Opinions of Peter Belmont
Speaking Truth to Power
| Contrasting Two Theories of Climate Change, Especially Sensitivity to Excess Atmospheric CO2 |
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by Peter A. Belmont / 2024-12-05
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SUMMARY
We know there is excessive CO2 in the atmosphere. The range of attempts to explain the significance and likely effects of present (and increasing) atmospheric CO2 may be bracketed by two contrasting theories which seek to explain the effect of this excess CO2 on the climate. Theory[1] (the “thermostat” theory) holds that the TEMPERATURE of the atmosphere is proportional to the amount of excess CO2, so that if the concentration of CO2 stops changing, the temperature will also stop changing. Theory[2] (the “foot on the gas” theory) holds that the RATE OF INCREASE in atmospheric TEMPERATURE is proportional to the amount of excess CO2, meaning that even a complete cessation of CO2 emissions would leave the earth with continuing rising temperature until the atmospheric CO2 concentration could be brought down to baseline levels. ESSAY A recent article begins: One of the most important concepts in climate science is the idea of committed warming — how much future warming is coming from carbon dioxide that we’ve already emitted. I felt this comforting conclusion was dangerously wrong and explain why here. What follows began as a “comment” on the article cited above, but has been expanded. As a “comment” it could not be published because I did not subscribe to the publication. Two Conflicting Theories of Climate Change Climate articles (e.g., here) often begin with the information that atmospheric CO2 concentrations have increased about 50% since “baseline” amounts, 278ppm in 1800. Some people use a different “baseline”, 300ppm (about 1920). At those levels, we could say that human-caused climate change had not, or had hardly, started. The Climate Restoration Foundation makes returning to 300ppm a goal, and looks for means to achieve that goal, rather than accept higher numbers and worse, likely disasterous, climatic conditions later. At the extremes, there are two quite different understandings of how the “thickness” of the CO2 “blanket” (the excess of atmospheric concentration of CO2 over baseline 300ppm) acts on the retained heat in the earth-system (atmosphere, earth, oceans) (below, called “HEAT”). Since climate science is complex, neither theory is “correct” but each is instructive, and it is important to know which theory is more nearly correct if people are to choose climate action responsibly. THEORY [1] The “thermostat” theory: constant “thickness” leads to constant excess earth-system heat. Earth-system heat (and therefore temperature) will stabilize when we (fully) stop adding CO2 to the atmosphere. HEAT ~ excess atmospheric CO2 concentration dHEAT/dt = 0 for constant excess atmospheric CO2 concentration THEORY [2] The “foot on the gas” theory: the sun’s daily contribution to retained earth-system heat is proportional to the excess of atmospheric CO2 (and of course CH4 etc) over baseline (1910) levels (CO2 at 300ppm). Holding the excess of CO2 constant causes a constant daily increment of heat to the earth-system and thus of atmospheric and earth and ocean temperatures. dHEAT/dt ~ excess atmospheric CO2 concentration As a non-specialist, my belief is that [2] is more nearly correct, more “instructive” as a guide to action, and that we need urgently to reduce the “thickness” of the CO2 blanket. Supporting my belief in [2] is another article from 2010 which says Stable atmospheric concentrations of greenhouse gases would lead to continued warming, but if carbon dioxide emissions could be eliminated entirely, temperatures would quickly stabilize or even decrease over time.(leading me to wonder what “quickly stabilize” means). The article cited above supports theory [1] rather than [2] but then admits (as a complicating factor) that the reason atmospheric temperature is (somewhat) reduced over time is absorption of heat (as also of CO2) by oceans. In other words (per idea [2]) the large excess concentration of CO2 in the atmosphere DOES cause a continuing heating of the earth-system (atmosphere, earth, oceans), but some or much of the increase in heat due to the thick (and presently ever thickening) blanket is absorbed by the oceans, as also much of the excess CO2 itself. My “bon mot” for all this, these days, is that The climate-caused-unwanted-events of today (floods, droughts, fires, storms, ice-melts, sea-level rises, changes in distribution of life on earth’s surface) were not caused by the GHG emissions of tomorrow. In other words, the climate-caused-unwanted-events of today are caused by today’s excess earth-system heat. And, per [2], that heat must be expected to rise even with ZERO EMISSIONS (that we are in any case not even close to achieving in any near future). And if theory [2] is more nearly correct, then the need for massive removal of atmospheric CO2 (and as time goes by, of CO2 released from the oceans where it has been stored) is an absolute, immediate, and urgent necessity. If theory [2] is more nearly correct, leaving the excess atmospheric CO2 concentration at its present level as a constant will not lead to a constant, but rather to an increasing, earth-system heat (and temperature). |
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