Editing Cloud feedback (section)

=== Challenges ===
It is difficult to detect the reason for a change in the SW and LW radiation due to cloud feedback, because there are a lot of cloud responses which could be the cause for a specific radiation feedback.<ref name="Zelinka-2012" /> Furthermore is it difficult to not count in clear sky effects<ref name="Zelinka-2012" />. There are techniques to decompose the cloud feedbacks in models and their triggers in detail by showing the cloud fraction as a function of cloud-top pressure and the optical depth of the cloud. In the GCM, which are mostly used, the main challenge is the parametrization of clouds, especially in coarse-resolution models. The characteristics of clouds need to be parametrized  in such a way, that the different feedbacks and physical interactions are as correct as possible in order to decrease the uncertainty of the models.<ref name="Zelinka-2012" />

Another challenge when dealing with (high) cloud feedbacks, is that the LW and SW part often cancel each other out, so that only a small total feedback is left.<ref name="Zelinka-2012" /> The positive and negative feedback parts are not neglectable, since they can change independent of one another with rising temperature.<ref name="Zelinka-2012" />