Where will 2026 rank among the hottest years on record?
I assess a 36% chance that 2026 will be the hottest year on record according to the NASA GISTEMP No_Smoothing annual value, slightly higher than the current market-implied probability because long-term warming and episodic extremes keep the tail risk of a record elevated despite ENSO uncertainty.
Analysis
Observed global temperatures have trended upward for decades, shifting the baseline so that recent years dominate the top-of-records list; this structural warming materially raises the prior probability that any recent year, including 2026, can reach the top rank even absent an exceptionally strong ENSO event. The key physics — ocean heat uptake, ongoing greenhouse forcing, and Arctic amplification — continue to bias annual anomalies upward, which means the distribution of possible 2026 values is shifted toward record territory compared with pre-2000 years.
The dominant short-term determinant is the ENSO state during the 2026 peak months (boreal spring-summer) and the months used to compute the annual mean in GISTEMP; strong El Niño years have historically produced the warmest global annual means and are the most common cause of new records. Multi-year strong El Niño events are uncommon, and after a major El Niño the climate system often drifts toward neutral or La Niña, which would reduce the chance of a 2026 record; because I do not have a definitive ENSO forecast in this summary, ENSO uncertainty is the largest single source of forecast variance.
Market sentiment, as reflected in the present Yes price of ~29.5%, appears to incorporate the view that a new record this year is possible but not likely; my independent assessment nudges that probability upward to 36% because of (a) an elevated baseline from long-term warming, (b) the possibility of strong seasonal extremes (heat waves, persistent blocking) that can lift the annual mean, and (c) sampling uncertainty in GISTEMP annual values where relatively small differences separate top-ranked years. The resolution mechanics (GISTEMP No_Smoothing annual row for 2026 and the market's tie rule) mean that even small positive anomalies or differences in rounding can flip the outcome, raising the effective probability of a tie-or-top placement above naive expectations.
Other external factors introduce asymmetry: a large tropical volcanic eruption or an abrupt shift to a strong La Niña would materially lower the odds of a record, while a late-season heatwave series or an extended weak-to-moderate El Niño could push 2026 over the top; because those events have non-negligible probability before the NASA annual number is posted, they keep the forecast uncertain and justify a probability materially above zero but well below 50 percent.
Arguments
For
- The long-term trend in global temperatures has shifted the climatological baseline upward, making new records more likely now than in past decades.
- If ENSO is in an El Niño phase during the months that contribute most to the annual mean, the odds of a record year rise sharply.
- Persistent hemispheric heat waves or blocking patterns in 2026 could produce sufficient positive anomalies to surpass the current record.
- Ocean heat content and slow-varying modes can release additional heat to the surface, producing higher-than-expected annual means.
- Small positive differences in the GISTEMP annual number can be decisive due to the narrow margins separating recent top-ranked years.
Against
- If 2026 is neutral or La Niña-dominated, the probability of beating recent top years drops substantially.
- A major volcanic eruption prior to or during 2026 could inject aerosols that cool the global mean and prevent a new record.
- Recent record years are already very warm, so surpassing them requires another large positive anomaly that is not guaranteed.
- Natural internal variability can offset the long-term warming signal in any single year, making records sporadic rather than monotonic.
- Measurement and sampling noise plus the specific GISTEMP method mean small differences might favor other years even when 2026 is unusually warm.
Key drivers
- ENSO phase during 2026 (a strong El Niño substantially raises the probability of a record).
- Long-term greenhouse-gas-driven warming trend which raises the baseline of annual means.
- Seasonal and regional extremes (e.g., persistent hemispheric heat waves) that can boost the annual global mean by tenths of a degree.
- Timing and exact methodology of the NASA GISTEMP No_Smoothing annual calculation and rounding conventions around the top-of-record years.
- Potential for a major tropical volcanic eruption introducing stratospheric aerosols and cooling the globe in 2026.
- Short-term internal variability in the ocean-atmosphere system that can either amplify or dampen global-mean surface temperature on annual timescales.
Risk factors
- ENSO could shift to neutral or La Niña during 2026, reducing the chance of a record.
- A large volcanic eruption before the annual averaging period could cool global temperatures and preclude a new record.
- GISTEMP annual estimates can be separated by amounts smaller than their uncertainty, creating resolution sensitivity to small measurement or dataset differences.
- Regional cooling patterns or anomalous ocean heat uptake could disproportionately lower the global mean despite a high baseline.
- Data availability and the market rule requiring NASA data by March 1, 2027 could lead to alternative resolution if NASA delays or alters publication.
- My assessment may under- or over-weight the probability of extreme seasonal heat events that materially affect the annual mean.
Scenarios
Best case
A continuation or re-intensification of El Niño through the peak 2026 months combined with broad-seasonal heatwave activity and minimal volcanic aerosol forcing produces a sufficiently high annual global mean in GISTEMP No_Smoothing to make 2026 the hottest year on record.
Most likely
ENSO remains neutral to weak-forcing during 2026 and internal variability produces some regional extremes, yielding a year that is among the warmest on record (likely in the top 3-6) but with less than even odds of being the single hottest year.
Worst case
A shift to La Niña or a large volcanic eruption early in 2026 produces significant negative anomalies that place 2026 below recent top years, resulting in a clear No resolution with 2026 outside the top rank.
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