Sep 5, 2023 - Energy & Environment

World likely has hottest summer on record

Global average June-August temperature
Data: ECMWF/ERA5 via Brian Brettschneider; Chart: Axios Visuals

The first of many batches of temperature data is in for August — and not only did the globe have its hottest such month on record, but temperature anomalies secured meteorological summer's place in the history books.

The big picture: The unmistakably large jump in meteorological summer's global average surface temperature compared to past years is a telltale reflection of deadly heat waves and record warm oceans.

  • According to preliminary data from the Copernicus Climate Change Service's ERA5 data set, the global average surface temperature for June through August was about 0.65°C (1.17°F) above the 1991-2020 average.
  • This beat the previous record warm summer of 2019 by nearly 0.3°C (0.54°F).
  • August alone had a global average surface temperature of 0.71°C (1.29°F) above the 1991-2020 average, crushing August 2019, which was only about 0.37°C (0.66°F) above the long-term average.
  • June and July were each record warm months, with July ranking as the warmest month ever recorded since the dawn of the instrument era in the 19th Century.

Zoom in: Numerous U.S. cities in the southern tier set records for their hottest June-through-August periods.

Of note: In Tokyo, a city of about 14 million, daytime highs rose above 86°F every day during August, which was a first for any month since data began there in 1875, according to meteorologist Sayaka Mori.

Between the lines: These examples from land miss some of the most important and far-reaching effects of climate change during the past few months and longer: record-warm oceans.

  • Across the globe, ocean temperatures are at record highs, and the heat going into the oceans has significant consequences for those on land, since it adds more moisture and heat to storm systems.
  • For example, record warmth in the Gulf of Mexico elevated air temperatures from Miami to Houston, and also provided the fuel needed for Hurricane Idalia, which struck Florida last week, to rapidly intensify when nearing landfall.
  • Record water temperatures are already fueling an unusually active El Niño hurricane season in the tropical North Atlantic Ocean. Corals are bleaching and dying from the Florida Keys to the Caribbean.

The intrigue: There is no great mystery surrounding what is helping to drive these heat records, on land and sea, with the burning of fossil fuels for energy along with deforestation and agricultural practices are increasing the amounts of heat-trapping greenhouse gases in the air.

  • A periodic El Niño event in the tropical Pacific Ocean is also adding additional heat to the global climate system.
  • This has been a summer featuring a fusillade of extreme events, however, which has the potential to yield changes in national and possibly international climate policies.

Yes, but: Climate scientists are not seeing unanticipated climate events play out, since most of what is happening is contained in the volumes of studies on the topic.

  • But some of the recent impacts are happening sooner than previously expected, and having greater societal consequences than initially thought.

What's next: During the next two weeks, official data will emerge from global climate monitoring centers. These are unlikely to change the major themes of the climate change story of 2023: a record-warm year that is increasingly likely to break all-time annual milestones, to be followed by an even hotter year in 2024.

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