Tag Archives: ENSO

ENSO, Alaska, and correlation, what’s the connection?

The climate.gov article Moose tracks through Alaska and ENSO  by Brian Brettschneider (6/23/2022) is a great example of using statistics in a real world setting; in this case the Pearson correlation. The graph copied here is interesting but the footnote may be even more so:

This statistical analysis uses the Pearson correlation of a linear regression, which measures how well two variables (like ENSO and Alaskan temperature) remain in sync. Correlation values range from -1 (completely out of sync) to +1 (completely in sync). Also, because Alaska’s temperatures have such a strong warming trend, the anomaly for each year was compared against a trailing 30-year average (or climatology). This mostly, but not entirely, removes the trend. We are interested in removing the climate trend in these maps because we are interested in isolating the ENSO signal (which does not include climate change signals).

Quick summary of the results:

The winter and spring seasons have the greatest connection between ENSO (as measured by the Oceanic Niño Index) and departures from average air temperature, and the correlation is positive. This means that El Niño tends to bring above-average temperatures; it also means La Niña is linked with below-average temperatures. Areas adjacent to and closer to the North Pacific Ocean tend to have a stronger connection with ENSO than areas inland. In the summer, the relationship weakens quite a bit (as indicated by the lighter shading) and is mostly nonexistent by fall.

The Oceanic Niño Index links to a data set. There are a few other maps in the article and a couple more footnotes.

 

How hot was 2021, ENSO version?

From NOAA’s Global Climate Report – Annual 2021:

The year 2021 began with an episode of cold phase El Niño Southern Oscillation (ENSO) episode, also known as La Niña, across the central and eastern tropical Pacific Ocean, which had developed in August 2020. As seen in the graph below, ENSO can have an effect on global temperatures. La Niña episodes tend to cool global temperatures slightly, while the warm phase ENSO (also known as El Niño) tends to boost global temperatures. Although the monthly global temperatures were above average throughout the year, February 2021 was the coldest month of 2021 for the globe. The global temperature departure for February 2021 was +0.64°C (+1.15°F) — the coolest February since 2014. However, after the month of February, temperatures were at 0.80°C (1.44°F) or higher for the remaining months of 2021.

The net result:

The year culminated as the sixth warmest year on record for the globe with a temperature that was 0.84°C (1.51°F) above the 20th century average. The years 2013–2021 all rank among the ten warmest years on record.

Time series data available at the top. ENSO status data must be somewhere but there doesn’t appear to be a link; just the graph.