In 2024 we emitted more greenhouse gases into our atmosphere in a single year than any year before it. The increase from 2023 was small—0.8 percent—but still, global emissions continue to rise, despite science telling us we should have bent the global emissions' curve downward by 2020.

The emissions in our atmosphere are at work, heating the planet, acidifying our oceans, and leading to climate-fueled disasters: heat waves, fires, flooding, droughts, and storms. For some climate impacts, devastation can be followed by the painstaking work of recovery. But for many natural systems, like our tropical coral reefs, the stress we are putting on them is reaching the realms of permanent decline and ultimate collapse.

As we near 1.5 degrees Celsius of global warming—the globally agreed upon limit of the Paris Agreement—we risk triggering tipping points. They are slumbering giants that in their healthy state dampen stress and cool the planet; systems with thresholds that, once crossed, lead to irreversible shifts, from dampening to amplifying stress, causing loss of resilience of the planet and accelerating the pace of change.

Once tipping points are crossed, there is also a nontrivial risk of dangerous cascades, where the first set of tipped systems have knock-on effects on other tipping elements, pushing them across their thresholds, triggering a domino sequence, and increasing further the likelihood of Earth drifting away from its stable state.

Many tipping elements are now well-known: the Amazon rainforest, the Greenland Ice Sheet, the Atlantic Meridional Overturning Circulation (or AMOC). But exactly at what level of warming they will cross their tipping points is still being investigated and narrowed down by science.

For some systems though, we have much higher certainty. Tropical coral reef systems—the rainforests of the ocean—are famous for their biodiversity, unimaginable richness in color and life, being the breeding ground for a myriad of fish species, and providing livelihoods for over 400 million people. They are also likely to be one of the first ecosystems we lose completely to climate change if we do not see a step change in action to reduce our emissions.

This would be devastating. In addition to their unique environmental significance, coral reefs are the ecological basis for massive sectors of the global economy, including tourism and fisheries, worth tens of billions of dollars. They are also vital 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 is when corals expel the algae in their systems and turn a ghostly white. Corals are animals living in symbiosis with the algae, and while they can survive bleaching events, they need time to recover. Yet the Great Barrier Reef also experienced one in 2024. And in 2022, 2020, 2017, and 2016.

Because our emissions have continued at unprecedented rates over the past decade, we’ve moved very quickly from a place where corals had time to recover from horrific stress to next to no time at all. A year without bleaching is becoming the exception rather than the rule.

Recent science estimates 50 percent of the Great Barrier Reef has been lost to climate change. We’re witnessing a collapse in real time from biodiversity-rich hard-coral systems to slimy, diversity-poor, soft algae systems.

In 2026, as we move toward another El Niño cycle and ocean temperatures in the Pacific rise, it’s very likely there will be another mass bleaching event at the Great Barrier Reef, pushing it further into a state of decline and closer to a brink from which it will not be able to recover. This places an enormous responsibility and creates great incentives for global action away from danger, for the Australian government, which is now vying to host the 2026 UN climate negotiations.

However, it’s not a problem for just one country’s government. In 2023-24 the world’s coral reefs experienced a very rare global bleaching event. Bleaching events are usually localized to a region that is experiencing a heat wave. But for only the fourth time in history, though the second in a decade, the US National Oceanic and Atmospheric Administration announced a global bleaching event, because the entirety of our world’s oceans are just too hot.

Our Earth’s resilience to change is fast being worn by our escalating transgressions of its livable boundaries. Our work at the Potsdam Institute of Climate Impact Research to map these boundaries shows that six of nine have already been exceeded.

The world now urgently needs global action that matches the assessment of global risk. Global emissions from fossil fuels need to be reduced by over 5 percent per year, to reach zero by 2050. This is necessary in order to have a chance of deviating from unmanageable outcomes. But this will not be enough. In addition to the global transition away from fossil fuels, we also—urgently—need to transition our food systems from a carbon source to a carbon sink and by 2050 be permanently removing more than 5 billion tons of carbon dioxide every year through different technologies.

The hard reality of our situation is that, even in an ideal future in which we do all we can from this moment on to combat rising temperatures, we could still lose our coral reefs. They are the canaries in the coal mine for the climate crisis. Our best and last chance to save them is to act now, with all the resources we can bring to bear to try to save these precious ecosystems for the generations to come.