Ernesto Rodríguez Camino
Senior State Meteorologist and president of Spanish Meteorological Association
El Niño is the positive phase of a quasi-periodic phenomenon - called El Niño-Southern Oscillation (ENSO) - mainly related to the warming of the eastern equatorial Pacific Ocean. Historically, it is known to recur with a frequency of between 2 and 7 years, starting to develop between April and June and reaching its maximum intensity between October and February. It typically lasts between 9 and 12 months, although it has occasionally lasted 2 years. The phenomenon is the cause of climatic anomalies in remote areas of the Earth - the so-called climate teleconnections - which make it possible to establish relationships between these anomalies - e.g. heavier precipitation, droughts, etc. - and the phase and intensity of the ENSO phenomenon.
The intensity of ENSO - measured as the warming (or cooling in negative phases) of specific areas of the eastern equatorial Pacific Ocean - also determines the intensity of climate anomalies in remote areas. Years in which a strong El Niño event occurs favour an increase in the average surface temperature of the atmosphere, and if this is coupled with the global warming trend due to greenhouse gases emitted by the increasing use of fossil fuels, the annual average temperature of the atmosphere is quite likely to break records.
The WMO has declared the beginning of a positive ENSO phase and seasonal predictions from a variety of models indicate that this phase will continue for the time being over the next few months. Whether a record annual mean temperature will be broken will depend, among other factors, on the eventual intensity of the El Niño event that is now beginning. Intense events are associated with significant climate anomalies in certain areas of the globe, particularly in land areas around the equatorial Pacific Ocean, but they are hardly detected in Western Europe as other factors affecting climate variability are often more relevant over this part of the globe.
In short, we are likely to see an impact on global mean warming, although this warming is not likely to be reflected in an exceptional way over Spain in the coming months beyond the gradual warming caused by greenhouse gas emissions.