Rephrase the title:Our planet is already hotter by 1.5°C since industrial times, analysis of sea sponges show

From captivating generations of young kids glued to their cartoons to helping their parents scrub themselves and their utensils, sponges hold a surprising versatility within our homes. But beyond the bathroom, another hidden purpose of these porous wonders awaits, one you might never have imagined!

Deep beneath the Caribbean waves, a handful of ancient sponges hold secrets of a warming world. The growth of these creatures is heavily dependent on the temperature of their environment, and this has turned these unassuming 300-year-old specimens into living archives. Now, their skeletons have begun to drag the skeletons out from humanity’s closet, adding more validity to a theory many climate scientists have been echoing for years: we don’t have much time left.

Growing at a snail’s pace, sea sponges accumulate strontium and calcium in amounts that reflect the temperature of the water they grow in. A new study analysed six of these long-lived sponges extracted from a depth of 60 metres under the ocean.

Since this is a relatively deeper point, it subdues any major fluctuations in sea surface temperature, helping provide a better estimate of the overall average temperature. Further, the areas surveyed are relatively freer from the influence of cyclical warming events, like El Niño and La Niña, which should theoretically help it portray a more accurate picture of average global temperatures through 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 localised data, sponges filter water from a wider range, offering a more comprehensive picture of ecological shifts. Studying these six sponges helped produce a detailed record of water temperatures dating back all the way to the 1700s.

The findings are stark: the record revealed that the Earth has already surpassed the internationally agreed-upon limit of 1.5°C warming, and are on track to reach 2°C by the end of this decade. If the sponge data holds true, it means we have a decade less than previously thought to curb emissions and mitigate the worst impacts of climate change.

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

The urgency remains clear. Regardless of the exact numbers, the message from the sponges is undeniable: climate change is real, it’s happening faster than we thought, and we need to act now.

The findings of this research have been published in Nature Climate Change.