Hotting up
New research suggests we may have already passed important climate tipping points
The world may have already passed several key climate “tipping points” and be in the process of passing others, according to a paper published in the journal Nature. The growing threat of these “abrupt and irreversible changes” to the climate must compel political and economic action on emissions, argue the researchers behind the report.
“If damaging tipping cascades can occur and a global tipping point cannot be ruled out, then this is an existential threat to civilisation,” the paper says. "No amount of economic cost-benefit analysis is going to help us.”
In just one of nine examples given by the paper, models suggest that the Greenland ice sheet, which is now melting at an accelerating rate, could pass a tipping point threshold at 1.5°C of warming – just half a degree above the 1°C of warming the world has already experienced.
“At some point the ice sheet’s current state becomes unstable and passes a tipping point, as it does so the system
starts transitioning irreversibly into the other state,” explains Prof Tim Lenton, the report’s lead author and director of the Global Systems Institute at the University of Exeter.
This alone could result in a sea level rise of seven metres, the paper says, while additional melting in the Antarctic ice sheet could increase this to 10 metres. Estimates of how fast this melting would happen range from thousands to tens of thousands of years, depending on how much temperatures rise above the 1.5°C threshold, the paper adds.
Another potential tipping point is the Amazon, which could reach a critical point where deforestation leads to an increased fire risk and climate feedback, according to the paper. This in turn would lead to yet more deforestation in a downward spiral.
Researchers have been discussing these potential climate
“We’re running serious risks with climate change and these systems in particular”
tipping points for at least two decades, however it was initially thought they would only be breached with a global average temperature rise of 5°C or above. But more recent research suggests the tipping points could be exceeded with just 1-2°C of warming, according to the paper. This realisation “requires an emergency response,” its authors state.
Lenton also says evidence is appearing of interactions between tipping points, which could lead them to trigger one another. “You put this evidence together in a sort of risk assessment framework and it becomes clear that we’re running serious risks with climate change and these particular systems,” he adds.