Global sea levels rose faster than expected last year, NASA says

Euronews

14-03-2025

Global sea levels rose faster than expected in 2024 as the world experienced its hottest year on record, a new study has found.
This was due to an unusual amount of ocean warming combined with meltwater from land-based ice such as glaciers, according to the NASA-led analysis.
'Every year is a little bit different, but what's clear is that the ocean continues to rise, and the rate of rise is getting faster and faster,' said Josh Willis, a sea level researcher at NASA's Jet Propulsion Laboratory in Southern California.
Since the satellite recording of ocean height began in 1993, the rate of annual sea level rise has more than doubled. In total, the global sea level has gone up by 10 centimetres since 1993.
This long-term record is made possible by an uninterrupted series of ocean-observing satellites starting with TOPEX/Poseidon in 1992.
According to the NASA-led study of the information sourced via the Sentinel-6 Michael Freilich satellite, 2024 saw a rate of sea level rise at 0.59 centimetres per year, compared to the expected rate of 0.43 centimetres per year.
The upcoming Sentinel-6B satellite will continue to measure sea surface height down to a few centimetres for about 90 per cent of the world's oceans.
In recent years, about two-thirds of sea level rise was from the addition of water from land into the ocean by melting ice sheets and glaciers. About a third came from thermal expansion of seawater.
But in 2024, those contributions flipped, with two-thirds of sea level rise coming from thermal expansion.
'With 2024 as the warmest year on record, Earth's expanding oceans are following suit, reaching their highest levels in three decades,' said Nadya Vinogradova Shiffer, head of physical oceanography programs at NASA Headquarters in Washington.
There are several ways in which heat makes its way into the ocean, resulting in the thermal expansion of water.
Normally, seawater arranges itself into layers determined by water temperature and density.
Warmer water is lighter and floats on top of cooler water, which is denser. In most places, heat from the surface moves very slowly through these layers down into the deep ocean.
But extremely windy areas of the ocean can agitate the layers enough to result in vertical mixing.
Very large currents, like those found in the Southern Ocean, can tilt ocean layers, allowing surface waters to slip down deep more easily.
The massive movement of water during El Niño - in which a large pool of warm water normally located in the western Pacific Ocean sloshes over to the central and eastern Pacific - can also result in the vertical movement of heat within the ocean.
The UN has warned that rising sea levels are endangering vast numbers of people living on islands or along coastlines.
Particularly vulnerable areas include low-lying coastal communities in India, Bangladesh, China and the Netherlands, as well as island nations in the Pacific and Indian Oceans.
In 2022, the UK experienced an unprecedented heatwave, with temperatures reaching 40C for the first time in recorded history.
This extreme heat was accompanied by widespread fires across London and elsewhere in England, which destroyed houses and prompted evacuations.
A new study has assessed the contribution of human-induced climate change to the fire and weather conditions over this period.
The analysis, conducted by the Met Office, the UK Centre for Ecology & Hydrology and the University of Exeter, reveals at least a 6-fold increase in the probability of very high fire weather due to human influence.
'As we experience more hotter and drier summers as temperatures continue to rise, the frequency and severity of fires are likely to increase, posing significant risks to both natural ecosystems and human populations,' the authors write.
'This study underscores the need for further research to quantify the changing fire risk due to our changing climate and the urgent requirement for mitigation and adaptation efforts to address the growing wildfire threat in the UK.'
The study highlights how rising temperatures and drier conditions driven by climate change are dramatically increasing the risk of extreme fire weather in the UK.
England emerged as the most vulnerable UK nation in the paper, published in the journal Environmental Research Letters on Tuesday.
The researchers compared the present-day climate to one without human influence through greenhouse gas emissions to understand how climate change had impacted the chance of fire weather.
To do so, they combined data from advanced climate models and a 'fire weather index' - an indicator of hot, dry, windy weather conditions that provoke fires.
They looked at how changes in the weather affected the danger posed by fires - how far they were likely to spread and intensify - once they were ignited.
The results emphasise that climate change is not just a future concern but a present-day reality, with fire risks rising in tandem with global temperatures.
'The 2022 heatwave wasn't just record-breaking - it drastically increased the risk of fires, highlighting the growing danger climate change poses to the UK,' says lead author Dr Chantelle Burton from the Met Office.
'We found that the 2022 UK severe fires were made at least six times more likely due to human influence. With hotter, drier summers becoming the norm, fires are an emerging threat to the UK.'
One of the paper's key messages is the pressing need to adapt to rising fire risks while limiting further warming.
An urgent and significant reduction in global greenhouse gas emissions would limit the increase in future fire risks. Targeted adaptation measures could also help communities and ecosystems cope with the escalating threat.
Some actions to reduce fire risks could include enhanced land management, building away from areas at high risk, enhancing detection of fires or public campaigns to reduce accidental fires.
'The experiences of 2022 serve as a stark reminder of the urgent need to adapt to a changing climate and reduce carbon emissions to limit further warming,' says Burton.
The UK isn't the only place in Europe facing a higher risk of fire. A study published in Nature in 2024 looked at the future of fire risk for Europe as a whole.
The analysis explored the impact of a range of climate change projections on fire events compared to a baseline of fire danger using a 30-year fire weather index analysis.
The results show that areas in southern Europe could experience a tenfold increase in the probability of catastrophic fires occurring in any given year under a moderate warming scenario.
If global temperatures reach the +2C threshold, central and northern Europe will also become more susceptible to wildfires during droughts.
The increased probability of fire extremes in a warming climate, in combination with an average one-week extension of the fire season across most countries, would put extra strain on Europe's ability to cope in the forthcoming decades, the authors say.