El Nino or El No-no

Words of CAUTION
by William S. Kessler
NOAA / Pacific Marine Environmental Laboratory

It is important to remember that El Nino is not the only effect on weather. It is but one fluctuation among many, and the weather we experience is the sum of all of these overlaid and interacting. Most of these interactions are poorly understood, particularly the longer-term ones, and as we get longer and longer records we become aware of more and more complexity. The different El Ninos occur on different background states, at different times of year, and therefore have different total effects. Therefore, one cannot simply speak of the isolated effects of El Nino on weather in San Diego. There is only the ever-changing combination of influences. That is the main reason why we cannot produce reliable long-term forecasts.

Scientists study El Nino partly for its own effects, but also partly as an example of how this kind of climate oscillation interacts with the rest of the climate system. We know there are many such oscillations, and we would like to be able to fit the whole picture together. We hope that what we learn about the climate system from studying El Nino will help us understand other, less prominent, variability.