Of the many ways in which the climate crisis is unfolding, there is one that is both poetic and worrying: the Earth is losing its shine. The indiscriminate release of greenhouse gases since the industrial revolution has literally dimmed our planet.
Earth reflects about 30 percent of the sunlight that shines on it – this is called the albedo. Over the last two decades, the albedo of Earth dropped by 0.5 percent. The findings are reported in the journal Geophysical Research Letters.
Two methods were used to study the Earth’s albedo. One comes from the measurement of earthshine, the dim illumination of the night side of the moon due to light reflected from our planet. This was measured by the Big Bear Solar Observatory in Southern California between 1998 and 2017, and is quite a wide-angle reflectivity.
The other measurement comes from NASA's Clouds and the Earth’s Radiant Energy System (CERES) satellite that is more sensitive to narrower angles. Combining the two gave a good idea of what it’s going on, and the unexpected change in sunlight reflected.
“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,” lead author Philip Goode, a researcher at New Jersey Institute of Technology, said in a statement.
We know that the energy budget of our planet is out of whack. A lot more of the sunlight reaching Earth is getting trapped than it’s been reflected into space, due to the greenhouse gases in the atmosphere. The change in the albedo is believed to come from a reduction of bright, reflective low-lying clouds over the eastern Pacific Ocean in the most recent years according to the CERES project.
This is concerning. There was the idea that climate change might lead to cloudier skies, increasing the albedo. This might not have been enough to balance things out, but it could have bought us more time to get out our house in order. It seems that the opposite is true.
Anthropogenic global warming reducing the number of reflective clouds means that even more heat gets trapped by our planet. The effect of a smaller albedo could be significant enough to make our prediction of the effects of the climate crises an underestimate.
Bold action is needed to tackle the unfolding crisis and the time is now to make such changes. Governments worldwide need to act to avoid the worst-case scenarios.