Is White the New Green?

As a winner of the 100 Ways to Save the Planet competition in 2009, you may expect the brainchild of Peruvian inventor, Eduardo Gold to be rocket science. That it is not.

The 55-year-old's suggestion, now backed by World Bank funding to the tune of around £135,000, is the first in an experimental step to restore white peaks to the disappearing glaciers in a remote corner of the Peruvian Andes. In the first instance, the peaks will appear white not because of a fresh covering of snow or ice, but with an environmentally friendly white wash, currently being splashed around by a handful of happy to help locals. It is hoped that as the area whitewashed increases, so will the amount of heat that is reflected back from the land. This means that as the heat is not absorbed, the land will become cooler which could generate a cold micro-climate around the peak. This could in turn re-grow the glacier.

This would not only result in restoration of the picture perfect landscape, but would bring about noticeable changes to the climate of the region and consequently the livelihoods of the locals. Since the glaciers retreated there has been a significant drop in the river levels and the ambient temperatures have become extreme. Reliant on their animals, local people would enjoy better pasture for grazing and thus more productive livestock if the glacier were to return. According to a report from the World Bank in 2009, global warming has resulted in the melting of 22% of the world's tropical glaciers in the last three decades. A point to note is that Peru is home to over 70% of these tropical glaciers. The report also noted that if measures were not taken to lessen climate change, then the remaining glaciers could be just a memory by 2030. This would have far reaching impacts, going way beyond the Andean communities, with drastic consequences for hydroelectric power and the water supply to Peru's heavily populated coastal regions. It must be noted though that the area under current whitewash is a tiny proportion of the area which would need painting if we are to halt climate change this way.

Applying the same thought process to the urban environment, the US Secretary of Energy and Nobel prize-winning scientist, Steven Chu, suggested that where possible rooftops should be painted white. Research from the Lawrence Berkeley National Laboratory in California has estimated that if 63% of rooftops in 100 large cities in tropical and temperate areas worldwide where painted white, it would have climate benefits equivalent to taking all the cars in the world off the roads for just over a decade. Increasing the reflective surface area increases the proportion of the sun's rays that are reflected back into the atmosphere. This change to the earth's albedo should reduce the greenhouse effect. In addition, if the buildings painted are air conditioned, the reduction in building temperature could result in a 10-15% reduction in energy costs.

But how well would this work in the less than tropical climate of the UK? In theory it would work surprisingly well. In practice, there are a number of by-laws and regulations which may come into effect, preventing well meaning eco aware individuals from doing their bit. It may also prove difficult and costly to maintain such sparkling city surfaces. An important consideration must be that whilst reflecting heat in the warmer summer months is a positive action, this could be detrimental in the cold winter months.

One solution to this problem could be in the form of colour changing roof tiles. A team of MIT graduates have recently come first in the Making and Designing Materials Engineering Contest, a competition specifically devoted to projects aimed at improving energy efficiency through innovative uses of materials. When hot, the polymer within the thermo-activated tiles condenses, scattering light, producing a white surface. When cold, the polymer remains dissolved and the black backing is visible. Simple really! However in the grand scheme, the urban environment accounts for just 1.5% of the earth's surface so white paint and futuristic chameleon roof tiles may not be enough to save us.

Jake Hacker, a senior built-environment physicist at Arup thinks there could be many ways to reduce urban heat islands, commenting that a cooler urban region would potentially use less air conditioning therefore reducing CO2 emissions in that area. White surfaces may have a part to play but could urban heat islands also benefit from the straightforward addition of trees? The policy brief, Greening the Concrete Jungle (June 2009) from the Woodland Trust, suggests this is the case. Green space and trees specifically, provide direct shade and reduce the temperature through evaporation from the plant leaves and soil. It is estimated that a single mature tree transpires up to 450 litres of moisture a day; equivalent to five air conditioners running for 19 hours. Trees also help to keep the air clean and breathable. This may not be the immediate solution to climate change, but it is as easy and natural as solutions come and in the long run, something future generations would be certain to thank us for.

Pro Enviro July 2010