The Bodele Depression was the source of some very impressive dust storms that swept over West Africa and the Cape Verde Islands in February 2004, the date of this image. The remnants of Lake Chad appear in olive-green amid the tan and light brown hues of the surrounding landscape where the countries of Chad, Niger, Nigeria and Cameroon all share borders. Once heaved aloft, the dust can be carried for hundreds or even thousands of kilometers.

The small grains of the silty sand are easily swept up by the strong wind gusts that occasionally blow over the region. As the waters receded, the silts and sediments resting on the lakebed were left to dry in the scorching African sun. But persistent drought conditions, coupled with increased demand for freshwater for irrigation, have reduced Lake Chad to about 5 percent of its former size. In the mid-1960s, Lake Chad was about the size of Lake Erie. Once serving as part of the floor for a much larger Lake Chad, the area now known as the Bodele Depression, located at the southern edge of the Sahara Desert in north central Africa, is slowly being transformed into a desert landscape. Lake Chad, Africa February 7 and 11, 2004. More methane, on the other hand, puts more water vapor into the atmosphere, because sunlight breaks methane up into water molecules at high altitudes. In the mesosphere, carbon dioxide radiates heat into space, causing cooling. These changes may be happening because of increased levels of heat-trapping greenhouse gases such as carbon dioxide and methane in the atmosphere.

Studies suggest that night-shining clouds are becoming brighter and more common, which is linked to the mesosphere getting colder and more humid. This happens most often in countries at high northern and southern latitudes (above 50 degrees) in the summer, when the mesosphere is coldest. They only form when the temperature drops below –130 degrees Celsius (-200 degrees Fahrenheit), whereupon the scant amount of water high in the atmosphere freezes into ice clouds. The clouds' high position in the atmosphere allows them to reflect sunlight long after the sun has dropped below the horizon. These rare clouds are technically called 'noctilucent' or 'polar mesospheric' clouds, and form at high altitudes, 80 to 85 kilometers (50 to 53 miles) high, where the mesosphere is located.

These night-shining clouds were spotted over Billund, Denmark on July 15, 2010.

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