Final answer:
Carbon dioxide (CO2) and sulfur dioxide (SO2) are two harmful gases emitted from volcanoes that contribute to greenhouse warming and acid precipitation, and can influence climate change.
Step-by-step explanation:
The two gases emitted from volcanoes that are harmful to the environment are carbon dioxide (CO2) and sulfur dioxide (SO2). Carbon dioxide is a significant greenhouse gas, which contributes to the warming of the Earth's atmosphere by trapping heat. Sulfur dioxide can react in the atmosphere to form aerosols, which result in haze-effect cooling, a phenomenon that blocks sunlight and lowers global temperatures. While haze-effect cooling can lead to short-term climate changes, sulfur dioxide also contributes to acid rain, which can damage ecosystems and man-made structures. Volcanic eruptions can emit sizable quantities of these gases, affecting the climate and the environment both locally and globally.