In 2024, we emitted more greenhouse gases into our atmosphere in one year than in any previous year. The enhance compared to 2023 was modest – 0.8 percent – but global emissions continue to rise even though science tells us we should have bent the global emissions curve down to 2020.
Emissions in our atmosphere are heating the planet, acidifying our oceans and leading to climate disasters: heatwaves, wildfires, floods, droughts and storms. In some climatic impacts, devastation may be followed by tedious repair work. However, for many natural systems, such as tropical coral reefs, the stress we are placing on them is reaching levels of indefinite decline and eventual collapse.
As we approach 1.5 degrees Celsius of global warming – the globally agreed limit of the Paris Agreement –we risk tipping points. They are sleeping giants that, when well, suppress stress and frigid the planet; systems with thresholds that, when exceeded, lead to irreversible changes, from stress suppression to stress amplification, causing the planet to lose its resilience and accelerating the rate of change.
Once tipping points are crossed, there is also a non-trivial risk of threatening cascades forming, in which the first set of tilting systems has a domino effect on other tipping elements, pushing them beyond their thresholds, setting off a sequence of dominoes and further increasing the likelihood of the Earth moving away from a stable state.
Many of the features of the overturn are now well known: the Amazon rainforest, the Greenland ice sheet, the Atlantic Meridional Overturning Circulation (AMOC). However, science is still investigating and narrowing down the exact level of warming at which they will exceed their tipping point.
However, for some systems we have much higher ones confidence. Tropical coral reefs – the ocean’s rainforests – are celebrated for their biodiversity, unimaginable abundance of color and life, are breeding grounds for countless species of fish and provide the livelihoods of over 400 million people. They are also likely to be among the first ecosystems to be completely lost as a result of climate change unless we see a radical change in our actions to reduce our emissions.
It would be devastating. In addition to their unique environmental importance, coral reefs provide the ecological basis for huge sectors of the global economy, including tourism and fishing, worth tens of billions of dollars. They are too key natural protection for many coastal regions against storms and erosion.
The largest coral reef in the world and the richest marine ecosystem on Earth – the Great Barrier Reef in Australia –experienced another mass bleaching event in 2025. Bleaching happens when corals expel algae from their bodies and become ghostly white. Corals are animals that live in a symbiotic relationship with algae, and while they can survive bleaching, they need time to recover. However, the Great Barrier Reef experienced something similar in 2024 and in 2022, 2020, 2017 and 2016.