Haze warming Arctic, holding pollution in winter

A University of Utah study says Arctic haze, which is made of particles blown north from southern industrial areas, mixes with thin clouds, making them better able to trap heat.

This makes the Arctic temperatures up to five degrees warmer during cloudy periods than it would be if the air was clean, says the study by meteorologists Tim Garrett and Chuanfeng Zhao.

Their study was published in the April 6 issue of the journal Nature.

Garrett and Zhao collected data at two research sites near Barrow, Alaska. They found that when clouds were present and the air was polluted, the clouds stopped the surface from releasing its heat to outer space.

Scientists already knew particulate pollutants can make clouds reflect sunlight, which reduces surface temperatures.

But the two researchers found particulate pollution also changes clouds, so they warm the surface. This effect is most pronounced in Arctic winter when it is dark and there is no sunlight, little air movement and almost no precipitation to wash out the pollutants.

Arctic haze has been seen since the industrial revolution began around 1750. That’s when whalers and explorers noticed what looked like pollution and couldn’t figure out where it was coming from.