12. A non-transitory computer-readable storage medium storing instructions configured to, when executed by a computing system, cause the computing system to perform operations for identifying comparatively trending topics, the operations comprising: receiving, as post parameters, one or more parameters that distinguish social media postings; obtaining, over a network and based on the received post parameters, at least two groups of posts; generating, for each selected group of posts of the at least two groups of posts, a corresponding ranked list of topics by: identifying topics from the selected group of posts wherein each identified topic comprises one or more words; and computing a rank score for each of the identified topics; associating, with an individual topic from a selected one of the corresponding ranked lists, a difference score computed as a difference between: the rank score for the individual topic from the selected one of the corresponding ranked lists, and a rank score for the individual topic computed from one or more of the ranked lists other than the selected one of the corresponding ranked lists; comparing the difference score to a specified threshold; in response to determining that the difference score is above the specified threshold, identifying the individual topic as a comparatively trending topic.
14. The non-transitory computer-readable storage medium of claim 12 wherein receiving post parameters comprises: receiving a first subset of the post parameters with corresponding parameter types; receiving an alternate parameter with a specified type matching one of the corresponding parameter types; and creating a second subset of the post parameters with of the parameters of the first subset except for the parameter of the first subset with the type matching the specified type replaced by the alternate parameter; and wherein obtaining, based on the received post parameters, at least two groups of posts is performed by: selecting a first of the at least two groups of posts using the first subset of the post parameters; and selecting a second of the at least two groups of posts using the second subset of the post parameters.