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This image of Earth was compiled from tens of thousands of images from the Copernicus Sentinel-2 mission. Thanks to the age of satellites, we are in a better position to understand the intricacies of our planet, especially in relation to global change. Credit: Contains modified Copernicus Sentinel (2019-20) data processed by ESA and NASA Cloud Layer.
Warming oceans cause fewer bright clouds to reflect sunlight back into space, allowing more energy to enter Earth’s climate system.
Rising ocean water temperatures have led to a decrease in the brightness of the Earth, a new study has found.
The researchers used decades of measurements of Earth’s luminosity – the light reflected from the Earth that illuminates the surface of the Moon – as well as satellite measurements to see that there was a significant decrease in the reflectance of Earth, or albedo, over the past two decades.
The Earth now reflects about half a watt of light per square meter than it did 20 years ago, with most of the decline in luminous Earth data having occurred in the past three years, according to the new study published in AGU magazine. Geophysical research letters, which publishes succinct, high-impact reports with immediate implications in all Earth and space sciences.
This equates to a 0.5% reduction in Earth’s reflection. The Earth reflects about 30% of the sunlight that shines on it.
Earth’s annual mean albedo 1998-2017 expressed in watts per square meter (W / m2). Albedo CERES annual 2001-2019 is shown in blue. The line of best fit for CERES data (2001-2019) is represented by a dashed blue line. Average error bars for CERES measurements are 0.2 W / m2. Credit: Goode et al. (2021), Geophysical research letters
Philip Goode, researcher at New Jersey Institute of Technology and lead author of the new study, referring to Earth data from 1998 to 2017 that he collected Big Bear Solar Observatory in Southern California. When the most recent data was added to previous years, the tendency towards opacity became apparent.
Two things affect the clear sunlight that reaches the Earth: the brightness of the sun and the reflection of the planet. The changes in the Earth’s albedo that the researchers observed were not associated with periodic changes in the Sun’s brightness, meaning that the changes in Earth’s reflection are caused by something on Earth.
Specifically, there has been a decrease in low, bright and reflective clouds over the eastern Pacific Ocean in recent years, according to satellite measurements made as part of the NasaThe Clouds and Earth Radiant Energy System (CERES) project.
This is the same region, off the western coasts of North and South America, where increases in sea surface temperatures have been recorded due to the reversal of a climatic condition called oscillation. Pacific decade, with possible links to global climate change.
The darkening of the Earth can also be seen in terms of the amount of solar energy captured by the Earth’s climate system. Once this important additional solar energy is in the Earth’s atmosphere and the oceans, it can contribute to global warming, since the additional sunlight is roughly the same size as the total impact of anthropogenic climate over both. decades.
“This is really concerning,” said Edward Schwitterman, a planetary scientist at the University of California, Riverside, who was not involved in the new study. For a while, he said, many scientists hoped that a warmer Earth would lead to more clouds and greater albedo, which in turn would help mitigate global warming and balance the system. climate. “But it shows that the opposite is true.”
Reference: “Earth’s Albedo 1998-2017 as measured from the luminosity of the Earth” by PR Goode, E. Pallé, A. Shoumko, S. Shoumko, P. Montañes-Rodriguez and SE Koonin, August 29, 2021, Geophysical research letters.
They: 10.1029 / 2021GL094888
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