Earth recorded its hottest day on record on Thursday, making it the fourth straight to set or tie the record for warmest day globally.
Why it matters: The daily records are a symptom of the heat that human emissions of greenhouse gases are adding to the climate, combined with an El Niño event in the tropical Pacific Ocean.
By the numbers: The NOAA data shows the global average temperature climbed to an unprecedented 17.23°C (63.02°F) on Thursday.
- This was 1.02°C (1.8°F) above the average for the date, and an increase from the previous record-holder of 17.18°C (62.9°F) set just one day before.
- The period from July 3 through 6 is now the hottest four days on record globally.
- The global mean temperature statistic masks the extreme events taking place worldwide.
- These include an unprecedented marine heat wave in the North Atlantic, a recently concluded long-duration heat wave in Texas and Mexico, record heat in China, plus extreme heat and wildfires still raging out of control in Canada.
Between the lines: The reliable, though preliminary, global daily records are a new phenomenon given improvements in climate monitoring.
- The data comes from a computer model run by NOAA's National Centers for Environmental Prediction, displayed via a University of Maine climate data website,
- The model, known as the Climate Forecast System Reanalysis (CFSR), incorporates temperature readings from land surface stations, weather balloons, satellite measurements and ocean buoys to arrive at a best estimate for the planet's mean temperature at hourly intervals throughout any given day.
- While the CFSR data only goes back to 1979, studies tracking the planet's climate history further back in time show it is likely that these daily global average temperatures are unprecedented in the context of human history.
The intrigue: The global heat records reflect the influence of a natural climate cycle as well, with a strengthening El Niño event in the Pacific Ocean. El Niño tends to cause global average temperatures to climb on top of human-caused global warming.
- The oceans absorb about 90% of the extra heat from climate change, and during El Niño, some of this heat is released back into the atmosphere.
- Reflecting the long-term climate trend, each El Niño year has tended to be hotter than the last, as temperatures march ever higher.
What's next: July tends to be the planet's hottest month, and between that and El Niño, climate scientists warn that more records could be broken, both regionally and globally, in the near future.
