Scientists cite 'heat island effect'

It's usually hotter in the Twin Cities than the surrounding area, and a pair of University of Minnesota researchers say they're getting a good idea of just how hot.

Peter Snyder and Tracy Twine are looking at the so-called urban heat island effect here and around the world. This week they say it's been making parts of the Twin Cities even more uncomfortable.

Snyder says it's a measurable effect.

"For the Twin Cities, just in the last several days when we've had this record-breaking warmth, particularly at night," he says, "we've seen urban heat island signature of about 3 to 4 degrees Fahrenheit warmer in the downtown core area. At night it's even stronger -- we've seen nighttime signatures over the last several days on the order of about 7 degrees Fahrenheit."

They says some cities, like Sacramento, Calif., have been able to counter some of the effect with aggressive tree planting programs. Others have helped cool cities by urging the use of cooler building materials and white roof coatings.