An analysis of Pacific Ocean sediments shows that doubling CO2 in the atmosphere could increase the Earth’s temperature by up to 14 degrees, which exceeds the predictions of the Intergovernmental Panel on Climate Change, according to Scitechdaily.
The research was published in the journal Nature Communication. PHOTO Shutterstock (Archive)
Doubling the level of CO2 in the atmosphere could increase the Earth’s average temperature by 7 to 14 degrees Celsius, according to the analysis of sediments in the Pacific Ocean off California by researchers from NIOZ and the Universities of Utrecht and Bristol.
The results were recently published in the journal Nature Communication.
“The temperature rise we found is far greater than the 2.3 to 4.5 degrees Celsius that the UN’s IPCC has so far estimated,” said first author Caitlyn Witkowski.
“Organic matter is not broken down as quickly by microbes”
The researchers used a core extracted 45 years ago from the bottom of the Pacific Ocean.
“I realized that this core is very attractive to researchers because the ocean floor in that place has been devoid of oxygen for many millions of years”, said Professor Jaap Sinninghe Damste, Principal Researcher at NIOZ and Professor of Organic Geochemistry at Utrecht University.
“As a result, organic matter is not broken down as quickly by microbes and more carbon is retained“, Damste also declared.
“Carbon dioxide from the past 15 million years has never before been examined from a single locationWitkowski said.
The top 1,000 meters of the drill core correspond to the last 18 million years.
From this record, the researchers were able to extract information on past seawater temperature and information on ancient CO2 levels in the atmosphere using a new approach.
The scientists found out the temperature using a method developed two decades ago at NIOZ, called the TEX86 method. “This method uses specific substances that are present in the membrane of archaea, a distinct class of microorganisms“, explained Damste.
“These archaea optimize the chemical composition of their membrane according to the temperature of the water in the upper 200 meters of the ocean. Substances in that membrane can be found as molecular fossils in oceanic sediments and analyzed to this day.”
“An image of what the future might hold”
Researchers have developed a new approach to determine the CO2 content of the past atmosphere by using the chemical composition of two specific substances commonly found in algae: chlorophyll and cholesterol. This is the first study to use cholesterol for quantitative CO2 and the first study to use chlorophyll for this time period. To create these substances, algae must absorb CO2 from the water and retain it through photosynthesis.
“A very small fraction of the carbon on Earth is found in a “heavy form”, 13C instead of the usual 12C. Algae have a clear preference for 12C. However: the lower the concentration of CO2 in the water, the more algae will also use 13C, a rare form. Thus, the 13C content of these two substances is a measure of the CO2 content of ocean water. And this, in turn, in accordance with the laws of solubility, correlates with the CO2 content in the atmosphere.”, Damaste said.
Using this new method, it appears that the concentration of CO2 dropped from about 650 parts per million 15 million years ago to 280 just before the industrial revolution.
When researchers compared temperature and atmospheric CO2 levels over the past 15 million years, they noticed an important relationship. The average temperature 15 million years ago was more than 18 degrees Celsius: 4 degrees Celsius higher than today and about the level that the UN’s Intergovernmental Panel on Climate Change, IPCC, predicts for the year 2100 in the most extreme scenario.
“So this research gives us a picture of what the future might hold if we take too little action to reduce CO2 emissions and also if we implement too few technological innovations to offset thee”, declared Damste.
