Sea Surface Temperature anomalies in degrees Celsius, or "SST anomalies" for short, are how much temperatures depart from what is normal for that time of year. This makes sense; we might say that we had a "warm winter" even though it was still much colder than summer. What we mean is that it was warmer than a normal winter; in our parlance, we would say that it was a "positive anomaly". An unusually cold winter would be a "negative anomaly". For Pacific SST, an anomaly in the range of 1.5 to 3.5 degrees Celsius would be considered characteristic of an El Niño; the warmer and more widespread the water, the stronger the El Niño.
Last modified: 25 June 1997
Copyright © 2000 David W. Pierce. All rights reserved.