One of the most pressing questions facing climate scientists, and the world at large, is whether human-caused global warming could trigger changes in the climate system that will radically reshape the Earth as we know it. The evidence is mounting that these vast changes are not only possible, but increasingly likely as the Earth warms. But how close the world is to crossing these so-called “tipping points” is a matter of vigorous scientific debate.
The phrase “tipping point” was first coined by sociologist Morton Grodzins to describe segregation and white flight in the 1950s. It was later popularized in the early aughts by Malcolm Gladwell, who published a blockbuster popular science book called The Tipping Point, which looked at sudden social shifts through an epidemiological lens—how ideas spread like viruses. It wasn’t until 2008 that the metaphor formally entered climate science, when Tim Lenton and his colleagues published the paper “Tipping elements in the Earth’s climate system” in The Proceedings of the National Academy of Sciences.
The idea that there could be sudden and irreversible changes within the Earth’s climate system was not new. In the mid-20th century, scientists studying ice and sediment cores found evidence of abrupt warming and cooling periods in the Earth’s geologic history and inferred that abrupt climatic shifts could happen again. In past reports by the Intergovernmental Panel on Climate Change, these were called “climate surprises,” or the more cumbersome “large-scale discontinuities in the climate system.” But the tipping point metaphor caught on in a way these other phrases didn’t.
Jessica S. McKenzie 