According to the Union of Concerned Scientists, "Air pollution occurs when the air contains gases, dust, smoke from fires, or fumes in harmful amounts. Tiny atmospheric particles - aerosols - are a subset of air pollution that are suspended in our atmosphere." 

"The stockpiling of greenhouse gases [a by-product of pollution] in the atmosphere over the years changes how our climate system acts and reacts — rain patterns change, ocean currents alter, heat and droughts intensify. Most of the worst greenhouse gases emitted are not visible."  

The United Nations defines climate change as, "long-term shifts in temperatures and weather patterns. These shifts may be natural, such as through variations in the solar cycle. But since the 1800s, human activities have been the main driver of climate change, primarily due to burning fossil fuels like coal, oil, and gas. Burning fossil fuels generates greenhouse gas emissions that act like a blanket wrapped around the Earth, trapping the sun’s heat and raising temperatures."