Period of reflection could help to offset CO2 emissions

Earth and sun
In terms of practicality, if you have proper policies in place, you could saturate the market in less than 30 years; I am talking about almost 100 per cent implementation.
Dr Hashem Akbari
Canadian researchers have investigated how the resurfacing of rooftops and pavements in urban areas could help to combat global warming. The team contends that by increasing the reflectance, or albedo, of every urban area, billions of tonnes of carbon dioxide (CO2) could be offset.

The study, published in the journal Environmental Research Letters and conducted by scientists at Concordia University, examines what effect a global increase in surface albedo would have on our planet's temperature and on CO2 emissions.

Albedo is measured using a scale ranging from 0 to 1, whereby 0 represents a perfectly black, non-reflecting surface, and 1 represents a perfectly white, reflective surface. The team estimates that by increasing the albedo of every urban area by 0.1, we could offset between 130 and 150 billion tonnes of CO2. Assuming that a single car produces four tonnes of CO2 per year, this would be equivalent to removing every car from the road for 50 years. Such an initiative would also save billions of dollars in carbon offsetting costs.

The researchers used the Global Rural and Urban Mapping Project (GRUMP), a dataset of all global urban areas, to estimate the potential impact of global albedo change. In addition to offsetting CO2, the team predicted that such measures could result in a 0.07C reduction in temperature.

Concordia University's Dr Hashem Akbari, the study's lead author, spoke to ScienceOmega.com about the practicalities involved in implementing global albedo change.

White apartments"Most roofs need to be changed every 10 to 30 years," he explained. "Roofs are available in an assortment of colours and you can select a white colour with no incremental cost. For example, if you are choosing a PVC membrane, you can select a black membrane, a grey membrane or a white membrane; the costs are exactly the same. When the time comes, you simply have to select the right one."

Dr Akbari was pleased that in the West, uptake of these technologies has been brisk.

"Quite a lot of authorities in the United States have adopted these standards for commercial, flat-roofed buildings," he said. "They prescribe using materials that are highly reflective. Of course, they have been conservative during the preliminary stages, limiting adoption to regions in which the climate is very hot. However, results are showing that such technologies have proven effective as far north as Montreal in Canada.

"As far as residential areas are concerned, there are several estates that have adopted these standards. In California, every single flat roof that needs to be changed has to be white. If the owner or contractor decides not to install a white roof, they have to come up with additional measures that would compensate for the effect of selecting a dark roof. Since there is no incremental cost, Californians seem happy to go in this direction."

Whilst the scale of global albedo change might seem daunting, Dr Akbari contends that if the political will can be mustered, implementation could be achieved fairly rapidly.

Mediterranean buildings"This is not a new technology; it has been around for thousands of years," he explained. "Around Mediterranean and Middle Eastern countries, white is the builders' colour of choice for exactly the reasons that we have been discussing. Nowadays, architects in developing countries are mimicking the designs of Western constructions, and more attention is being paid to environmentally friendly practices such as the use of reflective materials. There is a gradual move towards the re-implementation of these historic, passive technologies.

"In terms of practicality, if you have proper policies in place, you could saturate the market in less than 30 years; I am talking about almost 100 per cent implementation. Of course, there are some historical buildings for which this strategy will not be appropriate, but they typically account for less than one per cent of roofing areas across urban environments.

"The real issue is that of political will," concluded Dr Akbari. "In Western society and in some Eastern societies, such codes and practices are already in place, and policymakers are very open to the improvement of these strategies. When it comes to some developing nations, however, in which there exists political instability, the rate of adoption is dependent on social factors. I'm afraid that in this respect, I really shouldn't comment."

Despite certain political obstacles, Dr Akbari was optimistic about the possibility of global albedo change. If these obstacles can be overcome, it seems that highly reflective urban environments could become commonplace within the space of a generation.

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