Analysis of sediments in the Pacific Ocean shows that doubling atmospheric carbon dioxide could warm the Earth by up to 14 degrees, exceeding the Intergovernmental Panel on Climate Change’s projections, with historical data suggesting significant future climate impacts.
doubling carbon dioxide in the atmosphere2 Rising levels of greenhouse gases could raise the Earth’s average temperature by 7 to 14 degrees. Celsius (13 to 25.2 degrees Fahrenheit), according to an analysis of sediments from the Pacific Ocean near California conducted by researchers from the National Institute of Oceanography in Zimbabwe and the Universities of Utrecht and Bristol.
The results were recently published in the journal Nature Communications.
“The temperature rise we found is much greater than the 2.3 to 4.5 degrees Celsius (4.1 to 8.1 degrees Fahrenheit) that the UN Climate Panel (IPCC) has estimated so far,” said first author Kaitlin Witkowski.
45 year old heart drill
The researchers used a 45-year-old sample from the bottom of the Pacific Ocean. “I realized that this sample was very attractive to researchers because the ocean floor in that area has been devoid of oxygen for millions of years,” said Professor Jaap Sinning-Damste, a senior scientist at the National Institute of Oceanography in Zurich and professor of organic geochemistry at Utrecht University.
“As a result, the organic matter is not decomposed as quickly by the microbes, and more carbon is retained,” said Damesti. He was also Witkowski’s supervisor, whose doctoral thesis included this research.
unique time series
“CO”2 “None of these samples have been examined from a single site for the past 15 million years,” Witkowski said. The top 1,000 meters of the drill core correspond to the past 18 million years.
From this record, the researchers were able to extract an index of past seawater temperature and an index of carbon dioxide in the ancient atmosphere.2 Levels, using a new approach.
derived temperature
The researchers inferred the temperature using a method developed 20 years ago at the National Institute of Atmospheric Sciences, called TEX.86 “This method uses specific materials found in the membrane of archaea, a distinct class of microorganisms,” explains Damesti.
“These archaea optimize the chemical composition of their membrane depending on the temperature of the water in the upper 200 meters of the ocean. Materials from this membrane can be found as molecular fossils in ocean sediments, and are analyzed to this day.”
carbon monoxide2 Of chlorophyll and cholesterol
Researchers have developed a new approach to extracting carbon dioxide from the atmosphere in the past.2 Contents Using the chemical composition of two specific substances common in algae: chlorophyll and cholesterol. This is the first study to use cholesterol to measure carbon dioxide quantitatively and the first to use chlorophyll for this time period. To create these substances, algae must absorb carbon dioxide.2 From water and repair it by Photosynthesis.
Damesti: “A very small fraction of the carbon on Earth is in ‘heavy form,’ 13c instead of usual 12C. Algae have a clear preference for 12A. However: The lower the level of carbon dioxide,2 The higher the concentration in the water, the more rare algae will be used as well. 13C. Therefore, 13The carbon content of these two substances is a measure of carbon dioxide.2 Ocean water content. This in turn, according to the laws of solubility, is related to the carbon dioxide content.2 “Atmospheric content.”
Using this new method, it appears that carbon dioxide2 The oxygen concentration dropped from about 650 parts per million, 15 million years ago, to 280 parts per million just before the Industrial Revolution.
Stronger relationship
When the researchers plotted the inferred temperatures and atmospheric carbon dioxide levels over the past 15 million years, they found a strong correlation. The average temperature 15 million years ago was more than 18 degrees Celsius (64.4 degrees Fahrenheit): that’s four degrees Celsius (7.2 degrees Fahrenheit) warmer than today, the level the U.N. Intergovernmental Panel on Climate Change (IPCC) predicts for 2100 in its most extreme scenario.
“So this research gives us a glimpse of what the future might hold if we take very little action to reduce carbon dioxide emissions.2 “We are working to reduce emissions and implement a few technological innovations to offset emissions,” Damest said. “The clear caveat of this research is: CO22 “The focus is likely to have a stronger effect on temperature than we currently consider!”
Reference: “Continuous δ13C record of styrene and phytane reveals a significant decrease in CO2 since the mid-Miocene” by Kaitlin R. Witkowski, Anna S. von der Heydt, Paul J. Valdez, Marcel T. J. van der Meer, Stefan Schouten, and Jaap S. Senning-Damste, 18 June 2024, Nature Communications.
doi: 10.1038/s41467-024-47676-9
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