“Observations confirmed that 2023-2025 experienced the fourth global coral bleaching event on record, and the second within the past decade,” wrote the authors of the Global Tipping Point report, led by scientists at the University of Exeter. “In this event, coral bleaching affected every ocean basin, with 83.7 per cent of corals experiencing bleaching-level heat stress by April 2025.”
Loading
The scientists wrote that the tipping point had been breached because at 1.5 degrees of warming, waters have already become too hot for warm-water corals to thrive. Other tipping points the world was approaching was the dieback of the Amazon rainforest and the collapse of climate-regulating ocean currents.
A second study published in the journal Nature on Thursday shows that Australia’s tropical rainforests are no longer sucking carbon from the atmosphere but are instead emitting carbon, the chief warming agent in the atmosphere, because more trees are dying due to extreme heat.
Between 1971 and 2000, these forests acted as a sink, absorbing an average of 0.62 tonnes of carbon per hectare per year, the study found. This has dramatically reversed, with the forests now releasing an estimated 0.93 tonnes of carbon per hectare per year between 2010 and 2019. This decline is occurring at a rate of 0.041 tonnes of carbon per hectare per year, a rate greater than observed in the Amazon and African tropics.
“The cause of this decline in carbon sink strength … is the escalation of carbon losses … associated with increasing tree mortality,” says the study. This increased mortality has not been offset by new growth, as biomass gains from stem growth have remained stable or even slightly decreased over time. While there has been an increase in recruitment of new trees, these gains are small compared to the losses from mature tree deaths.”
Signatories to the Paris Agreement will meet next month in Belem, Brazil, for negotiations that will cover how to accelerate the transition from fossil fuels to slow global warming.
Get to the heart of what’s happening with climate change and the environment. Sign up for our fortnightly Environment newsletter.