The 2023 climate event revealed the greatest failure of climate science

From Climate Etc.

by Javier Vinos

We have been fortunate to witness the largest climate event to occur on the planet since the advent of global satellite records, and possibly the largest event since the eruption of Mount Tambora in 1815. It is clearly a naturally occurring, externally forced climate event. However, mainstream climate scientists are not treating it appropriately. This is because climate science does not function like other sciences and is subject to strong confirmation bias. The first step to learning from the 2023 event is accepting its exceptional nature, which many fail to do.

1. An externally forced extraordinary event

If you are still not convinced of the extremely anomalous nature of the climatic event of 2023, let’s review some of the events of 2023-24. Taken together, they make it clear. The following list is incomplete and comes from my notes:

• Extraordinary ocean warming that models can’t explain.[1]
• Record-low Antarctic sea ice.[2]
• A record-breaking Amazon drought in 2023.[3]
• 31 atmospheric river events in the western US from November 2022 to March 2023. Nine made landfall in California marking the record in the 70-year database.[4]
• The snowiest season in 71 years occurred in California after a 1-in-54-year event.[5]
• NYC had the least snowy season on record, breaking a 50-year record on latest first snow.[6]
• Cyclone Freddy in the Indian Ocean was the longest-lasting tropical cyclone ever.[7]
• ITCZ displacement and unusual rains in the Sahara in 2024.[8]
• The first half of the 2024 hurricane season was surprisingly quiet, and models can’t explain it.[9]
• In 2023, 42% of the globe experienced heat exceeding two standard deviations. Louisiana, for example, had its hottest summer in 129 years of records.[10]
• 2023 was the warmest year on record, and 2024 was even warmer.
• In October 2024, the North Polar Vortex was the weakest in 40 years. The three sudden stratospheric warming events that occurred in the same season are a one-in-250-year event according to models.[11]
• The biggest global low cloud cover anomaly ever recorded occurred in 2023.[12]

Figure 1. ERA5 Zonal-mean anomaly in low cloud cover suggests that 2023 planetary albedo may have been the lowest since at least 1940.12

No one seems to be connecting the dots indicating that a series of extraordinary atmospheric events took place in 2023–24. These events suggest that an external factor significantly impacted atmospheric circulation. Climate science focuses heavily on a relatively uninformative and uncertain parameter called surface temperature anomaly, which is the variation in the average of the daily maximum and minimum temperatures across widely disparate areas. Nevertheless, even this inadequate parameter reflects the unusual nature of the 2023 event.

Figure 2. The 2023 climate event can be seen most clearly in the global sea surface temperature anomaly (NOAA, 60°N–60°S, baseline 2021). It began in December 2022. By November 2025, 90% of the warming from the 2023 event has disappeared.

Many 2023 temperatures were not only record temperatures, they also broke the previous records by the largest margin in the datasets, as I pointed in the article I wrote for Climate Etc. in July 2024 “Hunga Tonga volcano: impact on record warming”. Rantanen and Laaksonen (2024) selected September 2023 in ERA5 reanalysis as the 2023 record warming month by the largest margin and, using the CMIP6 ensemble for the likely transient climate response, as recommended, found only a 0.2 % probability that it could be due to the unforced internal variability and the forced greenhouse gas-induced trend.10 They conclude that an external forcing is required and point to the Hunga Tonga eruption and the removal of sulfur pollution from ships as possibilities.

2. Rounding up the usual suspects in an unusual crime

One might think that the lack of precedents for such an unusual event would make scientists skeptical of the factors affecting the climate over the last hundred years, since nothing similar appears in the records. However, to publish another paper, scientists must explain what happened, and the models are incapable of providing explanations outside their programming. This programming obviously does not include extraordinary events of which we had no prior knowledge.

Therefore, it has been argued that El Niño in 2023 may have been one of the main causes. However, in my article of 2024 I presented two compelling reasons why the 2023 El Niño cannot be held responsible. First, the warming of the globe oceans occurred simultaneously with El Niño, rather than subsequently, as was the case in previous Niños. Second, unlike all other Niños except the one caused by the eruption of Mount Pinatubo in 1992, the PDO was in a negative state during the 2023 El Niño.

Despite supporting ENSO’s involvement in what happened, Minobe et al. (2025) provide further arguments.[13] First, they demonstrate that the extraordinary warming event of 2023 started in the Southern Ocean in November 2022, which was four months prior to the tropical Pacific’s warming and the onset of El Niño. A consequence cannot precede its cause. Second, they demonstrate that the Earth’s energy imbalance anomaly between 2022 and 2023 was over 75% larger than during the onset of similar recent El Niño events. This unprecedented event first impacted the top of the atmosphere and began in 2022. Furthermore, the set of atmospheric and oceanic indicators included in the multivariate El Niño index (MEI) suggests that the 2023 El Niño event was not particularly intense. An El Niño event like many others cannot cause an unprecedented event.

Figure 3. a) Global top of the atmosphere anomalies of shortwave (downward) and longwave (downward) radiation and Multivariate ENSO Index (MEI). A strong increase in shortwave radiation started in 2022. Global warming caused a strong increase in upward longwave radiation in 2023 in advance of an average intensity El Niño. b) Monthly anomaly time series of sea surface temperature in selected regions of the Southern Ocean and the Tropical Pacific. The anomaly started around November 2022 in the Southern Ocean, about 4 months before El Niño started in the Pacific.13

Those who believe ENSO played a significant role in the 2023 event point to the three years of La Niña preceding it. They claim this overloaded the heat system, causing it to explode with the 2023 El Niño event. However, there are precedents for three consecutive Niñas in the records, in 1974-1976 and 1999-2001, yet nothing like the 2023 event occurred. While explanations can be sought as to why the three Niñas produced such a different result this time, given that things never repeat exactly the same way, these explanations are still ad hoc with no evidence to back them up.

More surprising is the argument that the event was caused by anthropogenic factors. Anthropogenic forcing is small and constant, and can only produce noticeable changes over long periods of time, decades or centuries. Interannual changes, by definition, are due to natural factors or internal variability. As an example, after 50 years of global warming, it is still unclear what changes we can expect in the ENSO system if the warming continues for another 50 years.

One exception to this long-term anthropogenic forcing is the reduction in sulfur emissions due to the maritime fuel regulations that came into force in 2020, and was therefore abrupt. However, we can rule this out as a cause of the 2023 event because the reduction is permanent, whereas the ocean warming that occurred in 2023 was essentially reversed in 2024 and 2025 (see Figure 2).

3. Most scientists are ignoring the cooling that has taken place since the 2023 event.

The truth is that climate scientists have much more difficulty explaining cooling than warming when CO2 levels increase. This inherent bias embedded in the models probably indicates that there are fundamental aspects of the climate that are not well understood. This may explain why the 2023 warming generated a multitude of headlines and articles, while the 2024 and 2025 cooling is characterized by scientists’ silence in the face of something equally spectacular.

For example, the annual scientific reports titled “10 New Insights in Climate Science” by the Future Earth organization, publisher of the journal Anthropocene, are worth highlighting.[14] Two of the ten insights in each of the 2023, 2024, and 2025 reports refer to abrupt warming. However, despite cooling beginning in early 2024, no article refers to it.

It is difficult to find any mention of ocean cooling. In 2024, New Scientist magazine reported that a part of the Atlantic Ocean was cooling at a record speed:

“Over the past three months, temperatures in that part of the Atlantic cooled off more rapidly than at any time in records extending back to 1982. This sudden shift is perplexing because the strong trade winds that normally drive such cooling have not developed, says Franz Philip Tuchen at the University of Miami in Florida. ‘We’ve gone through the list of possible mechanisms, and nothing checks the box so far.’”[15]

We can add ocean cooling as another anomaly that remains unexplained in terms of its magnitude, speed, and cause.

When an El Niño event transitions to a La Niña event, the equatorial Pacific usually cools rapidly. However, the cooling in 2024 was global. Although La Niña conditions occurred in the winter of 2024–2025, they were not intense enough and long enough to qualify as an actual La Niña event. In other words, the tremendous cooling of the planet’s oceans has included the equatorial Pacific, but the equatorial Pacific has not induced it.

4. The only known extraordinary factor is the eruption of Hunga Tonga.

According to Occam’s razor, a climatic event of unparalleled magnitude in modern records requires an exceptional cause. The factors responsible for normal climate variability are insufficient. The only extraordinary factor preceding the 2023 event was the explosion of the Hunga Tonga underwater volcano. The 150 megatons of water vapor that it released into the stratosphere are without precedent in our records. We do not know all the effects this may have had on the climate. Eruptions that reach the stratosphere have radiative, chemical, and dynamic effects. However, only the first two are well known.

There are several aspects of the Tambora eruption in April 1815 that scientists have not yet explained satisfactorily. First, the effects were delayed, as the anomalies that led to the year without a summer in 1816 did not begin until 15 months after the eruption. The usual explanation is that atmospheric dynamics delayed the radiative effects in the Northern Hemisphere. However, this explanation conflicts with the second unexplained aspect: the climatic effect on the Northern Hemisphere was much greater than on the Southern Hemisphere. The cause of this inequality between the hemispheres is unknown since volcanic aerosols and their radiative effects are distributed across both hemispheres in a tropical eruption.

Figure 4. The inability of models to reproduce the climatic effects of large volcanic eruptions calls into question the reliability of their diagnosis that the Hunga Tonga eruption had little effect on the surface climate. a) All models reproduce a cooling effect in the southern hemisphere as a result of the 1815 Tambora eruption, but this effect is not supported by evidence.[16] b) The models greatly exaggerate the cooling of sea temperatures that occurred as a result of the 1815 Tambora eruption and a previous one in 1809. The observations (in black) show a much smaller cooling.[17]

Climate models do not adequately reproduce the effects of the 1815 Tambora eruption, suggesting that dynamic atmospheric changes caused by stratospheric eruptions or other factors have a much greater impact on climate than previously thought. It is striking that the evolution of the ocean temperature anomaly generally coincides with the evolution of water vapor anomalies in extratropical middle-stratospheric latitudes in the Northern Hemisphere but not in the entire stratosphere.

Figure 5. The global sea surface temperature anomaly (NOAA, 60°N–60°S, baseline 2021) is shown in red over a background image of the water vapor anomaly in the stratosphere at 45°N.

Because models cannot adequately incorporate the effects of stratospheric eruptions on atmospheric circulation dynamics, the conclusion that the Hunga Tonga eruption had minimal effects on the surface climate is not convincing.[18] This conclusion is based primarily on knowledge of the radiative properties of water vapor. Studies support a relationship between these eruptions and changes in global atmospheric circulation, the polar vortex, El Niño–Southern Oscillation, evaporation, and cloud cover.

Without a doubt, we know that the climatic event of 2023 was caused by a drastic decrease in global cloud cover, the largest in at least 40 years (see Figure 1). This reduction caused the planet to absorb more solar energy and warm up. However, we do not know what controls changes in clouds. It’s astonishing that we claim to understand the cause of recent climate change yet remain ignorant of such a fundamental aspect.

Clouds cannot form without evaporation. In their recent work, Fajber et al. (2023) present compelling evidence that the evaporation gradient between the tropics and the poles controls the amount of heat transported through the atmosphere.[19] However, they made the common mistake of assuming that evaporation is controlled by temperature via the Clausius–Clapeyron relation. This error stems from the assumption that wind is constant at the global level. The Clausius–Clapeyron relation is accurate at the microscopic level, at the interface between water and air. However, at the macroscopic level, wind speed has a greater impact on evaporation than temperature or humidity. In a cold, humid environment, clothes hung out to dry will dry if there is enough wind. However, few climate scientists have experience hanging clothes out to dry in the wind. Furthermore, wind speed is not constant; rather, it exhibits significant changes and opposing trends over oceans and land. These changes lead to important changes in evaporation, cloud formation, and their transport and distribution.[20]

If changes in the clouds caused the temperature changes, then we cannot use the temperature changes as the cause of the cloud changes. The most likely cause is the change in atmospheric circulation, which occurred due to the atmospheric anomalies that have taken place since the end of 2022, as discussed in Section 1.

For anyone who is not committed to the explanation of climate change due to the radiative properties of greenhouse gases, the Hunga Tonga eruption is currently the best explanation for the 2023 climate event. In July 2025, I analyzed that “if Hunga Tonga is responsible for the 2023-24 warming event, a clear prediction is that we should observe most of this warming disappear in 3-5 years.“[21] This projection does not arise from any of the other considered causes. By December 2025, four years after the eruption, this prediction had come true: the ocean temperature anomaly in November was only 0.05°C higher than in November 2021, before the eruption. 90 % of the ocean warming from the 2023 climate event has disappeared.

5. The greatest failure of climate science

Climate science has failed the test of an externally forced natural climate event. Most scientists who have published studies on the 2023 climate event have not recognized its nature. Any climatological manifestations of the event that do not align with the dominant consensus have been treated as either natural variability or rare events whose probability has increased due to anthropogenic climate change. No studies have addressed the climatic event in all its manifestations or analyzed its possible causes without relying on models clearly not designed to shed light on something we did not know was possible.

Rather than trying to determine the causes of the event, scientists have attempted to fit it into the dominant theory using models. In light of evidence of major natural climate change, this approach reveals its greatest flaw: the theory relies on an excessive focus on greenhouse gases and aerosols as the cause and temperature changes as the effect.

Personal note:

2026 will mark the tenth anniversary of my first post on Judith Curry’s Climate Etc. blog. Believe it or not, I began researching climate change in 2015 because I was concerned about its potential impact on our society. As a scientist from a different field entirely, I trusted my fellow scientists, learned societies, and scientific journal editors to evaluate the risk. As an avid reader of scientific literature from many disciplines, I immersed myself in hundreds and then thousands of papers, convinced that evidence of dramatic human-caused climate change was there. However, I came away empty-handed and profoundly skeptical of everything I had been told without ever being shown the evidence. I realized natural climate change is greatly misunderstood and insufficient effort is being done to correct that. Over these past 10 years, I’ve spent a lot of time trying to straighten out the science of climate, and I will spend 10 more years doing so if necessary. If you would like to hear more often from me, you can find me on 𝕏 @JVinos_Climate

[1] Schmidt G (2024). “Climate models can’t explain 2023’s huge heat anomaly — we could be in uncharted territory” Nature, 627, 467.

[2] Gilbert E & Holmes C (2024). “2023’s Antarctic sea ice extent is the lowest on record” Weather, 79, 2, 46-51.

[3] Espinoza JC et al. (2024) “The new record of drought and warmth in the Amazon in 2023 related to regional and global climatic features” Sci Rep 14, 8107.

[4] Kawzenuk B et al. (2023) “Mesoscale analysis of landfalling atmospheric rivers in California during December 2022 and January 2023” Atmospheric River Reconnaissance Workshop 2023.

[5] Marshall AM et al. (2024) “California’s 2023 snow deluge: Contextualizing an extreme snow year against future climate change” PNAS 121, 20, e2320600121.

[6] Silive.com (2024) “2023 least snowiest year in NYC on record, says National Weather Service“.
New York Post (2023) “Snowless NYC breaks 50-year record of longest winter without flurries“.

[7] NOAA (2024) “Australia to Africa in 36 days: Tropical Cyclone Freddy (2023), the longest-lasting tropical cyclone in history“.

[8] Live Science (2024) “Sahara desert hit by extraordinary rainfall event that could mess with this year’s hurricane season“.

[9] Klotzbach PJ et al. (2025) “The Remarkable 2024 North Atlantic Mid-Season Hurricane Lull” Geophys Res Lett, 52, 19, e2025GL116714

[10] Rantanen M & Laaksonen A (2024) “The jump in global temperatures in September 2023 is extremely unlikely due to internal climate variability alone” Clim Atmos Sci 7, 34.
Yale Climate Connections (2023) “Summer 2023 broke dozens of all-time monthly heat records“.

[11] Severe Weather EU (2024) “Unusually weak Polar Vortex is developing in the Stratosphere, linked with the Weather patterns over the United States and Canada“.
Met Office UK (2024) “One in 250-year event underway high in the atmosphere“.

[12] Goessling HF et al. (2024) “Recent global temperature surge intensified by record-low planetary albedo” Science, 387, 6729, 68-73.

[13] Minobe S et al. (2025) “Global and regional drivers for exceptional climate extremes in 2023-2024: beyond the new normal” Clim Atmos Sci, 8, 138.

[14] 10 New Insights in Climate Science.

[15] New Scientist (2024) “Part of the Atlantic is cooling at record speed and nobody knows why“.

[16] Neukom R et al. (2014) “Inter-hemispheric temperature variability over the past millennium” Nature Clim Change, 4, 362–367.

[17] Brohan P (2012) “Constraining the temperature history of the past millennium using early instrumental observations” Clim. Past, 8, 1551–1563.

[18] APARC (2025) “Hunga Eruption Atmospheric Impacts Report” APARC Report No. 11, WCRP Report No. 10/2025.

[19] Fajber R et al. (2023) “Atmospheric heat transport is governed by meridional gradients in surface evaporation in modern-day earth-like climates” PNAS, 120, 25, e2217202120.

[20] Yu L (2007) “Global Variations in Oceanic Evaporation (1958–2005): The Role of the Changing Wind Speed” J Climate, 20, 21, 5376–5390.

[21] Vinós J (2025) https://x.com/JVinos_Climate/status/1941827393368281431