[TheEnemy]

State of the Climate | Global Analysis - Annual 2012

Note: On January 15, 2012, NCDC announced as part of its 2012 Global Climate Report that 2012 was the warmest La Niña year on record. While there are a variety of approaches for defining a La Niña or El Niño year, NCDC's criteria is defined as when the first three months of a calendar year meet the La Niña or El Niño threshold as defined by NOAA Climate Prediction Center's (CPC) Oceanic Niño Index (ONI). The list of historical La Niña years released on January 15 was based on an ONI dataset in force in early 2012 and used a 1971–2000 base period. During the course of the year, CPC introduced an ONI dataset using different base periods for determining anomalies for each year, with the most recent years (1995 to date) utilizing the 1981–2010 base period. Because of long-term warming trends in the equatorial Pacific Ocean, applying this more recent base period allows for better discernment of the temperature patterns needed to identify El Niño and La Niña years. In the most recent version of the dataset, using the newer base period methodology, 2006 and 2009 are now classified as La Niña years. The global average temperature in both 2006 and 2009 was 0.02°C (0.04°F) higher than 2012, making these two years the warmest La Niña years on record. NCDC has updated (via strikeout) our Annual Global Climate report to reflect the most current CPC ONI dataset.

With binary definitions of El Niño or La Niña, small changes in processing the data can affect the classification of weak El Niños or La Niñas. Despite these reclassifications, the general conclusions are similar from previous work: (1) global temperature anomalies for each phase (El Niño, La Niña, and neutral) have been increasing over time and (2) on average, global temperatures during El Niño years are higher than neutral years, which in turn, are higher than La Niña years.

NCDC continually examines its practices and definitions as science, datasets, and the understanding they bring improve. Thus, given the nature of our current method of classifying years as El Niño or La Niña, NCDC plans to re-examine and employ the best available definitions and datasets to robustly characterize the influence of El Niño and LaNiña on annual global temperatures.

Maybe they should go to a sliding scale based on severity, like -10(la Nina) to +10(El Nino).