There are three recent questions that are asking about how things would be different on a fictional "alternate earth" with different parameters:

* https://earthscience.stackexchange.com/questions/7098/altering-the-milankovitch-cycles
* https://earthscience.stackexchange.com/questions/7085/great-lakes-earth-the-americas
* https://earthscience.stackexchange.com/questions/7077/if-the-oceans-were-deeper

It's previously been [established][1] that geoscience questions related to other (real) planets are on topic, but that's a little different to "if earth were different in parameters A and B, how would things X and Y be different".

We've previously discussed ["movie science" questions][2], although I'm not sure whether consensus was reached, but these questions are different - they're reasonable geoscience questions (albeit mostly too broad at the moment) that happen to relate to a fictitious, hypothetical scenario. They would certainly be on topic at [Worldbuilding][3], but that doesn't mean that they don't also belong here.

Should these questions be on-topic at Earth Science? If so, how should they be signposted to make it clear that they do not refer to reality? (a tag? A prefix to the title?)

  [1]: https://earthscience.meta.stackexchange.com/a/7/39
  [2]: https://earthscience.meta.stackexchange.com/questions/343/should-we-discourage-wildly-hypothetical-questions
  [3]: https://worldbuilding.stackexchange.com/