A recently published paper found that the 2023 global warming spike was driven by the El Niño–Southern Oscillation (“ENSO”).

ENSO is an internal variability in the climate system (a natural climate variability) that comprises a positive phase, El Niño, and a negative phase, La Niña. It occurs every few years, typically every 3-7 years, in the tropical Pacific Ocean, affecting global temperatures, winds and atmospheric conditions.

According to the study, it is ENSO, and not external factors such as “emissions” due to human activity, that caused the 0.29^oC spike (give or take 0.04^oC) in global temperatures last year.  And it’s not the first time on record that ENSO has caused such a spike.

On 10 October, a paper titled ‘The 2023 global warming spike was driven by the El Niño–Southern Oscillation’ was published in Atmospheric Chemistry and Physics. The research was funded by the National Oceanic and Atmospheric Administration (“NOAA”).

At the beginning of this year, NOAA reported that “2023 was the world’s warmest year on record, by far.”  NOAA Chief Scientist Dr. Sarah Kapnick said. “We will continue to see records broken and extreme events grow until emissions go to zero.”

By “emissions” she is, of course, referring to aerosol pollution caused by human activity, or, as the mantra goes, anthropogenic (human-caused) climate change.

The study’s authors agree with NOAA’s first statement but not with its Chief Scientist Kapnick.  In their paper, they demonstrated that the 2023 global warming spike was driven by ENSO and that global warming spikes occur without human influence.

“Potential causes for this year-on-year spike include anthropogenic reasons such as greenhouse gas increases and aerosol pollution reductions or natural reasons such as increased solar activity, volcanic-induced stratospheric water vapour increases, and natural climate variability such as the El Niño–Southern Oscillation phenomenon (ENSO),” the paper said.

“Most studies have focused on the external forcing aspects, particularly the role of aerosol pollution reductions, rather than quantifying the role of internal variability. This study focuses on the latter, and we will argue that ENSO is the primary reason for global warming spikes,” the authors explained.

The study refers to temperature measured in Kelvin (K) which is the unit for temperature in the International System of Units (“SI”). It is an absolute temperature scale that starts at the lowest possible temperature, known as absolute zero which is −273.15 degrees Celsius (^oC); 0K converts to -273.15^oC, 1K converts to -272.15^oC, 2K converts to -271.15^oC and so on. It follows that a change in temperature of 1K is the same as a change in temperature of 1^oC and a change of 0.25K equates to 0.25^oC etc.

The study found that the 2023 global warming spike, which saw a rapid increase of 0.29K in global mean surface temperature (“GMST”) from 2022 to 2023, was driven by ENSO and noted that this large interannual global warming spike is not unprecedented.  A similar spike occurred in 1977 with an increase of 0.31K.  Both the 1977 and 2023 spikes occurred during an El Niño year, following a prolonged La Niña period (1973-1976 and 2020-2022, respectively).

Observational records suggest a strong correlation between global warming spikes and ENSO, the authors said, with two out of four long La Niña-El Niño transitions since 1950 leading to spikes.

To further investigate this correlation, the study analysed 58,021 years of multi-centennial to multi-millennial global climate model simulations from 64 models with no human influence. In each model, the researchers quantified:

• the probability of a spike,
• the probability of a spike occurring given a long La Niña–El Niño transition,
• the probability of a spike occurring given a long La Niña occurring in prior years,
• the probability of a spike occurring given an El Niño occurring that year, and
• the probability of a spike associated with an El Niño occurring during the year.

They found that spikes happen 1.6% of the time on average.  And the probability of a spike increases over 6-fold when a long La Niña is followed by an El Niño during the spike year, indicating that global warming spikes become much more likely during El Niño events preceded by a long La Niña.

The study’s findings suggest that ENSO plays a critical role in generating global warming spikes and that internal variability within the climate system (natural climate variability) can produce large spikes in GMST without invoking external forcing. 

As mentioned earlier in this article, external forcing are factors that drive climate change from outside the Earth’s climate system such as solar activity, volcanic eruptions, aerosol concentrations and, the climate alarmists’ favourite, greenhouse gas concentrations.

Not only does ENSO play a critical role, but the findings suggest ENSO is the primary reason for global warming spikes, rather than external factors such as anthropogenic forcing.  It underscores the importance of considering internal variability in climate models.

“If the probability of spikes given these ENSO events remains the same, this would imply that in the future, the number of global warming spikes increases or decreases depending on ENSO frequency changes,” the authors wrote.

The authors suggested that future research should investigate the impact of other internal variability forms such as the Atlantic Multidecadal Oscillation and its relation or co-occurrence with ENSO on the 2023 spike in global temperature.