The beginning of summer is an annual reminder that our
world is driven by sunlight, and new Terra satellite
measurements show just how much the Sun influences the
Earth’s climate system.

The first observations, from March 2000 to May 2001, of the
Clouds and the Earth’s Radiant Energy System (CERES)
instruments aboard Terra are the most accurate global
radiation or energy measurements ever and include the first
complete year of such essential data since 1987. These new
CERES data, available at NASA Langley Research Center’s
Atmospheric Sciences Data Center, Hampton, VA, capture
incoming and outgoing energy over the whole planet and
provide new insights into climate change.

“The new data will play a critical role in narrowing the
uncertainties in predictions of future climate change,
especially for the undefined role of the Earth’s cloudiness,”
said Bruce Wielicki, a CERES principal investigator at
Langley, where the CERES mission is managed.

For scientists to understand climate, they must also
determine what drives the changes within the Earth’s
radiation balance. CERES measured some of these changes over
the last year, producing new images that represent data
collected twice per day over the whole planet. CERES captured
the May 2001 heat wave that swept across the southwestern
United States. Temperatures soared to as high as 109 F in
parts of California, setting new records.

The recent U.S. heat wave is only one example of outgoing
energy from the Earth. Everything, from an individual person
to the Earth as a whole, emits energy. As Earth absorbs solar
energy, it warms up. To keep our planet at an overall
hospitable temperature, the Earth must emit some of this
warmth, or energy, into space.

Earth’s outgoing energy has two components: thermal radiation
emitted by the Earth’s surface and atmosphere, as in last
month’s heat wave, and solar radiation reflected back to deep
space by the oceans, lands, aerosols and clouds.

It is the balance, which scientists refer to as the Earth’s
“radiation budget,” between the incoming energy from the Sun
and outgoing energy back to space that determines Earth’s
temperature and climate. This balance is controlled by both
natural and human-induced changes, giving scientists a wide
range of questions to study.

Even though CERES has the ability to capture short-term
changes like the recent heat wave, “the real power of the
CERES data will come from the analysis that integrates CERES’
highly accurate measurement of energy with other measurements
from Terra of the individual components of the climate
system,” Wielicki said.

The international CERES team is now completing an integration
of satellite data over the entire planet from space-borne
instruments on seven different spacecraft to test the
accuracy of global climate models, a task never before
attempted. This will allow a new picture of the energy
balance from the top of the atmosphere, all the way down to
the surface of the Earth. Analyzing how well climate models
compare to CERES will tell the researchers which areas most
closely illustrate the Earth’s natural responses.

“CERES Terra is providing an unprecedented observational
basis, at just the time when major progress in understanding
our environment by theory and climate modeling is taking
place,” said Leo Donner, a CERES science team member and
climate modeler at the National Oceanic and Atmospheric
Administration’s Geophysical Fluid Dynamics Laboratory,
Princeton University, Princeton, NJ.

The Terra spacecraft is part of NASA’s Earth Science
Enterprise, a long-term research effort being conducted to
determine how human-induced and natural changes affect our
global environment.

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