First came science fiction—with brave new worlds, meteors, earthquakes, and rising sea levels causing mass exodus, war, and worse—and there was no reason to react because it was science fiction.
Then came fiction—with well-researched accounts of Climate Wars to come in the not-so-distant future—and there was no reason to react because it was still in the future.
Then came science—with Nature publishing an analysis that shows how climate changes were a factor in a fifth of all civil conflicts between 1950 and 2004—and now there is no place left to hide and deny a link between climate and human suffering to the point of flat-out war.
Annual Conflict Risk increases in countries connected to El Niño, not in those unconnected. (Source: Hsiang, S. M., Meng, K. C. & Cane, M. A. Nature 476, 438–441 (2011).)