Earth’s temperature may have already exceeded the 1.5°C threshold, study of ancient sponges reveals

Earth’s temperature may have already exceeded the 1.5°C threshold, study of ancient sponges reveals

Invertebrate sponges of the Caribbean

(Dr. Dwayne Meadows/NOAA/NMFS/OPR)

From captivating generations of young children glued to their cartoons to helping their parents clean themselves and their utensils, sponges have an amazing variety within our homes. But outside the bathroom, another hidden purpose awaits these porous wonders, one you probably never imagined!

Deep in the waves of the Caribbean Sea, a handful of ancient sponges hold secrets about a warming world. The growth of these creatures depends heavily on the temperature of their environment, turning these humble 300-year-old specimens into living archives. Now, their skeletons are starting to pull skeletons out of humanity’s closet, adding more validity to a theory many climate scientists have been repeating for years: We don’t have much time left.

Marine sponges grow at a snail’s pace, accumulating strontium and calcium in amounts that reflect the temperature of the water in which they grow. A new study analyzed six of these long-lived sponges recovered from 60 meters below the ocean.

Because this is a relatively deeper point, it reduces any large fluctuations in sea surface temperature, helping to provide a better estimate of the overall average temperature. Moreover, the regions studied are relatively free from the influence of periodic warming events, such as El Niño and La Niña, which should theoretically help them paint a more accurate picture of average global temperatures over the ages.

What makes these sponges unique is their ability to record environmental changes over vast areas. Unlike coral, tree rings and ice cores, which provide local data, sponges filter water from a broader scale, providing a more comprehensive picture of environmental shifts. Study of these six sponges helped produce a detailed record of water temperatures dating back to the 18th century.

The results were stark: the record revealed that the Earth had already surpassed the internationally agreed temperature limit of 1.5 degrees Celsius, and was on track to reach 2 degrees Celsius by the end of this decade. If the sponge data is correct, it means we have less than a decade than previously thought to reduce emissions and mitigate the worst effects of climate change.

The study also supports the theory of accelerating climate change. Observed extreme weather events—floods, storms, droughts, and heatwaves—appear more consistent with the sponge data than previously assumed levels of warming.

The urgency remains clear. Regardless of the exact numbers, the message the sponges are sending is undeniable: climate change is real, it’s happening more quickly than we thought, and we must act now.

The results of this research were published in The nature of climate change It can be accessed here.


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