Pacific climate system
Every few years, the Pacific Ocean rewires the world's weather.
Drought in Australia. Floods in Peru. California can dry out, or drown. El Nino shifts rainfall, clouds, and reflected sunlight across the Pacific.
Can you predict where those shifts happen?
The Pacific pattern
The map is a composite showing the typical Pacific-wide pattern across 1950–2014. Start with the El Nino Fingerprint, then peel apart the layers to see how ocean warming lines up with rainfall, clouds, and reflected sunlight.
Dataset: CESM2 historical climate model output from 1950–2014, comparing El Nino-like months against neutral months.
Scroll down to step through each layer — the globe updates automatically.
Each layer compares El Nino-like months against neutral months in CESM2 historical data.
Fingerprint
The fingerprint combines ocean warming, rainfall, clouds, and reflected sunlight into one normalized index. Strong positive areas show where several El Nino signals line up across the Pacific basin.
The eastern and central Pacific light up in unison — a stark contrast to the weaker or opposite signal in the west.
You can drag and scroll the globe to explore freely.
SST Warming
Sea-surface temperature rises across the tropical Pacific. This warm water is the trigger that reorganizes the atmosphere above it.
The Niño 3.4 region (5°N–5°S, 170°W–120°W) is the key monitoring zone — scientists declare an El Niño event when warming there exceeds +0.5 °C for several consecutive months.
You can drag and scroll the globe to explore freely.
Rainfall Shift
El Nino shifts rainfall eastward across the Pacific. Some regions become wetter while others dry out — which is why the same event can mean floods in one place and drought in another.
Red areas received more rain during El Nino-like months; blue areas dried out.
You can drag and scroll the globe to explore freely.
Cloud Cover
Cloud cover changes as tropical convection moves. The atmosphere responds to the ocean pattern instead of staying fixed in place.
Positive values (cloudier) in the central Pacific and negative values (clearer) near Indonesia show how dramatically the convective zone migrates.
You can drag and scroll the globe to explore freely.
Radiation
Clouds affect how much shortwave radiation leaves the top of the atmosphere. El Nino changes the Pacific energy balance, not only ocean temperature.
Where clouds increase, more sunlight bounces back to space. The pattern closely mirrors cloud cover, confirming the tight coupling between clouds and reflected energy.
You can drag and scroll the globe to explore freely.
Behind the comparison
+0.5 °C thresholdMonths above this line become the El Nino-like group used in the map.
The Niño 3.4 region (5°N–5°S, 170°W–120°W) is the standard benchmark for ENSO. When its monthly sea-surface temperature anomaly stays above +0.5 °C, that month is counted as El Niño-like in this analysis. Months below −0.5 °C are La Niña-like; everything in between is Neutral. The 65-year record below shows how frequently each phase has appeared since 1950.
Now that you have seen the Pacific-wide pattern, test whether your intuition matches the science. Each question will ask you to predict one El Nino effect, then compare your guess against the map layers.
El Nino is not one isolated ocean effect. It begins with unusual warming in the tropical Pacific, and that warming lines up with shifts in rainfall, cloud cover, outgoing shortwave radiation, and regional climate patterns.
The project succeeds when users can see those variables as one connected Pacific-wide system.