Calcutta spews about 9.3 million tonnes equivalent of carbon dioxide emissions into the atmosphere each year through energy used by homes, offices, industries, streetlights, transportation, and water pumping stations, the analysis has shown.

The International Council for Local Environmental Initiatives, South Asia, the non-governmment agency that carried out the analysis in collaboration with municipal authorities in each city, does not have comparable figures for Delhi and Mumbai yet. In the absence of data from these two metros, Visakhapatnam and Ahmedabad have emerged the second and third highest emitters.

“We’re seeing expected patterns of emissions — no surprises yet. But we’re hoping such hard data will spur local governments into action to limit the growth of emissions,” Emani Kumar, executive director of the council, said.

The study, funded by the British high commission’s strategic programme fund, is intended to get municipal authorities to begin thinking of short and long-term measures to improve energy efficiency, Kumar said.

Short-term options include retrofitting of streetlights with intensity regulators and timers and improving energy efficiency of water pumping stations. In the long term, cities could invest in alternative public transport options, he said.

Local authorities, he said, could also launch community awareness campaigns to conserve energy.

Climate change experts have long argued for significant improvements in India’s public transport systems and policy steps to draw people away from private transport.

Such lifestyle changes, experts say, will contribute to limiting the future growth of emissions. “We need clear actions from governments for the creation of infrastructure that encourages (the use of) public transport,” said Rajendra Pachauri, the chair of the Intergovernmental Panel on Climate Change, a UN body that is assessing scientific studies on patterns and impacts of climate change worldwide.

Council officials say any action to limit emissions growth will help local governments and individuals save money. “This is an incentive to drive actions,” an official said.

The study’s findings have been shared with the environment ministry and the Bureau of Energy Efficiency.

The differences in per capita emissions that show up in the study, in some cases, appear to mirror local energy and transport infrastructure.

Jamshedpur, for instance, has the highest per capita (2.76 tonnes of carbon dioxide) emission among the 25 cities. “But this merely reflects the city’s high concentration of industries — it’s not because the people of Jamshedpur use up more energy,” Kumar said.

However, Gurgaon’s high per capita emission of 2.1 tonnes is possibly because of the widespread use of diesel generators, the virtual absence of public transport and the large number of malls, he said.

The project will cover 40 cities across India and 12 others in the South Asia region. Project officials said a key limitation of the study is that it has examined energy consumption exclusively within municipal limits.

Such a study design will leave out all energy use outside city limits. But, project officials say, such an exercise could be a step towards the energy ranking of cities that may reveal energy efficiency differences. “Calcutta, for instance, appears to spend a lot less energy in pumping water to its inhabitants than the energy used for this by Bangalore,” Kumar said.

Some cities such as Coimbatore, Nagpur, Thane, and Vijayawada, have already begun to use the data to initiate corrective actions involving streetlights to reduce emissions, said Ravi Ranjan Guru, a senior project officer with the council.