There is a way... You know how when you go to load a saved game, to left of the selection queue there's a window that shows what civ you used, map settings, etc.? If it's a modded save, in the bottom right hand corner it should say "MODS". Click on that and it will show you what mods were used in the game. Hopefully that made sense.
However, you can't load any new mods into a modded save, nor can you load a modded save if one of its mods are missing from your MODS directory. The exception: mods that have "Affects Saved Games" set to "No". Although, almost no mods actually do that, and the ones that do are mostly graphic mods.