Climate Indices

Climate indices are simple diagnostic quantities that are used to characterize an aspect of a geophysical system such as a circulation pattern. They track droughts, ENSO events, wind patterns, internal modes of climate variability, and extreme events like wildfires and heatwaves. Climate indices play a key role in climate monitoring and prediction. The climate index overview page summarizes the philosophy of climate indices.

To find a specific climate index, jump to the search box below or click your desired index from among the blue sub-category buttons.

To see only the indices with in-depth commentary, select the "Datasets with guidance" button when using the search box.

Dataset Overviews

Climate datasets

Has expert guidance
NAO PC-based Index (DJFM) Hurrell North Atlantic Oscillation (NAO) Index (PC-based)

  • Years of Record

  • 1899-01 to 2025-03

The principal component (PC)-based indices of the North Atlantic Oscillation (NAO) are the time series of the leading Empirical Orthogonal Function (EOF) of SLP anomalies…

Main variables and Earth System components

Atmosphere Sea Level Pressure
NAO DJFM Station-based Index Hurrell North Atlantic Oscillation (NAO) Index (station-based)

  • Years of Record

  • 1865-01 to 2023-06

The winter (December thru March) station-based index of the NAO is based on the difference of normalized sea level pressure (SLP) between Lisbon, Portugal and…

Main variables and Earth System components

Atmosphere Sea Level Pressure
Atlantic Multi-decadal Oscillation (AMO) Atlantic Multi-decadal Oscillation (AMO) and Atlantic Multidecadal Variability (AMV)

  • Years of Record

  • 1870-01 to 2021-03

The Atlantic Multi-decadal Oscillation (AMO) has been identified as a coherent mode of natural variability occurring in the North Atlantic Ocean with an estimated period of…

Main variables and Earth System components

Ocean SST - sea surface temperature
The NAM (or Arctic Oscillation) is defined as the first EOF of NH (20°-90°N) winter SLP data. It explains 23% of the extended winter mean (December-March) variance, and it is clearly dominated by the NAO structure in the Atlantic sector. Hurrell wintertime SLP-based Northern Annular Mode (NAM) Index

  • Years of Record

  • 1899-01 to 2025-03

The NAM (or Arctic Oscillation) is defined as the first EOF of NH (20°-90°N) winter SLP data. It explains 23% of the extended winter mean (December-March) variance, and it…

Main variables and Earth System components

Atmosphere Sea Level Pressure
timeseries of signal and noise in the SOI Southern Oscillation Indices: Signal, Noise and Tahiti/Darwin SLP (SOI)

  • Years of Record

  • 1866-01 to 2025-03

The Southern Oscillation Index (SOI) is a time series used to characterize the large scale sea level pressure (SLP) patterns in the tropical Pacific. Monthly mean SLP at…

Main variables and Earth System components

Atmosphere Sea Level Pressure
Overview: Climate Indices Overview: Climate Indices

  • Years of Record

A climate index is a simple diagnostic quantity that is used to characterize an aspect of a geophysical system such as a circulation pattern. A variety of methods have been…

Main variables and Earth System components

Atmosphere Ocean

  • Experts contributing reviews

  • N/A
Meridional Modes and their indices Meridional Modes and their indices

  • Years of Record

In each of the world’s tropical ocean basins, year-to-year climate variability is primarily governed by fluctuations in the zonal sea surface temperature (SST) gradient and…

Main variables and Earth System components

Atmosphere Wind Ocean SST - sea surface temperature