Saturday, June 26, 2010

Sprawling Cities Getting Hotter Faster

An interesting new paper has been published (ahead of print) in Environmental Health Perspectives: Stone et al. (2010). It's being widely reported in the media (e.g Yahoo! News.) It finds that:
Our results find the rate of increase in the annual number of extreme heat events between 1956 and 2005 in the most sprawling metropolitan regions to be more than double the rate of increase observed in the most compact metropolitan regions.
The primary author, Brian Stone, is also quoted by OurAmazingPlanet as follows:
"These findings show that the pace of climate change is greater in sprawling cities than in others, which has not been shown before."
The study uses "urban sprawl" as the independent variable, which is more sophisticated than simply using a city's population size. That said, these findings essentially confirm what I stated in my post titled Urban Heat Island Effect - A Model. Briefly, I had determined that the UHI effect on the 130-year temperature trend depends logarithmically on the size of a station's associated town, but only if the town's population is greater than about a million people.


Eric L said...

Odd that the warming trend would be predicted by the population or sprawl rather than the rate of growth in one or the other -- are we just looking at an indirect effect due to the growth being correlated with the size, or is this evidence of some interaction, say higher infrared radiation in darker (urban) areas increasing the greenhouse effect?

Eric L said...

From the study: "Variation in the size or rate of growth in metropolitan populations did not diminish the measured statistical association between land-use patterns and the rate of increase in EHEs in these cities (r = 0.34; p < 0.05). These findings are consistent with the hypothesis that urban sprawl contributes to EHE frequency."

So it's not growth, size affects the rate of warming, it doesn't just add a few degrees.

Maybe because people run their AC more as it warms?

Anonymous said...

Joseph, another challenge...