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2024 confirmed as first year to pass 1.5C threshold

Scientists warn efforts to limit the long-term temperature rise to 1.5°C will fail as data confirms 2024 was the hottest year in human history

New Scientist, By James Dinneen and Madeleine Cuff, 10 January 2025 

Hopes of keeping global warming below 1.5°C above pre-industrial levels have been all but extinguished after new data confirmed 2024 was the first calendar year to see average temperatures breach that critical threshold.

Last year was the hottest ever recorded in human history, the World Meteorological Organization (WMO) declared on 10 January, in the latest stark warning that humanity is pushing Earth’s climate into uncharted territory.

The average global temperature for the year exceeded 1.5°C above the pre-industrial baseline for the first time, the agency also confirmed, temporarily breaching the threshold set by the Paris Agreement.

The WMO’s assessment is calculated using the average global temperature across six datasets, with the period of 1850 to 1900 used to provide a pre-industrial baseline. Temperature datasets collected by various agencies and institutions around the world vary slightly, mainly due to differences in how ocean temperatures have been measured and analysed over the decades. Some of those datasets come in just below the 1.5°C mark, but others are well above.

The UK’s Met Office weather service puts 2024’s average temperature at 1.53°C above pre-industrial levels, with a margin of error of 0.08°C. That is 0.07°C above 2023, the previous warmest year on record. Meanwhile, the European Union’s climate change service Copernicus has 2024 temperatures at 1.6°C above pre-industrial levels, 0.12°C above 2023’s record.

Berkeley Earth, a climate research group in California, finds a rise of 1.62°C, the second time in its dataset the rise in global average temperatures has breached 1.5°C, after 2023. Temperature data from NASA puts the rise in temperature a bit lower at 1.47°C above pre-industrial levels, and the US National Oceanic and Atmospheric Administration finds a 1.46°C rise above pre-industrial levels. The WMO finds an average rise of 1.55°C across the six datasets, with a margin of error of 0.13°C.

Scientists agree that the surge in temperature was caused mostly by the continuation of human-caused climate change and an El Niño weather pattern, which tends to push up global temperatures. But the scale and persistence of the heat has shocked many experts, who expected temperatures to subside once El Niño ended in May 2024. Instead, they remained at record levels throughout the rest of the year.

The world’s oceans have been most affected, with sea surface temperatures staying at record levels for most of 2024, playing havoc with marine ecosystems. The year also brought no shortage of extreme weather on land, with fierce heatwaves, sharp declines in polar ice, deadly flooding and uncontrollable wildfires. “This was a year when the impacts of climate change are right across the planet,” says David King, former chief scientific adviser to the UK government and founder of the Climate Crisis Advisory Group.

Technically, the Paris Agreement target of limiting warming to below 1.5°C is calculated using a 20-year average, so a single year above the threshold doesn’t signal a formal breach of the target. But given the pace of warming in recent years, many scientists say the long-term Paris goal is now out of reach………………………………………..
https://www.newscientist.com/article/2463480-2024-confirmed-as-first-year-to-breach-1-5c-warming-limit/

January 13, 2025 - Posted by Christina Macpherson | climate change