record. I decided to take a simple approach at looking at the effect of ENSO.  Using GISTemp Land/Ocean Index values and Nio 3.4 values, I computed 12-month running averages of Nio 3.4 and compared them to the average GISTemp values at lags of 0, 3, and 6 months.  Foster and Rahmsdorf used a diferent ENSO index and found optimal lags between 2 and 5 months.  So one would guess that a 3-month lag would fit the data best in my case, and indeed it did. The normal threshold for El Nio or La Nia, as applied by the Climate Prediction Center, is for five consecutive months of at least 0.5 C above or below normal in a key region of the tropical Pacific.  For working with annual data, I decided to call an annual average above 0.5 C an El Nio and an annual average below -0.5 C a La Nia.  Then I plotted it up, color-coding each year for whether it was El Nio, La Nia, or neither (neutral).  Here's the result: GISTemp global temperatures, 1951-2011 We see the latter half of the mid-century flat period, followed by the warming since 1970 and the relatively flat recent few years.  We also see a few years that were exceptionally cold and whose timing fits with the known injection of aerosols into the stratosphere by the mighty volcanic eruptions of Agung and Pinatubo.  It's easy to see that both of these eruptions caused global temperatures to drop by about 0.3 C