Did We Just Enter the Era of 1.5°C Warming? Scientists Say It’s Likely

New research suggests 2024 may not just be another record-breaking year — it could mark the start of a long-term shift into sustained 1.5°C global warming, with profound consequences for climate, ecosystems, and society

In 2015, as I was getting ready to leave Australia after spending four years doing my PhD there, we were asked to share why we cared about reaching a deal to limit global warming. Just like other students, I shared a picture of myself as I was completing the Overland Track in Tasmania. #EarhtToParis, read the hashtag.

In 2024, the world crossed a line that climate scientists have been watching for years: the first full calendar year with global temperatures exceeding 1.5°C above pre-industrial levels.

It was the hottest year on record, fueled by human-caused climate change and a strong El Niño. But what does that really mean? Is this just another record-breaker, or have we stepped into a new climate reality?

A new study in Nature Climate Change suggests that 2024 might be more than just a hot year; it could be a warning that we’ve officially entered a long-term phase of 1.5°C warming.

And if we use history as a guide, which, as a paleontologist, I’ve been trained to do, that means we should expect some serious changes ahead.

But how did scientists figure this out?

The researchers behind the study took a deep dive into historical climate data and computer models, looking at past warming patterns. To do so, they examined when previous temperature milestones — like 0.6°C, 0.7°C, or 1.0°C — were first reached in a single year and compared that to when the world settled into a longer-term average at those levels.

Time lag of the first single year at or above a global warming level from the time of entry in the first 20-year period that reaches the same level. a, The time lag is denoted by Δt, with positive values implying that the first year above a warming level occurred within the 20-year period reaching the same warming level (vertical light orange band). The blue dots indicate different observational datasets. The box plots (showing median and interquartile range) are derived from models under a moderate emissions scenario SSP2–4.5 (black whiskers extend to the most extreme data points within 1.5 times the interquartile range from the box). b, The same as the box plot in a but for 1.5 °C warming under different emission scenarios (here, grey whiskers display the full range if it exceeds black whiskers). The number of models employed (those compatible with observed recent warming trends20) is shown in brackets. The fraction of simulations that fall in the shaded area is also provided — Bevacqua, Emanuele, et al. “A Year above 1.5 °C Signals That Earth Is Most Probably within the 20-year Period That Will Reach the Paris Agreement Limit.” *Nature Climate Change*, 2025, pp. 1–4, https://doi.org/10.1038/s41558-025-02246-9. Accessed 10 Feb. 2025.

Their analysis showed a consistent pattern: when a single year breaks a temperature threshold, it almost always falls within the first 20-year period where that level becomes the new normal.

Using this approach, they investigated whether 2024’s record heat signals that we’ve started the 20-year period where global temperatures will average at least 1.5°C.

Their results strongly suggest that’s the case.

Was 2024 a year of warnings, then?

Well, the numbers make it clear: 2024’s global surface temperature averaged 1.55°C above pre-industrial levels. But even before that, 2023 had already hit 1.43°C, and the long-term trend is unmistakable.

Climate scientist Dr. William Ripple said, “Every fraction of a degree beyond this level translates into more extreme weather, biodiversity loss, and human suffering.”

This warming isn’t just about the numbers; it’s about what’s happening in the world around us. This means that the past year was a preview of what life at 1.5°C looks like.

Fires tore through forests and homes, deadly heat waves strained power grids, and flooding displaced thousands. The cost?

Swiss Re, one of the world’s leading providers of reinsurance, insurance, and other forms of insurance-based risk transfer, estimated global natural disaster damages hit $310 billion in 2024 alone. In the U.S., AccuWeather predicted fire-related damages in Los Angeles alone could exceed $250 billion in 2025.

Strong warming trends place the first 1.5 °C year within the 1.5 °C 20-year period. a,b, Examples of time series with weak (a) or strong (b) temperature trends, with the first single year above 1.5 °C falling outside or within the 20-year warming level period (vertical light orange band), respectively. c, The probability of the first year at or above a warming level falling within the 20-year period reaching the same level, derived from an idealized experiment for different trends (y axis) and standard deviations (x axis) of the temperature time series. Blue-filled symbols show trends and standard deviations from observational datasets during the 20-year warming level period (colours as in Fig. 1a). Red-filled symbols denote probabilities from climate models, plotted against the multimodel median of trends and standard deviations (note, the symbols for 0.5 °C in SSP1–2.6 and SSP2–4.5 overlap). d, The dots show the probability of a first 1.5 °C year falling within the 1.5 °C 20-year period as a function of the warming rate, assuming that the first 1.5 °C year is reached under the currently observed trend and standard deviation. Uncertainty ranges (vertical bars) reflect combined uncertainty in the currently observed trend (5–95th percentile range1) and standard deviation (range across observational datasets; Methods). The bottom-right bar shows the currently observed trend and its 5–95th percentile range1 (0.026 (0.02, 0.04) °C yr−1) — Bevacqua, Emanuele, et al. “A Year above 1.5 °C Signals That Earth Is Most Probably within the 20-year Period That Will Reach the Paris Agreement Limit.” *Nature Climate Change*, 2025, pp. 1–4, https://doi.org/10.1038/s41558-025-02246-9. Accessed 10 Feb. 2025.

These impacts are arriving sooner than many expected. While past climate projections warned that we might reach a 1.5°C world in the 2030s, new research suggests it may already be happening.

I know what you’re thinking. What’s next?

Well, the big question is: does this mean we’ve officially “breached” the Paris Agreement’s 1.5°C limit? Not quite.

The agreement defines warming as a long-term global average, not a single year. Right now, that average sits around 1.3°C. But if the researchers are correct, we’re likely within a decade of crossing the Paris threshold for good — unless drastic action is taken.

Another independent study, published alongside this one, backs up the findings. In other words, two teams reached similar concussions independently after studying the same hypothesis. That’s why I love science so much, no coincidence, just facts.

Indeed, Canadian climate scientist Dr. Alex Cannon used a different approach but reached a similar conclusion: if warming continues at its current rate, the long-term breach of 1.5°C could happen before 2029.

The UN’s climate experts have estimated a 50/50 chance of reaching that level in the early 2030s, but recent trends suggest we might get there even sooner.

Observed and projected crossing of the 1.5 °C global warming threshold. a, ERA5 global temperature anomalies (≥1.5 °C in purple). The histogram shows the distribution of time between first occurrence of 12 months above 1.5 °C and long-term threshold exceedance (CMIP6 SSP 2–4.5; 26 members) superimposed over the observed occurrence date. b, Histograms of year of occurrence of Paris Agreement threshold crossing (grey) and first occurrence of 12 months above 1.5 °C (purple). In a and b vertical dashed (dotted) lines indicate the median (5th and 95th percentiles). c, Probability that the first occurrence of n consecutive months above 1.5 °C coincides with the Paris Agreement threshold already having been breached. Horizontal dotted lines show probabilities for 12 consecutive months — Cannon, Alex J. “Twelve Months at 1.5 °C Signals Earlier than Expected Breach of Paris Agreement Threshold.” *Nature Climate Change*, 2025, pp. 1–4, https://doi.org/10.1038/s41558-025-02247-8. Accessed 10 Feb. 2025.

So, what’s next?

There’s no sugarcoating it: this is the real fork in the road.

Scientists have spent decades warning that 1.5°C warming would be a tipping point for worsening climate impacts. Coral reefs could decline by up to 90%, Arctic sea ice could disappear in summer, and ice sheets holding enough water to raise sea levels by meters could become unstable.

Yet our message remains clear: it’s not too late to act. This study isn’t just about ringing alarm bells; it’s a reminder that every tenth of a degree matters. Drastic emissions cuts, transitioning away from fossil fuels, and ramping up climate adaptation efforts can still change the trajectory.

“A year above 1.5°C is not the time for despair, but a call to action,” the study’s authors emphasized.

History has shown that climate projections can sometimes underestimate how fast change is happening. But it’s also shown that when societies take climate action seriously, progress can be made.

At the end of the day, the decisions made in the next few years will shape whether this new era locks us into more warming and its consequences — or whether we can still pull back from the brink. It’s up to us.

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I’m thrilled to have you here. Stay curious, and thank you for being part of this journey!

Best,

Sílvia P-M, PhD Climate Ages

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