The 1997-98 El Niño raised the global average surface temperature by 0.2°C above the long-term warming trend line.
This figure is from Hansen et al PNAS 2006, showing why the 1983 and 1998 El Niños were labeled, in turn, "El Niño of the century":
Last week's Nino3.4 temperature anomaly jumped up to +0.4°C, higher than it's been since November 2012. (An official El Niño happens when, I think, the 3-month running average of this region's anomalies is above +0.5°C.)
(*) Really, is there anything else?