In What is Cli-fi? And Why I Write It in The Guardian author Sarah Golding describes climate fiction as "fiction that foregrounds climate change." Her interest in writing it appears to go beyond using it as a setting, world, or spring board for a plot. She's trying to do something specific with her cli-fi books for young readers. She hopes that her characters' concern for the environment will spread to her readers.
On a related note, you might want to take a look at The Necessary Evolution of Environmental Writing by John Yunker at the Ecolit Books blog. He writes about needing stories "that inspire lasting change and have the power to change our worldview."
So both writers are talking about using environmental fiction in a proactive way, at least, if not one that is actually instructive.