Global Temperature in 2025, 2026, 2027
- Hakan Sener
- 4 minutes ago
- 4 min read
Earth's temperature hit +1.47°C in 2025 (2nd warmest year). Hansen projects new record of +1.7°C in 2027, confirming accelerated warming at 0.31°C/decade.
A December 2025 analysis by James Hansen and colleagues reveals that global temperature reached +1.47°C in 2025 relative to the 1880-1920 baseline, marking the second warmest year on record.
The 2023-2025 mean stands at +1.5°C. Despite current La Niña conditions, the researchers project temperatures will decline to a minimum of about +1.4°C in early 2026 before rising to a new record of +1.7°C in 2027 as climate models indicate El Niño development in the second half of 2026.
This projection provides a critical test of the global warming acceleration hypothesis and challenges the persistence of protective atmospheric patterns that have temporarily modulated surface warming.
Key Findings: From El Niño Peak to Projected Record
2025 Marks Second Warmest Year Despite Post-El Niño Cooling
Global temperature of +1.47°C in 2025 represents approximately 0.1°C cooling from the 2024 El Niño-spurred maximum in the GISS (Goddard Institute for Space Studies) analysis. The 3-year mean (2023-2025) of +1.5°C relative to 1880-1920 marks sustained breach of the symbolic 1.5°C threshold established in the Paris Agreement.
The decline from 2024's peak is consistent with the transition from El Niño to La Niña conditions, but the temperature remains substantially elevated above previous post-El Niño minima, confirming the underlying acceleration of global warming beyond natural variability.
Accelerated Warming Rate of 0.31°C per Decade
Linear fit analysis shows global warming has increased from 0.18°C per decade (1970-2010) to 0.31°C per decade (2010-present)—a 72% acceleration in the warming rate. This acceleration is attributed to recent shifts in aerosol effects, where long-term global cooling from aerosols has transitioned to warming.
The projected 2027 record of +1.7°C will occur only four years after the 2023 El Niño peak, representing approximately 0.1°C of additional underlying warming at this accelerated rate, separate from ENSO (El Niño-Southern Oscillation) variability.
La Niña Conditions Transitioning to El Niño by Late 2026
The tropical Pacific Ocean is currently in its cool La Niña phase, with the Nino3.4 sea surface temperature anomaly below the -0.5°C threshold. The 12-month running-mean temperature is expected to reach a minimum of about +1.4°C in the first half of 2026 as La Niña effects persist.
Multiple climate models, including the NOAA NCEP (National Center for Environmental Prediction) ensemble forecast issued December 15, show development of El Niño conditions beginning in the second half of 2026. The ensemble projects Nino3.4 index values rising from current La Niña conditions through neutral phase (January-March 2026) to El Niño threshold by mid-to-late 2026.
Rapid Global Warming Distorts ENSO Signal Interpretation
Analysis reveals that rapid global warming over the past half-century is perturbing the quantitative significance of the Nino3.4 index. The strongest El Niño relative to its surroundings was 1997-98, while the 2015-16 and 2023 El Niño strengths appear exaggerated by the effect of global warming on the Nino3.4 index.
Background warming also diminishes the apparent strength of recent La Niñas when measured against historical baselines, complicating traditional ENSO cycle interpretations and requiring careful separation of the underlying warming signal from natural oscillations.
Projected 2027 Record of +1.7°C Tests Acceleration Hypothesis
Based on the expected El Niño development and continued accelerated warming trend, Hansen and colleagues project global temperature will reach approximately +1.7°C in 2027—a new all-time record exceeding the 2024 maximum by ~0.1-0.2°C.
This projection assumes at least a moderate El Niño beginning in 2026, consistent with multiple dynamical model forecasts. The timing and magnitude of this record will provide empirical validation or refutation of the global warming acceleration hypothesis, testing whether post-El Niño temperatures fall to previous baseline levels or remain elevated due to underlying acceleration.
Why This Matters: A Testable Prediction of Accelerated Warming
This research delivers three critical messages for climate science and policy:
Bold Predictions Advance Scientific Understanding: The researchers explicitly frame their projection as a test of the acceleration hypothesis, following the principle articulated by Wally Broecker that scientific progress depends on "people who have the knowledge and the courage to attempt an interpretation of available data, which are always incomplete and contain measurement flaws." Even if predictions prove incorrect, they stimulate research, expose flaws, and drive improvements in understanding.
Surface Cooling Does Not Indicate Pause in Global Warming: The current La Niña-driven surface cooling to +1.4°C in early 2026 represents temporary redistribution of heat within the climate system, not a reversal of long-term warming. The 12-month running-mean temperature remaining above +1.4°C—compared to previous post-El Niño minima near +0.8-1.0°C—demonstrates the irreversible nature of accumulated warming and the accelerated baseline from which natural variability now operates.
Aerosol Transition Amplifies Greenhouse Gas Forcing: The acceleration from 0.18°C to 0.31°C per decade is fundamentally driven by the recent shift in aerosol effects from net cooling to warming. This transition means that the climate system is now experiencing the full force of greenhouse gas accumulation without the historical masking effect of industrial aerosols, explaining why current warming exceeds previous model projections calibrated against the slower 1970-2010 trend.
Beyond Scientific Reticence
The 2027 projection forces a fundamental shift in how climate predictions are communicated. Rather than conservative statements of current conditions or cautious ranges that avoid specific claims, Hansen's approach embraces the scientific value of testable, falsifiable predictions. The anticipated +1.7°C record—if it materializes—will provide definitive confirmation that global warming has entered a new, accelerated phase requiring immediate recalibration of climate targets, adaptation strategies, and emissions reduction timelines.
The projection establishes a clear benchmark against which the scientific community's understanding of climate acceleration can be evaluated, moving beyond incremental analysis of past trends to bold forecasting that drives urgent policy action based on the emerging reality of a rapidly destabilizing climate system.
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