NASA calls for reflective roofs to cool towns

Increasing the reflectivity of roofs and pavements could result in significant cooling, buying time for carbon-cutting initiatives that would slow global warming in the longer term.

This is the conclusion of research carried out by NASA's Goddard Space Flight Centre and the Lawrence Berkeley National Laboratory.

It has long been known that dark roofs and asphalt road and pavement surfaces absorb the sun's heat during daylight hours, acting like a huge storage heater.

When combined with the additional warmth from energy using and heating, this creates what's known as the urban heat island effect.

In large cities, this can see urban temperatures rise to several degrees above those of the surrounding countryside.

The US research suggests that increasing the reflectivity - or albedo- of the country's roofs by an average of 25% and pavements by 15% could have the same result as cutting CO2 emissions by around 57 billion tonnes.

"Increasing urban albedo is something that should be done now to buy time for implementing other near-term and long-term climate mitigation strategies," said Durwood Zaelke, president of the Institute for Governance & Sustainable Development.

Introducing "cool roofs" and more reflective paving materials could replace some of the albedo that has been lost through the melting of Arctic sea ice.

"Although it does not solve the root of the climate change problem - substantial reductions in CO2 and other climate forcers are essential for that - urban albedo can delay the onset of more severe climate impacts, and reduce the risk of passing the thresholds for abrupt and irreversible climate changes."

Because CO2 emissions can remain in the atmosphere for up to 1,000 years, there is an urgent need for complementary, fast mitigation measures that will result in significant near-term reductions to avoid passing the tipping points for abrupt climate change, which may only be decades away.

In addition to increasing urban albedo, such strategies might include reducing emissions of black carbon soot, methane, and tropospheric ozone, as well as using the Montreal Protocol ozone treaty to phase down hydrofluorocarbons, which could prevent the emissions of more than 100 billion tonnes of CO2 equivalent by 2050.

Sam Bond



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