Challenges to the CO2 Global Warming Hypothesis (12): CO2 from Antimicrobials Far Exceeds CO2 from Fossil Fuels

My series on challenges to the CO₂ global warming hypothesis has featured a number of possible alternative sources to CO₂ as the source of warming, as well as scenarios that question the greenhouse effect. This post reports a new challenge that embraces the greenhouse effect and the CO₂ hypothesis, but disputes the belief that increased CO₂ comes primarily from burning fossil fuels.

The revolutionary proposal attributes the bulk of human CO₂ emissions into the atmosphere to a biological source, namely antimicrobials or, more precisely, antimicrobial resistance. This heretical idea comes from UK husband-and-wife team Frank and Jeanette Sams-Dodd, scientists with backgrounds in biology and veterinary medicine, respectively.

So what exactly are antimicrobials and how do they inject so much CO₂ into the air? Antimicrobials are simply chemical compounds that kill microbes. These include antibiotics, antiseptics, antifungals, antivirals, antiparasitics, disinfectants, surfactants, pesticides and herbicides.

Antimicrobial resistance occurs when microbes are able to withstand antimicrobials at the concentration they are exposed to in their environment. Use of antimicrobials eliminates nonresistant species, bolstering antimicrobial resistance and disrupting the microbiome. A microbiome is a community of bacteria and other microbes in the air, soil and water; everything on Earth has its own microbiome.

Disruption of microbiomes by antimicrobials, the Sams-Dodds explain, sets off a chain of events that leads to a severe imbalance in ecological systems that rely on a microbiome to release, absorb and retain certain gases, moisture and nutrients. This is illustrated in the figure below.

As indicated, antimicrobials find their way to sewage plants or landfills, from where they enter the wider environment unhindered, carried by water leaching through the soil. Antimicrobials are also carried by water that evaporates into the air, where they are transported through the atmosphere by winds and clouds before falling back to the earth as precipitation.

This widespread dispersal of antimicrobials is a major source of atmospheric CO₂.

As far back as 1954, it was shown that adding antibiotics to soil releases substantial amounts of CO₂ into the atmosphere. Several subsequent studies have confirmed that antimicrobials not only cause enhanced release of greenhouse gases, including CO₂, methane (CH₄) and nitrous oxide (N₂O), from soil and aquatic environments, but they also reduce carbon capture and storage. It is microbial communities that mainly regulate the earth’s carbon, nitrogen and other biogeochemical cycles.

To quantify the effect of antibiotics alone on CO₂ emissions, the Sams-Dodds have performed a detailed calculation of how a standard course of tetracycline affects the ability of soil to store carbon. They first estimate that the amount of tetracycline from a single course that escapes metabolic breakdown at a sewage treatment plant and is released into the environment is 2.0 grams.

They then draw on a 2023 study which found that 1.155 milligrams of tetracycline in soil reduces its storage capacity by 1.55 kilograms of carbon, or 5.68 kilograms of CO₂, per square meter of soil surface. Dividing 2,000 milligrams of tetracycline by 1.155 milligrams per square meter of soil surface equals 1,732 square meters. Multiplying by 5.68 kilograms of CO₂ per square meter gives a total of 9,835 kilograms (9.84 tonnes) of CO₂ released per course of tetracycline.

This calculation is based on data from cattle graziers, some of whom feed antibiotics to their cattle and some of whom don’t. A more realistic number for the reduction in carbon storage capacity worldwide from tetracycline use is a lower 3.82 kilograms of CO₂ per square meter of soil surface. When this number is multiplied by the area of fertile soil surface, which constitutes about 10% of the earth’s land surface, the reduction in long-term CO₂ storage capacity from tetracycline alone is 194.8 gigatonnes (214.7 gigatons).

What this means is that 194.8 gigatonnes (214.7 gigatons) of the CO₂ currently in the atmosphere, or about 6% of the total 3,341 gigatonnes (3,683 gigatons), would have been sequestered in soil were it not for the spread of human-made antimicrobials. More importantly, the CO₂ no longer stored in the soil is 5.2 times the estimated CO₂ emissions from fossil fuel combustion and industrial processes, of 37.6 gigatonnes (41.4 gigatons) in 2024.

So, if one subscribes to the CO₂ global warming hypothesis, CO₂ from fossil fuels makes only a minor contribution to warming; the major contribution by far comes from antimicrobial CO₂. Curbing fossil fuel emissions is therefore a fool’s errand.

Such a finding also turns on its head the conventional wisdom in the healthcare community that the increase in antimicrobial resistance over the last 70 years is a result of the CO₂-induced warming of approximately 1.25 degrees Celsius (2.25 degrees Fahrenheit) during that period. Rather, the Sams-Dodds conclude, the increase in antimicrobial resistance is responsible for the lion’s share of that warming.

The two scientists note that the rapid increase in the atmospheric CO₂ level since the late 1950s coincides with an upturn in use of both antimicrobials and fossil fuels.

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