Recent studies have shown that a doubling of atmospheric CO2 levels could lead to a significantly greater increase in global temperatures than previously estimated.
This discovery comes from an analysis of sediments from the Pacific Ocean near California by researchers from NIOZ Royal Netherlands Institute for Marine Research and the Universities of Utrecht and Bristol.
Important findings from the analysis of ocean sediments
The study involved a 45-year-old man drill core from the Pacific Ocean, revealing insights into Earth’s climate over the past 18 million years. This drill core, preserved under oxygen-free conditions for millions of years, provided a rich source of organic material. The study found that doubling the atmospheric CO2 can lead to an average value increasing the Earth’s temperature varying from 7 to 14 degrees Celsius.
This is significantly higher than the 2.3 to 4.5 degrees predicted by the Intergovernmental Panel on Climate Change (IPCC). Caitlin Witkowskithe lead author of the study, emphasized the significance of these findings: “The temperature increase we found is much larger than the 2.3 to 4.5 degrees that the UN’s climate panel, the IPCC, has estimated so far.”
The preserved core allowed the researchers to analyze ancient organic matter, which according to Prof Yap Sininghe Damste, senior scientist at NIOZ, “offers a unique view of past climate conditions.” The long-term anoxic condition of the ocean floor slowed the breakdown of organic material, allowing the preservation of carbon compounds that provide insight into historical atmospheric conditions. This analysis marks a significant step in understanding the long-term sensitivity of the climate to CO2.
Methodology: Combining TEX86 and new approaches
The researchers used TEX86 method to estimate past sea temperatures. This method uses specific substances present in the membranes of archaea, microorganisms that adapt their membrane composition based on water temperature. These molecular fossils, found in ocean sediments, provided important data on temperature. This method, developed 20 years ago at NIOZ, relies on analysis of the chemical signatures left by archaeawhich are particularly persistent and informative due to their long-term preservation in sedimentary layers.
To evaluate the past atmospheric CO2 levels, the team developed a new approach involving the analysis of chlorophyll and cholesterol found in algae. The chemical composition of these compounds varies with the concentration of CO2 in water, correlating with atmospheric CO2 levels. Damste elaborated: “A very small fraction of Earth’s carbon occurs in the ‘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 use the rare 13C. Thus the 13C content of these two substances is a measure of CO2 content of ocean water.” This innovative method provided a more accurate historical record of CO2 levels, demonstrating a decline from approximately 650 parts per million 15 million years ago to about 280 parts per million just before the Industrial Revolution.
Unprecedented levels of CO2: Historical insights and future climate implications
The results of the study show that the relationship between CO2 levels and global temperature is higher than previously thought. By plotting the resulting temperatures and atmospheric CO2 levels over the past 15 million years, the researchers observed a significant correlation. The average temperature 15 million years ago was over 18 degrees Celsius, which is 4 degrees warmer than today and similar to the extreme scenarios predicted by the IPCC for 2100. This historical perspective suggests that future climate conditions could be more extreme if CO2 levels continue to rise uncontrollably.
Damsté emphasized the importance of these findings: “So this research gives us a glimpse of what the future might hold if we take too little mitigation action CO2 emissions and also implementing several technological innovations to offset emissions. The clear warning from this research is that CO2 concentration is likely to have a stronger impact on temperature than we currently consider.” The study highlights the potential for more severe climate impacts than currently expected, underscoring the urgent need for enhanced climate action and innovative solutions to reduce CO2 emissions.
The methodology and results of this study suggest a critical reappraisal of climate models and predictions. By providing a more detailed and extended historical climate record, the study challenges existing assumptions and highlights the need for revised climate sensitivity parameters in predictive models. This insight is critical for policymakers and scientists working to develop effective strategies to combat global warming and its associated impacts on the planet’s ecosystems and human societies.
