Scientists have created an instrument designed to help determine the shapes and sizes of tiny ice crystals typical of those found in high-altitude clouds, down to the micron level, according to a new study published Thursday in the journal Optics Letters.

The data produced using this instrument likely will help improve computer models used to predict climate change, said the team of scientists from the United Kingdom and Colorado State University in the United States.

Among the hundreds of factors climate scientists must take intoaccount in modeling weather, the nature of clouds is one of the most important and least understood. The best researchers could do in the past to measure cloud ice crystals was to try to record images of them, but for crystals below 25 microns, the images weretoo blurred to allow accurate determination of the crystal's shape.

Researchers need to know the shape and sizes of these ice crystals because these properties influence how much incoming sunlight gets absorbed in the atmosphere and how much gets reflected right back out into space. This, in turn, can have a huge impact on the magnitude of possible global warming or cooling.

The research team developed an optical scattering instrument that can evaluate the size of the crystals in a different way. Using this instrument, the researchers have been able to determine sizes and shapes of cloud ice crystals all the way down to the tiniest micron levels.

"The new instruments should help map out a more complete understanding of complex crystal shapes found in atmospheric clouds, especially cirrus clouds, which on any day can cover more than 20 percent of the Earth's surface," says Paul Kaye, one of the researchers. "We believe that this optical scattering instrument could help climate modelers reduce one of the greatest areas of uncertainty in interpreting the influence of clouds and in making more accurate climate predictions."

(Xinhua News Agency July 18, 2008)