Weather forecast may be wrong for urban

Heat from buildings, cars, and factories in big cities can cause temperatures in areas thousands of kilometers away to increase or decrease compared to the forecast of meteorologists.

Dr. Guang Zhang, an expert at Scripps Oceanographic Institute in the United States, and colleagues investigated the impact of urban heat on the climate, Science Daily reported.

They found that winds could carry heat from cities to all over the globe, disturbing air systems thousands of kilometers from the city. That phenomenon may increase temperatures in North America and North Asia in the winter, but reduce temperatures in Europe in the fall. Maximum increase and decrease is 1 degree centigrade.

"Fossil fuel burning activities not only emit greenhouse gases, but also directly affect air temperatures. Although most urban heat is concentrated in large cities, it still has can change temperatures in areas a few thousand kilometers from the city , " said Dr. Aixue Hu, an expert at the US National Center for Atmospheric Research. Hu also participated in Zhang's research.

Scientists also analyze the total energy that mankind has used. They said that in 2006, the total energy consumed by the world was 16 trillion watts - equivalent to having 10 billion light bulbs 100 watts lit continuously for a year.