How do scientists know that the human activity is the major force behind climate change?

It is because of Various things that we do, If we did not exist, several animals that went extinct because of us, would have thrived, If it wasn't for us filling the sky with so much CO2's, we wouldn't have the Earth heating up even more. Also, other things that we do such as Urbanization, Desertification, and Deforestation. All of these words will be defined under this text.

Explanation:

Deforestation: When humans cut down too many trees can result in habitat loss/ more CO2's

Desertification: When land used to be a grassland but humans used too much of a resource and turned it into a hot, sandy wasteland.

Urbanization: When you take land and fill it with tons of buildings, homes, and businesses. This can result in over-crowding, and spreading of diseases.

gas

explanation:

smoke is the matter of a gas