When the electricity went out in northern India this past summer, alarm bells went off among global energy experts. They’re still ringing as one hemisphere eases out of the hot season and the other warms up.

The roots of the blackout -- increasingly prosperous consumers putting more and more demand on an energy sector that couldn’t keep up -- are common to so many economies, it looks like an omen.

Air conditioning is one of the biggest sources of new demand on electricity grids in emerging economies. In the near future, the energy required by the residents of just one Indian city, Mumbai, to cool their indoor air to 70 degrees Fahrenheit (21 degrees Celsius) could be a quarter of that used by all Americans, a recent study estimated.

In China and India, annual sales of AC units are growing at a 20 percent clip. As it happens, many of the world’s booming cities -- Istanbul, New Delhi, Rio de Janeiro, Shanghai -- are also hot much of the year.

Barring a change in the way our air conditioners work, their increasing use not only will require huge expansions of the energy supply but also will take a direct toll on the environment. That’s because of provisions in the 1987 Montreal Protocol. This international climate accord put the ozone layer on a path to recovery and for a time reduced global warming.

An unintended consequence of its success, however, is now heating things up. The agreement phased out the use of ozone-depleting and climate-warming chlorofluorocarbons, which had been used as coolants in air conditioners, in favor of less harmful hydrochlorofluorocarbons. Wealthy countries have moved on from using hydrochlorofluorocarbons to using hydrofluorocarbons, which pose no danger to the ozone layer but have 1,600 times the effect on global warming that carbon dioxide has.

Already, atmospheric observations show that harmful HFC emissions are increasing at a rate of 10 percent to 15 percent a year, compared with 4 percent for carbon dioxide. It’s about to get worse. Next year, under the Montreal Protocol, developing countries, too, must start phasing out HCFCs, which means they will start using mostly climate-warming HFCs in their air conditioners.

An amendment to the Montreal agreement -- similar versions of which have been proposed by the Federated States of Micronesia and a group composed of the U.S., Canada and Mexico -- would address both the energy-supply and environmental challenges posed by burgeoning air conditioner use. The idea is to bring HFCs within the Montreal accord, then phase out at least the most harmful types in stages, first in wealthier countries and then in poorer ones.

Already, a quarter of new industrial air-conditioning systems employ alternatives to HFCs such as ammonia, hydrocarbons and carbon dioxide. These technologies are nascent in home and vehicle air conditioning, and require additional innovation. They present an opportunity for energy savings as well as environmental benefits. Precedent suggests that when designers are invited to retool a product, they implement saved-up ideas that achieve improvements on multiple fronts. When manufacturers re-engineered appliances to eliminate the use of CFCs, they realized energy savings of 30 percent.

By tradition, the Montreal Protocol has been modified only by consensus, which has been interpreted to mean an absence of any strong opposition among the 197 member states. China and India have used this custom to block formal negotiations on the amendment to phase out HFCs, which will come up again at a meeting in November. Both countries’ AC manufacturers worry that moving rapidly to a new generation of appliances could reduce their market share. The protocol’s multilateral fund, however, pays developing countries the full cost of switching to a new coolant, including the expense of technology transfers.

In any case, the Chinese and Indian governments have larger interests at stake. Climate change, a global matter, might not be their immediate concern. Whether power grids can consistently fuel the air conditioners that ever-more-prosperous citizens demand, however, has direct national and political implications. Phasing out HFCs would not only help keep the planet cool, it could keep the power on, too.

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Today’s highlights: the editors on why GM must remain Government Motors awhile longer and on why Europe must get its banking union back on track; Betsey Stevenson and Justin Wolfers on Mitt Romney and taxes; William D. Cohan on JPMorgan’s missing $6 billion; Albert R. Hunt on the best way to handle Iran; Jeff Rubin on the end of growth; Luigi Zingales on why Romney would have done better than Obama.

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