The world has been told the irreversible rise in sea levels can be contained if the planet rapidly reduces its fossil fuel use.

The warning came in the conclusions of a special report on sea-level rise commissioned by the United Nations secretary-general, published in Palau and presented during the UNSG’s daily media briefing at UN headquarters by an expert panel including Climate Analytics’ CEO Bill Hare (above pic).

It found sea-level rise around the world is accelerating due to humanity’s greenhouse gas emissions, and the rise to-date is ‘essentially irreversible’ on human timescales. But a swift and timely switch away from fossil fuel use can constrain the rate of sea-level rise, moderating threats to the estimated 1.2 billion people at risk of flooding and other impacts.

The report added: “Rising seas are no longer a distant threat: they are happening now, faster than at any point in recorded history, and the pace is accelerating, making sea level rise one of the most profound threats to populations around the world in developed and developing states alike.

“The acceleration is driven primarily by melting glaciers and the thermal expansion of warming oceans as a direct consequence of human-induced global warming. Between 2014 and 2023, global sea level rose by 4.7 mm per year. In 2024 alone, the sea level rose 5.9 mm, a new record, driven primarily by exceptional ocean warming – in some regions faster than at any time in the past 4,000 years – and this rate is expected to continue to increase through 2050 owing to warming already locked into the climate system.

“The annual rate of sea level rise was 4.75 mm during the period 2012–2025, with the 2025 global mean sea level remaining comparable to the record-high levels of 2024, following a rapid, approximately 5 mm rise during 2023–2024 owing to exceptional ocean warming associated with El Niño.”

“Because of serial failures to reduce fossil fuel use by the world’s richest and biggest emitting countries, all coastal countries, and the small island developing states in particular, face a future of steadily rising climate impacts which in most cases they have done little to cause,” said  Hare. “The Secretary-General’s report does an excellent job at laying out the scale of the threat and also the various ways in which the global community needs to respond – which includes stepping up on finance for adaptation and Loss and Damage, and must also include aligning emissions reductions with the 1.5°C limit in the Paris Agreement.”

During the panel event,  Hare presented evidence showing that:

• the annual rate of sea-level rise has more than doubled in recent decades, accelerating from 2.1mm per year in 1992 to 4.5mm per year in 2024 – and projections indicate this will surpass 10mm per year by the end of the century

• greenhouse gas emissions have made extreme sea level events four times more common since 1900

• most atolls are likely to become uninhabitable by mid-century, as sea-level rise exacerbates flooding from waves

• stabilising global warming at 1.5°C would not be enough to prevent sea-level rise of several metres from Antarctic ice melt, meaning that governments should aim to reduce global warming well below 1.5°C before the end of the century.

“Even in isolation this report would be a wake-up call to the leaders of major emitting countries that their failure to act is creating major risks for the future alongside the impacts we can already observe around us,” warned Hare. “But when those impacts are as tangible as they have been recently – many hundreds if not thousands dead from flooding in Nepal, tens of thousands from heatwaves across Europe, economic damages already estimated in hundreds of billions of dollars – the wake-up call is deafening.”