PARIS — Scientists sketched a vision on Friday of converting the world’s cities into giant sunlight reflectors to help fight global warming but met with scepticism from fellow academics.
Gradually replacing traditional urban roofs and roads with white or lighter-coloured materials would yield a cooling benefit that, over 50 years, would be the equivalent of a reduction of between 25 and 150 billion tonnes of carbon dioxide (CO2), researchers in Canada said.
At the top end of the scale, this equals the emissions of all the world’s cars over the same period, their study published in Britain’s Institute of Physics’ journal Environmental Research Letters stated.
Light-coloured materials help reflect the Sun’s rays rather than absorb and convert them into heat, a phenomenon known as albedo in scientific terms.
Pavements and roofs make up more than 60 percent of urban surfaces and, by trapping solar energy, are largely to blame for “heat islands”, where cities or districts become local hotspots.
Urban heat islands also gobble up energy in air conditioning and inflict health costs through smog.
The cost of reflectors need not be prohibitive as rooftops and paved surfaces need to be resurfaced every so often anyway, the scientists argued.
“All it means is that when the time comes, they would select a cool roof,” Hashem Akbari of Concordia University in Montreal told AFP.
He conceded that some of the new materials may be slightly more expensive than before, but the cost would still be “lower than the … savings they produce” in cooling.
French climate consultant Jean-Marc Jancovici, however, said the proposals would have only a localised effect.
“If you decrease significantly the temperature in local places with something like painting the roofs in white, it doesn’t ensure that you will have a decrease in the temperature in remote places,” he said.
Alfredo Stein of the Global Urban Research Centre at Britain’s University of Manchester also predicted practical difficulties, particularly for the world’s sprawling slum areas.
“It will require very strong advocacy by whoever will be selling the roofs,” he told AFP, especially considering that about 70 percent of houses worldwide are built by the owners themselves, mainly in informal settlements.
People’s choices for roofing materials are largely determined by affordability and availability, Stein argued.
In a 2009 probe into so-called geo-engineering options to brake global warming, Britain’s Royal Society gave low marks to “white roof” methods.
There would be benefits locally in hot countries, it said.
But only 0.05 to one percent of the world’s land surface would be covered, which meant it would lack effectiveness on a global scale, the prestigious academy said.
And it estimated the cost at “about $300 billion a year, making this one of the least effective and most expensive methods considered.”
Republicans’ laughable effort to attack Adam Schiff lands with a thud
Republicans' effort to castigate California Democrat Rep. Adam Schiff, the chair of the House Intelligence Committee spearheading the impeachment inquiry, met a quick and sudden defeat on Monday in a vote of 218-185.
Spurred on by President Donald Trump's attacks on the chairman, GOP House Minority Leader Kevin McCarthy led an effort to censure Schiff on the House floor. On what grounds? It's almost too absurd to make up: lying.
The party of Donald Trump — who lied more times in the hours before the censure vote than Schiff even stands accused of — actually claimed that it's the California lawmaker who should be called out for dishonesty.
Lindsey Graham leaves open the possibility of voting to impeach President Donald Trump
Sen. Lindsey Graham, R-S.C., left open the possibility that he would vote to impeach President Donald Trump if he saw evidence that the commander-in-chief had engaged in a quid pro quo during an interview with "Axios on HBO" broadcast Sunday night.
After telling Axios’ Jonathan Swan that he would need to see evidence of an actual “crime,” Graham added that “if you could show me that, you know, Trump actually was engaging in a quid pro quo outside the phone call, that would be very disturbing."
CNN’s Toobin says all evidence points to Trump running an extortion scheme for political dirt
On Monday's edition of CNN's "Anderson Cooper 360," chief legal analyst Jeffrey Toobin laid out how all the evidence points to President Donald Trump attempting to extort Ukraine for political dirt — even the evidence Trump himself has put forward to the public voluntarily.
"May 14th, Trump tells Vice President Pence not to attend Zelensky, the Ukrainian president's inauguration," said Cooper. "July 18th, Trump decides to withhold nearly $400 million in aid to Ukraine that's already been passed by Congress. July 25th is that Trump and Zelensky phone call. I mean, I don't know if it's, you know, if it begins with the call from Putin, but there certainly is a lot of activity, a lot of dominos falling."