Human-generated air pollution particles may alter the temperature cycle in China's industrialized region, and lead to nighttime warming in winter of about 0.7 degrees per year, scientists said on Tuesday.

Human-generated aerosols, tiny particles such as those found in car exhaust and soot, can affect the climate indirectly by acting as seeds around which condensation can coalesce and form raindrops and snowflakes.

The aerosols can also absorb long-wave radiation, through which the Earth cool itself at night, said Yan Huang, a Chinese researcher at the Georgia Institute of Technology, adding that more aerosol pollutants could result in higher nighttime temperature.

Based on climate models, Huang calculated that in some industrialized regions in China, nighttime temperature in winter could increase by 0.7 degrees Celsius, and the daily temperature range could decreases by 0.7 degrees every year because of more aerosol pollutants.

This study was published in the latest issue of US scientific journal The Proceedings of National Academy of Sciences.

The researchers' models suggested that aerosols had the greatest effect during wintertime and over highly industrialized parts of China.

"The most affected regions include the Guangdong Province and the Yangtze River Delta," Huang told Xinhua in a telephone interview, "the most industrialized regions in China."

The aerosols increase the number of clouds over the region as well as the amount of liquid water contained within them, Huang explained.

These changes increased the radiation emitted by the atmosphere that reached the planet's surface, resulting in a negligible daytime cooling and obvious night warming.

"Our calculation is based on a regional climate model," Huang said, "but the results are broadly consistent with the observed diurnal temperature range decrease and warmer winter nights as reported recently."

According to the researchers, this trend will not slow down, and China will see warmer winter nights in coming years with its population growth and industrialization.

"Earlier studies indicated that aerosols might weaken the greenhouse effect, but our work reveals they are more likely to add up to the warming," Huang said.

(Xinhua News Agency March 8, 2006)