Comment »Posted on Saturday 30 May 2009 at 2:24 pm by Sam Wong
In Climate Change & Environment

Can you put a figure on the impact of climate change? Yesterday, the Global Humanitarian Forum, a humanitarian organisation set up by former UN secretary general Kofi Annan, did. According to their report, climate change is already killing 300,000 people a year, mainly through environmental degradation. They put the economic cost of global warming at 125,000 USD a year. As The Times reports,

The research was carried out by Dalberg Global Advisers, a consultancy firm, who collated all existing statistics on the human impacts of climate change. The report acknowledges a “significant margin of error” in its estimates.

Given the unavoidably large degree of uncertainty in the estimates, I’m not sure putting a figure on the death toll is particularly helpful. We already know that climate change is a big problem, and these numbers are not going to persuade anyone who’s sceptical.

‘Copenhagen needs to be the most ambitious international agreement ever reached,’ Kofi Annan said. But yesterday others were warning that setting overly ambitious targets would scupper any chance of a global deal. Carlo Carraro, Professor of Environmental Economics at the University of Venice, cautioned that the kind of measures necessary to keep CO2 levels to 550 parts per million by 2100 would be viewed as overly restrictive by China and India.

What’s often overlooked in discussions about climate change is the simple things we can do immediately that cost us nothing, or even save money. This was highlighted by Steve Chu this week when he spoke at the Nobel Laureate Symposium in London this week (you can watch his speech in full here). Professor Chu is the Nobel-winning physicist who was appointed Energy Secretary by Barack Obama when he became president. It’s the first time that a career scientist has run the Department of Energy since it was set up in 1977.

Chu argued that we ought to be doing a lot more to ensure that buildings are designed with energy efficiency in mind. The most intriguing suggestion he made was that we give our cities a makeover with the aim of reducing the amount of sunlight they absorb:

If you replace all the building roofs today with white roofs, and you go to cement-style pavement instead of black-top style pavement, it would be a reflection of sunlight back into space that would be the equivalent of if you took off all the automobiles in the world for eleven years.

Chu’s claim was based on a study whose authors included Art Rosenthal, Chu’s colleague at the Lawrence Berkeley National Laboratory and a member of the California Energy Commission. The study said that repainting a dark roof that reflects 20 per cent of sunlight so that it reflects 60 per cent of sunlight could offset 10 tonnes of CO2 emissions – roughly the amount produced by an average American household in a year.

Urged on by Rosenthal, California has led the way in introducing legislation to this effect: since 2005, state law has required all new flat roofs on commercial buildings to be white. From July, sloped roofs will have to be cool-coloured. Making roofs more reflective cools the building, saving energy on air conditioning, but also means less heat absorbed by the planet, reducing global warming.

We can’t make roads and pavements white, but Rosenthal’s study claims that making black surfaces cement-coloured offsets four tonnes of CO2 per 100m². Combine this with roof-whitening in the world’s 100 largest cities and you get reduction in global warming equivalent to cutting 44 billion tonnes of CO2 emissions.

Making roofs and pavements more reflective saves on energy and makes cities more comfortable. The incentives are local; there’s no need for international agreement. What are we waiting for?


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