Comparing Temperatures -- This El Niño vs. The 1997-98 El Niño
This year's El Niño is neck-and-neck with the 1997-98 El Niño, according to the Niño3.4 index (sea surface temperature anomalies in a central region of the eastern equatorial Pacific ocean). But surface temperatures (right-hand scale) are about 0.3°C warmer:
It's almost like something has been causing the surface to warm in the interim.....
Note 8/19/15: issues with incorrect graph labeling have been corrected.