Record heat, melting glaciers, and oceans warming at an unprecedented pace made 2024 the hottest year ever recorded, delivering consequences that scientists warn are now irreversible for hundreds of years.
Global temperatures soared past the critical 1.5C threshold above pre-industrial levels in 2024, the World Meteorological Organisation (WMO) has confirmed. Earlier, a report from the EU’s Copernicus Climate Change Service also confirmed it in January this year.
But new details from the WMO’s State of the Global Climate report show how this heat reshaped the planet, unleashing permanent damage to oceans, glaciers, and ecosystems, and displacing millions from their homes.
“It’s frightening to see our climate report looking so dire yet again,” said Dr Linden Ashcroft, a senior lecturer in climate science at The University of Melbourne.
“I’ve been providing comments like these for my entire career, and honestly, I’m not quite sure what to do next. Scream these findings from the tops of buildings? Write my comments in capitals? Saying all this while dancing on TikTok? I don’t know. But unless we see real climate leadership from governments and businesses, I will save this response and send it through again next year.”
Crossing 1.5C for a single year doesn't mean the Paris Agreement, which uses long-term averages to track warming, has failed. But scientists warn this year's extreme heat is a clear sign the planet is heading toward dangerous territory.
Dr Paul Read, director of the Future Emergency Resilience Network at UTS, said the world needs to brace for a "1.5 world," with a third of the Arctic nearing tipping points and permafrost melting three times faster than elsewhere.
“Your average five-year-old now faces a future with seven times more heatwaves, triple the floods, droughts and crop failures, double the wildfires,” he said.
However, WMO secretary-general Celeste Saulo stressed the difference between one-year spikes and longer-term trends.
“While a single year above 1.5C of warming does not indicate that the long-term temperature goals of the Paris Agreement are out of reach, it is a wake-up call that we are increasing the risks to our lives, economies and to the planet.”
The report shows atmospheric carbon dioxide reached 420 parts per million, the highest level in at least 800,000 years, with no signs of slowing down. This rising concentration is driving global heating, sea-level rise, and ocean acidification, and threatening marine ecosystems and fisheries globally.
Dr Xuebin Zhang, principal research scientist at CSIRO Environment, warned that these past emissions mean some changes are now unavoidable.
“Ocean heat content will continue to increase, leading to long-term sea-level rise even if emissions are significantly reduced,” Dr Zhang said.
“This committed response, driven by past greenhouse gas emissions, must be accounted for in any long-term climate adaptation planning.”
WMO documented an unprecedented surge in ocean temperatures in 2024, which reached record highs for the eighth consecutive year. Ocean heat content is now rising twice as quickly as the average from 1960 to 2005. This heat trapped in the ocean is expected to drive sea-level rise for centuries, even if emissions drop sharply today.
Sea levels rose 4.7 mm per year between 2015 and 2024, more than double the rate recorded in the decade after satellite measurements began, according to the WMO. This rapid rise now poses existential threats to low-lying coastal communities around the world.
“Data for 2024 show that our oceans continued to warm, and sea levels continued to rise. The frozen parts of Earth’s surface, known as the cryosphere, are melting at an alarming rate: glaciers continue to retreat, and Antarctic sea ice reached its second-lowest extent ever recorded. Meanwhile, extreme weather continues to have devastating consequences around the world,” said Ms Saulo.
Temperatures were boosted in the first half of 2024 by the natural El Niño climate phenomenon, but remained very high in the second half of the year even when El Niño dissipated.
The WMO report says the largest three-year loss of glacier mass ever recorded was from 2022 to 2024. Antarctic sea ice shrank to its second-lowest extent on record, compounding the rapid loss of Arctic ice, where the 18 lowest extents have all occurred in the past 18 years.
Dr Andrew King, associate professor in climate science at the University of Melbourne, said the impacts of this warming are now unmistakable.
"Not only was 2024 the hottest year on record for the planet but we also saw record warm oceans and record high sea levels. Humanity's fingerprint can also be seen in the loss of sea ice and glacier mass, in the acidification of the ocean, and in the increasing frequency and intensity of extreme heat events."
Extreme weather events linked directly to the climate crisis led to the highest number of people displaced since 2008. Communities around the world faced destructive storms such as Typhoon Yagi in Vietnam and the Philippines, Hurricanes Helene and Milton in the United States, and Cyclone Chido in Mozambique and Malawi, all of which were found to be influenced by climate crisis.
Earlier reports have also found how global heat driven by greenhouse gas emissions intensified rainfall in Spain and led to monstrous flash floods.
Food security in 18 countries deteriorated significantly due to these compounded impacts, exacerbated by floods, droughts, and severe heatwaves.
“This year’s WMO report makes it clear: climate change is no longer a distant threat - it is a lived reality, displacing record numbers of people, straining food systems, and disrupting lives,” said associate professor Michele Barnes, an expert in climate adaptation at The University of Sydney.
These warnings come ahead of crucial international climate negotiations in November 2025, where countries are expected to submit new, stronger emissions targets to the UN amid United States president Donald Trump’s decision to pull his country out of the Paris Agreement and rollbacks of environmental regulations to boost fossil fuel production.
Scientists warn that current political responses are falling dangerously short of what's required. Professor James Renwick from Victoria University of Wellington said despite alarming evidence, there's little sign political leaders are taking climate commitments seriously.
"All extremely worrying, yet apparently of little concern to the world’s policy-makers, since there is no sign the world is living up to the Paris Agreement to limit warming to 1.5-2°C," he said. "Our busy day-to-day activities have consequences that will last for centuries, even millennia."
Experts say the world needs an immediate shift from recognition to decisive action.
“Incrementalism is no longer an option,” professor Martina Linnenluecke, director of the centre for climate risk and resilience at the University of Technology Sydney, said.
Dr Linnenluecke added that insurance companies are already retreating from high-risk areas, showing "that climate risks are no longer hypothetical but economic realities."
Professor Nick Golledge, also from Victoria University of Wellington’s Antarctic Research Centre, added that stabilising emissions at current levels won't be enough, and much tougher policies are urgently required.
"Stringent mitigation is now critically important if we are to retain a habitable climate for our planet," he warned.
Despite these warnings, the WMO says it is still possible to limit the damage by quickly scaling up climate services and early warning systems globally. Right now, only half the countries in the world have adequate protection against climate-related disasters.
"We are making progress but need to go further and need to go faster," said WMO Secretary-General Celeste Saulo. "Investment in weather, water and climate services is more important than ever to meet the challenges and build safer, more resilient communities."
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