The residence time of CO2 in the atmosphere refers to the average duration a CO2 molecule remains in the atmosphere before being removed through natural processes like absorption by oceans, plants, or soils.

This is distinct from the adjustment time (also called perturbation lifetime or e-folding time), which measures how long it takes for the atmospheric CO2 concentration to return to equilibrium after a perturbation, such as added emissions.

The carbon cycle describes how carbon moves between reservoirs: atmosphere, oceans, land biosphere, soils, and fossil fuels.

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From No Trick Zone

By Kenneth Richard

The Intergovernmental Panel on Climate Change (IPCC) has for decades advocated net-zero governmental policies to reduce anthropogenic CO2 (aCO2) emissions.

This advocacy is rooted in the non-physical assumption that aCO2 molecules are special, as they remain in the atmosphere for decades to centuries.

Proponents of the anthropogenic global warming (AGW) narrative even claim aCO2 removal can “take up to several hundreds of thousands of years.”

While AGW proponents insist that “once in the atmosphere, carbon dioxide can continue to affect climate for thousands of years,” they (and the IPCC) simultaneously acknowledge the residence time of “natural” or non-anthropogenic CO2 is only about 4 years.

In reality, a new study references the Equivalence Principle in emphasizing nature’s sinks indiscriminately and equivalently absorb both aCO2 and natural CO2 in about 4 years (Müller, 2025). There is no physical reality for IPCC claims of “specialized” absorption time for a CO2 vs. natural CO2 molecules.

The IPCC assumes exactly 50% of aCO2 emissions remain in the atmosphere for decades to millennia. It is consequently assumed net-zero policies that propose to halve aCO2 emission will lead to the stabilization of atmospheric CO2 concentrations. Because “anthropogenic CO2 has the same [4-year] residence time of natural CO2,” this assumption is physically invalid.

Net-zero policies will literally have no detectable effect on atmospheric CO2 concentrations. In sum, “the IPCC’s assumptions and fundamentals are wrong.”