the Earth reflects 30% of the sunlight that illuminates it; however, this figure has now fallen by 0.5%. The planet now reflects about half a watt less light per square meter than it did 20 years ago. And it seems that the figure is still falling, as CERES data show. This is a NASA satellite observation program that monitors weather and cloud data.
Two possible explanations
There are only two phenomena that can affect the amount of light that the Earth reflects. The first has to do with the main source of that light; the Sun. If there are periodic fluctuations or changes in the Sun’s brightness, this will be reflected in the amount of light that the Earth returns to space. The second factor is precisely the reflectivity of the planet. But the researchers found no changes in the Sun’s brightness in the last three years, so the darkening of the Earth must be linked to internal processes on the planet.
And this is where climate change kicks in. There has been a decrease in cloud formation over the eastern Pacific Ocean in recent years. A region that coincides with the monitoring of rising seawater temperatures linked to climate change. In that sense, the darkening of the Earth also tells us how much solar energy is being trapped by our atmosphere. With greenhouse gases failing to escape back into space, global warming is spiraling into a dead-end spiral. Its consequences have already reached even outside our planet, with the Earth losing its brightness and getting darker in the process.
Text and photos courtesy of Ecoosfera
Translated by María Isabel Carrasco Cara Chards