2023 was officially the hotest year on record.

A study by NASA's Goddard Institute for Space Studies has confirmed that 2023 was the hottest year on record, according to a press release issued on 12 January 2024, with global temperatures averaging 1.2°C above the average for the period 1951-1980 (used as a baseline by NASA) and 1.4°C above the average from 1880-1990, which is also widely used as a baseline. Every month from June to December was the hottest that calender month has ever been, which is to say June was the hottest June ever recorded, July was the hottest July ever recorded, etc.. Furthermore, July 2023 was the hottest month ever recorded, with higher average global temperatures than recorded in any calendar month since records began.

This data visualization, which is updated monthly, shows the seasonal cycle of temperature variation on the Earth’s surface, and how those temperatures deviate from the average from 1951 to 1980. The data come from the GISS Surface Temperature Analysis and are publicly accessible here. The seasonal temperature offsets are based on the MERRA-2 reanalysis data here. NASA Scientific Visualization Studio.

The consequences of the extreme temperatures manifested themselves in a number of ways, including extreme heat, wildfires, intense rainfall, coastal flooding, and rising sea levels.

While the overall trend towards higher temperatures is driven by Human activity, and in particular the release of carbon dioxide from the burning of fossil fuels, yearly temperatures are also driven by natural phenomena such as volcanic eruptions and the El Niño - Southern Oscillation climate system.

Sea surface temperatures in the equatorial Pacific oscillate between two states, a warm El Niño phase and a cool La Niña phase. From 2020 until 2022 the equatorial Pacific was in a La Niña phase, which tends to supress global average temperatures. In May 2023 this switched to a warm El Niño phase, causing global temperatures to climb from that point. As the El Niño - Southern Oscillation climate system has the most influence during the Southern Summer, it is likely that the temperature elevation caused by this swing will be most strongly felt in February-April 2024. 

This map of Earth in 2023 shows global surface temperature anomalies, or how much warmer or cooler each region of the planet was compared to the average from 1951 to 1980. Normal temperatures are shown in white, higher-than-normal temperatures in red and orange, and lower-than-normal temperatures in blue. NASA Scientific Visualization Studio.

The climate in 2023 was also affected by the Hunga Tonga-Hunga Ha’apai undersea volcanic eruption in January 2022, one of the largest volcanic eruptions in recorded history, which pumped vast amounts of volcanic aerosols into the atmosphere. These aerosols reflect sunlight back into space, cooling the atmosphere, with the Hunga Tonga-Hunga Ha’apai eruption estimated to have caused a 0.1°C drop in atmospheric temperature in the Southern Hemisphere.

Independent studies by the National Oceanic and Atmospheric Administration in the US and the Hadley Centre in the UK both concluded that sea surface temperatures in 2023 were the highest recorded for any year since records began, corroborating the conclusions reached by NASA's Goddard Institute for Space Studies.

See also...