With current global warming at about 1.4°C, warm-water reefs are passing their thermal tipping point of about 1.2°C. This means coral reefs on any meaningful scale will be lost unless the global temperature returns towards 1°C warming or below very quickly.
Crashing
In contrast, potential tipping points with slower response times – such as polar ice sheets – may be less sensitive to temporary overshoot.
“Therefore, we need to develop a proper risk assessment for tipping elements,” said study co-lead author Nico Wunderling from PIK and Goethe University Frankfurt. “This paper begins that work, but more is urgently needed.
“It’s concerning that, even with a small and relatively brief overshoot of the 1.5°C target, up to five Earth system tipping points could be triggered.
“Like an individual assessing the risk of a house fire or a plane crashing, we can’t simply plan based on a ‘best guess’ – we need to anticipate the dangerous outcomes and take action to prevent them.”
Critical
The researchers say that “additional human pressures” – such as deforestation in the Amazon or pollution and overfishing of coral reefs – can lower their temperature tipping points.
Norman Steinert, co-lead author from CICERO, concluded: “Minimising the peak of an overshoot is crucial, but arguably minimising the duration is even more important.
“However, it’s important to note that these things are related: the higher the peak temperature, the more difficult it is to reverse temperature below critical levels and the longer it’s likely that we’ll remain in ‘overshoot’.”
The paper, published in a special issue of the journal Environmental Research Letters, is entitled The implications of overshooting 1.5°C on Earth system tipping elements – a review.
This Author
Brendan Montague is a member of the editorial team at The Ecologist.