+-- {: .standout} This is a [[Blog articles in progress|blog article in progress]], written by [[John Baez]]. To see discussions of the article as it is being written, visit the [Azimuth Forum](http://forum.azimuthproject.org/discussion/1385/blog-el-nino-project-part-4/?Focus=11364#Comment_11364). If you want to write your own article, please read the directions on [How to blog](http://www.azimuthproject.org/azimuth/show/How+to#blog). =-- Here is the result (click to enlarge): <div align = "center"> <a href = "http://math.ucr.edu/home/baez/ecological/el_nino/ludescher_replication.jpg"> <img src = "http://math.ucr.edu/home/baez/ecological/el_nino/ludescher_replication_small.jpg"></a> </div> This is almost but not quite the same as the graph in Ludescher <i>et al</i>: <div align="center"><a href="http://www.pnas.org/content/early/2013/06/26/1309353110.full.pdf+html"> <img width="450" src="http://math.ucr.edu/home/baez/ecological/el_nino/ludescher_el_nino_cooperativity_2a.jpg" alt="" /></a></div> <h3> Niño 3.4 </h3> In Part 3 I mentioned a way to get Niño 3.4 data from NOAA. However, Graham started with data from a different source: • [Monthly Niño 3.4 index](http://www.cpc.noaa.gov/products/analysis_monitoring/ensostuff/ONI_change.shtml), Climate Prediction Center, National Weather Service. The actual temperatures in Celsius are close to the NOAA data I mentioned last time. But the anomalies, which actually give the Niño 3.4 index, are rather different, because they are computed in a different way, that takes global warming into account. See the website for details. [Code at Github](https://github.com/azimuth-project/el-nino/blob/8ab1178b91d7df7c3676e5767c541f1a673bde2e/R/grj/ludescher.R). It took about 35 minutes to run. category: blog, climate [[!redirects Blog - El Nino project (part 4)]]