How does rising atmospheric CO2 affect marine organisms?

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They've Left Life Out of the Equations ...
Volume 13, Number 42: 20 October 2010

Climate modelers, enamored of the devices of their own creation, are drawing conclusions far beyond the bounds of what their models can rationally justify. In a highly-hyped paper that appeared in the 15 October 2010 issue of Science, for example, four researchers from NASA's Goddard Institute for Space Studies claim that atmospheric CO2 is the "principal control knob governing earth's temperature," being correct in one sense (of which, however, they appear to be oblivious), but wrong in another (the view, unfortunately, that they espouse in their paper). But let us explain.

Lacis et al. (2010), using models that employ only physical principles, profess to have proven that carbon dioxide -- not water vapor -- should hold the title of "principal controller of earth's temperature," due to the fact that water vapor, being a condensable greenhouse gas at current temperatures, is a "fast responder" to temperature changes induced by variations in both solar radiation intensity and non-condensable greenhouse gas concentrations, the most significant of which is CO2. And, therefore, by meekly "following in the footsteps" of CO2 (decreasing in concentration when the atmosphere's CO2 content drops and air temperatures cool), water vapor's role as an instigator of climate change is essentially preempted, as changes in its atmospheric concentration are clearly preceded by -- and therefore dictated by -- changes in air temperature that are induced by changes in the concentrations of the air's non-condensable greenhouse gases, among which CO2 stands preeminent.

If the air's CO2 concentration was either gradually or suddenly reduced and the atmosphere was to cool accordingly, for example, the view of the NASA scientists is that the atmosphere's water vapor content would also thus decline either gradually or suddenly, pretty much in lockstep with the initial CO2-induced change in temperature, thereby greatly amplifying the gradual or sudden cooling induced by the change in CO2, and vice versa if CO2 either gradually or suddenly rose, which suggests to them that CO2 is -- as they say in the title of their paper -- the "principal control knob governing earth's temperature."

All else being equal, we would tend to agree with Lacis et al. on this point. However, as we all know, "all else being equal" is hardly ever the case in the real world; and in the case in point, CO2 affects earth's climate in several more ways than through its thermal radiative properties. CO2 is, after all, the elixir of life, promoting plant growth, both on land and throughout the surface waters of the world's oceans. And this vast assemblage of plant life has the ability to impact earth's climate in a number of different ways, all of which tend to counteract the heating or cooling effects of carbon dioxide's thermal radiative forcing as its concentration either rises or falls, thereby helping to maintain earth's temperature within a range that is conducive to the continued existence, and even flourishing, of the planet's myriad life forms.

Time and space do not allow us to go into great detail about these several phenomena in this editorial; but in our website's Subject Index, under the general heading of Feedback Factors (Biophysical), we report the results of numerous observational studies that describe how earth's plants -- ranging all the way from unicellular algae in the sea, to grasses, shrubs and majestic trees on land -- emit copious quantities of gases that are converted to particles in the atmosphere, forming aerosols that reflect significant amounts of incoming solar radiation back to space, thereby cooling the planet, or that serve as condensation nuclei for cloud droplets that create more numerous, more extensive, longer-lasting and brighter clouds that also cool the globe. Therefore, depending on whether the air's CO2 content is increasing or decreasing, these phenomena result in changes in global radiative forcing similar in magnitude but opposite in sign to the direct thermal forcing induced by the increases or decreases in the air's CO2 concentration, which suggests that CO2 might well be considered the "principal control knob governing earth's temperature." However, CO2 controls the planet's temperature in such a way as to prevent the occurrence of both unduly hot and cold temperature extremes. Thus, the end result of these several simultaneous and interacting phenomena is that the ongoing rise in the air's CO2 content is of great benefit to the biosphere, helping to increase both the amount and quality of life on earth, while not materially altering the globe's temperature, by stimulating biological phenomena that ultimately tend to negate the greenhouse gas's own global warming potential.

Sherwood, Keith and Craig Idso

Lacis, A.A., Schmidt, G.A., Rind, D. and Ruedy, R.A. 2010. Atmospheric CO2: Principal control knob governing earth's temperature. Science 330: 356-359