Journal Article

How Extreme Were Daily Global Temperatures in 2023 and Early 2024?

Ribes, Aurélien, Cariou, Enora, Cattiaux, Julien

2024

Overview

Global temperatures were exceptionally high in 2023/24. Every month from June 2023 to June 2024 set a new record, and September shattered the previous record by 0.5$0.5$ °C. The 2023 annual average approached 1.5$1.5$ °C above pre‐industrial levels. This results from both long‐term warming and internal variability, with the occurrence of an El Niño episode. However the amplitude of the 2023/24 anomalies was remarkable and surprised the scientific community. Here we analyze the rarity of 2023/24 global temperatures from a climate perspective. We show that a ‘normal’ year 2023 would have roughly equaled the previous annual record, and that the most extreme events of 2023/24 rank among the most extreme since 1940. Our analysis suggests that the 2023/24 event can be reconciled with the long‐term trend and an intense, but not implausible, peak of internal variability. Plain Language Summary 2023 was the warmest year on record at global scale, and early 2024 has continued to break records. This remarkable episode has received a great deal of attention from the general public and the scientific community. It is well established that it is linked to the long‐term global warming and the occurrence of an El Niño episode, but some temperature anomalies appeared so high, shattering previous records, that several scientists suggested that global warming may have been underestimated, which would have serious implications for future projections. Here we take a step back from the 2023/24 event, precisely quantify its rarity and compare it with other hot years. Using climate monitoring and extreme event attribution methods, we first show that at the current rate of warming, a ‘normal’ year 2023 would have equaled the ‘old’ record of 2016, even without any help of El Niño. We also find that the most extreme events of 2023/24 are among the most extreme of the entire record, but remain comparable with some past events. Our analysis thus suggests that the 2023/24 event is extreme but not incompatible with current estimates of global warming. Key Points At the current rate of global warming, a normal year 2023 would have equaled the record of 2016, without any help of El Nino The most extreme anomalies of 2023/24 rank among the most extreme of the entire record since 1940 The 2023/24 heat can be reconciled with current estimates of global warming and an extreme but not implausible peak of internal variability

• Publisher: John Wiley & Sons, Inc,American Geophysical Union,Wiley
• Subject: Anomalies / Climate / Climate change / Climate monitoring / El Nino / El Nino phenomena / event attribution / extreme event / global temperature / Global temperatures / Global warming / Ocean, Atmosphere / Sciences of the Universe / Temperature anomalies / Variability