In the latest Global Tipping Points Report, Timothy Lenton and colleagues present data on the state of vulnerable earth systems, notably warm-water coral. They focus on tipping points, a critical threshold which when passed causes a large self-perpetuating system-wide change. But what makes temperature such a significant factor in this system’s collapse?
Coral is an organism that is especially vulnerable to temperature change, as it relies on a symbiotic relationship with microscopic algae called Zooxanthellae. At an upper limit of heat stress, zooxanthellae are expelled leaving only the white coral skeleton behind, referred to as coral bleaching.
With global surface temperature exceeding 1.2°C warming, compared to pre-industrial temperatures, mass bleaching is a certainty. At current emission rates, temperatures will continue to spike to 1.5°C within the next ten years. Immediate mitigation is needed to limit warming below this point, however, even if warming is curbed, there is still a 99 per cent chance of global coral death. Is this a new reality we must come to terms with, where coral reefs teeming with life are a thing of the past?
Warm-water corals have a transformative impact on marine ecosystems, building reefs that support almost a million species, many of which are at risk of extinction. People and communities are reliant on warm-water corals, with ecosystem services like food, coastal protection, and livelihoods for a billion people now at risk. Their importance simply cannot be understated. This is the first of many predicted tipping points as a direct consequence of global warming. Similarly vulnerable systems like the Amazon rainforest, Atlantic ocean circulation, and mountain glaciers will be altered irreversibly if their respective points are reached. This report also highlights the most extreme gaps in preparedness are in the most vulnerable nations. Small island developing states face complete uninhabitability (with no resources) if warming continues.
But it’s not all bad. Lenton introduces the concept of positive tipping points. These are interventions that accelerate beneficial change, “triggering self-propelling change towards a more sustainable state”. Examples include the adoption of solar and wind power or the switch to electric vehicles. These points have already ‘tipped’, with public sentiment and financial investment rooted in these as opposed to traditional carbon sources. This has a run on effect impacting social norms and legislation for decarbonisation in other sectors. The overall sentiment is that these positive tipping points are opportunities to rebalance and transition towards a net zero world.
Ahead of the COP 30 Climate Summit, the Global Tipping Points Report not only informs us of the status of the most vulnerable earth systems but provides direction towards a sustainable world. For warm-water coral, it’s a devastating new reality of bleaching and possible extinction, while for humankind it’s a final plea that demands action.
