Exceptional climate conditions in 2023

Attribution of the record-shattering global annual heat in 2023 to human and/or natural factors is fundamentally required for reliable predictions of upcoming global warming and its impacts. An observation-model comparison of global hot areas supports a key role for human-induced climate change, with a small contribution from El Niño.

Quasi-stationary and transient anticyclones contributed to the hot Argentinian summer 2022/23 through circulation and moisture feedbacks respectively, and climate change exacerbated heatwave intensity by 0.5 to 1.2 °C relative to previous decades, according to an evaluation of ERA5 reanalysis data.

Record-low sea ice coverage around Antarctica in 2022 and 2023 co-occurred with substantial subsurface ocean warming, which could be indicative of a change in the mechanisms that govern Antarctic sea ice, suggests an analysis of sea ice extent and ocean temperatures since 1979.

In 2023, global full-depth ocean heat content (OHC) reached a record increase of 464 ± 55 ZJ since 1960, with strong heat gain observed in the Southern and Atlantic Oceans. OHC was 16 ± 10 ZJ higher than in 2022, continuing the long-term increasing trend that started in 1960.

Antarctic sea ice extent was the lowest on record in 2023, with an annual mean of 9.81 million km², beating the previous minimum of 2022. Arctic sea ice extent was also low, with an annual mean of 10.49 million km², but did not break any records.

Wildfires burned 384 Mha of land in 2023, the highest since 2017 but 5% lower than the 2001–2022 average. These fires emitted an estimated 2,524 Tg C, 30% of which came from Canada’s record fire season.

Global greening continued into 2023, reaching near-record values that were dominated by regional enhancement in the mid-western USA, Europe, northern Australia and parts of equatorial Africa. In contrast, climatic events contributed to browning signals in Russia, Canada, Mexico and tropical drylands.

Multiple relentless heatwaves occurred in 2023, with much of the world experiencing at least 20 more heatwave days than the 1991–2020 average. Prominent and record-breaking events included exceptional wintertime and spring heat in South America, large heatwaves over Europe, Africa and Asia, and a prolonged event over south-eastern USA and Central America.

2023 saw a multitude of extreme precipitation events across the globe, causing flash flooding, countless fatalities and huge economic losses. Fuelled by a combination of a strong El Niño, record ocean warmth and anthropogenic warming, these events highlight the ongoing risks posed by extreme precipitation in a warming climate.

Global CO₂ emissions for 2023 increased by only 0.1% relative to 2022 (following increases of 5.4% and 1.9% in 2021 and 2022, respectively), reaching 35.8 Gt CO₂. These 2023 emissions consumed 10–66.7% of the remaining carbon budget to limit warming to 1.5°C, suggesting permissible emissions could be depleted within 0.5–6 years (67% likelihood).