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geophysical research letters

Study Finds Space Shuttle Exhaust Creates Night-shining Clouds

Exhaust from the main engines of NASA’s space shuttle, which is about 97 percent water vapor, can travel to the Arctic in Earth’s thermosphere, the highest part of the atmosphere, where it forms ice to create clouds that shine at night, according to a new study. The thermosphere is above 88 kilometers [55 miles] altitude. The clouds settle to around 82 kilometers [51 miles] altitude in the layer directly below, called the mesosphere. The stratosphere and the troposphere lie in that order below the mesosphere.

Atmospheric Mercury Has Declined — But Why?

The amount of gaseous mercury in the atmosphere has dropped sharply from its peak in the 1980s and has remained relatively constant since the mid 1990s. This welcome decline may result from control measures undertaken in western Europe and North America, but scientists who have just concluded a study of atmospheric mercury say they cannot reconcile the amounts actually found with current understanding of natural and manmade sources of the element.

New Climate Model Predicts Greater 21st Century Warming

For the first time, scientists have incorporated multiple human and natural factors into a climate projection model. They predict that increased carbon dioxide in the atmosphere, due to changes in the carbon cycle, combined with a decrease in human-produced sulphates, may cause accelerated global warming during the 21st century, as compared with simulations without these feedback effects.

Black Water Turns the Tide on Florida Coral

A patch of “black water”spanning over 100 kilometers [60 miles] in diameter formed off southwestern Florida in early 2002 and contributed to severe coral reef stress and death in the Florida Keys. The “black water” contained a high abundance of toxic and non-toxic microscopic plants. When scientists examined the data collected by divers from the dark water area in the Florida Keys, they discovered a 70 percent decrease in stony coral cover, a 40 percent reduction of coral species, and a near-elimination of sponge colonies at two reef sites after the dark water passed. By examining satellite images and field survey data, they concluded that the coral reef ecosystem was stressed by microscopic organisms and toxins contained in the dark water.