1. What are the roles of atmospheric carbon dioxide?a) CO2 for photosynthesis (光合作用)b) CO2 is the most criticized greenhouse gas (温室气体)2. What are the roles of water vapor in the atmosphere? (书9.5 课件)答：Green house gases.Air with a given relative humidity can undergo any of several processes to reach the saturation point at which water vapor condenses in the form of rain or snow. Water vapor condenses (rain) as the air cools with the increasing altitude Provide nucleation bodies
