The greenhouse effect may be happening much faster than previously believed, scientists in Finland and the United States report.

The University of Helsinki's Anatoli Bogdan and colleagues, who include chemistry Nobel laureate Mario J. Molina, reached that conclusion from laboratory studies of the low-temperature thin and subvisible cirrus (SVC) clouds that have such a powerful impact on climate.

SVCs cover about one-third of the planet and affect global temperatures by reflecting sunlight back into space and preventing terrestrial heat from escaping into space. In addition, ice particles in SVCs have a drying or dehydrating effect on the upper troposphere.

"Here we show, to our best knowledge for the first time, that the small ice particles are not completely solid, as is usually believed, but rather coated with a sulfuric acid/water overlayer," the researchers state. Their study is scheduled for publication in the Nov. 16 issue of the ACS weekly Journal of Physical Chemistry A.

The coating reduces the rate at which ice particles grow and remove water vapor - a key greenhouse gas - from the upper troposphere. That leaves more water vapor to contribute to the greenhouse effect. The coating further affects greenhouse warming by slightly increasing reflection of sunlight back into space and reducing the escape of terrestrial heat.

SOURCE: American Chemical Society