Subtitles section Play video Print subtitles This research really got started with people thinking about, are there tipping points - places where you push a system and push a system and push a system and then it breaks - in our climate, our ecosystems and even our planet's chemistry. And surprisingly, or maybe sadly, we're finding that it's true in all of those situations, that there are kind of thresholds that we shouldn't cross. One particularly frightening example is what could happen in the oceans. Part of the greenhouse gas emissions, carbon dioxide, we put in the air, of course, causes global warming, but a little bit of that carbon dioxide actually dissolves in the oceans, making them more acidic - so-called ocean acidification. Well, if oceans' pH, how acidic they get, if they go lower and lower and lower, at a certain threshold, coral reefs can't survive anymore. You can't make coral reefs and a whole bunch of life in the oceans could just kind of disappear. So that's a really important tipping point in the oceans. We can't let the oceans get more acidic than about here, or we'll have some serious problems. Imagine you're driving at night over a mesa in a jeep and you don't have a map and you don't have any headlights. That's essentially what we're doing. We're driving at full speed all over there. We know there are some cliffs out there, but we're not too worried about where they are right now. Well, you could argue that, already, one of our tires is off the edge. Do we want to keep driving or do we want to start to have a map? Maybe we should turn the lights on and see where we're going. This paper is really the first attempt to kind of draw that map of where is it safe for humanity to operate? Where can we take our environment without going off the edge of the cliff and causing us to have a different planet than we've ever seen in all of human history. Why we should care about this is because it's a disruption from everything we've ever known as a civilization. Our entire history for 10,000 years has been in one kind of climate, one with certain kinds of climate and weather patterns, with certain kinds of ecosystems, with certain ways rivers work, and so on. If that fundamentally unravels within the next generation, everything that we've done - how we build our cities, where we build our cities, where and how we farm, how we get our water, where we put our waste, how we get our raw materials - that could all change. We're talking trillions and trillions of dollars of economic disruption, let alone what it does to safety, hazards, national security and so on. This isn't just about hugging trees and hoping they stay here. This is about keeping the planet we know intact for future generations.