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How will changes in urbanization affect climate in the Southeast?

WABE, NPR’s radio station in Atlanta, produced a story today about projected urbanization changes in the Southeast.  At current growth rates, we could see a nearly continuous string of urban areas stretching from southwest of Atlanta all the way to Raleigh NC and northeast.  How would the increase in urbanization affect local climate conditions?  The link to the story is at http://wabe.org/post/could-explosive-growth-lead-southern-megalopolis.

A team of researchers at the US Geological Survey and North Carolina State University studied the growth of cities and published projected maps of the areas most likely to be urbanized by 2060.  The map which shows the likelihood of urbanization is shown below.

In general, urbanized areas are warmer than surrounding areas due to the absorption of heat by pavement as well as increased emission of heat pollution from refrigeration and combustion.  This is known as the “urban heat island” and can be seen in smaller cities (like Athens GA at 100,000 people as well as even smaller ones) as well as the largest cities.  The particles that are emitted can also lead to increased rainfall, especially downwind of the cities (and this can change depending on which way the wind is blowing).  So we can expect temperatures and rainfall to increase from just changes in urbanization.  This would be in addition to warming from greenhouse gases around the globe, which makes cities especially vulnerable to heat effects in a warmer climate.  The excess rains can also lead to more local flooding from strong thunderstorms dropping rain on impermeable surfaces.

If you live in or near a city, you may have a longer growing season because of the heat island, and so can grow plants that might not survive in more rural areas.

Changes in land use over time have been known to affect regional climate in many locations, both current and historical.  So it is likely that urbanization increases will provide their own local “flavor” to climate changes in the Southeast in the future, regardless of what happens with the global climate.

Source: Adam Terendo, USGS

Source: Adam Terendo, USGS