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The air conditioning trap: how cold air is heating the world

On a sweltering Thursday evening in Manhattan last month, people across New York City were preparing for what meteorologists predicted would be the

hottest weekend of the year. Over the past two decades, every record for peak electricity use in the city has occurred during a heatwave, as millions of

people turn on their air conditioning units at the same time. And so, at the midtown headquarters of Con Edison, the company that supplies more than 10

million people in the New York area with electricity, employees were busy turning a conference room on the 19th floor into an emergency command centre.

Inside the conference room, close to 80 engineers and company executives, joined by representatives of the city’s emergency management department,

monitored the status of the city power grid, directed ground crews and watched a set of dials displaying each borough’s electricity use tick upward. “It’s

like the bridge in Star Trek in there,” Anthony Suozzo, a former senior system operator with the company, told me. “You’ve got all hands on deck, they’re

telling Scotty to fix things, the system is running at max capacity.”

Power grids are measured by the amount of electricity that can pass through them at any one time. Con Edison’s grid, with 62 power substations and more

than 130,000 miles of power lines and cables across New York City and Westchester County, can deliver 13,400MW every second. This is roughly equivalent to

18m horsepower.

On a regular day, New York City demands around 10,000MW every second; during a heatwave, that figure can exceed 13,000MW. “Do the math, whatever that

gap is, is the AC,” Michael Clendenin, a company spokesman, told me. The combination of high demand and extreme temperature can cause parts of the system to

overheat and fail, leading to blackouts. In 2006, equipment failure left 175,000 people in Queens without power for a week, during a heatwave that killed 40

people.

This year, by the evening of Sunday 21 July, with temperatures above 36C (97F) and demand at more than 12,000MW every second, Con Edison cut power to

50,000 customers in Brooklyn and Queens for 24 hours, afraid that parts of the nearby grid were close to collapse, which could have left hundreds of

thousands of people without power for days. The state had to send in police to help residents, and Con Edison crews dispensed dry ice for people to cool

their homes.

As the world gets hotter, scenes like these will become increasingly common. Buying a VRF air conditioner is perhaps the most popular individual response to climate change, and air conditioners are almost uniquely power-

hungry appliances: a small unit cooling a single room, on average, consumes more power than running four fridges, while a central unit cooling an average

house uses more power than 15. “Last year in Beijing, during a heatwave, 50% of the power capacity was going to air conditioning,” says John Dulac, an

analyst at the International Energy Agency (IEA). “These are ‘oh shit’ moments.”

There are just over 1bn single-room air conditioning units in the world right now – about one for every seven people on earth. Numerous reports have

projected that by 2050 there are likely to be more than 4.5bn, making them as ubiquitous as the mobile phone is today. The US already uses as much

electricity for air conditioning each year as the UK uses in total. The IEA projects that as the rest of the world reaches similar levels, air conditioning

will use about 13% of all electricity worldwide, and produce 2bn tonnes of CO2 a year – about the same amount as India, the world’s third-largest emitter,

produces today.