Global warming driven by fossil fuel emissions is speeding up, and several of the planet's most important ecosystems are close to tipping points, according to Johan Rockstrom, director of the Potsdam Institute for Climate Impact Research.
Speaking at the Reuters Sustainability Europe conference on Tuesday, Rockstrom said damage to coral reefs and the Amazon rainforest is nearing the point where it cannot be reversed.
Coral, Amazon and the Atlantic current
Coral reefs bleach when water stays too warm for too long. Past a threshold, the algae that feed the coral do not return, and the reef structure erodes. The Amazon depends on its own rainfall, which large-scale forest loss can weaken.
Rockstrom also said parts of the Atlantic circulation system are close to collapse, including the current that carries warm water from the Caribbean and moderates Western Europe's climate. A shutdown would not happen overnight, but its effects on weather, sea level and agriculture would be long-lasting.
The 1.5C overshoot
The latest science puts the world on course to pass 1.5C of average surface warming within the next few years. That does not mean the target is meaningless, but it does mean governments and companies are now planning for a period above it, with more frequent and more intense extreme weather.
Rockstrom spoke ahead of COP31, the United Nations climate talks that start on November 9. The agenda is likely to be shaped by the gap between pledges and outcomes, and by the question of how countries pay for losses and damages already occurring.
What companies are being told
His advice to businesses was to treat climate and nature as one agenda rather than two. Firms should keep decarbonising, he said, and at the same time invest in preserving ecosystems, particularly biodiversity and freshwater reserves.
He was blunt about policy reversals, calling lobbying to ease rules on phasing out internal combustion engine vehicles "incredibly disturbing". Subsidies for petrol and diesel, he said, undercut consumer demand for electric vehicles and slow the transition that investment decisions depend on.