5 February 2013 – Cities generate climate change. That’s on top of the urban heat island effect. Major population centres have resulted in strong warming in Russia, northern Asia, and eastern China, reports Leon Gettler.
Cities generate climate change. Last June, the United Nations Conference on Sustainable Development otherwise known as Rio+20, found that the world’s cities occupy just 2 per cent of the space, but account for 60-80 per cent of energy consumption and 75 per cent of carbon emissions.
- Photo: Winter warming. See website
That will continue to accelerate because by 2030, almost 60 per cent of the world’s population will live in urban areas. Furthermore, cities don’t just generate greenhouse gases. Rapid urbanisation puts pressure on fresh water supplies, sewerage, the living environment, and public health.
Then again, cities might save the planet. The high density of cities can bring efficiency gains. There’s a lot of brain power living in our cities and technological innovation could reduce resource and energy consumption. That’s today’s challenge for the building industry, architects, town planners and councils.
They have a lot of work cut out for them.
First, if you live in the city, it could be affecting the weather. Take for example the heat islands. These are created when heat is stored and re-radiated by expanses of asphalt, concrete and other building materials. The result: urban areas warmer than rural areas.
Part of the problem comes from the demand for airconditioning in the summer.
This creates big costs for residents and business owners. With the cost of electricity projected to rise over the next few years, the impact of heat islands will be of increasing interest to householders and business owners. Needless to say, greater use of airconditioning increases greenhouse gas emissions from power plants.
Heat islands are everywhere, all over the world including Australia.
In addition to these islands, the United Nations Human Settlements Programme, UN-Habitat says cities generate heat and greenhouse gas from other more obvious sources.
“Transportation, energy generation and industrial production within the territorial boundaries of towns and cities generate GHG emissions directly,” UN-HABITAT writes. “Urban centres rely on inward flows of food, water and consumer goods that may result in GHG emissions from areas outside the city. In addition, individuals consume a range of goods and services that may have been produced locally or outside the urban area.”
Scientists have found that heat generated by everyday activities in metropolitan areas has a significant warming effect. This heat influences the character of the jet stream and other major atmospheric systems and generates greenhouse gases.
In other words, the world’s mega cities are creating heat during the winter months. As Monte Morin in the Los Angeles Times points out, that’s in addition to planetary warming caused by existing greenhouse gases. And worse still, that’s on top of the urban heat island effect.
“Overall, the waste heat produced by the globe’s cities is small. However, the heat is highly concentrated, and in many cases, positioned directly beneath major atmospheric troughs and ridges, according to (the) study authors,’’ Morin writes.
“In Russia and northern Asia, the effect can increase temperatures by almost 2 degrees Fahrenheit during the winter. In the northeastern US and southern Canada, the effect has raised winter temperatures by more than 1 degree”.
What’s disturbing is that the heat generated in one city can be felt in other places. Suzanne Goldenberg in The Guardian writes that the heat thrown off by major metropolitan areas on America’s east coast caused winter warming across large areas of North America, thousands of miles away from those cities. And it went far.
“Winter warming was detected as far away as the Canadian prairies,’’ Goldenberg writes. “In some remote areas, temperature rose by as much as 1 degree C (1.8F) under the influence of big cities, which produced changes in the jet stream and other atmospheric systems, the study found.
“Researchers found a similar pattern in Asia, where major population centres resulted in strong warming in Russia, northern Asia, and eastern China.”
While heat generated by mega cities is just a fraction of the warming caused by climate change or urbanisation, this study would help scientists account for additional warming not explained by existing climate models. Obviously, these findings need to be incorporated into climate warming models so we can get more accurate data about what’s happening to our planet.
So how do we address this? How can cities create a more sustainable planet?
Some are already doing it. At the end of last year, GreenMashUp introduced you to smart cities, places like Paris, London, Copenhagen, Toronto, Vancouver, Vienna, Barcelona, Tokyo and Sydney introducing innovations such as codes that requires all new buildings over a certain size to generate hot water from solar thermal energy, putting in infrastructure for vehicle charging, solar panels, lots of car sharing, homes filled with smart appliances and LED lighting, running programs of ecologically sustainable procurement practices, using thermal waste recycling and having biomass and industrial waste heat used for heating.
Dr Nick Williams from the University of Melbourne says planting vegetation is a simple and effective way to reduce heat islands. Widespread planting can decrease local surface and air temperatures with one study finding that vegetated spaces could be 2-8°C cooler than their surroundings. Strategic tree planting directly cools the interior of homes and buildings. It also decreases air conditioning costs and peak energy demand.
Williams says Chicago now has 11 per cent tree cover. Indeed, the value of air pollution removal by trees across the Chicago region is estimated to be $US9.2 million. Also, properly irrigated green roofs could reduce temperatures.
Growing food on city streets, or vertical farming, is another answer. As The Wall Street Journal points out, this could reduce the number of delivery trucks belching out exhaust, not to mention the use of pesticides and herbicides, which pollute the environment in agricultural runoff. And of course, it also means more trees.
Other solutions include resurfacing roads with pale pavements or painting roofs white, increasing their solar reflectance or “albedo”. As The Independent says, studies have found that painting roofs white and using light-coloured materials to surface roads and pavements would save the same amount of carbon as taking all the cars in the world off the roads for 50 years.
Councils will also have to change their planning processes and the Municipal Association of Victoria says councils are already moving in this direction. Net Balance, RMIT and Greater Geelong City Council for example have launched a Climate Change Adaptation Toolkit to integrate into planning processes.
Sustainable design in buildings is another way forward. Potentially, it’s a growth industry for the building and real estate sector. We have the technology to achieve low-carbon, low-water consumption buildings, made from low impact or recycled material.
One example is the Construction Industry Council’s Zero Carbon Building in Hong Kong. Engineered by Arup, it opened in June last year and is the first of its kind in Hong Kong. It is connected to the local grid and produces renewable energy on site, from a combination of photovoltaic panels and a biodiesel tri-generation system, to offset the power consumed on an annual basis. The excess is exported to the local grid. It also uses waste cooking oil to generate power.
Another example is the Marine and Freshwater Resources Institute in Queenscliff, Victoria. Again designed by Arup, its concrete structure is exposed on the inside, absorbing heat in summer and naturally warming the interiors in winter. Its inclined walls are solar controllers. In winter (when the sun is low) the sunlight streams in, warming the building and in summer (when the sun is higher in the sky) the building is protected from overheating. Warm air escapes in the evening through operable windows and cool night air circulates within the building. The concrete roof slab is covered in soil, grass and crushed rock, which also helps to insulate interior spaces.
And don’t forget older buildings. Most cities are full of structures built more than 20 years ago, so much more needs to be done to retrofit these buildings to make them more efficient.
Barbara Norman, foundation chair of urban and regional planning at the University of
Canberra, says an Australian Sustainability Commission, which she advocates, would facilitate a more integrated approach to managing cities.
It would bring different perspectives to the table for better decisions. It would also give government, industry and parliament independent advice on possible ways forward and monitor progress.
“A non-sustainable future is not an option,’’ she writes. “We want long-term transformation, and institutional reform that better joins parties together, supported by investment in education and research in sustainable cities to underpin our skills …Co-production of knowledge, and synthesis of integrated approaches to urban and regional futures is critical.”