Sign of the Times: The Humble Sponge

Admittedly, you do not think much of sponges, unless you enjoy the feel of a natural sponge in your bath. But members of the humble Spongia species tell a tale of woe for humanity. The long-lived creatures that create an exoskeleton we use. They live in well-oxygenated shallow seas around the globe. Consequently, the ratio of oxygen isotopes contained in their exoskeleton record the temperature level in the sea. 

Three hundred year old sclerosponges [photo left] from the Caribbean Sea predate the Industrial Revolution. Sponges that contain higher levels of Oxygen 16 (8 neutrons) compared to Oxygen 18 (10 neutrons) indicate warm sea temperatures, and vis-versa. Oxygen bonds with carbon to form calcium carbonate in their skeletons. These chemical variations show that sclerosponges experienced stable sea temperatures between 1700 and 1790. By the mid 1860s, sea temperatures began to rise after a period of some cooling probalby caused by volcanic eruptions blocking sunlight. By the middle of the 20th centrury the sponge record indicates that sea warming by one degree ℉ more than scientists expected using convential methods has occurred.

The Earth experienced its hottest year in recorded history occurred in 2023.  NOAA said that 2023 was the hottest year in its 174 year data set.  The World MeterologicalOrganization confirmed the record setting year. Future generations may look back at this year as the indicator of when humanity failed to take action against global climate change. James Hanson the NASA scientist who alerted the world to climate change in 1988 testimony to the Senate, told The Guardian, 2023 may be considered one of the cooler years in the future record because failure will be built into the climate system due to the continued burning of fossil fuels.