Nav: Home

New data on the variability of the Earth's reflectance over the last 16 years

May 18, 2016

The Earth's albedo, or reflectance, is a fundamental atmospheric parameter having deep implications for temperature and climate change. For that reason, experiments have been performed to monitor it over the past two decades to reveal how it evolves. One of these, in which the Instituto de Astrofísica de Canarias is a participant, has brought up to date the observations made since 2007 and adds to, and gives a new systematic record of the Earth's albedo covering the period between 1998 and 2014 from California. This study, whose first author is IAC researcher Enric Pallé, has been published in Geophysical Research Letters, and shows that although the albedo fluctuates both monthly and annually, but there is no trend over those years.

The effect of the albedo is important for life on Earth because it affects the energy budget of the planet: it plays a key role in the process by which the planet achieves an equilibrium between the solar radiation which enters the atmosphere and the radiation emitted as heat into space. The albedo is defined as the fraction of sunlight that the Earth reflects back directly into space, and it varies according to cloud composition, ice, snow, and the nature of the surface onto which the sun's rays fall. The term comes from the Latin "albus" (white), and a rise or fall in the albedo will have consequences for the planet's global warming or cooling.

To check how the albedo has evolved, since the 1990's it has been measured from space with instruments such as ERBE and CERES, whose estimations are made using absolute photometric measurements, which could be affected by any degradation in the instrument while in space.

However, a complementary way to measure the reflectance, which does not suffer the same calibration errors since it is a relative measurement, is from the ground, using telescopes that observe the so-called earthshine (the light reflected from the Earth to the night-time face of the Moon). This method has been used during the period 1998-2014 from the Big Bear Solar Observatory (BBSO) in California, and also, since 2007 from the Earthshine telescope at the Teide Observatory (Tenerife), to measure this climate parameter. These observations were aimed at increasing the temporal coverage of the measurements, and reducing the measurement errors.

The result of this study is that, applying strict quality criteria to the measurements of the earthshine, and after re-calibrating the measurements taken from the CERES instrument in space, the variations found in the value of the albedo not only agree in magnitude but also show identical, small annual variations over the 14 years that the two types of observations overlap. Philip Goode, lead earthshine researcher at BBSO explains that "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. This also coincides with a stabilization in the mean temperature of the planet", he says.

Even so, although a consensus has been reached about the results of the two types of measurements, the origin of the anomalies is not completely clear. "We need to continue the experiments to measure this phenomenon accurately and see where we get to in a few more years. 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", concludes Pallé.
-end-
BBSO is operated by New Jersey Institute of Technology.

Article: "Earth's albedo variations 1998-2014 as measured from ground-based earthshine observations" by E. Pallé (IAC-ULL), P. R. Goode (Big Bear Solar Observatory, Institute of Technology, EEUU), P. Pilar Montañés-Rodríguez (IAC-ULL), A. Shumko (Big Bear Solar Observatory, Institute of Technology, EEUU), B. González-Merino (IAC-ULL), C. Martínez Lombilla (IAC-ULL), F. Jiménez-Ibarra (IAC-ULL), S. Shumko (Big Bear Solar Observatory, Institute of Technology, EEUU), E. Sanroma (IAC-ULL), A. Hulist (IAC-ULL), P. Miles-Páez (IAC-ULL), F. Murgas (IAC-ULL), G. Nowak (IAC-ULL), S. E. Koonin (Center for Urban Science & Progress, New York University, EEUU). Geophys. Res. Lett., 43, doi: 10.1002/2016GL068025.

Instituto de Astrofísica de Canarias (IAC)

Related Climate Change Articles:

The black forest and climate change
Silver and Douglas firs could replace Norway spruce in the long run due to their greater resistance to droughts.
For some US counties, climate change will be particularly costly
A highly granular assessment of the impacts of climate change on the US economy suggests that each 1°Celsius increase in temperature will cost 1.2 percent of the country's gross domestic product, on average.
Climate change label leads to climate science acceptance
A new Cornell University study finds that labels matter when it comes to acceptance of climate science.
Was that climate change?
A new four-step 'framework' aims to test the contribution of climate change to record-setting extreme weather events.
It's more than just climate change
Accurately modeling climate change and interactive human factors -- including inequality, consumption, and population -- is essential for the effective science-based policies and measures needed to benefit and sustain current and future generations.
Climate change scientists should think more about sex
Climate change can have a different impact on male and female fish, shellfish and other marine animals, with widespread implications for the future of marine life and the production of seafood.
Climate change prompts Alaska fish to change breeding behavior
A new University of Washington study finds that one of Alaska's most abundant freshwater fish species is altering its breeding patterns in response to climate change, which could impact the ecology of northern lakes that already acutely feel the effects of a changing climate.
Uncertainties related to climate engineering limit its use in curbing climate change
Climate engineering refers to the systematic, large-scale modification of the environment using various climate intervention techniques.
Public holds polarized views about climate change and trust in climate scientists
There are gaping divisions in Americans' views across every dimension of the climate debate, including causes and cures for climate change and trust in climate scientists and their research, according to a new Pew Research Center survey.
The psychology behind climate change denial
In a new thesis in psychology, Kirsti Jylhä at Uppsala University has studied the psychology behind climate change denial.

Related Climate Change Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Jumpstarting Creativity
Our greatest breakthroughs and triumphs have one thing in common: creativity. But how do you ignite it? And how do you rekindle it? This hour, TED speakers explore ideas on jumpstarting creativity. Guests include economist Tim Harford, producer Helen Marriage, artificial intelligence researcher Steve Engels, and behavioral scientist Marily Oppezzo.
Now Playing: Science for the People

#524 The Human Network
What does a network of humans look like and how does it work? How does information spread? How do decisions and opinions spread? What gets distorted as it moves through the network and why? This week we dig into the ins and outs of human networks with Matthew Jackson, Professor of Economics at Stanford University and author of the book "The Human Network: How Your Social Position Determines Your Power, Beliefs, and Behaviours".