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Earth may reach temperature 'tipping point' in two decades, NZ professors find in startling new study

Plants could lose about half of their ability to absorb carbon emissions within two decades if warming continues at the rate it’s at, according to a new study by Kiwi and American researchers. 

Greenhouse emissions (file picture). Source: istock.com

It’s prompted researchers to call for immediate action to tackle climate change, saying they found the results were confronting. 

The study by Waikato University and Northern Arizona University, published in major journal Science Advances, finds combating climate change will become harder unless a significant change occurs. 

The study found photosynthesis — in which plants pull carbon dioxide from the atmosphere — peaked at 18C for a majority of plant ecosystems and declined at temperatures above that.

But respiration — which sees a plant release about half of the carbon dioxide they capture through photosynthesis — continues beyond the 18C mark. 

This could tip the balance of ecosystems to turn into carbon sources, instead of acting as carbon sinks that take in more carbon than they release. 

University of Waikato professor Louis Schipper said the fact that the planet’s ecosystems were taking up some of the carbon dioxide in the atmosphere was “buying us some time”. 

“The data that we've got from this paper suggests that the amount that ecosystems are going to do that service for us is going to decrease. So that buying of time is going to go away, and quite quickly.”

The study used two decades’ worth of data from measurement towers, including one from Paeroa, into every major type of ecosystem on the planet. 

Schipper said he remembered the moments the study concluded and the results had been analysed. 

“I just stared at the graph for, I don't know, 10 minutes, and just expletives run through your head,” Schipper said.

“You hope that you're right because you want to get your science right. 

“But, in some ways, you hope that you're wrong."

He said people were over-relying on ecosystems to offset emissions. 

“We should stop relying on that. We have to do at least two things: we have to plant trees to fix carbon, and we have to fundamentally change how we behave to reduce our emissions."

His colleague, professor Vic Arcus, also from the University of Waikato, said he found the results confronting. 

“When we saw this, I thought, 'I can't drive a car anymore.' So I sold my car and bought an electric bike. That was my response to these data."