CLOUDS -- Page Two

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There's more to clouds than the inspiration of daydreams. As a planet-wide system, clouds are understood to be fundamental in regulating temperature around the globe. Clouds simultaneously shield the Earth from too much solar radiation and insulate the Earth from losing valuable heat into space.

In recent years scientific debate has raged about the likelihood that an increasingly warm climate would cause more evaporation, prompting more cloud formation, and thus a more robust radiative shield for the Earth. The theory suggested that the increase in

clouds would inhibit sunlight, which would bring the planet's temperature back to normal.

Now, new research from NASA's Goddard Institute for Space Studies in New York says that clouds might not have as large a cooling effect on the Earth's climate as had been previously considered. The currently accepted range for global warming over the next century is between 3° and 8° F (1.5° to 4.5° C). But according to the report’s author Anthony Del Genio, the minimum overall warming prediction should be revised upwards by 1 degree, a significant increase in overall temperature change.

His paper appears in the October 2000 issue of the Journal of Climate.

Click on pic to begin animation.	Clouds not only yield rain, but also play an important role in regulating the Earth's temperature. The determining characteristic is called albedo. It's a measure of how much radiation, or light, is reflected from a body. Similar to how a white shirt helps keep a person cooler in the summer than a black shirt, the cumulatively vast area of cloud cover around the world reflects large amounts of solar radiation falling on the planet's surface. If the reflective or insulative properties of clouds changed significantly, sunlight that otherwise would have been reflected back into space would get absorbed by the darker, denser mass of ocean and land.
A dynamic fabric of suspended water floats above the earth: clouds. As we see in this animation, sunlight reaching the Earth bounces off the tops of clouds and is reflected back into space. Most of the rest reaches the Earth, warming the planet and powering the systems of life all around us. But much of that energy then radiates away from the surface of the planet. As it does, clouds floating above act as a blanket, trapping it in the form of valuable heat. This balancing act helps maintain a regular temperature range for the Earth.	Click on pic to begin animation.
	NASA's new spacecraft, Terra, carries an instrument called Ceres, for Clouds and the Earth's Radiant Energy System. Ceres studies the radiation balance on Earth--how much heat is absorbed and reflected around the globe. By looking at how different cloud formations play a part in that radiation balance, scientists can develop new predictive models about weather systems and how the Earth maintains its delicate temperature equilibrium.
Sometimes we take the natural world for granted. Like most things in the natural world, we can observe clouds in a variety of ways. These images show huge regions of the Earth mottled by clouds. We're seeing the images as delivered by one of the GOES (Geostationary Operational Environmental Satellite) satellites managed by NOAA (National Oceanographic and Atmospheric Administrations). If we regard these images as simply brief glimpses of the eternal atmospheric dance, we start to see how changes in clouds might dramatically alter the way the Earth not only looks but behaves.
	This image shows one technique researchers can use to study how the atmosphere works in relation to temperature. The filigreed strands of ice floating high in the sky are cirrus clouds. As indicators of atmospheric pollutants, as well as high altitude temperature changes, cirrus clouds become a useful research tool. By lifting the cirrus clouds off the main image a variety of analytic processes can be brought to bear. This image comes from MODIS, an instrument flying on the Terra spacecraft.
Sometimes we take the natural world for granted. Like most things in the natural world, we can observe clouds in a variety of ways. These images show huge regions of the Earth mottled by clouds. We're seeing the images as delivered by one of the GOES (Geostationary Operational Environmental Satellite) satellites managed by NOAA (National Oceanographic and Atmospheric Administrations). If we regard these images as simply brief glimpses of the eternal atmospheric dance, we start to see how changes in clouds might dramatically alter the way the Earth not only looks but behaves.
	Terra is a multinational orbiting research platform managed at NASA’s Goddard Space Flight Center. By synchronizing a sophisticated suite of sensors and instruments, Terra will help researchers pursue some of the grandest and most complex questions about the nature of our home planet. The satellite will simultaneously study clouds, water vapor, aerosol particles, trace gases, terrestrial and ocean properties, and systemic interactions on a planetary scale.