Shown below is a graph of the satellite-derived University of Alabama global temperature dataset (those fellows that each year in early January beat NOAA/NASA/MetOffice/WMO etc by being the first to say ‘how warm it was’). Clearly visible is the peak of the powerful 1997-1998 El Niño:
The UAH dataset shows relatively strong representation of tropical temperatures (and ocean, as it is a satellite set), and therefore relatively pronounced ENSO influence (extra hot El Niño years (1998!) & extra cool La Niña years (see for instance 2008 and 2011)). The tropical volcano-cooling of Mount Pinatubo in the early nineties is also clearly visible in the graph.
It serves to show how high a peak of a ‘super El Niño’ on the global average temperature trend can be. If we were to have a similar El Niño, that peak would rise about 0.2 degrees higher – as that is how much the base (30-year average) temperatures have increased since 1998. That is also the reason why also a moderate 2014-2015 El Niño* is very likely to bring new world temperature records.
[*) Apart from average temperature more things have changed about the global climate system since 1998. It is for instance unclear what a new ENSO temperature peak might have for an effect on Arctic sea ice, which has of course dramatically decreased since the last super El Niño.]
© Rolf Schuttenhelm | www.bitsofscience.org