Apr 2026 temperature increase?

Specific Oceanic Niño Index forecasts are unavailable for late 2025 through early 2026. The provided research does not explicitly offer specific numerical Oceanic Niño Index (ONI) anomalies or precise probabilistic forecasts for El Niño, La Niña, or Neutral conditions for this core period. However, major climate model centers such as NOAA's Climate Prediction Center (CPC), the International Research Institute for Climate and Society (IRI), and ECMWF routinely issue these types of forecasts ^[2]. These institutions' ENSO Diagnostic Discussions, Official ENSO Probabilities, and Quick Look forecasts typically provide ensemble predictions for ONI anomalies and probabilities for different ENSO states across overlapping three-month seasons, which would span the target timeframe.

ENSO forecast skill diminishes considerably beyond a 6-9 month lead time. Generally, climate model forecasts for the El Niño-Southern Oscillation (ENSO) tend to exhibit reduced skill and increased uncertainty as the lead time extends, especially beyond this 6-9 month window ^[1]. As lead times increase, probabilities for various ENSO states often converge towards a neutral condition, unless strong and persistent signals are projected. The question highlights critical thresholds, such as a strong El Niño (exceeding +1.5°C ONI) or a significant La Niña (below -1.0°C ONI), which would strongly influence global temperature outcomes.

Direct consultation of current forecasts is essential for specific ONI anomalies. To determine if strong El Niño or significant La Niña conditions are anticipated for late 2025 through early 2026, direct consultation of the latest forecasts from the cited institutions is necessary ^[1].

No volcanic eruption since mid-2024 has achieved a VEI of 6 or higher. Web research indicates no such event through 2024 and 2025 ^[1]. For example, the Ruang volcano in Indonesia, which erupted in April 2024, registered a Volcanic Explosivity Index (VEI) of 4 ^[2]. Other documented activities, such as the Kanlaon eruptions spanning 2024-2026, also do not indicate an event reaching a VEI of 6 or higher ^[4].

Current eruptions have not significantly elevated global stratospheric aerosol optical depth. The typical background level for global mean stratospheric aerosol optical depth (AOD) is approximately 0.005 ^[3]. While the April 2024 Ruang eruption (VEI 4) did inject a considerable amount of sulfur dioxide and ash into the stratosphere, leading to a detectable, regionally observed increase in stratospheric AOD in the tropics and Southern Hemisphere ^[2], this has not resulted in a sustained global mean stratospheric AOD significantly above the background level. Such a sustained increase would be required to exert a strong cooling pressure on the global climate, but the impact of a VEI 4 eruption is generally insufficient to significantly alter global mean stratospheric AOD to that extent ^[2].

The NOAA/NASA SWPC predicted a relatively weak Solar Cycle 25. The official forecast anticipated a smoothed sunspot number (SSN) peaking at 115 in July 2025 ^[1]. This prediction also included a peak in the F10.7cm solar radio flux around 150 solar flux units (sfu) ^[1]. The consensus among experts generally suggested a cycle strength similar to Solar Cycle 24 ^[3].

Solar Cycle 25 significantly surpassed initial predictions in strength and timing. Its maximum activity was observed in October 2024, notably earlier than the forecasted July 2025 peak ^[2]. The smoothed monthly total sunspot number reached 169.9 at this peak ^[2], considerably higher than the predicted 115, and marking the highest sunspot number in over two decades ^[4]. The F10.7cm solar radio flux also consistently tracked above its forecasted curve, further confirming a stronger cycle across various metrics ^[1].

The stronger, earlier peak of Solar Cycle 25 suggests marginal warming. This progression, significantly exceeding the NOAA/NASA SWPC forecast, implies a marginal warming forcing. The observed deviation indicates that solar activity, which contributes to the Earth's energy budget, has been more robust than initially anticipated for the current cycle.

NOAA GlobalTemp version 6.1 introduces significant methodological revisions for 2025-2026 data. Released in December 2023, this update to the NOAA GlobalTemp dataset primarily addresses polar region interpolation and homogenization. Version 6.1 utilizes artificial intelligence and improved computational methods to enhance spatial coverage, particularly in polar regions, through an AI-based gap-filling technique, and to improve the homogenization of station data. The ocean component of NOAAGlobalTemp V6.1 is derived from NOAA ERSST Version 5 ^[1], with the overall methodology representing a major update for integrating data and addressing gaps ^[4]. These changes are scheduled for application to 2025-2026 data.

NASA GISTEMP and HadCRUT methodologies remain largely consistent for 2025-2026 data. The NASA GISS Surface Temperature Analysis (GISTEMP v4) methodology is largely consistent, with its analysis unchanged. Updates are confined to routine processes, such as daily and monthly data updates and minor bug fixes, which typically alter reported anomalies by a few thousandths of a degree Celsius ^[2]. Similarly, the HadCRUT dataset's most recent minor release, HadCRUT5.1.0.0, implemented in December 2021, involved minor adjustments to its underlying HadSST4 data due to routine updating ^[3]. The fundamental methodology of HadCRUT5 itself, which improved Arctic coverage, was established in 2020. No further significant methodological shifts for GISTEMP or HadCRUT beyond routine data updates are scheduled for application to 2025-2026 data.

The final 12-month temperature anomaly calculation for a market resolving in April 2026 spans from April 2025 through March 2026. This timeframe is crucial because the prediction market event, "Apr 2026 temperature increase?", resolves within April 2026 ^[1]. Therefore, March 2026 represents the latest full month for which processed temperature data can be obtained. This defined period ensures the market resolves using verified data within its specified resolution month ^[1].

NASA GISS provides data with a typical two-to-three week lag. The designated source for global temperature anomaly data is NASA GISS, specifically their GISS Surface Temperature Analysis (GISTEMP v4) ^[2]. This agency typically publishes its monthly surface temperature analysis with an approximate 2-3 week delay following the close of the data month ^[3]. Consequently, the GISTEMP data for March 2026 is anticipated to be released by mid-April 2026. This schedule guarantees that all necessary data covering the April 2025 - March 2026 period will be available for calculation during the market's resolution window ^[3].