SME
Climatology
Climate variability
Record a season’s Niño-3.4 anomalies, three months at a time, and decide whether it was an El Niño, a La Niña or neutral.
Record and look
0 °C
0.5
−0.5
+0.2
+0.5
+0.7
+1.1
+1.4
+1.6
+1.5
+1.1
+0.6
JJA
JAS
ASO
SON
OND
NDJ
DJF
JFM
FMA
El Niño threshold, 0.5 °C
La Niña threshold, −0.5 °C
JJA
JAS
ASO
SON
OND
NDJ
DJF
JFM
FMA
Niño-3.4 anomaly (°C)
+0.2
+0.5
+0.7
+1.1
+1.4
+1.6
+1.5
+1.1
+0.6
Five or more seasons in a row at +0.5 °C or above make an El Niño (here eight, peaking at +1.6 °C).
Tap a bar at the height you want.
Assumptions
•
The Niño-3.4 index is the sea surface temperature anomaly of the central equatorial Pacific: how far it sits above or below its long-term mean, in °C.
•
Each column is the mean of three overlapping months (JJA is June, July and August), which smooths out single odd months.
•
Five or more seasons in a row at +0.5 °C or above make an El Niño; at −0.5 °C or below, a La Niña.
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