For many, relief is in sight. Because of the combination of population growth, rising incomes, falling equipment prices and urbanisation, the number of air-conditioning units installed globally is set to jump from about 1.6 billion today to 5.6 billion by the middle of the century, according to the International Energy Agency.

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That's encouraging news for US manufacturers of cooling systems such as Carrier (United Technologies Corp), Ingersoll-Rand and Johnson Controls International.

And because much of this growth will happen in Asia, Chinese companies such as Gree Electric Appliances, Qingdao Haier, Midea Group and Japan's Daikin Industries Ltd should be big beneficiaries.

There's just one glaring problem: What will all this extra demand for electricity do to the climate?

Vicious cycle

Carbon dioxide emissions rose another 2 per cent in 2018, the fastest pace in seven years. That increase was alarming in its own right, given what we know about the unfolding climate emergency.

But the proximate cause was especially troubling: Extreme weather led to more demand for air conditioning and heating in 2018, BP explained in its annual review of energy sector.

It's not too hard to imagine a vicious cycle in which more hot weather begets ever more demand for air conditioning and thus even more need for power. That in turn means more emissions and even hotter temperatures.

That negative feedback loop exists at a local level too. Air-conditioning units funnel heat outside, exacerbating the so-called "urban heat island" effect, which makes cities warmer than the countryside.

BNEF expects electricity demand from residential and commercial air conditioning to increase by more than 140 per cent by 2050 – an increase that's comparable to adding the European Union's entire electricity consumption. Air conditioning will represent 12.7 per cent of electricity demand by the middle of the century, compared to almost 9 per cent now, it thinks.

Thankfully, much of that extra demand will be met by solar power (the need for cooling is highest during daylight hours). But because temperatures don't always return to comfortable levels when the sun goes down, there's a danger some will be supplied by fossil power.

'Passivhaus' and LED revolution

Buildings have long been a blind spot in climate discussions even though they account for about one-fifth of global energy consumption. The inefficiency of air-conditioning systems or badly designed homes and offices simply aren't as eye-catching as electric cars and making people feel ashamed about flying.

At least Germany's "passivhaus" movement, a way of building homes that require very little heating or cooling, voluntary standard for energy efficiency in buildings, shows some people are starting to recognise the danger.

There are lessons to be learned from the world of lighting too. The LED revolution was spurred by innovation but also by better energy efficiency labelling on products and the phasing out of out-of-date technology. Something similar needs to happen with air conditioning.

There was a big step forward in January when the Kigali Amendment to the Montreal Protocol came into force. Though not well known, its aim is to phase out the use of potent greenhouse gases called hydrofluorocarbons, which are used widely in air conditioning systems. Unless substituted, these alone could cause 0.4C of additional warming by the end of the century.

Yet true to form, President Donald Trump's administration hasn't yet submitted Kigali to the Senate for ratification, even though American manufacturers would benefit from demand for the new technologies that it would spawn.

Trump knows all about the importance of good air con. He spends much of his time at his Palm Beach country club, a place that couldn't exist without it.

So he'd do well to remember this: You can air condition the clubhouse but not the golf course. And it's starting to get awfully hot outside.

Chris Bryant is a Bloomberg Opinion columnist covering industrial companies. He previously worked for the Financial Times.

Bloomberg