This work examines the students´ thoughts on climate change with a focus on carbondioxid through photosynthesis and the carbon emissions from cars. The study is based on two subject areas, one with a focus on enhanced greenhouse effect, and the other focusing on photosythesis. The survey was conducted by means of qualitative interviews with students in grades four and six. The results describe that student´s understanding for photosynthesis and the carbondioxids function for photosynthesis doesn´t change significantly from grade four to grade six. I have divided the students inte three levels based on their understandingof the various fields, and their use of adequate concepts. The study gives an understanding of how students perceive the different areas of research. The results show a marginal difference between the students and their explanations in the two grades.