Final answer:
Four human activities that increase atmospheric CO2 levels are burning fossil fuels, deforestation, industrial processes, and agricultural practices. These activities contribute to the greenhouse effect and global warming.
Step-by-step explanation:
Human activities that lead to an increase in carbon dioxide (CO2) in the atmosphere include:
- Burning fossil fuels: This activity releases significant amounts of CO2 and has been a major contributor to atmospheric CO2 levels since the Industrial Revolution.
- Deforestation: Cutting down forests reduces the number of trees that absorb CO2 through photosynthesis. The burning of trees also releases stored carbon back into the atmosphere.
- Industrial processes: Cement production and other industrial activities release CO2 as a byproduct.
- Agricultural practices: Animal husbandry and the use of land for farming can result in increased CO2 levels in the atmosphere due to respiration, methane production from livestock, and the use of fossil fuels in agricultural machinery.
All these human-induced actions exacerbate the greenhouse effect and contribute to global warming by increasing the concentration of CO2, a potent greenhouse gas, in the atmosphere.