Study: Heat from Big Cities in North America Causing Milder Winters

For years, scientists have been trying to determine how big cities, with their sprawls of buildings and cars, affect climate. Researchers now say that extra heat generated by large cities explains additional warming that is not explained by existing climate models, and in addition to the climate pollution caused by burning fossil fuels, the cities themselves have far-reaching affects on climate.

A study lead by Guang Zhang, a scientist at the Scripps Institution of Oceanograph, found that the heat thrown off by major metropolitan areas on America's east coast caused winter warming across large areas of North America, up to thousands of miles of away.

In fact, winter warming was detected as far away as the Canadian praries. The study, which was published in the journal Nature Climate Change, showed that in some remote areas, temperature rose by as much as 1 degree C under the influence of big cities. This 1 degree C increase produced changes in the jet stream and other atmosphere systems.

Researchers were able to find a similar pattern in Asia, where major population areas resulted in strong warming in Russia, northern Asia, and eastern China.

Changes in atmosphere conditions had an opposite effect on Europe, where it lowered autumn temperatures by as much as 1 degree C.

The researchers said that the extra heat generated by big cities was only a fraction of the warming caused by climate change or urbanization, but the study did help scientists to account for additional warming not explained by existing climate models.

The study found that global temperature averages were barely affected by the heat from the large cities, barely .01 C on average, but big cities were found to have a noticeable impact on regional temperatures almost on a continental scale.