"Can you turn the air con up, please?"
That should be a simple request. Only, what does it mean? Do you want to be cooler, or less cool?
When we say, "Turn the TV up," the message is, "I would like the volume to be louder." But when it comes to our air conditioners, the message is hazy. Does "up" mean the number on the display gets higher, as the volume reader would on a stereo system, from 18 degrees Celsius to 23 degrees, for example?
Mostly, what people want when they say this is for the room to get cooler. This means you would press the "down" button on your AC remote, but the amount of cool air being produced would increase.
Before we all turn on each other, squabbling about whether or not we have been clear in delivering AC instructions, let's take a look at our true adversary here: English, the language that also gives us the words "back", which can mean "in the past" or, when pushing a date back, "further into the future"; and "off", which can mean "to activate" ("the alarm went off …") or "to deactivate" ("… so I turned it off").
The Oxford Dictionary definition of "up" - in the context of machinery - is, "at or to a higher level of intensity, volume, or activity". It's literally impossible to turn the air con "up" without making it cooler.
Perhaps the solution is to shout "MAKE IT COLDER!" every time we get sweaty. While semantics are fun to mull over, they're not worth getting hot and bothered about.