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A doubling of atmospheric CO2 levels could increase the Earth’s average temperature by 7 to 14 degrees Celsius, according to a study led by researchers from the Royal Netherlands Institute for Sea Research (NIOZ) and the universities of Utrecht and Bristol.

These results contrast sharply with the 2.3 to 4.5 degrees predicted by the Intergovernmental Panel on Climate Change (IPCC).

Invaluable resource for studying

To collect data, the researchers used a 45-year-old core from the bottom of the Pacific Ocean. Due to the lack of oxygen, organic material was preserved in the core, making it a valuable source for studying historical climate conditions.

“I realized that this core is very attractive to researchers because the seafloor at this location has been oxygen-free for many millions of years,” said lead author Jaap Sinninghe Damsté, a scientist at NIOZ and professor of organic geochemistry in Utrecht.

15 million years of CO2 content

The experts succeeded in creating a unique time series of CO2 values ​​over the last 15 million years for a single location – an achievement that had never been achieved before.

To determine past seawater temperatures, they used the TEX86 method, a technique developed 20 years ago at NIOZ to analyze the chemical composition of archaea membrane lipids.

Previous atmospheric CO2 concentrations

In addition, they developed a new method to estimate past atmospheric CO2 concentrations using the chemical signatures of chlorophyll and cholesterol from algae. This approach is the first to use cholesterol for quantitative CO2 estimation and apply chlorophyll data to this time period.

The algae’s preference for the carbon isotope 12C over 13C at different CO2 levels allowed the researchers to draw conclusions about historical CO2 concentrations.

“The lower the CO2 concentration in the water, the more the algae use the rare 13C. The 13C content of these two substances is therefore a measure of the CO2 content of the seawater,” explains Damsté.

Future atmospheric CO2 concentrations

The study found that CO2 levels fell from about 650 ppm 15 million years ago to 280 ppm just before the Industrial Revolution. Plotting these CO2 levels against the corresponding temperatures revealed a stronger correlation than previously thought.

“So this research gives us a glimpse into what the future might hold if we take too few measures to reduce CO2 emissions and implement too few technological innovations to offset emissions,” Damsté said.

“The clear warning from this research is that CO2 concentration may have a greater influence on temperature than we currently assume!”

Factors contributing to atmospheric CO2

Atmospheric CO2 levels are influenced by a combination of natural processes and human activities.

Natural processes include the carbon cycle, in which CO2 is exchanged between the atmosphere, oceans and land.

Photosynthesis by plants and phytoplankton absorbs CO2, while it is released through respiration and decomposition. Volcanic eruptions also contribute to CO2 levels.

Human activities have significant impacts, particularly through the combustion of fossil fuels such as coal, oil and natural gas, which release large amounts of CO2.

Deforestation reduces the number of trees that can absorb CO2, leading to a further increase in CO2 concentration in the atmosphere.

Industrial processes such as cement production also release CO2. In addition, land-use changes and agricultural practices can affect soil carbon storage and methane emissions, thereby indirectly affecting CO2 levels.

Consequences of rising temperatures

Rising temperatures have far-reaching consequences for the planet. One major impact is the change in weather patterns, leading to more frequent and severe weather events such as hurricanes, heat waves and heavy rain.

These changes can lead to increased floods, droughts and other natural disasters that destroy ecosystems and human communities.

Climate change is also affecting the natural habitats of many species, causing shifts in their geographic ranges and threatening biodiversity. Many species could face extinction if they cannot adapt quickly enough or migrate to suitable environments.

In addition, higher temperatures are contributing to the melting of polar ice caps and glaciers, leading to sea level rise. This threatens coastal communities with flooding and erosion, potentially displacing millions of people and affecting freshwater supplies.

Agricultural productivity is also affected by rising temperatures. Heat stress can reduce crop yields and affect the quality of products, jeopardising food security. In regions already vulnerable to food shortages, this can exacerbate malnutrition and poverty.

In addition, higher temperatures can lead to an increase in pests and diseases affecting both crops and livestock, placing additional strain on agriculture.

Rising temperatures have a direct impact on human health. Increased heat can lead to heat-related illness and death, particularly among vulnerable populations such as the elderly and those with underlying medical conditions.

Higher temperatures can also worsen air quality and contribute to respiratory problems and other health issues.

The study was published in the journal Nature communication.

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