This is maybe the first time humanity has decided, together, to save us from ourselves. It's not a big enough deal, but it'll pave the way for the big deals in 5 and 10 years. Here's a couple summaries of what the deal means:
http://www.cnn.com/2015/12/12/opinions/sutter-cop21-climate-reaction/
http://grist.org/climate-energy/heres-what-you-need-to-know-about-the-new-paris-climate-agreement/
And here's a link about why you should care. Keep in mind this info is from 2011 and projections have gotten more dire since that time. Also includes a quick, effective video summary.
http://grist.org/climate-change/climate-change-is-simple-we-do-something-or-were-screwed/
Edited by TasteTheRainbow