ENSO and Global Temperatures

Natural climate patterns that persist for days, months, or even years can affect weather patterns around the world and impact the average global temperature. One such well-known global-scale pattern—the El Niño-Southern Oscillation (ENSO)—is a natural episodic fluctuation in sea surface temperature (El Niño) and the air pressure of the overlying atmosphere (Southern Oscillation) across the equatorial Pacific Ocean. Over a period of months to a few years, ENSO fluctuates between warmer-than-average ocean surface waters (El Niño) and cooler-than-average ocean surface waters (La Niña) in that region.

With NOAA's Climate Prediction Center ENSO records dating back to 1950, three of the four warmest years on record (2010, 1998, and 2003) are "El Niño years". The year 2011 currently ranks as the warmest "La Niña year" in the 1950–2011 period of record. A La Niña (El Niño) year is defined here as occurring when the first three months of a calendar year are classified under La Niña conditions. With La Niña conditions present through April before transitioning to ENSO-neutral and trending toward warm El Niño conditions, 2012 is on track to potentially break 2011's annual temperature of 0.53°C above average.

Global Annual Temperature Anomalies