Toronto has just launched a pioneering project to air-condition downtown office buildings by using ice-cold water from Lake Ontario. It’s a very neat idea, and it works like this: A company called Enwave pumps water from the bottom of the lake into a heat-transfer plant. At the plant, the coldness of the lake water cools down water in adjoining pipes — transferring the chill to Enwave’s system. That coldness is used to cool down the buildings. The lake water is never physically mixed with any other water, to prevent contamination; it is eventually pumped back out to the lake, albeit a bit warmer.

According to the Toronto Star, it’ll save so much energy — and thus reduce so much greenhouse-gas output — that it is the equivalent of taking 8,000 cars off the city’s streets. Enwave’s web site points out:

A permanent layer of icy-cold (4°C) water 83 meters below the surface of Lake Ontario provides naturally cold water. This water is the renewable source of energy that Enwave’s leading-edge technology uses to cool office towers, sports & entertainment complexes and proposed waterfront developments.

But here’s the problem: Just how “renewable” is the coldness of the lake? If the Enwave system were to grow massively, and every city on the shores of Lake Ontario were to set up heat-exchange systems, wouldn’t it eventually start to warm up the lake? That could lead to some pretty wild environmental effects, partly because the warming would be happening not at the surface — where the flora and fauna are more adaptive to fluctuations in heat — but down deep below.

I don’t mean to be alarmist about this. I actually think it’s a really cool idea, and odds are an environmental-impact study would show a net benefit from Enwave systems: i.e. even if they warmed the world’s oceans and lakes, they’d offset global warming in general by reducing greenhouse gases.

But what bothers me is how the language of this project fudges the basic laws of physics. The lake’s coldness isn’t “permanent” at all. It’s a historic and environmental artifact of the evolution of that region of the world’s geography, and it can and will change. When you pump coldness out of that system, you are — by definition — pumping heat back in, and there are no magical elvish air-conditioners sitting at the bottom of Lake Ontario making things colder just, y’know, because. Sure, the warming effect might be non-noticeable, but it’s not non-existent. I’d expect this sort of magical, free-lunch, 2+2=5 crap to come from the dinosaur thinkers in the oil, gas and coal industries, or their political cronies — but not from a genuinely environmental company.

Again, none of this is to detract from the coolness — no pun intended — of Enwave’s technology. I love it! But the public already misunderstands the basic physics of how the world works, and we don’t need more misdirection.