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According to the compilation of worldwide temperatures, 2023 was the warmest year on record, and the warmest year at least since the last interglacial period, some 125,000 years ago.

2023 was 1.48 degrees Celsius warmer than the 1850-1900 designated pre-industrial reference period average, and 0.6 degrees Celsius warmer than the 1991-2020 average.

More record-breaking months have been recorded moving into 2024.

For January 2024, the average surface air temperature was 1.66 degrees Celsius warmer than an estimate of the 1850-1900 January average, and 0.7 degrees Celsius above the 1991-2020 January average.

The month was 0.12 degrees Celsius above the temperature of the previous warmest January in 2020, according to the Copernicus Climate Change Service (CCCS).

February 2024: Another Record Breaker

And February 2024 was… the warmest February on record globally.

The average surface air temperature for February 2024 was 13.54 degrees Celsius, 1.77 degrees Celsius warmer than the 1850-1900 February average, and 0.81 degrees Celsius above the 1991-2020 February average.

The month was 0.12 degrees Celsius above the temperature of the previous warmest February, in 2016.

The CCCS daily global average temperature tracker also showed that during the first half of the month, global temperatures reached 2 degrees Celsius above the 1850-1900 levels on four consecutive days (February 8-11).

European temperatures in February 2024 were also exceptionally high, some 3.3 degrees Celsius above the 1991-2020 average for February.

Why Was (Is) It So Warm?

As an explanation for why it was so warm, we have the long-term warming trends associated with the increase in atmospheric greenhouse gases – which are then superimposed on the oscillations of the equatorial temperatures across the Pacific: The El Niño Southern Oscillation or ‘ENSO.’

After declaring an El Niño watch in April 2023, the arrival of a moderate/strong El Niño was declared by NOAA in June 2023. In an El Niño phase, the deep pool of hot water accumulated at the western edge of the equatorial Pacific breaks out and spreads east across the ocean, liberating vast amounts of heat.

The global average temperature for 2023 responded and was 14.98 degrees Celsius, some 0.17 degrees Celsius higher than the previous maximum in 2016, a strong El Niño year.

El Niño was also present between 2018-19 but was relatively weak so global temperature records were not exceeded, and then there was no El Niño until 2023.

Fading El Niño

The 2023 El Niño is now fading and is likely to pass into Neutral or La Niña (cooler than average equatorial Pacific) conditions into the second half of 2024.

However, as has already been seen, the influence of El Niño is still being felt in the record temperatures at the start of 2024. The CCCS suggests that even though El Niño continued to weaken in the equatorial Pacific, marine air temperatures, in general, remained at an unusually high level.

But once the current El Niño has dissipated, we can then expect a few years that are not quite as warm as 2023 until the next strong El Niño year breaks the 2023 record.

The next El Niño could be in three years, or as many as seven years, as with the gap from 2016 to 2023.  

Breaking the Paris Accord Temperature Bound

A few years further out from now, the average annual temperature will be 1.5 degrees Celsius warmer than the pre-industrial 1850-1900 temperatures. In early 2023, the IPCC predicted this 1.5 degrees Celsius line would most likely be crossed in the mid-2030s, but one study has suggested this could be as early as 2029.

Crossing the 1.5 degrees Celsius line would be a symbolic moment concerning the 2015 Paris Accord, which demanded that nations kept global temperatures within the 1.5 degrees Celsius bound. A few years further into the future every year will be above the 1.5 degrees Celsius threshold – until some big volcanic eruption introduces a year or two of temporary cooling.  

2023: Impacts of a Record-Breaking Temperature Year

With January and February 2024 already record-breaking months, looking at 2023, each month from June to December was also warmer than the same month in previous years.

Digging deeper, measured against the global temperature averages from 1991-2020, the most anomalous month was September, with July and August being the hottest of all months. From April through December 2023, global average sea surface temperatures also reached record levels. 

Inevitably, hotter average temperatures in 2023 brought hotter extreme temperatures in the tail of the temperature distribution. In the northern hemisphere summer of 2023, there were more heatwaves, longer heatwaves, and stronger heat waves.

In July 2023, heat waves affected North Africa from Algeria to Egypt, also China, Japan, southern Europe, and the southwest U.S. Heatwaves and drought brought unprecedented wildfires in Canada, Greece, and Hawaii. Towards the end of summer intense rainfall records were broken in China, Turkey, Greece, Italy, and Libya.

There were also marine sea-surface temperature heatwaves in parts of the Mediterranean, the Caribbean, the Gulf of Mexico, and the North Atlantic.

In the Atlantic, high SSTs fought against more shear associated with El Niño during the 2023 hurricane season. While many tropical cyclone circulations formed in 2023, few matured into intense storms, and those that formed did not last long.  

The logic follows that preserving the high Atlantic sea surface temperatures but taking away El Niño results in early hurricane forecasts for 2024 that could point toward an active hurricane season.

Once El Niño is out of the equation, all eyes will be back on the global thermometer to see what the non-El Niño baseline is, and to gauge the potential temperature rise when El Niño eventually returns, and if the 1.5 degrees Celsius bound will be broken sooner rather than later.

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Robert Muir-Wood
Robert Muir-Wood
Chief Research Officer, Moody's RMS

Robert Muir-Wood works to enhance approaches to natural catastrophe modeling, identify models for new areas of risk, and explore expanded applications for catastrophe modeling. Robert has more than 25 years of experience developing probabilistic catastrophe models. He was lead author for the 2007 IPCC Fourth Assessment Report and 2011 IPCC Special Report on Extremes, and is Chair of the OECD panel on the Financial Consequences of Large Scale Catastrophes.

He is the author of seven books, most recently: ‘The Cure for Catastrophe: How we can Stop Manufacturing Natural Disasters’. He has also written numerous research papers and articles in scientific and industry publications as well as frequent blogs. He holds a degree in natural sciences and a PhD both from Cambridge University and is a Visiting Professor at the Institute for Risk and Disaster Reduction at University College London.

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