A rogue butterfly may flaps its wings and cause a hurricane a continent away, but waste heat from cities is causing widespread climate change closer to home and on a regular basis, new research suggests. Burning fossil fuels to heat cities and power the cars on their streets has a heating and cooling effect on areas thousands of miles around, the National Center for Atmospheric Research in Colorado claims, with atmospheric circulation change causing fluctuations of up to 2-degrees Fahrenheit remotely from the city itself.
Based on North American city research, the team identified temperature rises in northern North America and northern Asia, believed to have been a result of the excess heat pumped out. Meanwhile, areas of Europe conversely fall in temperature, usually in the fall.
While the net effect of the fluctuations on the global mean temperature is "nearly negligible" according to the researchers, its impact on climate change predictions could be far more significant. The regional variations may well explain some of the previously puzzling warmer winters than experts had expected. Since many cities are underneath major atmospheric troughs and jet streams, they contribute more significantly to alterations in those circulation systems.
The "urban heat island" effect - where buildings, pavement, and other city elements absorb heat and then radiate it - has already been well documented, but the NCAR team is keen to highlight the differences between it and their newly-observed heat systems. Unlike the "urban heat island" model in which the sun itself loads the infrastructure with heat energy, this newer study looks at the impact of transportation, HVAC, and other man-made activities.