The Hackernews news guidelines define appropriate content as "anything that gratifies one's intellectual curiosity." [1] It's a personal measure, to be sure, but count me as one curious data point that finds considering major ecological changes in the world intellectually gratifying.
There's thousands of humanitarian discussions that we could discuss - human trafficking, politics, wars, global warming etc. Speaking for myself, it's not that I don't want to discuss these issues - it's just that I come to HN for tech-specific topics. I don't think the community should be judged as having no compassion or care of the environment just because they want to keep the HN topics focused on tech.
But regardless, the story made it to the front page so obviously enough people felt it was relevant.
May be one should put it different: If connection lines get interrupted by tornadoes, storms, what ever, would this topic then qualify your subjective criteria? Or even more to the point, would you support a HTTP error code 456 indicating service interrupted by climate change?
[1] http://ycombinator.com/newsguidelines.html