Scientists have found evidence from ocean sponges that suggests the Earth has been warming for a longer period of time than previously thought. However, some scientists are skeptical of this evidence.

Scientists have found evidence from ocean sponges that suggests the Earth has been warming for a longer period of time than previously thought. However, some scientists are skeptical of this evidence.

Several ancient sponges, dating back centuries and found deep in the Caribbean, have prompted some researchers to consider the possibility that human-induced climate change began earlier and has had a greater impact on global warming than previously believed.

They calculate that the world has already gone past the internationally approved target of limiting global warming to 1.5 degrees Celsius (2.7 degrees Fahrenheit) since pre-industrial times, hitting 1.7 degrees (3.1 degrees Fahrenheit) as of 2020. They analyzed six of the long-lived sponges — simple animals that filter water — for growth records that document changes in water temperature, acidity and carbon dioxide levels in the air, according to a study in Monday’s journal Nature Climate Change.

The study’s assertion that the world has warmed significantly more than previously believed was met with skepticism from other scientists. However, according to the study authors, if the calculations involving sponges are accurate, there could be significant consequences.

In summary, the timeline for reducing emissions to prevent severe climate change is being accelerated by ten years, according to marine geochemist and lead author of the study, Malcolm McCulloch from the University of Western Australia. In other words, we are running out of time.

“We actually have one decade less than we had previously thought,” McCulloch informed The Associated Press. “It’s essentially a record of a looming catastrophe.”

In recent years, researchers have observed an increase in severe and damaging weather events, such as floods, storms, droughts, and heat waves. This is occurring at a faster rate than initially predicted for the current level of global warming. One possible explanation for this is that the amount of warming is greater than originally estimated by scientists, according to Amos Winter, a co-author of the study and a paleo oceanographer at Indiana State University. This study also provides evidence for the idea put forth by former NASA chief scientist James Hansen last year, which suggests that climate change is speeding up.

Cornell University climate expert Natalie Mahowald, who was not involved in the research, stated that this is concerning for the issue of global climate change as it suggests further warming.

Several species of sponges have a lengthy lifespan and their skeletons serve as a record of the surrounding environmental conditions as they continue to develop. For generations, researchers have utilized sponges as well as other natural indicators such as tree rings, ice cores, and corals to document environmental changes spanning centuries. This practice aids in supplementing data from time periods preceding the 20th century.

According to Winter and McCulloch, sponges have the unique ability to capture water from a wide range of sources, unlike coral, tree rings, and ice cores. This allows them to document a larger area of environmental fluctuations.

New measurements from an uncommon type of small and sturdy sponges were utilized to generate a temperature record for the 1800s, which significantly differs from the recognized versions used by the Intergovernmental Panel on Climate Change (IPCC) of the United Nations. The findings of the study reveal that the mid-1800s were approximately 0.5 degrees Celsius colder than previously believed, with the effects of heat-trapping gases becoming evident about 80 years earlier than the measurements utilized by the IPCC. The IPCC data indicates that warming began only after 1900.

According to McCulloch and Winter, it is logical that the warming began prior to the timeline stated by the IPCC, as the Industrial Revolution had already commenced and carbon dioxide emissions were increasing in the mid-1800s. It has been scientifically established that climate change is caused by the release of carbon dioxide and other gases from the combustion of fossil fuels.

According to Winter and McCulloch, these long-lasting sponges, which have a rusty orange color, are unique and serve as an excellent tool for measurement. They are even more effective than the ones used by scientists in the late 1800s, with at least one of them being over 320 years old at the time of collection.

Winter described them as grand structures that hold a wealth of information about human history, documenting levels of carbon dioxide in the atmosphere, water temperature, and water pH.

“He expressed admiration for their beauty and noted how difficult they are to locate, requiring a skilled team of divers.”

This is due to the fact that they reside at depths of 100 to 300 feet (33 to 98 meters) in the darkness, according to Winter.

The IPCC and the majority of scientists rely on temperature data from the mid-1800s that was collected by crews on ships using wooden buckets to measure water temperature. However, some of these readings may be unreliable due to potential influences such as proximity to a warm steamship engine. To obtain more precise measurements, scientists are able to use sponges to track consistent deposits of calcium and strontium on their skeletons. A higher proportion of strontium to calcium indicates warmer water, while a higher proportion of calcium to strontium suggests cooler water, according to Winter.

Michael Mann, a climate scientist at the University of Pennsylvania who was not involved in the study, has held a different viewpoint from the IPCC’s baseline and believes that warming began earlier. However, he remained doubtful of the results of the study.

Mann expressed disbelief in the notion that the instrumental record is inaccurate based on paleo-sponges from a single region. This idea does not seem logical to him.

During a press conference, Winter and McCulloch consistently supported the use of sponges as a reliable indicator of global temperature fluctuations. They explained that, with the exception of the 1800s, their reconstruction of temperature using sponges aligns with data collected from instruments and other methods such as coral, ice cores, and tree rings.

Despite being limited to the Caribbean, McCulloch and Winter argue that these sponges serve as a reliable proxy for other areas of the world. This is because they are located at a depth that is not significantly impacted by the fluctuations of El Nino and La Nina, and the water temperature aligns with global ocean temperatures, according to McCulloch and Winter.

According to Michael Oppenheimer, a climate scientist at Princeton University who was not involved in the sponge study, the McCulloch team’s findings about cooler temperatures in the 1800s should not alter the severity levels established by scientists in their reports. This is because the danger levels were not based on the exact preindustrial temperature, but rather on the degree to which temperatures have changed since then.

The research ended in 2020 and showed a 1.7 degrees Celsius (3.1 degrees Fahrenheit) increase in temperature since pre-industrial times. However, a new record high in 2023 has raised that number to 1.8 degrees (3.2 degrees Fahrenheit), according to McCulloch.

McCulloch stated that the rate of change is exceeding expectations and this is leading to potentially hazardous situations in the future. The only solution to prevent this is to urgently decrease emissions, with a sense of utmost urgency.


This report was contributed by Teresa de Miguel from Mexico City.


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