Urban Cold Islands

In a story today in the Los Angeles Times entitled “To slow global warming, install white roofs,” author Margot Roosevelt reports on a recent study that concludes, if you take it at face value, that all we have to do is paint all of our urban rooftops and pavements white and “the global cooling effect would be massive.”

According to Hashem Akbari, a physicist with the Lawrence Berkeley National Laboratory, a 1,000-square-foot roof — the average size on an American home — offsets 10 metric tons of planet-heating carbon dioxide emissions in the atmosphere if dark-colored shingles or coatings are replaced with white material… Globally, roofs account for 25% of the surface of most cities, and pavement accounts for about 35%. If all were switched to reflective material in 100 major urban areas, it would offset 44 metric gigatons of greenhouse gases.”

It would be interesting to understand exactly what Akbari means by this. Is this 44 metric gigatons per year? If not, over what period of time would reflective roofs collectively offset these 44 gigatons? Considering all the nations of the world combined are still emitting somewhat less than 30 gigatons per year, this is a very impressive statistic, no matter how you slice it.

Dr. Akbari’s study isn’t what one should necessarily question, however. We have always insisted the role of land use changes are greatly underestimated when assessing regional climate trends; from tropical deforestation to enhanced thermal absorption due to aquifer depletion to urban heat islands. More pertinent is why the role of urban heat islands – dismissed by the press as a Crichtonian fabrication – has never had credibility, but suddenly the global cooling potential of urban cold islands is cause to legislate? Read the IPCC’s 4th Summary for Policymakers (watch out, it’s 3.6 MB) – you will note the role of land use in causing global warming is minimized, and the role of urban heat islands is negligible. Can you have it both ways?

Another interesting paradox here is the following statement from the report “Globally, roofs account for 25% of the surface of most cities, and pavement accounts for about 35%.” Well maybe if we let people have yards again instead of cramming them into cluster homes, there would be enough land for people to plant trees and create an urban canopy. And if our cars are all soon to run on wind and solar power, maybe we should quit trying to force people out of them and into government operated light rail, busses, and “jitneys.”

The real take-away here is, once again, that there is very little certainty regarding the causes, the severity, or even the direction of climate change. The rhetoric and the conventional wisdom is way behind the latest science and observational data. The policymakers and pundits who have ridiculed the notion of an urban heat island are the same people who are uncritically reporting we must now make every road and roof reflective to mitigate this heat island. There’s nothing wrong with making rooftops reflective to save energy – but does every sensible green product have to incorporate avoiding doomsday in their marketing and lobbying strategy?

Climate change is not a trivial issue. Concern about climate change is nothing to be mocked. But if you removed from the alarmist coalition the people who condone this alarm because they like the side effects – bigger government, more funds for environmental groups, nonprofits and academia, more taxes so the public sector can avoid fiscal reform, more subsidies and regulations so large corporations can crush emerging corporations, and greater energy independence – the only good side effect on that list – you aren’t left with much. At the least, journalists and scientists should recover their innate skepticism, the lifeblood of their professions, and not abdicate their responsibility to point out this contradiction – the IPCC dismisses the heat island effect, yet today’s latest scientific study claims if we made our cities reflective “the global cooling effect would be massive.”

2 Responses to “Urban Cold Islands”
  1. JamesG says:

    Yet another physicist trying to get his name in the paper. A simple area calculation would have shown that total urban surface area is miniscule and far less likely to affect weather than agricultural areas, which in turn are far less likely to affect climate than deserts and rainforests which in turn are far less likely to affect climate than the oceans. Like most global warming claptrap it fails on it’s primary erroneous assumption. It’s also self-defeating because CO2 free solar panels are uniformly black. All that has been demonstrated is that it’s too easy to get a PhD and pretend to be intelligent, while demonstrating the opposite.

  2. Mr. Awin says:

    Hello…good evening.

    I am a teacher and teaching for geography. I still confuse about “urban cold island”. What does it meaning in term of geography? If anyone have been writing articles about it, please send to me.



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