According to most scientists, climate change is caused by human activities. Obviously, the large number of people in the world today is causing the dramatic increase in emissions and air pollution. There is a direct connection between increased population and increased use of fossil fuels for energy use after the industrial revolution.
The population of the World is responsible for climate change. This is not to say they are the only ones responsible but they do have a large effect. More people is more gases produced and more pollution being produced in the atmosphere. More people causes more problems in the long run.