For four consecutive days, Earth experienced its hottest day on record.

  • On Monday, July 3, the global average temperature was 16.2ºC (61.16ºF); that was the hottest day ever recorded.
  • The next day, July 4, broke that record by far, reaching 17.18ºC (62.92ºF).
  • Wednesday tied the July 4 record.
  • Thursday set a new record for the hottest day, at 17.23ºC (63.01ºF).

To understand how significant this is, you need to consider that the global average temperature includes the current temperatures for all of the places, including Antarctica, that are in deep winter. That Monday’s all-time record for the hottest day was breached by more than 1ºC globally is a major deviation from climate conditions that have persisted throughout the entire history of the human species.

No human being has ever lived on a planet this hot. Ice core samples and the geological record indicate that Earth has not seen this kind of global heat in at least 125,000 years. More importantly, we are losing the climate regulating systems that help moderate surface temperatures.

June 2023 was the hottest year on record for temperatures in the North Atlantic. This ocean heating is part of what has driven a sustained string of record-breaking temperatures in June. Image credit: EU Copernicus Climate Change Service/ECMWF.

In January, it was reported that 2022 was the hottest year on record for global ocean temperatures. In fact, 2022 was the fourth year in a row of record ocean temperatures. The ocean comprises the vast majority of the climate system and the biosphere; if it is unable to absorb excess heat from the atmosphere, or if ocean life is unable to sink enough carbon to slow global heating, then the surface temperates people experience will get hotter faster.

Some parts of Mexico and Texas have experienced four consecutive weeks with heat index values above 100ºF. Some have had more than 20 days during that period with heat index values above 105ºF. As the heat dome set in, scientists have reported an unprecedented fragmentation of multiple jet stream currents.

Jet streams are major planetary wind currents that define climatic regions and shape what kind of weather and ecology a given region experiences. They tend to balance out over time and show fairly consistent behavior. The Polar Vortex, for instance, normally circles the Arctic; when temperatures in the Arctic warm too much, the defined climatic difference from lower latitudes is blurred, and the polar jet stream bleeds to lower latitudes.

In May, NASA reported that summer heat was arriving early to northern latitudes. This level of climate pattern disruption, driven by excess thermal energy (heat) in Earth’s atmosphere, leads to effects where jet streams change behavior and extreme conditions can linger in some areas. Image: NASA.

This is why it is helpful to reflect on the chain of cause and effect: heat-trapping carbon-based compounds, known as ‘greenhouse gases’ cause global heating; global heating causes climate disruption, and disrupted climate patterns lead to anomalous extreme impacts, ranging from shock storms, floods, and fires, to slow-moving disasters like multi-year drought or ecosystem breakdown.

Last month was by far the hottest June on record, globally. As extreme and rising heat sets in across regions and planetary climate zones, there is rising concern that some critical climate-regulating systems could break down. For instance, if ocean currents that circulate globally, and which are driven by differences between warm and cold water temperatures, slow down or stop, entire regions, and even continents could find the climate they have known for millennia irreversibly altered.

As recently as May, this was thought to be a conversation for 20 to 50 years from now, but there are signs ocean currents are slowing down. The climate system is a global web of energy transfer mechanisms. This includes jet streams and ocean currents, the water cycle, including the cryosphere (ice caps, glaciers, sea ice, and seabed ice), and the sinking of carbon compounds in ecosystems full of carbon-based life-forms.

When we talk about nature-loss, biodiversity conservation, and ecosystem degradation or restoration, we are also talking about the Earth’s ability to regulate climate patterns to minimize extreme events and impacts. Early July continues to show the heat dome lingering over Texas and northern Mexico, with heat index values well above 100ºF projected 7 to 10 days out.

2023 has been far hotter, far earlier than 2022. The string of four consecutive record hottest days from July 4 through July 7 is just the latest. July 2022 was extreme by historical standards, and in comparison to the geological record. Warm ocean temperatures, disrupted jet streams, and transfer of heat from the atmosphere and ocean into stalled weather systems left much of North America and Northern Africa facing catastrophic heat conditions.