POWER!!!! Fortescue Future Industries, page-3099

I'm no expert, but I thought the SOI is about pressure differences between Darwin & Tahiti, and it's used in conjunction with water temperatures and other factors to predict the strength of El Nino / La Nina. The SOI in isolation doesn't give you a lot in terms of seeing what is different today verse 150 years ago. A pressure difference is just a ratio. Surface sea pressure may be affected by temperature, and many other factors, but looking at this ratio may not tell you a lot. eg. The temperature in Darwin & Tahiti may have risen 5 degrees in both places, and caused the surface sea pressure to rise (or fall) in both locations, however, this isn't necessearily going to do much to the comparision ratio between those two locations..