John said

> Note that since [the NINO3.4 index] is defined in terms of sea surface temperatures, we can think of the challenge this way: use current sea surface temperatures to predict aspects of future sea surface temperatures. Of course there’s no need to restrict ourselves to using current sea surface temperatures - we could use the Dow Jones industrial average if that helped. But using just sea surface temperatures makes it into an interesting self-contained game: “how much do sea surface temperatures now know about future sea surface temperatures”?

It was in this spirit that I made this image earlier today.

The box is roughly the area for defining the NINO3.4 index. It is not hard to see that 1958 is warmer in the box than 1957. The tricky question is: can you see it coming? You could use more data: further back into 1956 or earlier; you could look at days, not ten-day averages; and you could use finer spatial resolution (the NOAA data is one point per 2.5 degrees, these images and the Ludescher paper use 7.5).