The ENSO year 2017–2018 was the fourth hottest year on record even though it was a La Niña year.
The El Niño–Southern Oscillation (ENSO) year 2017–2018 (i.e., July 2017 to June 2018) was the fourth hottest on record. The previous year (2016–2017), also a La Niña year, was the second hottest on record. In addition to overall global warming since 1950 (1.37 °C/100 years), El Niño (1.34 °C/100 years), Neutral (1.25 °C/100 years), and La Niña (1.55 °C/100 years) years are all demonstrating significant warming trends. The last two La Niña years were above the post-1950 El Niño trend line.
The ENSO cycle typically does not follow a calendar year, with El Niño and La Niña cycles often starting around late spring or early summer in the northern hemisphere. Consequently, ENSO years can be viewed as a more appropriate approach to understanding ENSO events and global warming.
Chart: Annual temperature anomalies since 1950. Each circle represents an annual temperature and is colored according to whether it was an El Niño event (red), La Niña event (blue), or a neutral year (grey). The size of each red and blue circle is proportional to the intensity of the El Niño/La Niña event ranging from weak (small), through moderate and strong, to very strong (large). The trend line (dotted lines) and r-squared values are reported for each set of events (i.e., El Niño, La Niña, and neutral years).
Methods and data: Global temperatures and El Niño–Southern Oscillation (ENSO) data are sourced from NOAA1,2. Monthly ENSO data are publicly available from NOAA since 1950 (annual data, on a calendar year basis, are available back to 1900). The data were compiled and visualized using Microsoft Excel3.