UN scientists have warned that this year is on course to become the second or third hottest globally, as an “unprecedented streak” of extreme temperatures persists.
The World Meteorological Organisation (WMO) said global average surface temperatures from January to August 2025 were 1.42C higher than pre-industrial levels, a slight drop from the record-breaking 1.55C recorded in 2024, reports RTE.
As world leaders meet in Belém, Brazil, for the latest round of UN climate talks, the WMO warned it is “virtually impossible” to prevent global temperatures from temporarily exceeding the 1.5C limit agreed under the Paris Agreement.
However, WMO Secretary-General Celeste Saulo said it is “still entirely possible and essential” to reduce temperatures to the 1.5C target by the century’s end, reports RTE.
Taoiseach Micheál Martin was among the leaders addressing the summit’s opening session this afternoon.
The current UN conference comes after a year marked by devastating climate and weather extremes worldwide, including flooding, storms, drought, and wildfires — even as several governments move to slow down or reverse climate action, reports RTE.
This year has been slightly cooler than 2024, as the El Niño climate event in the tropical Pacific — which amplified global temperatures in 2023 and 2024 — has now transitioned to neutral conditions.
The El Niño/La Niña system continues to shape global climate patterns, alongside human-driven warming caused by fossil fuel combustion and deforestation, which release heat-trapping gases, elevate sea levels, and intensify extreme weather, reports RTE.
According to WMO analysis, every year since 2015 — when nations adopted the Paris Agreement — ranks among the 11 hottest on record.
The last three years have been the warmest since global temperature records began 176 years ago, reports RTE.
The UN’s meteorological agency also cautioned that concentrations of greenhouse gases, which reached record highs in 2024, have continued to rise throughout 2025.
Ms Saulo said: “This unprecedented streak of high temperatures, combined with last year’s record increase in greenhouse gas levels, makes it clear that it will be virtually impossible to limit global warming to 1.5C in the next few years without temporarily overshooting this target,” reports RTE.
“But the science is equally clear that it’s still entirely possible and essential to bring temperatures back down to 1.5C by the end of the century,” reports RTE.
UN Secretary-General Antonio Guterres warned: “Each year above 1.5C will hammer economies, deepen inequalities and inflict irreversible damage,” reports RTE.
“We must act now, at great speed and scale, to make the overshoot as small, as short, and as safe as possible – and bring temperatures back below 1.5C before the end of the century,” reports RTE.
In its updated climate report released to coincide with the start of COP30 in Brazil, the WMO said ocean heat in 2025 has surpassed last year’s record levels, damaging ecosystems, fuelling stronger storms, accelerating ice melt, and raising sea levels.
Sea level rise has doubled over the long term, with 2024 setting a new record for annual global averages, although a slight decline this year may only be temporary, reports RTE.
The WMO also noted that Arctic sea ice reached its lowest levels on record after winter, while Antarctic sea ice was the third lowest for both its seasonal minimum and maximum extents.
Levels of carbon dioxide, methane, and nitrous oxide in the atmosphere all hit new highs in 2024, with data indicating they are climbing even higher this year, reports RTE.
Responding to the findings, Gareth Redmond-King of the Energy and Climate Intelligence Unit said: “Nations are gathering for the start of the COP30 climate summit at the end of a year that has seen devastating hurricanes, wildfires and flooding across the world; here at home, we’ve seen the second worst harvest as a result of climate change,” reports RTE.
He said that news of 2025 being set to become the second or third hottest year on record, combined with warnings that current pledges still lead to dangerous temperature rises, “should focus leaders’ minds,” reports RTE.
“Net zero emissions is the only solution we have to halt climate change, to limit the worsening danger and rising costs which this represents, and bring the climate system back into balance,” reports RTE.
Brazilian President Luiz Inacio Lula da Silva, host of COP30, said that “extremist forces” are condemning future generations to live on a planet permanently changed by global warming.
Mr Lula criticised “extremist forces (that) fabricate fake news … to obtain electoral gains and imprison future generations,” warning that the window to prevent catastrophic climate change is “closing rapidly,” reports RTE.
He referenced a recent UN study predicting Earth will warm by 2.5C by 2100 compared to pre-industrial levels.
This rise would result in about 250,000 deaths annually and cut global GDP by nearly one-third, Mr Lula told leaders gathered in Belém, reports RTE.
“Now is the moment … to face reality and decide if we will have the courage and the necessary determination to transform things,” the president said, reports RTE.
But he cautioned that “selfish immediate interests” too often prevail over long-term collective good, reports RTE.
Mr Lula said global climate efforts have been weakened by “insecurity and mutual mistrust” — comments made amid a dispute with US President Donald Trump, whose administration did not attend the talks.
The Brazilian leader also unveiled a new fund to protect global forests, vital absorbers of planet-warming carbon, reports RTE.
Mr Lula described the initiative, known as the Tropical Forest Forever Facility, as “one of the main tangible outcomes” of the summit, aimed at raising $125 billion from governments and private investors, with $10 billion in initial funding still pending.
“When forest destruction reaches irreversible points, its effects will be felt across the world. Forests are worth more standing than cut down. They should be part of the GDP of our countries,” said Mr Lula, reports RTE.
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