When it charts its low-carbon road map, Shanghai should take into account such national standards as energy and carbon intensity per unit of GDP to achieve relatively green growth. However, over the long run, the city should aim for absolutely carbon-neutral growth. Realization of this goal entails foresighted study of when its carbon emissions will peak.

The Expo has shone a light on low-carbon commitments by London, Tokyo, New York, Seoul, Singapore and Hong Kong. Their experiences have something in common - formulation of a holistic and long-term low-carbon strategy.

By contrast, many Chinese cities' understanding of low-carbon growth is synonymous with churning out more environment-friendly goods and projects. They still fall short of drawing a blueprint for green growth. Besides, these goods and projects can do little to limit fossil fuel consumption and carbon emissions.

Shanghai's odds of turning itself into a green city rely on its ability to assign emission quotas to initiate socioeconomic transition.

Clean energies including solar, wind, biological, hydro and nuclear power were hyped at the Expo as substitutes for coal, oil and natural gas. But since these carbon-based energies are likely to stay as a primary choice for a long time to come, Shanghai needs to make more efficient use of them, especially in industry, transport and construction, rather than becoming obsessed with new energies.

Meanwhile, massive tree-planting campaigns are also required to expand greenery to trap and store carbon.

Many urban best practices on display at the Expo suggest that low-carbon plans are shaped by local preferences. They fall into roughly three categories. Take New York, London and Tokyo, the first-tier metropolises. They are committed to having less carbon-intensive construction; for Hong Kong, in the second-tier, the focus is on cutting carbon generated by public transport; the other cities target industrial emissions.

Under the low-carbon model, Shanghai, with two thirds of its total carbon emissions coming from industry, needs to mandate zero-increase in industrial carbon consumption in the next 10 years.

Meanwhile, engineering know-how such as heat insulation through thicker walls, external sun shade and better ventilation design were underscored at the Expo.

Chinese cities' focus on tapping into advanced clean technologies has largely sidelined mature means of slashing carbon footprints. Shanghai should invest more in employing homegrown low-carbon wisdom, as the single-minded pursuit of costly alternative energies will delay the city's low-carbon moment.