Sydney: urban expansion or the Southerly Change? Your choice.

I’ve actually had this conversation a few times with my father, but wandering about in New York today reminded me of it. Specifically, places like PC Richards around the corner are still packed to the rafters with well-selling air-conditioners, but on days like today (bright, humidity increasing) restaurants run their air-conditioners with doors and windows open. Why? No idea. Sometimes it’s because the air-conditioning is set too high, but it can also be because patrons want (or owners think patrons want) fresh air, the sound of the street, who knows. It’s bloody idiotic, though. Would you turn your refrigerator up to maximum and then leave the door ajar? Of course not. And yet…

Air-conditioning isn’t the sole cause of the dying-out of the Southerly Change, but it’s a big one and it has other consequences, so the focus is on that.

First, background: the second law of thermodynamics states that, first, heat will not flow from a colder area to a hotter area, without energy used to make it so (heat would move from the hotter area to the colder area). So the second you get your house cooler than outside, you need to work to keep it that way, let alone make it colder still (e.g. you want 20 degrees indoors while it’s 35 degrees outdoors means more energy than keeping it 34 degrees, which still requires energy). Thus the air-conditioner, a cooling engine that must use energy to force this flow. In the process, it will generate heat of its own. So we have two things happening: the movement of heat from indoors to outdoors, and the generation of heat by the engine affecting that movement (through the creation of cold area using chemical reactions)

It is also the so-called entropy law, which says that entropy (chaos, disorder) will increase or remain the same. ‘Things’, naturally, do not order themselves when you leave them alone (weeded your garden, lately?). Putting an environment in order (i.e. stable cool air in a house) generates disorder (in this case more heat, outside).

That’s the physics, more or less, of how air-conditioners make urban enrvironments hotter – and this is irrespective of energy use/efficiency itself, which is a small part of this discussion. So by making your house cooler, you’re making the city you’re in hotter, exacerbating the need for you to make your house cooler. You’re currently shooting yourself in the foot with a Freon Gun. Soon you’ll be shooting yourself in the head.

Second. Sydney has a recurring phenomenon called the Southerly Change. This occurs during the Summer when winds shift from being hot Westerly and Nor’Westerly winds (which come from the desert, as you can see below):

Australia satellite mpa

And come instead from the South-Southeast, off the ocean (Sydney is on the East coast, towards the bottom. Green is arable/habitable land, brown/orange is …not. See why our population is so low?). For those of you meteorologically inclined, here’s an example progression:

Australia southerly map

That’s the southerly just off the map on the lower right.

Sydneysiders hang out for this. With days on end above 40 degrees Celsius, humidity and UV ratings through the roof, you bake in the Summer, and the Southerly is your respite. Even firefighters will bet their success on one. More importantly, though, the Southerly turns heating of Sydney into cooling of Sydney. Cool winds blow over water and concrete, highways, train lines, skyscrapers, and allow the city to cool down overnight. Here’s where urban expansion and air-conditioning come in.

I’m talking about the combined effects of several things:

  • Air-conditioner ‘deepening’ has gone from 49% to 64% of households in Sydney
  • More concrete (buildings, motorways, driveways, patios, you name it
  • Fewer waterways (less surface area, less wetlands)
  • Less natural vegetation (see point 2)

These mean more heat comes off Sydney than ever before. From that 2nd law of thermodynamics, heat doesn’t move from cold areas to hot areas. So as the Southerly Change approaches Sydney, it is a cold front that meets a hotter and hotter front. On normal days, it will divert, probably back East to the Ocean. Meaning

  1. Sydney gets no Southerly Change
  2. Sydney doesn’t cool down overnight, the way it should
  3. Sydney starts each day hotter, as Sydney, like Tokyo and Singapore, comes to resemble an oven
  4. People use their air-conditioners more, at higher settings, longer, earlier in the day, you name it
  5. FOR I = 1 TO 4
    loop body
    NEXT I

This was – more or less – the conversation I had with my father, while I sat in my office in York and he stood on his front verandah waiting for an ever-later-to-arrive Southerly breeze to come through.


The environmental consequences of this are plain enough. Sydney can’t cool down in Summer, Sydney dies (and Sydneysiders, too). On non-ordinary days, that diversion isn’t as benign as I make it sound, and Sydney has it’s ass handed to it by storms, which are getting worse.

The economic consequences are also significant, and bleed into the environmental, somewhat. Electricity supply needs to be able to meet the highest demand. So for Sydney, that means the middle of Summer when everyone has their air-conditioning on. And it needs to be able to accommodate spikes, like Sydney in the middle of Summer at 6pm when the air-conditioners all go on. Or something. We’re talking about ever larger infrastructure for Sydney to meet the energy use requirements of itself. This energy requirement is projected to grow by 20%, and the ecological footprint of Sydney grows with it (Australia is 3rd after the US and Canada in ecological footprint terms). This all means the price of energy has to go up.

At the moment our government(s) keep trying to absorb it – bigger plants, new plants, talk of nuclear power plants – which only encourages us. We’re using resources, one way or another, that could go towards other things, and we use more of those resources, the price to do so has to go up. And use those resources we will. As we use more air-conditioners, which are very energy-intensive. Which we will, because Sydney, like the entire South-East of the Continent, and like the rest of the Continent, is getting hotter and more dry, hence hotter still. Our government(s) try – and will continue to try – to change the efficiency standards, which is fine – but we’re talking about units that last a bloody long time, so the bulk of air-conditioning will never meet those standards. To give you some perspective:

Almost one kilowatt-hour of electricity out of every five consumed in the United States in a full year goes to cooling buildings. Much of the nation’s excess power-generating capacity, which sits idle until needed to satisfy quick spikes in demand, has had to be built because of air-conditioning.

The electricity used annually to air-condition America’s homes, stores, offices, factories, schools, churches, libraries, domed stadiums, hospitals, warehouses, prisons and other buildings (not including what’s used to cool manufacturing processes and military facilities) exceeds the entire electricity consumption of the world’s second and fourth most populous nations – India and Indonesia – combined.

We’re not likely to get that bad – there’s only 21 million of us, not 300 million, but you get an idea. At a time when we’re already at the limit of Sydney’s ability to provide power, further expansion, or increasing urban density, will not help.

This also, by the by, ignores completely the other environmental consequence: the carbon load of air-conditioners and the electricity generated for those air-conditioners. Some other time, maybe. I’m more worried about Sydney losing the Southerly Change more or less permanently, the consequences of which are far more immediate.


No comments yet

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s

%d bloggers like this: