Amidst this summer’s biblical floods, cataclysmic fires and life-threatening heatwaves, people are wondering whether we have reached a climate change tipping point. Climate scientists and ecologists who study critical points say they are only exacerbated by extreme events Global warming, They have been warning about climate change to the point for years. Now people are listening.
Research published last year in Science suggests that the risk of a global tipping point accelerating climate change begins to become significant when worldwide average temperatures rise to 1.5°C above pre-industrial levels, which is likely to occur in the 2030s.
In science, the tipping point refers to the straw that breaks the camel’s back, where a small change in input makes a big difference in outcome.
When climate scientists talk about tipping points, they are looking at changes in feedback loops – disruptions to stabilizing feedback loops and the introduction of new ones that amplify change. Physicists call this a positive feedback loop, but from our point of view it would not be beneficial.
Scientists have documented dozens of regional and local climate change points. Long ago, Earth experienced points of planet-wide fluctuations when the climate changed from an ice-free hot-house to a snowball and back again.
Looking back at its history for an Earth Day column a few years ago, I spoke with scientists who marveled at Earth’s ability to stabilize feedback loops for about 4 billion years. For most of that history there were only bacteria. Abrupt changes in climate feedback cycles shook the planet and, following the arrival of complex life, this led to mass death and extinction.
Another reason to be concerned today: The changes we’re bringing to the planet are “geologically unusual,” as planetary scientist Andy Knoll told me then.
Now, scientists are concerned about regional changes that could lead to global disasters. Timothy Lenton, President Climate change and Earth System Science at the University of Exeter, refers to “tipping elements” – systems of glaciers, forests and coral reefs whose collapse could trigger a form of global warming that feeds on itself. He and his colleagues first identified many of these in a 2008 study, but he said they are now generating much more interest.
He led a recent review of studies that highlighted elements that pose an immediate threat: the destruction of the West Antarctic and Greenland ice sheets, thawing permafrost and the destruction of the world’s coral reefs.
He said the extreme events in the news this summer may represent what he calls flickering – a brief trip to the other side of a critical point. “A complex system can sometimes begin to sample a different regime or state before more permanent changes to that state take place,” he said. “I hope this is not the case.”
Tipping point events have caused local ecological collapse before, said Simon Wilcock, an interdisciplinary researcher at Rothamsted Research in the UK. An example of this is the Sahara Desert, which has cycled from lush to dry, possibly the most recent desert aided by humans. In a paper published in Nature Sustainability, he and his colleagues created complex models of ecosystem collapse using two examples of tipping points in relatively recent history – Chilika Lagoon in India, where fish populations plummeted, and Easter Island, where deforestation and environmental stress led to the extinction of local human populations.
They found that ecological tipping points occurred much faster than in previous models when multiple stressors were taken into account, such as overgrazing, deforestation, Agriculture runoff and overfishing. Natural fluctuations make tipping points more likely. Think of standing on the edge of a cliff, with random gusts pushing you further and further away from the ledge, he said. And consider someone nearby in the still air on a similar rock. “Who will be the first to fall off the cliff?” He asked. “It’s obvious, isn’t it?”
They also worry that the clearing of the Amazon could dry things up and lead to massive fires, which would leave the area drier, kill more trees, spark more fires and release more carbon into the atmosphere. This will make the climate hotter and drier and forest loss will accelerate in a vicious cycle.
Our civilization is fragile, with population centers dependent on agriculture and clean water. Although humanity survived the transition from an ice age to a warmer inter-glacial period, humans have enjoyed a quiet period for the past 12,000 years, as we settled and started farming.
A single point of climate change could make life very difficult for our species. We haven’t reached the top of the cliff yet, but we’re dancing dangerously close to the edge.
Faye Flamm is a Bloomberg Opinion columnist covering science