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Study reveals Earth's varying reflectance over last 16 years

Researchers say the task of tracking the Earth's albedo requires a more expansive scientific infrastructure.

By Brooks Hays
Study reveals Earth's varying reflectance over last 16 years
Researchers used earthshine data from ground-based observatories to confirm reflectance measurements made by space satellites. Photo by IAC/BBSO

SAN CRISTóBAL DE LA LAGUNA, Canary Islands, May 18 (UPI) -- Earth's reflectance, or albedo, is the amount of solar energy reflected by the planet and its atmosphere. How much solar radiation is absorbed or reflected and where has tremendous implications for Earth's climate.

In recent years, researchers have ramped up efforts to track Earth's albedo. A new study, published in the journal Geophysical Research Letters, provides vital data on the variability of Earth's albedo from 1998 to 2014.

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Earth's reflectance is affected by cloud composition, ice, snow and surface type -- all variables in constant flux.

The latest albedo observations were made via ground-based telescopes. Researchers used the data to supplement and verify measurements taken from space via satellite.

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Earthshine data compiled by observatories in California and the Canary Islands is in agreement with satellite observations -- both in terms of magnitude and annual variations. Earthshine is the amount of sunlight reflected by the Earth's surface onto the face of the moon.

"Although the measurements that we have made of the albedo over the past 16 years show monthly and annual variations, there is virtually no change in the long term," Philip Goode, lead earthshine researcher at California's Big Bear Solar Observatory, said in a news release. "This also coincides with a stabilization in the mean temperature of the planet."

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Though the latest efforts have filled in data gaps, researchers say the task of tracking the Earth's albedo requires a more expansive scientific infrastructure.

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"We need to continue the experiments to measure this phenomenon accurately and see where we get to in a few more years," said Enric Pallé, a researcher with the Instituto de Astrofísica de Canarias. "For example, the construction of a global network of robotic telescopes around the world or the launching of a micro-satellite dedicated to the study of earthshine will give us data to improve our knowledge of changes in the albedo, and see how they affect the climate."

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