 According to this article, it's one and a half degrees Celsius. Critical marker as the number... It doesn't matter what you're measuring from, right? I mean, that's the case. They've been using a century as a benchmark for a long time. The problem with that is there was a warming period in the 30s, and they're about to have to run away from that. They're going to have to go to pre-industrial period instead of the last 100 years. Well, they keep revising the 30s temperatures, though.