Global Climate Report - September 2018
Monthly temperature anomalies versus El Niño

« Global Climate Report - September 2018

Monthly temperature anomalies versus El Niño

The graphic below depicts the monthly global temperature anomalies—that is, each month compared its 20th century average—since 1980, and the influence of the El Niño - Southern Oscillation (ENSO) phenomenon.

The height of the bar represents the global temperature anomaly for the month. The color of the bar represents the ENSO status, as defined by the Oceanic Niño Index (ONI), which is the three-month average temperature anomaly in the Niño3.4 region centered on that month. Months colored in red had ONI values indicating an El Niño episode active (at least five consecutive months with the three-month Niño3.4 temperature more than 0.5°C (0.9°F) above the working "normal". Blue represents La Niña episodes, more than 0.5°C (0.9°F) cooler than normal. Months in grey indicate ENSO-neutral conditions, when neither El Niño nor La Niña were present.

Because the ONI for the most recent month is never available (for example, the September ONI would use August, September, and October 2018 Niño3.4 temperatures, of which October is not yet available), the condition from the previous month is used.

Several factors are apparent in the figure. First, nearly every month since 1980 has been above the 20th century average, and has generally warmed through the period. Second, El Niño-like conditions (those months in red) tend to be warmer than neighboring periods, and La Niña-like conditions (blue) tend to be cooler. Third, protracted El Niño-like episodes tend to warm through the event, while La Niña-like episodes tend to cool through the event. Fourth, and finally, there are exceptions to all of the above points.

Monthly global temperature anomalies since Jan 1980, with Nino3.4 conditions shown
Global monthly temperature anomalies, with Niño3.4 conditions

Citing This Report

NOAA National Centers for Environmental Information, State of the Climate: Global Climate Report for September 2018, published online October 2018, retrieved on August 22, 2019 from