Time to chill out about air conditioning’s carbon footprint
HOW DID the fossil-fuel era begin? With Europeans heating their houses in winter.
The Industrial Revolution would likely never have started if medieval Britain hadn’t turned to coal swept from the beaches of Northumbria to replace firewood from its dwindling forests. One of the world’s first air pollution laws was a 1306 proclamation prohibiting the burning of “sea-coal” in London. We’ve been heating our homes for so long that we take the practice, and its carbon footprint, for granted.
That’s a mistake. With temperatures across the globe breaking record after record in recent weeks, there’s no shortage of alarm about the rising climate impact from the energy we’ll use to cool our homes. People in sweltering developing economies will buy a billion air conditioners by the end of this decade.
Even so, under almost every plausible scenario, the climate in 2050 will be suffering more from heating homes than cooling them. If we want to see an energy transition that addresses human welfare and global inequality, we should be more relaxed about the rise of air conditioning in developing countries, and much more worried about the persistence of conventional heating in rich ones.
The numbers are stark. Globally, heating caused about four times more emissions than cooling last year, according to the International Energy Agency.* Electric heaters alone account for about two-thirds more emissions than every air conditioner on the planet — and that’s the tip of the iceberg, since the majority of domestic heating is done with boilers powered by gas, fuel oil, or coal.
The benefits of this aren’t evenly spread, either. Europe, the former Soviet Union and the Americas, with about a quarter of the world’s population, will account for about 59% of emissions from space heating and cooling in 2025, according to one 2021 study, led by Alessio Mastrucci of Austria’s International Institute for Applied Systems Analysis. Add in China, which has largely hit developed-world standards on this front, and the share rises to 84%.
Why, then, is there so much more concern about the relatively small carbon footprint from cooling?
One factor is that the direction of travel is different. A warmer planet where incomes are climbing fastest in countries close to the equator is one where cooling demand will rise rapidly in the Global South. Meanwhile, milder winters, stagnating population growth, and the spread of insulation and heat pumps should reduce the footprint from heating in the Global North.
Even so, emissions in 2050 from warming homes in Europe, the former Soviet Union, and North America will be greater than the entire world’s cooling footprint, according to Mastrucci’s 2021 study.
There’s good reason for optimism that technology, efficiency, and a warming climate will, indeed, make heating less carbon-intensive over the coming decades — but that’s not happening yet. Over the decade through 2022, it rose by 158 million metric tons of CO2, little less than the 180 million-ton increase in cooling.
It’s true, too, that the rise of air conditioners will pose fresh challenges to the world’s energy systems, quite aside from their climate impact. All those gas and fuel oil boilers mean that home heating doesn’t stress electrical grids the way that AC does.
In Delhi, peak power demand jumped 64% over the decade through 2018, compared to a 42% increase in total electricity consumption, thanks largely to the uptake of air conditioners that often account for half of the city’s energy usage. That peak-and-trough pattern is fiendishly difficult for grid planners to manage, especially as households are more likely to use air-con in the evening and at night, rather than in the middle of the day when solar panels are humming.
The solution to this, however, is not to scold the billions in developing countries who will buy their first cooling units over the coming decade. In many cases, those appliances could literally be life-savers when the temperature rises to levels that strain the limits of survivability. Instead, we should look for ways to give everyone a better standard of living with a lower carbon footprint.
Providing incentives for people to buy the most efficient air conditioners (and fans for periods of less intense heat) would help reduce strains on the grid, emissions, and electricity bills. That could provide a minor boost for fossil fuels, since propane from natural gas might be a more climate-friendly refrigerant than the fluorine compounds that currently predominate.
Building codes should also be introduced, enforced, and tightened. Air conditioners are often just making up for the deficiencies of bad design. Generous shading and floor plans that allow cross-ventilation are the best way to reduce cooling demand in the billions of homes that rapidly urbanizing developing countries will build over the coming decades.
Above all, though, the world should accept that a just energy transition is inevitably going to see poorer countries use more air-con to reach levels of domestic comfort that richer locales take for granted.
Developed nations still struggling to give up their fossil-fired boilers for more efficient heat pumps — let alone turn their thermostats down a degree or two, insulate their roofs and walls, or keep windows closed in the depths of winter — must get their own house in order before they start preaching to the rest of the world.
BLOOMBERG OPINION
* The IEA’s numbers include water heating as well as space heating, but separate data confirms the same picture where space heating’s footprint is vastly greater than that from space cooling.
