Since the early 1990s the conventional assumption, aligned with modeling, has been that a molecule of human CO2 emission stays in the atmosphere – its residence time – for centuries. This fits the anthropogenic global warming (AGW) narrative. But empirical evidence contradicts these model-based assumptions. Residence time is closer to 5-10 years.
In Table 1 of a new study, Stallinga (2023) compiled a list of 36 published estimates of CO2 residence time spanning the decades 1957-1992. All of these scientists determined CO2’s atmospheric residence time is about 5 to 10 years or less.
Image Source: Stallinga, 2023
Of course, these were the pre-IPCC decades in climate research, when “the science” was pursued independent of government interference. For example, it was still acceptable in the 1950s to early 1990s for scientists to publish actual ice core measurements showing the atmospheric CO2 content ranged up to 700 ppm, even 2,450 ppm, in the ice sheets and glaciers examined throughout the last 10,000 years (Jaworowski et al., 1992).
An actual residence time that is 20 to 40 times shorter in duration than what an AGW modeled thought experiments allow undermines the dangerous greenhouse gas accumulation talking points, as “if the residence time is below 30 years, injections of CO2 in the atmosphere would, just as water, not affect the climate” (Stallinga, 2023).
In addition to compiling an exhaustive list of past estimates supporting a 5-10 year residence time, Dr. Stallinga cites the evidence from atomic bomb tests, the lack of any atmospheric CO2 effect from the pandemic lockdowns and associated sharp drop in emissions, and the lead-lag relationship CO2 emission has with temperature as evidence supporting the once commonly-accepted conclusion that CO2 residence is closer to 5 years, not centuries.
And if residence time is only 5 years, nearly “90% of all anthropogenic carbon dioxide has already been removed from the atmosphere.”
Image Source: Stallinga, 2023
Stallinga’s conclusions are very similar to that of Dr. Chauncey Starr (1993), a nuclear physicist who emphasized that a centuries-long residence time claims are derived from “global carbon cycle models which are adjusted to fit the assumption that anthropogenic emissions are primarily the cause of the observed rise in atmospheric CO2.”
Starr provided empirical support for the conclusion residence time is 4-5 years. For example, the high altitude 1964 nuclear bomb testing revealed how quickly (3-11 years) the atmosphere cycled through these perturbations. The constancy of the amplitude of seasonal cycle of CO2 and the magnitude of the swing in annual concentrations are both consistent with photosynthesis as the driver of CO2 variability, further affirming a residence time of 5 years or less.
Also, similar to Dr. Stallinga’s analysis, Starr reported “only about 15% of the fossil-fuel emissions remain in the atmosphere.”