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In 2024, the average annual global temperature anomaly surpassed the 1.5 degrees Celsius threshold, marking a milestone in the planet’s long-term warming trend. This is the latest evidence from climate change research, which suggested the world has now entered a phase of sustained warming.
Almost every month in recent years has individually exceeded this threshold, signalling that the target of limiting global temperature rise since preindustrial period (1850-1900) to below 1.5°C — set by the Paris Agreement in 2015 — is almost certain to be exceeded.
The annual average global temperature in 2024 was approximately 1.55°C above pre-industrial levels, based on six different datasets, according to the World Meteorological Organization.
The European Commission’s Copernicus Climate Change Service (C3S) further revealed that 18 of the last 19 months had recorded temperatures above the 1.5°C mark, with January 2025 reaching an extraordinary 1.75°C of warming, despite the ongoing and generally cooling La Niña phenomenon in the equatorial Pacific Ocean.
The first paper was published in the journal Nature Climate Change on February 10, 2025 by Emanuele Bevacqua and Jakob Zscheischler from the Department of Compound Environmental Risks, Helmholtz Centre for Environmental Research, Leipzig, Germany and Carl-Friedrich Schleussner from the International Institute for Applied Systems Analysis, Laxenburg, Austria.
It suggested that “without very stringent climate mitigation, the first year above 1.5 °C occurs within the first 20-year period with an average warming of 1.5 °C.”
This means that the world will see sustained warming of at least 1.5°C over the next two decades. This indicates that 2024 is not an isolated event but the start of a new climate era where average warming remains above the 1.5°C threshold.
Currently, global warming anomaly stands at 1.3°C above pre-industrial levels, as reported by C3S. The Paris Agreement’s goal of limiting warming to 1.5°C is assessed over long periods, usually spanning decades.
The Intergovernmental Panel on Climate Change (IPCC) assessed human-indued global warming over the course of two decades in its Sixth Assessment Report (AR6). There are numerous approaches to assessing long-term temperature trends and this remains an open problem in climate change science.
The level of global warming is the reference point for understanding the major drivers of warming-related impacts and risks, the IPCC stated in its AR6.
The latest research showed that identifying the start of a 20-year period with average temperatures at or above 1.5°C is not just about tracking records but understanding the long-term impacts and risks associated with this level of warming — crossing the 1.5°C threshold in a single year often serves as an early warning of a sustained warming trend.
“Addressing the question of when we will enter a 20-year period with average warming at that level (1.5°C) is thus not just an exercise of tracking the global temperature record but also informs on the onset of a 20-year period where the risks documented in the scientific literature at a 1.5°C warming level are expected to emerge,” the scientists stated in the study.
With this in mind, the experts used climate observations and simulations with the Coupled Model Intercomparison Project Phase 6 (CMIP6) models to investigate how single years of warming above the threshold related to the start of the 20-year global warming period.
They discovered that the first year of crossing a warming threshold served as an early warning of a long-term trend for global warming thresholds of 0.6 °C, 0.7 °C, 0.8 °C, 0.9 °C and 1.0 °C, respectively.
The same pattern was observed in climate model simulations too, with a 66 per cent to 99 per cent probability that the first year of crossing the threshold occurred within the 20-year temperature trend. The scientists predict that the climatic impacts that IPCC scientists predicted at 1.5°C will begin to emerge as this trend takes hold.
Under the IPCC Shared Socioeconomic Pathway (SSP) 2-4.5 scenario, which most closely represents the current trends of climate change policy, “all models indicate that the first single year at 1.5°C warming falls within the 20-year period.”
More stringent scenarios, such as SSP1-1.9 and SSP1-2.6, would slightly lower this probability, but even in these cases, there remains a 75 per cent chance that the 1.5°C threshold will be crossed within the next two decades.
A second research paper was also published in Nature Climate Change on February 10, from the Climate Research Division, Environment and Climate Change Canada, Victoria, British Columbia, Canada. It assessed how consecutive months of warming above 1.5°C signalled the likely crossing of the Paris Agreement target.
This study found that the first 12-month period with temperatures above 1.5°C, recorded up to June 2024, indicates that the 1.5°C threshold has likely already been breached.
“Hence, in CMIP6 simulations, 12 consecutive months above 1.5 °C indicates that the Paris Agreement threshold is likely to have already been crossed,” said the paper.
However, the study cautioned that external factors, such as volcanic eruptions and reduced aerosol emissions from shipping, which are not fully accounted for in climate models, could have played a significant role in recent warming.
Meanwhile, alarming new research published in the journal Science on February 7, 2025 highlighted the devastating impacts of a 2.7°C global temperature rise, particularly on the Arctic.
The study suggested that “with the current level of global warming of around 1.5°C, the Arctic is already markedly different from its preindustrial state. Even if we were to stabilize future temperatures immedi- ately at 1.5°C, the Arctic cryosphere will continue to shrink across a wide range of temporal and spatial scales.”
"Unless rapid action is taken, 2024 will be remembered not as an anomaly, but as the beginning of a new climate era—one defined by escalating risks,” William Ripple, professor at Oregon State University, told science website Phys.org.