Atmospheric carbon dioxide levels jumped by a record amount in 2024 to push concentrations to their highest point since measurements began, the UN鈥檚 World Meteorological Organization (WMO) has reported.

Between 2023 and 2024, the global average concentration of CO2 surged by 3.5 parts per million (ppm) to reach 423.9 ppm, the WMO has said. This is the largest increase since modern measurements started in 1957 and is well in excess of the 2022 to 2023 increase of 2.3 ppm.

It marks the latest in a trend of accelerating annual increases, with growth rates tripling since the 1960s. The last time Earth experienced a comparable concentration of CO2 was 3 million to 5 million years ago.

Excess CO2 in the atmosphere will have a warming effect on the planet for centuries to come, the WMO warns. 鈥淭he heat trapped by CO2 and other greenhouse gases is turbocharging our climate and leading to more extreme weather,鈥� at the WMO said in a statement.

Ongoing emissions from fossil fuels, alongside a surge in emissions from wildfires and a slump in the carbon uptake by the world鈥檚 lands and oceans, were the key drivers of last year鈥檚 record surge, according to the WMO.

Researchers expected a slump in the uptake of carbon by oceans, forests and other ecosystems in 2024 due to the recent El Ni帽o weather pattern, which pushed up global temperatures and dulled carbon absorption by driving heat, fires and drought in key regions like the Amazon. The amount of tropical forest lost in 2024 was double that of 2023, scientists noted earlier this year. 鈥淚t is normal for some tropical lands to be drier and store less carbon during warm El Ni帽o years such as 2024,鈥� says at the University of Reading, UK.

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But there is concern that this dip in carbon uptake by the planet 鈥� particularly by the land 鈥� is part of a longer-term trend that could mean climate change is weakening the planet鈥檚 ability to soak up excess carbon.

鈥淭here has been some suggestions that the land sink was particularly low in 2023 and 2024, even for El Ni帽o years, and that there has been a worrying reduction over time, particularly in the northern hemisphere outside the tropics,鈥� says r, a climate scientist at the Breakthrough Institute. 鈥淚n short, there are worrying signs that the land sink in particular is declining, but it鈥檚 too early to know with confidence without another few years of data.鈥�

In the meantime, it is more urgent than ever for humanity to curb ongoing fossil fuel emissions, says at the University of Leeds, UK. 鈥淭he biggest reason for the ongoing increase [in CO2 concentrations] is fossil fuel emissions being at a persistent all-time high and not yet coming down.鈥�

A recent surge in ocean temperatures has caused the widespread bleaching and death of warm-water corals around the world, officially triggering the first climate tipping point for one of Earth鈥檚 ecosystems, scientists have declared.

The collapse of one of the world鈥檚 most diverse and fragile ecosystems poses a 鈥渉uman health and security hazard鈥� that governments are unprepared for, warns at Healthy Reefs for Healthy People, a conservation programme operating in Central America.

Warm-water coral reefs聽support up to and provide food, coastal protection and a source of income for up to a billion people around the world. Reef services .

Yet corals are highly sensitive to changes in water temperature. Record-breaking global temperatures documented since 2023 have pushed ocean heat levels to new highs, triggering a mass bleaching event that has affected more than 80 per cent of all the world鈥檚 corals. Bleaching is when corals expel the algae living in their tissues in response to high water temperatures, which turns them white. This leaves corals vulnerable to disease, and prolonged bleaching can kill them off altogether by depriving them of their primary food source.

The latest bleaching event has been a 鈥渄ifferent order of magnitude鈥� to anything scientists have previously witnessed, says McField. 鈥淲e鈥檙e in the tipping point,鈥� she confirms. This is generally defined as a critical threshold that, if passed, could cause dramatic and probably irreversible changes in the climate system.

McField was one of the authors of the chapter on corals in the , released today. The report, the first update since 2023, is compiled by 160 scientists from around the world and co-ordinated by the University of Exeter in the UK and campaign group WWF. It warns that warm-water corals are the first Earth system to cross over into their tipping point and are now in the throes of an 鈥渦nprecedented crisis鈥�.

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Central academic estimates suggest that the thermal limit of warm-water corals is reached when global atmospheric temperatures hit 1.2掳C above pre-industrial levels, with an upper threshold of 1.5掳C. In 2024, global average temperatures exceeded 1.5掳C above pre-industrial levels for the first time in recorded human history, an event that has pushed the world鈥檚 coral reefs beyond the limits of their endurance, according to at the University of Exeter, who led the report.

鈥淲e鈥檝e taken a sample of the 1.5掳C world, and we have seen the consequences,鈥� he told reporters at a press briefing ahead of the report鈥檚 launch. 鈥淎 majority of coral reefs are under risk of extensive dieback [or bleaching] and tipping into the alternative seaweed-dominated, algal-covered state.鈥�

The best hope of saving the world鈥檚 warm water corals from almost complete extinction now lies in bringing global average temperatures down to 1.2掳C above pre-industrial levels as soon as possible, he says. Whether or not such an ambitious goal 鈥� which goes well beyond the demands of even the 1.5掳C temperature target 鈥� is feasible to achieve is a separate question, says Lenton.

at James Cook University in Australia warns there are now 鈥渁lmost no unbleached reefs left anywhere in the world鈥�. But the situation can still be mitigated. 鈥淲here coral reefs end up in the next few decades is under our control, if global greenhouse gas emissions are rapidly curtailed,鈥� he says.

Is climate change accelerating and is it worse than we expected?

With temperature records tumbling, it is only natural to worry about cascading tipping points, but the reality is far more nuanced

Often the point at which climate tipping points could be triggered is highly uncertain, but researchers warn the widespread decline of the Amazon rainforest, the melting of polar ice sheets聽and the collapse of the crucial AMOC ocean current could all happen at warming levels below 2掳C.

But people can also trigger 鈥減ositive tipping points鈥� to mitigate the risk, Lenton stresses, highlighting the exponential growth of renewable energy over the past decade and the rapid take-up of electric vehicles. Rapid adoption of cleaner technologies has the potential to deliver emissions cuts at the scale needed to keep warming below 2掳C, the report notes.

In a statement, Lenton said urgent action is needed from world leaders at the upcoming COP30 summit in Brazil to accelerate emissions cuts across the global economy and minimise the amount of time global temperatures spend above 1.5掳C. 鈥淲e are rapidly approaching multiple Earth system tipping points that could transform our world, with devastating consequences for people and nature. This demands immediate, unprecedented action from leaders at COP30 and policy-makers worldwide,鈥� he said.