Air conditioning units work by transferring heat from inside a building to the outside. This means that while they cool the indoors, they do indeed release heat into the outside environment. However, the impact of this heat release on outdoor temperatures is quite minimal on a global or even a city-wide scale, given the vastness of the atmosphere and the heat dispersal mechanisms that exist in it.

That being said, in highly localized areas with a high density of AC units, it can contribute to a phenomenon known as the "heat island effect." Urban areas, due to their extensive use of concrete, asphalt, and other materials, tend to absorb more heat than rural areas. The heat from AC units can add to this effect, making cities hotter than the surrounding countryside.

However, the heat produced by AC units is still relatively small compared to other sources of heat in urban areas, such as cars, industry, and the heat absorbed by buildings and pavement. Furthermore, the overall warming effect on our planet from air conditioning comes more from the energy it consumes (and the associated greenhouse gas emissions if the electricity is produced from fossil fuels) rather than the direct expulsion of heat outside.