El Niño and Probability

Overview

The laws of probability are useful for day-to-day activities, such as beating a friend at a game of poker, trying to win the lottery, and even guessing the chances that a favorite sports team will win a big game.

As researchers from NOAA's Physical Sciences Laboratory (PSL) recently reported, these rules of chance are also essential for climate forecasting. In a paper published in the Journal of Climate, Prashant Sardeshmukh, Gilbert Compo, and Cécile Penland used probability calculations to show that a large set of data is the key for learning how the El Niño Southern Oscillation (ENSO) affects weather outside of the tropics. Furthermore, a dataset this large can be used to detect the impact of ENSO related shifts in the mean state and changes in variability on the risk of seasonal climate extremes.

The results from this study indicate that it's not enough to use instrumental data collected from thermometers, barometers and other weather-measuring devices over the past 100 years, since this instrumental record contains no more than a few dozen ENSO events. Rather, the PSL research team found that using climate models to create larger data sets can give additional useful information about how ENSO affects weather around the world.