Answer:
Two human activities that increase CO2 levels in the atmosphere are:
1. Burning Fossil Fuels: Using coal, oil, and natural gas for energy releases CO2 into the air, mainly through power generation, transportation, industry, and heating.
2. Deforestation and Land Use Changes: Clearing forests for agriculture or urbanization releases stored CO2 and reduces the Earth's ability to absorb CO2, contributing to climate change.