Knowledge is a key variable in science communication, especially in terms of the knowledge deficit model or the Public Understanding of Science approach. According to this, it is assumed that the lay public's knowledge of science topics needs to be increased through science communication (especially via the media) in order to strengthen positive attitudes toward science and its topics. However, previous studies have mainly revealed only small correlations between media use, knowledge and attitudes. One of the reasons for this might be methodological deficits, since the question what knowledge about science topics actually is has hardly been discussed so far. Therefore, this research project focuses on the following aspects: how knowledge about topics such as climate change should be theoretically conceptualized, which dimensions exist, and how knowledge can be operationalized within survey studies.