OK, some quick points.this is just water surface temperature of the earth. Since light from the Sun only hits the surface and the Earth radiates from the surface, this ignores interaction with the very hot molten core.
Also, this actual Average global temperature (13.9 C) — 27.1 °C difference. Because the earth is not bare rock. Instead, it has a wonderful atmosphere that protects us from living if the world was actually that cold.
What would the Earth be like at that temperature? There are already colder places on Earth, many of which can drop below -90°C in Antarctica. Only a few scientists live on bases in Antarctica, but there are others in Yukon, Alaska. So based on temperature alone, we shouldn’t assume that colder Earths are uninhabitable for humans and other organisms, although most of them would probably be densely populated. towards the warmer parts of the earth. (Recall that minus 13.2 degrees Celsius is the average, so the poles will be colder than the equator, just like the earth today. Both the south and north poles will be much colder than they are today. .)
Also, the average minus 13.2 degrees Celsius means that most of the earth is below freezing point (0 degrees Celsius), so much of the water will turn into ice. Still, depending on the atmospheric pressure, there could be liquid water at slightly higher than average locations.
Surprisingly, you still need a refrigerator to store your food and drinks. However, rather than keeping things cold, this refrigerator insulates them from the outside temperature to prevent them from freezing.
Earth would still be warmer than Mars, which has an average temperature of about minus 63 degrees Celsius. The atmosphere is very thin and contains very little oxygen. Without an atmosphere, Earth would also have had this problem. Life forms here would have to evolve without the need for oxygen, and visitors like humans would need some sort of spacesuit for protection and breathing.
Luckily for us Earthlings, we actually have an atmosphere. Mostly nitrogen, but also rich in oxygen, 0.04% carbon dioxide (by volume). Carbon dioxide, along with water vapor, absorbs the infrared radiation emitted by the Earth’s surface and keeps things at a temperature we can handle.
But carbon dioxide is a growing problem. Too much means the atmosphere will get even hotter, leading to all the potential problems of climate change, including catastrophic melting of glaciers, rising sea levels and extreme weather events. This is why the Paris Agreement is the international goal of keeping warming at 1.5°C above pre-industrial levels. The bad news is that the past nine years have been the hottest on record. As temperatures continue to rise, the Earth will no longer be perfect for humans, or for many other life forms on Earth.
