Original sentence: Carbon also exists in various forms in the atmosphere.Carbon dioxide (CO2) is partly responsible for the greenhouse effect and is the most important human-contributed greenhouse gas.Changes in the amount of atmospheric CO2 are considerably altering weather patterns and indirectly influencing oceanic chemistry.In the past two centuries, human activities have seriously altered the global carbon cycle, most significantly in the atmosphere
Edited sentence: Carbon exists in various forms in the atmosphere and gaseous Carbon dioxide (CO2) is partly responsible for the greenhouse effect after water vapour.Changes in the amount of atmospheric CO2 may have altered weather patterns and influenced oceanic chemistry.In the past two centuries, human activities may have altered the global carbon cycle, most significantly in the atmosphere.It is the most important anthropogenic greenhouse gas