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Earth reflects less light as its climate continues to change, new research suggests.
A beautiful phenomenon links climate and light: clouds. Clouds are a notoriously complicated piece of the climate puzzle – scientists struggle to model how clouds will react to climate change and how those responses in turn will shape the future climate. But the scientists behind the new study believe that the discovery of reflectivity depends on the dynamics of clouds over the Pacific Ocean.
The research is based on two decades of observations of a phenomenon called “shard of earth“, which is the light that the Earth reflects off the surface of the far side of the Moon, combined with satellite observations of the Earth’s reflectivity, or albedo, and the sun’s brightness.
Related: Top 10 views of Earth from space
Different features on Earth reflect different amounts of light: very few oceans, land about twice as much. During this time, clouds reflect about half of the sunlight that hits them, and snow and ice reflect the majority of the light they receive.
Scientists at the Big Bear Solar Observatory in Southern California have been studying fluctuations in the earth’s brightness since 1998, looking for changes on time scales ranging from daily to decade. (The researchers note that these measures are only relative and call for more robust observations, perhaps even from cubesats or a lunar observatory.)
In the new research, scientists have combined this data with observations from NASA Clouds and the Earth’s radiant energy system (CERES), which has been operating since 1997 with instruments on a multitude of NASA and National Oceanic and Atmospheric Administration (NOAA) satellites.
The researchers put the two sets of data together to find out if and how the Earth’s brightness has changed. Over the full two-decade period, the amount of light reflected from Earth dropped by about 0.5%, or about half a watt less light per square meter. (One square meter equals just under 11 square feet.) Most of the changes have occurred over the past three years of the Earthshine dataset, which the researchers analyzed through 2017; CERES data continues through 2019 and shows an even steeper drop at the end.
And meanwhile, the researchers determined that the brightness of the Sun – who went through two periods of peak activity and a quiet period during the study – did not have a significant association with the decline in reflectance. So a change in the amount of light the Earth reflects must come from a change on the Earth itself, the scientists explained.
In particular, the CERES data noted a loss of bright low-level clouds over the eastern Pacific Ocean off the west coast of the Americas, where scientists are also recording large increases in surface temperature. of the ocean.
And because unreflected light to space is trapped in the Earth’s system, the change in light also has implications for the future of the climate, potentially increasing the rate of human-caused climate change.
The research is described in a paper published August 29 in the journal Geophysical Research Letters.
Email Meghan Bartels at [email protected] or follow her on Twitter @meghanbartels. Follow us on Twitter @Spacedotcom and on Facebook.
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