Notable findings from the international report include:

Earth’s greenhouse gas concentrations were the highest on record. Carbon dioxide, methane and nitrous oxide⁠—Earth’s major atmospheric greenhouse gases⁠—once again reached record high concentrations in 2023. Annual growth in global mean CO₂ has increased from 0.6±0.1 ppm yr⁻¹ in the early 1960s to an average of 2.5 ppm yr⁻¹ during the last decade of 2014–23. The growth from 2022 to 2023 was 2.8 ppm, the fourth highest in the record since the 1960s. 

Record temperatures notable across the globe. A range of scientific analyses indicate that the annual global surface temperature was 0.99 to 1.08 of a degree F (0.55 to 0.60 of a degree C) above the 1991–2020 average. This makes 2023 the warmest year since records began in the mid to late 1800s, surpassing the previous record of 2016 by 0.23 to 0.31 of a degree F (0.13 to 0.17 of a degree C). The transition in the Pacific Ocean from La Niña at the beginning of the year to a strong El Niño by the end of the year contributed to the record warmth. All seven major global temperature datasets used for analysis in the report agree that the last nine years (2015–23) were the nine warmest on record. The annual global mean surface temperature has increased at an average rate of 0.14 to 0.16 of a degree F (0.08 to 0.09 of a degree C) per decade since 1880, and at a rate more than twice as high since 1981.

El Niño conditions contributed to record-high sea surface temperatures. El Niño conditions in the equatorial Pacific Ocean emerged in boreal spring 2023 and strengthened throughout the year. The mean annual global sea-surface temperature in 2023 was record high, surpassing the previous record of 2016 by 0.23 of a degree F (0.13 of a degree C). Each month from June to December was record warm. On August 22, an all-time high globally averaged daily sea-surface temperature of 66.18 degrees F (18.99 degrees C) was recorded. Approximately 94% of the ocean surface experienced at least one marine heatwave in 2023, which is defined as sea-surface temperatures in the warmest 10 percent of all recorded data in a particular location on that day for at least five days. The eastern tropical and North Atlantic Ocean, the Sea of Japan, the Arabian Sea, the Southern Ocean near New Zealand, and the eastern tropical Pacific, were in a marine heatwave state for at least 10 months of 2023. The ocean experienced a new global average record of 116 marine heatwave days in 2023, which was far more than the previous record of 86 days in 2016, and a new record of 13 marine cold spell days, far below the previous record of 37 days in 1982.

Ocean heat and global sea level were the highest on record. Over the past half-century, the oceans have stored more than 90 percent of the excess energy trapped in Earth’s system by greenhouse gases and other factors. The global ocean heat content, measured from the ocean’s surface to a depth of 2000 meters (over 6,500 feet), continued to increase and reached new record highs in 2023. Global mean sea level was record high for the 12th-consecutive year, reaching about 4.0 inches (101.4 millimeters) above the 1993 average when satellite altimetry measurements began. This rise is an increase of 0.3±0.1 of an inch (8.1±1.5 millimeters) over 2022, the third highest year-over-year increase on record. 

Heatwaves and droughts contributed to massive wildfires around the world. During late spring and a record-warm summer, approximately 37 million acres burned across Canada, an area more than twice the size of Ireland and more than double the previous record from 1989. Approximately 232,000 people were evacuated due to the threat of wildfires, and smoke from the wildfires impacted regions across Canada and also affected the heavily populated cities of New York City and Chicago, and even areas of western Europe. With August to October 2023 being the driest three-month period in Australia in the record dating to 1900, millions of acres of bushfires burned for weeks in the Northern Territory during September and October. From mid-August to early September, the largest wildfire since the start of the record in 2000 for the European Union burned in the Alexandroupolis municipality of Greece. The fire burned almost 232,000 acres. Overall, the total area burned in Greece in 2023 was more than four times its long-term average.

The Arctic was warm and navigable. The Arctic had its fourth-warmest year in the 124-year record, with summer (July to September) record warm. Below-ground, permafrost temperatures were the highest on record at over half of the reporting sites across the Arctic. Permafrost thaw disrupts Arctic communities and infrastructure and can also affect the rate of greenhouse gas release to the atmosphere, potentially accelerating global warming. The seasonal Arctic minimum sea-ice extent, typically reached in September, was the fifth-smallest in the 45-year record. The amount of multiyear ice—ice that survives at least one summer melt season in the Arctic—continued to decline. Since 2012, the Arctic has been nearly devoid of ice that is more than four years old. Both the Northern Sea Route and Northwest Passage became accessible to non-ice-hardened marine traffic. The Northern Sea Route, connecting the European Arctic to the Pacific Ocean via the north coast of Russia and Bering Strait, saw 75 ship transits in the 2023 open season, the second-highest number of ships on record. The Northwest Passage, which connects the Atlantic Ocean to the Pacific via northern Canada and Alaska waters, saw a record number of ship passages. A total of 42 ships made the complete Northwest Passage transit, far surpassing the previous record of 33 ships in 2017.

Antarctica sea ice sets record lows throughout 2023. Eight months saw new monthly mean record lows in sea ice extent and sea ice area, and 278 days in 2023 set new daily record-low sea ice extents. On February 21, Antarctic sea ice extent and sea ice area both reached all-time record lows, surpassing the previous record lows that were set just a year earlier in February 2022. On July 6, a new record-low daily sea ice extent was 695,000 square miles (1.8 million square kilometers) lower than the previous record low for that day.

Tropical cyclone activity was below average, but storms still set records around the globe. There were 82 named tropical storms during the Northern and Southern Hemisphere storm seasons last year, which was below the 1991–2020 average of 87. Seven tropical cyclones reached Category 5 intensity on the Saffir–Simpson Hurricane Wind Scale. Globally, the accumulated cyclone energy—a combined measure of the strength, frequency, and duration of tropical storms and hurricanes—rebounded from the lowest in the 43-year record in 2022 to above average in 2023. Typhoon Doksuri (named Egay in the Philippines) caused $18.4 billion U.S. dollars in economic losses in the northern Philippines and China. Beijing received 744.8 mm of rain from remnants of the storm in a 40-hour period, which was the city’s heaviest rainfall in its 140-year record and caused floods that killed 137 residents. Tropical Cyclone Freddy became the world’s longest-lived tropical cyclone on record, developing into a tropical cyclone on February 6 and finally dissipating on March 12. Freddy crossed the full width of the Indian Ocean and made three landfalls in total: one in Madagascar and two in Mozambique. In the Mediterranean—outside of traditional tropical cyclone basins—heavy rains and flooding from Storm Daniel killed more than 4,300 people and left more than 8,000 missing in Libya. 

The State of the Climate report is a peer-reviewed series published annually as a special supplement to the Bulletin of the American Meteorological Society. The journal makes the full report openly available online. NCEI’s high-level overview report is also available online.

• Full Report for 2023
• Climate.gov Highlights 

Past Bulletin of American Meteorological Society (BAMS) annual State of the Climate reports, as well as author tools and information.

State of the Climate Reports (BAMS)

Climate Assessment (NCEI)