The 4BYO Climate Symphony
A compound teleconnection stack on a single 15-year timeline - ENSO, NAO, AMV, and the polar vortex - past and present with the official forecast. Toggle any driver in What-If mode to see how the combined picture shifts.
Combined Global Footprint
Climate is ENSO, NAO, AMV and the polar vortex acting together. Switch the live stack, an upcoming-winter forecast, or any of the 16 combinations.
Methodology & Sources
How the Climate Symphony is built
The Symphony is built from the same per-pillar snapshots that drive the individual tracker pages (ENSO, NAO, Polar Vortex), fused into a single multi-pillar forecast-stack JSON. Every number on the chart, the world map, and the pillar pills is sourced from the same artefact - they cannot disagree.
Observed (history) data
- ENSO / Niño 3.4 / ONI - NOAA Climate Prediction Center Oceanic Niño Index (3-month running mean ERSSTv5 SST anomaly, Niño 3.4 region) plus weekly OISST.v2.1. Monthly updates.
- NAO - NOAA CPC daily & monthly NAO index (500 hPa EOF-based, 1950-present).
- PNA - NOAA CPC daily & monthly Pacific-North American teleconnection index.
- AO (proxy for stratospheric polar vortex state) - NOAA CPC daily & monthly Arctic Oscillation index.
- SSW catalogue - Major Sudden Stratospheric Warming events from the Free University Berlin / NOAA SSW chronology.
- AMV - NOAA Physical Sciences Laboratory Atlantic Multidecadal Variability (unsmoothed monthly SST anomaly, North Atlantic basin).
- Global surface temperature - NOAA Climate at a Glance Global Land + Ocean monthly anomaly.
Forecast data & models
- ENSO - official NOAA CPC / IRI ENSO consensus probability forecast, 9 overlapping 3-month seasons (DJF, JFM, FMA, ...). Updated monthly. Confidence: high.
- NAO / PNA / AO - persistence-decay model:
value₀ · exp(-Δmonths / τ)with τ = 2 months. This honestly reflects how little operational seasonal skill these atmospheric indices have at lead. Confidence: moderate at 1 month, downgraded to low by 3 months and climatological beyond. - AMV - persistence (carry-forward of the latest observed value). Justified by AMV being a decadal background phase with autocorrelation r ≈ 0.8 over a year. Confidence: moderate.
Operational seasonal NAO products (Met Office GloSea, ECMWF SEAS5, DePreSys) do exist with modest skill in some winters - when their data feeds are wired in they will replace the persistence-decay defaults for NAO and AO. The method field in the forecast-stack JSON already supports the swap.
Compound stacking matrix
The 16-cell matrix is an evidence-based lookup keyed by the sign (+ or -) of each pillar. Cell narratives are synthesised from the peer-reviewed teleconnection literature and the documented impacts maintained by NOAA CPC, the Met Office and ECMWF. Each cell carries region-specific impact text for the UK / NW Europe, central + eastern Europe, North America and the ENSO-impacted Southern Hemisphere regions.
The ENSO Ratchet Effect
The amber dashed lines on the Global Temperature panel mark the post-El Niño temperature floor: the 12-month mean global anomaly for the year starting 6 months after each major event’s ONI peak. After the 1997–98, 2009–10, 2015–16, and 2023–24 El Niño events, temperatures never returned to the pre-event baseline during the following La Niña - each event left a higher floor than the one before (+0.13, +0.08, +0.21, and +0.32 °C respectively). This “staircase” pattern reflects primarily the underlying anthropogenic warming trend: each El Niño spike rides a rising baseline, so even the La Niña cooling that follows still lands above the pre-event level.
A secondary contribution may come from El Niño-induced feedbacks - Arctic sea-ice albedo loss, ocean heat redistribution - that are not fully reversible on multi-year timescales. With a new El Niño now developing (NOAA/IRI consensus probability >90 % by JJA 2026), the global temperature baseline can be expected to step higher again; the exact magnitude depends on event strength but historical analogues suggest a floor lift of roughly +0.1–0.25 °C above the current post-2023-24 level.
Foster & Rahmstorf (2011, Environ. Res. Lett. 6 044022) provide the canonical framework for separating the ENSO signal from the underlying warming trend. Their analysis shows ENSO has a total range of ~0.39 °C on the global surface temperature record, with global warming lagging the MEI index by 2–5 months.
Frequently Asked Questions
Climate Symphony - Common Questions
What is the Climate Symphony?
The Climate Symphony is an interactive view of how Earth's major climate "drivers" stack together to shape weather and climate at any moment. It combines four pillars - ENSO (El Niño / La Niña), the NAO (North Atlantic Oscillation), the AMV (Atlantic Multidecadal Variability) ocean background, and the stratospheric polar vortex (SPV) - into a single compound state. The same page also shows the PNA, AO and global surface temperature on one timeline, so you can see past, present and the official forecast in one place.
Why look at all the climate systems together rather than one at a time?
Because no single driver acts in isolation. A +NAO winter feels very different depending on whether ENSO is in El Niño or La Niña, whether the AMV ocean background is warm or cool, and whether the stratospheric polar vortex is strong or disrupted. The four pillars stack into 16 possible sign combinations and each combination has a documented signature in the historical record. Looking at one pillar at a time hides the most important question: what is the combined state right now, and what is it expected to be next season?
What does the compound stacking matrix show?
The matrix is a 16-cell lookup keyed by the sign (+ or -) of each pillar - ENSO, NAO, AMV and SPV. Each cell carries an evidence-based narrative for what that combined state means for the UK and northwest Europe, central and eastern Europe, North America, and the ENSO-impacted Southern Hemisphere regions (Australia, India / SE Asia, South America, Southern Africa, East Africa). The system selects the cell that matches the live observed state, the forecast state for any upcoming CPC season, or any combination you build in What-If mode.
Where does the forecast come from?
The fused multi-pillar forecast uses different methods per pillar because operational seasonal skill varies enormously. ENSO uses the official NOAA CPC / IRI consensus probabilistic forecast (high skill at 1-9 months). NAO, PNA and AO use a persistence-decay model (last observed value with a 2-month e-folding decay toward climatology) - this honestly reflects the fact that seasonal atmospheric skill is genuinely low. AMV uses persistence (carry-forward of the latest value), valid because the AMV is a decadal background phase with autocorrelation r ≈ 0.8 over a year. Each pillar carries its own confidence flag (high / moderate / low / climatological) so the front-end is honest about what is well-known and what is a baseline guess.
Why does the NAO forecast often look near zero?
Because that is the honest answer at seasonal lead. The atmospheric drivers (NAO, PNA, AO) have very little operational predictive skill beyond a few weeks. Persistence-decay correctly collapses the forecast to climatology (≈ zero) within a couple of months. Showing a confident +NAO or -NAO signal 6-12 months out would be misleading. Operational seasonal NAO products (Met Office GloSea, ECMWF SEAS5, DePreSys) do exist with modest skill in some winters - we plan to swap them in for the persistence-decay default once their data feeds are wired up.
What is the difference between Now, Forecast and What-If modes?
Now: the live observed state of all four pillars from the latest snapshot of each index. Forecast: step through the next ~12 months of CPC seasons; the matrix and the world map update to show the dominant fused stack for each season. What-If: toggle any pillar to any sign you want and see which historical analogue (and which combined regional impacts) you have just constructed - useful for asking questions like "what would a +NAO winter look like if AMV were cool?"
Why do the chart and the map sometimes disagree on the NAO sign?
They no longer do. The map dot colour is driven by the numeric forecast value with the same dead-band the chart uses (NAO / PNA / AO ±0.5 standardised anomaly, AMV ±0.10 °C). A near-zero climatological forecast now reads as a neutral grey dot on the map AND a near-zero dashed line on the chart - matching the value shown on the pillar pills.
What is the AMV and why does it matter?
AMV stands for Atlantic Multidecadal Variability - the slow basin-wide warm/cool background phase of the North Atlantic sea surface temperatures, with a typical period of 60-80 years. A warm AMV tilts the NAO negative on average, boosts Atlantic hurricane activity, and adds ~0.05 °C to global mean temperature; a cool AMV does the opposite. AMV phase is one of the main reasons certain decades feel persistently stormier or drier than others, even when ENSO is neutral.
What is the stratospheric polar vortex (SPV) and how is it linked to weather?
The SPV is the ring of fast westerly winds that circle the North Pole each winter in the stratosphere (~30 km up). When it is strong, midlatitude weather tends to stay zonal and mild (+NAO bias). When it weakens or is disrupted (a sudden stratospheric warming, or SSW), the signal couples downward over 2-4 weeks and pushes the surface into a -NAO regime - cold spells across northern Europe and the eastern US. The Symphony page uses the AO (Arctic Oscillation) as an observational proxy for the SPV state.
How often is the data updated?
All observed pillars are refreshed monthly (and most also have daily updates). The CPC ENSO probability forecast updates monthly. The fused forecast-stack JSON is rebuilt whenever any underlying pillar snapshot changes, so the chart, the map and the pillar pills always carry the same numbers.
Why call it the Climate Symphony?
Because no single driver tells the whole story. Each pillar is one instrument; the weather we experience is the chord they play together. The Symphony page is the score - the live arrangement and the forecast for the next few months - so you can see the whole orchestra at once instead of listening to one violin in isolation.
Why do temperatures stay high after an El Niño ends?
After each major El Niño event, global temperatures decline during the La Niña that follows — but they rarely return to the pre-El Niño baseline. Each event leaves a higher temperature "floor" than the one before, producing the "staircase" or "ratchet" pattern visible in the global temperature record. The 1997-98, 2009-10, 2015-16, and 2023-24 events lifted the post-event floor by +0.13, +0.08, +0.21, and +0.32 °C respectively. The primary explanation is the underlying anthropogenic warming trend: each El Niño spike rides a rising baseline, so even the subsequent La Niña cooling still lands above the pre-event level. Secondary feedbacks — Arctic sea-ice albedo loss, ocean heat redistribution — may make part of the step irreversible on multi-year timescales. The gold staircase line on the Global Temperature chart shows these post-event floors: the treads slope gently upward with the background warming trend, and the near-vertical steps mark each El Niño ratchet click. As of mid-2026, a new El Niño is developing with >90 % probability; based on historical patterns, another floor step of roughly +0.1–0.25 °C above the post-2023-24 level could be expected after the event peaks.