In Singapore, close to the Equator, temperatures regularly rise above 32 degrees Celsius (90 Fahrenheit) — but inside the soaring glass greenhouses of Gardens by the Bay, the country’s award-winning botanical park, it’s a pleasant 24 degrees.

The daffodils and tulips of the flower dome, along with two dozen nearby towers that are normally full of bankers, shoppers, residents, hotel guests and gamblers, are chilled by what is probably the world’s largest underground district cooling system. It’s a giant air conditioner that is attempting to solve one of the biggest problems of global warming: How to stay cool.

"As the world gets warmer, air conditioning and refrigeration are in greater need, using up energy and emitting greenhouse gases, which in turn worsens global warming,” said Vinod Thomas, visiting professor at the Lee Kuan Yew School of Public Policy in Singapore. "This is the feedback loop we urgently need to break.”