Cities hold the key to addressing climate change, says UN panel

Smart planning of  urban environments can spawn more efficient transport and energy use, says IPCC

(Pic: Bigstock)

(Pic: Bigstock)

By Gerard Wynn

New cities should use more efficient transport systems and better energy and waste recycling, to avoid locking in long term carbon emissions, a report by a UN panel of scientists found.

Greater efficiency could be achieved through greater adoption of existing technologies including mass public transit using trains and buses, and district heating to cut energy use.

The world will build more city space in the first three decades of this century than has been built in human history to date, given trends in population growth and urbanisation.

These new megacities would help set the path of future carbon emissions, the Intergovernmental Panel on Climate Change (IPCC) said, for example by determining how far people travelled to work.

“Investment in urban physical investment in these emerging megacities will have a significant long-lasting impact on greenhouse gas emissions.”

The IPCC reviews the latest published science on climate change every five to six years. Sunday’s release was the last instalment of the latest report, focusing on policy options to cut emissions, and compiled by some 235 authors.

They found that countries should roughly halve global carbon emissions by 2050, compared with present levels, which are still rising, to avoid the most dangerous climate change.

They said that “business as usual” was not an option, given expected temperature rises of 3 to 5 degrees Celsius without efforts to curb emissions, implying dangerous sea level rise, floods and droughts.


New cities could learn from past experience, found an academic study quoted by the IPCC.

The study compared energy use across 10 existing cities and found that transport demand was much less for compact cities like Barcelona, than sprawling ones like Denver in the United States.

Denver was also top in energy use in heating, reflecting its rather cold winters. But U.S. cities still performed worse than colder European and Canadian counterparts, perhaps because of relatively larger houses as well as more disposable income.

One way of cutting city transport emissions was to drive a shift from passenger vehicles to mass transit, as well as to reduce overall demand through more compact, mixed use development.

Some 40% of all transport energy consumption was in cities, the IPCC said, and greenhouse gas emissions from the sector were growing faster than any other.

Light vehicle ownership is expected to double in the next few decades from 1 billion vehicles presently, with two thirds of growth in non-OECD countries.

The IPCC report used the example of the Brazilian city of Curitiba, as a model of sustainable transport.

Curitiba pioneered the world’s first bus rapid transit system, achieving mass adoption through unified fares and high capacity bus lanes. It coordinated bus corridors with high density developments, further to encourage widespread use, and reduced overall transport demand through mixed developments of residential, business and commercial buildings.

As a result, vehicle kilometres travelled (VKT) in Curitiba were half of Brasilia, a sprawling Brazilian city with a similar population, the IPCC report found.

While building transit systems may have high upfront costs, they appear better value after including all the benefits, including lower ozone and other air pollution, less congestion and fewer car accidents, as well as much lower carbon emissions.

In addition, mass transit systems make transport more affordable for poorer people, improving access to markets, jobs, education, health and other services, supporting trade and competitiveness. Shifts away from petroleum dependence would boost energy security.


New cities would also have to use energy for heating and cooling more efficiently.

One example was district heating, which uses heat normally wasted and vented into the atmosphere from industrial facilities or power plants. The heat is trapped and supplied to homes and businesses via pipeline networks of hot water or steam.

By using waste heat from factories, district heating can source exceptionally low cost energy. Trapping and re-using heat can increase the operating efficiency of power plants by 30%.

The IPCC found adoption of district heating was on an upward trend after falling in the 1990s.

The main cost is in the upfront expense and disruption of building a pipeline network. But these costs were much reduced by focusing on local heating sources in high density developments typical of cities.

One recent example was the development of a district heating system in the northern Chinese city of Anshan, by Denmark’s Danfoss, for the use of surplus heat from AnGang steel plant, to supply 1.8 million residents.

The International Energy Agency reported annual growth of 17% in China’s district heated area from 2000-2005.

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