2024 is now almost certain to become the first year on record when average temperatures exceed 1.5掳C above pre-industrial levels, breaching the threshold set by the Paris Agreement.
鈥淎t this point, barring an asteroid impact or a massive volcanic eruption鈥� I think it鈥檚 safe to say this will be the first year above 1.5 degrees,鈥� says at US non-profit Berkeley Earth.
Last year, the average surface temperature across the globe was 1.45掳C above the 1850-1900 average, which is used as the pre-industrial baseline, with a margin of error of 0.12掳C, It uses an average of five major datasets to arrive at this figure.
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, the average temperature surpassed that for the same month in 2023, says the US National Oceanic and Atmospheric Administration. The average for this period was 1.54掳C above pre-industrial levels, according to data from the Met Office, the UK鈥檚 weather service.
Although the average for September was cooler than at the same time last year, there is little doubt that 2024 as a whole will exceed the global target for the first time. 鈥淚t would take quite a notable and unusual cooling event to bring the annual average below 1.5掳C,鈥� says at the Met Office.
Temperature datasets collected by various agencies and institutions around the world vary slightly, mainly due to differences in how ocean temperatures have been collected and analysed over the decades.
But the five main datasets are set to indicate 2024 temperatures settled around 1.5掳C above pre-industrial times, with several just above this mark, says Hausfather. 鈥淲hile not all of the datasets are going to be above 1.5掳C this year, it is going to be the first year where the average鈥� is above 1.5掳C,鈥� he says.
The primary driver of rising global temperatures is human-caused climate change, says at Copernicus, the European Union body that monitors climate. 鈥淭his is not coming out of the blue,鈥� he says. 鈥淭he main driver for this warming is increasing greenhouse gas in the atmosphere.鈥� A recent, strong El Ni帽o pattern 鈥� the Pacific Ocean phenomenon that generally brings higher global temperatures 鈥� is another significant factor.
But the scale and persistence of the heat has shocked many experts, who expected temperatures to subside once El Ni帽o ended in May 2024. Instead, the record-breaking heat continued well into the second half of the year, puzzling scientists.
Competing explanations abound. The sun reached a so-called solar maximum in 2024, slightly increasing the solar radiation hitting Earth. Meanwhile, changes to shipping pollution rules in 2020 have reduced air pollution over the world鈥檚 oceans, potentially magnifying heat absorption from the sun as certain pollutants are known to have a cooling effect.
But research into the impacts of these factors is still inconclusive, says at the University of Leeds, UK. 鈥淲e do not completely understand why this extra spike in surface temperatures has continued,鈥� he says.
He warns it may be that the rate of climate change has accelerated. 鈥淚f you just look at historical temperature changes, they do not increase in a monotonic way 鈥� they seem to go in fits and starts,鈥� he says.
The world has already experienced a 12-month period above 1.5掳C of warming, with temperatures between July 2023 and June 2024 1.64掳C above pre-industrial levels, .
Nevertheless, the passing of the 1.5掳C threshold in one calendar year is a totemic moment for the climate community. The limit has become a guiding light for it, after being included as a 鈥渟tretch goal鈥� in the 2015 Paris Agreement.
Yet years of failure to cut global emissions have made a breach almost inevitable, despite research since 2015 showing warming beyond 1.5掳C would be far more dangerous than first thought.
However, a single year above 1.5掳C of warming will not count as a breach of the Paris Agreement 鈥� which is judged on a 30-year average. On that basis, most climate models expect the 1.5掳C threshold to be exceeded at some point in the early 2030s, unless the world makes immediate, dramatic cuts to emissions.
Nevertheless, Hausfather hopes 2024 will underscore how fast the world is changing due to human activities. 鈥淗opefully it will serve as a wake-up call for policymakers, and then history will look back on it as the year when the world changed and started finally taking this problem as seriously as it deserves,鈥� he says.
Forster echoes this sentiment, arguing it should spur leaders into taking action to cut real world emissions and adapting societies to prepare for future climate change. 鈥淚 want to try as much as possible to connect this passing of 1.5掳C with what we have to do to protect our society from the impacts of climate change,鈥� he says.
