Climate and environment
In Depth
What does exceeding 1.5 °C really mean?
A single year above the threshold is not yet the same as exceeding the Paris Agreement goal. But it is an important signal.
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In Brief
- According to the World Meteorological Organization (WMO), 2024 was probably the first calendar year with a global average temperature more than 1.5 °C above the 1850–1900 period: the estimate is 1.55 °C, with an uncertainty margin of ±0.13 °C.
- The Paris Agreement goal, however, concerns long-term warming, not the temperature of a single year.
- In its report on 2024, the WMO estimated long-term warming to still be below 1.5 °C: about 1.34–1.41 °C depending on the calculation method used.
- Saying that the threshold has not been formally and stably exceeded does not mean the problem has gone away: according to the IPCC, every further fraction of warming increases risks and impacts.
What we know
Documented facts
- The global average temperature of 2024 was the highest in the instrumental record: the WMO places it at 1.55 °C above the 1850–1900 average, with an uncertainty of ±0.13 °C linked to the different datasets used.
- A very warm year depends both on the underlying trend, caused by greenhouse gas emissions, and on the natural variability of the climate system: phenomena such as El Niño and La Niña can push the annual temperature above or below the trend.
- This is why the WMO distinguishes the temperature of a single year from long-term warming, which in the report on 2024 is estimated to be in a range of about 1.34–1.41 °C depending on the method.
- The IPCC states that the observed warming is unequivocally caused by human activities and that risks and impacts grow with every further increase in temperature.
- The IPCC also states that limiting warming requires deep, rapid and sustained emissions reductions across all sectors, down to net-zero CO₂ emissions.
How sure are we?
Solid evidence
Numerous studies and authoritative sources converge.
The evidence is solid on observed warming, the role of greenhouse gases and increasing risks with rising temperature. The precise estimate of long-term warming, however, depends on the calculation method and remains subject to an uncertainty margin made explicit by the sources themselves.
How it can be read
Interpretations
- A year above 1.5 °C is not proof that the Paris Agreement goal has already failed, but it is consistent with a trend that continues to rise.
- Treating the threshold as a switch — below it everything is fine, above it everything is lost — is misleading: risk grows gradually and continuously.
What we don't know
- There is no single agreed method for measuring long-term warming: different estimates produce different values, even if close to one another.
- We do not know precisely in which year the 1.5 °C threshold will be stably exceeded: it depends on future emissions and natural variability.
- Some responses of the climate system, in particular the thresholds beyond which certain processes become difficult to reverse, are only incompletely known.
Why it matters
- Every extra fraction of a degree translates into greater frequency or intensity of extreme events, pressure on water and agriculture, and stress on ecosystems.
- The way the threshold is communicated influences decisions: believing it has already been definitively exceeded risks resignation; believing it is far away risks delay.
- Climate is not an isolated problem: it connects to water, food, health, the economy and social stability.
What we can do
- Read climate data always distinguishing the single year from the multi-year trend.
- Check news about global temperature against the original WMO and IPCC reports.
- Support emissions-reduction policies that act across all sectors, not just one.
The No-Extinction proposal
Proposals
- No-Extinction proposes treating climate targets as verifiable trajectories over time, with public indicators and regular updates, rather than as single symbolic thresholds.
Sources and data
The links lead to the original documents and open in a new tab. Every figure cited in this article comes from these sources.
World Meteorological Organization
State of the Global Climate 2024
report · 2025
wmo.int/publication-series/state-of-global-climate/state-of-global-climate-2024(opens in a new tab)IPCC
AR6 Synthesis Report — Longer Report / Summary for Policymakers
assessment report · 2023
www.ipcc.ch/report/ar6/syr/longer-report/(opens in a new tab)