Tue January 29, 2013
Report Shows Effect of Waste Heat on Urban Temperatures
A new study says the heat that’s released from buildings and transportation in major urban areas can affect the temperature in cities far away.
The study was published Sunday in Nature Climate Change, and is the first to look at the effects of waste heat on temperature changes. The researchers found that the heat that’s released from buildings and cars in urban areas in the northern hemisphere can raise the temperature by about one degree Celsius.
Dr. Aixue Hu of the National Center for Atmospheric Research was one of the study’s main authors. He says one degree Celsius isn’t a big change, but it matters.
“So this is not a huge amount in comparison to local temperature, but it does have a significant impact,” he said.
The net effect on global mean temperatures is nearly negligible—an average increase worldwide of just 0.01 degrees C (about 0.02 degrees F). This is because the total human-produced waste heat is only about 0.3 percent of the heat transported across higher latitudes by atmospheric and oceanic circulations.
However, the noticeable impact on regional temperatures may explain why some regions are experiencing more winter warming than projected by climate computer models, the researchers conclude. They suggest that models be adjusted to take the influence of waste heat into account.
Hu says his study showed its effects in the southeast are minimal. And he also says that the waste heat effect is distinct from the urban heat island phenomenon, which is caused by a loss of trees and an increase in structures that absorb heat (like pavement).
It’s also important to note that Hu found the waste heat happens no matter what kind of energy is used…whether it’s renewable or from fossil fuels. Reducing fossil fuels is important because they release greenhouse gases that are warming the planet, but will have little effect on waste heat.