Recent studies have shown that a doubling of CO2 levels in the atmosphere could lead to a significantly greater increase in global temperatures than previously estimated.
This finding comes from an analysis of sediments from the Pacific Ocean near California conducted by researchers at the NIOZ Royal Netherlands Institute for Sea Research and the universities of Utrecht and Bristol.
Significant findings from the analysis of ocean sediments
The study used a 45-year-old drill core from the Pacific Ocean, which reveals insights into Earth’s climate over the past 18 million years. This drill core, which was stored for millions of years under oxygen-free conditions, provided a rich source of organic material. The research showed that a doubling of atmospheric CO2 could yield an average temperature rise on earth varying from 7 to 14 degrees Celsius.
This is substantially higher than the 2.3 to 4.5 degrees predicted by the Intergovernmental Panel on Climate Change (IPCC). Caitlyn Witkowskithe lead author of the study, emphasized the importance of these findings: “The temperature increase we found is much greater than the 2.3 to 4.5 degrees that the UN climate panel IPCC has estimated so far.”
The preserved core allowed researchers to analyze ancient organic material, which, according to Professor Jaap Sinninghe Damste, senior scientist at NIOZ, “offers a unique insight into past climate conditions.” The long-term oxygen-free condition of the ocean floor slowed the breakdown of organic matter, allowing the preservation of carbon compounds that provide insight into historical atmospheric conditions. This analysis marks an important step in understanding long-term climate sensitivity to CO2.
Methodology: combination of TEX86 and new approaches
The researchers used the TEX86 method to estimate past sea temperatures. This method uses specific substances present in the membranes of archaea, microorganisms that adjust their membrane composition based on water temperature. These molecular fossils found in ocean sediments provided crucial temperature data. This method, developed twenty years ago at NIOZ, is based on analyzing the chemical signatures left behind archaeawhich are particularly resilient and informative due to their long-term preservation in sediment layers.
To estimate the past atmospheric CO2 levelsthe team developed a new approach involving the analysis of chlorophyll and cholesterol in algae. The chemical composition of these compounds varies depending on the CO2 concentration in water and correlates with it atmospheric CO2 levels. Damsté explains: ‘A very small part of the carbon on Earth occurs in a ‘heavy form’, 13C instead of the usual 12C. Algae have a clear preference for 12C.
However, the lower the CO2 concentration in the water, the more algae will also use the rare 13C. The 13C content of these two substances is therefore a measure of CO2 content of ocean water.” This innovative method provided a more accurate historical record of CO2 levels, showing a decline from about 650 parts per million 15 million years ago to about 280 parts per million just before the Industrial Revolution.
Unprecedented CO2 levels: historical insights and future climate implications
The results of the study indicate that the relationship between CO2 levels and global temperatures are stronger than previously thought. By mapping the inferred temperatures and atmospheric CO2 levels over the past 15 million years, the researchers found a significant correlation. The average temperature 15 million years ago was over 18 degrees Celsius, which is 4 degrees warmer than today and comparable 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 implications of these findings: “This study therefore gives us a glimpse of what the future could bring if we do not take enough measures to Co2 emissions and also implement few technological innovations to offset emissions. The clear warning from this study is that CO2 concentrations are likely to have a stronger impact on temperature than we currently consider. solutions to reduce CO2 emissions.
The methodology and findings of this study provide a critical reevaluation of climate models and projections. By providing a more detailed and comprehensive historical climate overview, 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.