Atmospheric CO2 could push temperatures much higher than expected

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

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

Invaluable resource for the study

The researchers used a 45-year-old drill core from the Pacific Ocean floor to gather their data. The core preserved organic matter due to the lack of oxygen, making it an invaluable source for studying historical climate conditions. 

“I realized that this core is very attractive for researchers, because the ocean floor at that spot has had oxygen-free conditions for many millions of years,” said senior author Jaap Sinninghe Damsté, a scientist at NIOZ and professor of organic geochemistry at Utrecht. 

15 million years of CO2 levels 

The experts were able to construct a unique time series of CO2 levels over the past 15 million years from a single location, a feat that had not been achieved before. 

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

Past atmospheric CO2 concentrations

Additionally, 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 estimates and to apply chlorophyll data to this time period. 

The algae’s preference for the carbon isotope 12C over 13C under varying CO2 levels allowed researchers to infer historical CO2 concentrations.

“The lower the CO2 concentration in the water, the more algae will also use the rare 13C. Thus, the 13C content of these two substances is a measure of the CO2 content of the ocean water,” Damsté explained.

Future atmospheric CO2 concentrations

The study revealed that CO2 levels decreased from about 650 parts per million 15 million years ago to 280 parts per million just before the industrial revolution. Plotting these CO2 levels against corresponding temperatures showed a stronger relationship than previously recognized.

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

“The clear warning from this research is: CO2 concentration is likely to have a stronger impact on temperature than we are currently taking into account!” 

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, where CO2 is exchanged between the atmosphere, oceans, and land. 

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

Human activities have a significant impact, primarily through the burning of fossil fuels such as coal, oil, and natural gas, which releases large amounts of CO2. 

Deforestation reduces the number of trees that can absorb CO2, further increasing atmospheric levels. 

Industrial processes, such as cement production, also release CO2. Additionally, land use changes and agricultural practices can affect soil carbon storage and methane emissions, indirectly influencing CO2 levels.

Consequences of rising temperatures

Rising temperatures have far-reaching consequences for the planet. One significant impact is the alteration of weather patterns, leading to more frequent and severe weather events such as hurricanes, heatwaves, and heavy rainfall.

These changes can result in increased flooding, droughts, and other natural disasters, which disrupt ecosystems and human communities.

The warming climate also affects the natural habitats of many species, causing shifts in their geographical ranges and threatening biodiversity. Many species may face extinction if they cannot adapt quickly enough or migrate to suitable environments. 

Additionally, warmer temperatures contribute to the melting of polar ice caps and glaciers, leading to rising sea levels. This threatens coastal communities with flooding and erosion, potentially displacing millions of people and affecting freshwater supplies.

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

Furthermore, warmer temperatures can increase the prevalence of pests and diseases that affect both plants and livestock, further straining agricultural systems.

Human health is directly affected by rising temperatures. Increased heat can lead to heat-related illnesses and deaths, particularly among vulnerable populations such as the elderly and those with preexisting health conditions.

Higher temperatures can also exacerbate air quality issues, contributing to respiratory problems and other health concerns.

The study is published in the journal Nature Communications.

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