If the population is growing quickly in a small area, than the ___must be increasing as well.

Population density.

Explanation:

Population density is a statistical data that allows graphing the number of people living in a given territory, dividing the number of inhabitants of that territory by its size, usually in square kilometers or square miles.

Thus, the more the population increases in a territory, the more its population density will increase. An example of territories with a high population density is Hong Kong, with about 7,000 inhabitants per square kilometer, while an example of a nation with a low population density is Canada, with 4 inhabitants per square kilometer.

it is very hard for the climatologists to precisely predict how will the global temperatures be changing so there's lots of models, some of which differ significantly, this is due to multiple factors, and probably the most important is the human activity.

humans have been a key factor in climate change around the globe since the start of the industrial revolution, and in the past few decades the consequences are becoming more obvious. there's lots of emission of pollutants in the atmosphere as well as changing the environment on the surface itself, so it's really hard to predict how will that go in the future because there's some countries that are reducing the damage and are going towards green energy, while others are stubbornly continuing with pollution and damages to the environment.