When we’re talking about social justice, a tipping point is a beautiful thing—a court case that shifts public opinion, for example. For a species, a tipping point can spell doom, as an environmental catastrophe pushes a population to the brink. When it comes to climate change, there isn’t just one tipping point but many that scientists are increasingly pulling into view.
Today in the journal Nature, a group of researchers argues that we’re closer to tipping nine climate demons than previously believed, and that we’re already starting to see some associated effects. “We argue that the intervention time left to prevent tipping could already have shrunk towards zero, whereas the reaction time to achieve net zero emissions is 30 years at best,” they write. “Hence we might already have lost control of whether tipping happens.”
We can still, however, act to lessen the damage. The bet we have to make is clearer than ever, but time is running out. “How are we going to look back in half a century’s time and regret the fact that we’ve built a more sustainable, flourishing future for many more generations to come?” asks lead author Tim Lenton, director of the Global Systems Institute at the University of Exeter. “Instead of just hanging in there with finite reserves of fossil fuels, and sort of embracing the apocalypse.”
The tipping points are grouped into three main categories.
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Ice
Think of a climatic tipping point, like the accelerating melting of Greenland’s ice sheet, as a chair. In its normal, stable state, the ice sheet is intact—a chair standing upright. “If you balance the chair backwards, you can find a sort of tipping point, where a little nudge in one direction or the other can determine whether the chair falls,” says Lenton. On its back is the alternate state, in which Greenland’s ice sheets melt until the system reaches a new equilibrium, and the chair just lies there sadly.
Such a tipping is already underway in both East and West Antarctica, argue Lenton and his colleagues. Here, ice and ocean and bedrock meet at so-called grounding lines. These lines are collapsing, and “it could destabilize the rest of the West Antarctic ice sheet like toppling dominoes,” the researchers write, “leading to about 3 metres of sea-level rise on a timescale of centuries to millennia.”
Land
On land, matters are equally grim. Deforestation in the Amazon leads to a terrifying cascade of ecological consequences: Chopped-up forests dry out along their exposed edges, providing ample fuel for wildfires set intentionally by ranchers clearing land. Thus we simultaneously lose the Amazon as a sequesterer of carbon, and the atmosphere takes on more carbon from the smoke. A tipping point of runaway effects could come once between 20 and 40 percent of the forest cover is lost, the researchers say, as the system switches from wet to dry, more like a savanna.
Up in the Arctic, which is warming twice as fast as the rest of the planet, wildfires are raging like never recorded before. Boreal forests are dying off, potentially tipping from a net carbon sink into a net carbon source. Peatlands, which store massive amounts of carbon in the ground, are drying out and burning, releasing still more CO2. Thawing permafrost is doing the same, only with methane, a far more potent greenhouse gas. More emissions means more warming, as tipping sets in around the world.
Sea
In the oceans, climate change is stressing coral reefs to their limits. When temperatures climb, the corals release the symbiotic algae that help them produce their energy, thus bleaching themselves. Combined with ocean acidification and pollution, an increase of 2 degrees C in the global average temperature could mean the loss of 99 percent of tropical corals.
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