Summer 2023: the hottest on record

The Copernicus Climate Change Service (C3S), implemented by the European Centre for Medium-Range Weather Forecasts on behalf of the European Commission with funding from the EU, routinely publishes monthly climate bulletins reporting on the changes observed in global surface air temperature, sea ice cover and hydrological variables. This month, highlights on the boreal summer 2023 and sea surface temperature are also included in this press release. All the reported findings are based on computer-generated analyses using billions of measurements from satellites, ships, aircraft and weather stations around the world.

2023 June-July-August Season highlights:

  •  The June-July-August (JJA) season for 2023 was the warmest on record globally by a large margin, with an average temperature of 16.77°C, 0.66°C above average.
  • The European-average temperature for summer was 19.63°C, which at 0.83°C above average, was the fifth warmest for the summer season
  • JJA 2023 has seen record-breaking high sea surface temperature (SST) anomalies in the North Atlantic and for the global ocean.
  • Summer 2023 saw marine heatwaves in several areas around Europe, including around Ireland and the UK in June, and across the Mediterranean in July and August.
  • JJA 2023 saw above-average precipitation over most of western Europe and Türkiye, with local rainfall records broken leading to flooding in some cases, and in western and north-eastern North America, parts of Asia, Chile and Brazil, and north-western Australia
  • In contrast, Iceland, the Alpine arc, northern Scandinavia, central Europe, large parts of Asia, Canada, southern North America and most of South America experienced drier-than-average conditions. In some regions, these dry conditions led to significant wildfires

August 2023 – Surface air temperature highlights:

August 2023 was the warmest August on record globally, and warmer than all other months except July 2023.

  • The global-mean surface air temperature of 16.82°C for August 2023 was 0.71°C warmer than the 1991-2020 average for August, and 0.31°C warmer than the previous warmest August in 2016.
  • The month is estimated to have been around 1.5°C warmer than the preindustrial average for 1850-1900.
  • Heatwaves were experienced in multiple regions of the Northern Hemisphere, including southern Europe, the southern United States, and Japan.
  • Well-above average temperatures occurred over Australia, several South American countries and around much of Antarctica.
  • Marine air temperatures were well above average in several other regions.
  • The global temperature anomaly for the first 8 months of 2023 (January–August) ranks second-warmest on record, only 0.01°C below 2016, currently the warmest year on record.

According to Samantha Burgess, Deputy Director of the Copernicus Climate Change Service (C3S): "Global temperature records continue to tumble in 2023, with the warmest August following on from the warmest July and June leading to the warmest boreal summer in our data record going back to 1940. 2023 is currently ranked as the second warmest, at only 0.01ºC behind 2016 with four months of the year remaining. Meanwhile, the global ocean saw in August both the warmest daily surface temperature on record, and it’s the warmest month on record. The scientific evidence is overwhelming – we will continue to see more climate records and more intense and frequent extreme weather events impacting society and ecosystems, until we stop emitting greenhouse gases.”

August 2023 – Sea surface temperature highlights:

  • Global average sea surface temperatures continued to rise in August, after a long period of unusually high temperatures since April 2023.
  • Every day from 31st July to 31st August 2023 has seen global average sea surface temperatures exceeding the previous record from March 2016.
  • August as a whole saw the highest global monthly average sea surface temperatures on record across all months, at 20.98°C, and was well above average for August, with an anomaly of 0.55°C.
  • North Atlantic sea surface temperatures broke the previous daily record of 24.81°C, set in September 2022, on 5th August, and almost every day since has remained above this level, reaching a new record of 25.19°C on 31st August.
  • Marine heatwave conditions developed in the north Atlantic west of the Iberian Peninsula, but reduced across most of the Mediterranean.
  • El Niño conditions continued to develop over the equatorial eastern Pacific.

August 2023 – Sea Ice Highlights

  • Antarctic sea ice extent remained at a record low level for the time of year, with a monthly value 12% below average, by far the largest negative anomaly for August since satellite observations began.
  • Sea ice concentrations were most below-average in the northern Ross Sea and in the South Atlantic and Indian Ocean sectors while above-average concentrations prevailed in the Bellingshausen–Amundsen Sea sector.
  • Arctic sea ice extent was further below average than in July, at 10% below average, but well above the record minimum from August 2012.
  • While most of the central Arctic Ocean saw below-average sea ice concentrations, a stretch of above-average concentrations persisted north of the Kara and Laptev Seas.

August 2023 – Hydrological variables highlights:

  • August 2023 saw wetter-than-average conditions over a large part of central Europe and Scandinavia often with heavy rainfall leading to flooding. It was wetter than average also in a longitudinal band in Eastern Europe.
  • Over the Iberian Peninsula, southern France, Iceland and much of Eastern Europe, including the southern Balkans, it was drier than average, with wildfires occurring in France, Greece, Italy, and Portugal.
  • It was wetter than average in northeast and western North America, with Hurricane Hilary hitting California and western Mexico and triggering floods. It was also wetter than average in large regions of Asia, with rainfall causing landslides in Tajikistan, and parts of Chile and Brazil.
  • Drier-than-average regions included the southern USA and Northern Mexico, two latitudinal bands across Asia, and much of South America.