User-Friendly Carbon Dioxide: The Greenest Gas

When French President Macron addressed a joint session of the U.S. Congress last month, he encouraged President Trump to reconsider his intention to withdraw from the Paris Climate Accord.

Trump’s decision not to participate further in the agreement came about based on evidence that efforts to reduce U.S. carbon dioxide emissions to 1992 levels would impose heavy economic costs and unduly burden American consumers. The total effect of our compliance would be to reduce temperature by an immeasurably scant three tenths of a degree Celsius by 2100.

A series of international conferences had culminated in an agreement in 2015 to take full effect in 2020.

The rationale behind Paris is that burning of fossil fuel causes a build-up of carbon dioxide, a greenhouse gas, in the atmosphere that in time would lead to its overabundance and an irreversible increase in global temperatures.

On close examination, the prospect of dire consequences raised in the 1980’s has failed to materialize in the early 21st century. On the contrary, rising levels of CO² may turn into more of a blessing than a curse.


All animal life on our planet owes its existence to the ability of plants to photosynthesize basic sugars from carbon dioxide and water, using chlorophyll and sunlight.

Without help from our green friends, energy supplies invested in plant-derived foods would quickly dwindle to the point where there would be none left to sustain the animal kingdom.

Below a threshold of about 140 part per million (ppm) CO² in the atmosphere, plants can no longer take in sufficient amounts to manufacture sugar, and they die.

During previous continental glaciations, CO² levels had fallen to nearly 200 ppm before rising again during the current warmth known as an “interglacial period,” in response to warming oceans.

Atmospheric CO² now stands just above 400 ppm and is slowly increasing, with small seasonal fluctuations. 

In geologic ages long past the atmosphere contained as much as 20 times more CO² as at present. During the Carboniferous Period large ferns came into being and early precursors of the dinosaurs roamed the land. No runaway warming ensued.

Because the past twenty years of satellite temperature records show no statistically significant upward trend despite steadily increasing CO², the debate had shifted away from global warming to focus instead on man-caused “climate disruption”—a term so vague as to be impossible to verify and quantify, and thus impossible to test. But increasing CO² can bring huge benefits.

Greenhouse practices and controlled crop field studies point toward a conclusion that current-day CO² levels are not yet high enough to reach optimal photosynthesis. Experimenters find plants essentially “starved” for carbon dioxide at the current low level (geologically speaking) of 400 ppm.

Plants respond positively if CO² is doubled or even trebled in controlled trials. Remarkably, many plant types do not achieve their optimum growth potential unless exposed to 1,500 ppm CO², nearly four times that of the present-day atmosphere. 

Why? Sherwood, Craig and Keith Idso, all Ph.D. research agronomists at Arizona State University, explain that plant “stomata,” tiny breathing pores on the surfaces of leaves, respond to CO².

When abundant CO² is present, the stomata constrict, like an iris diaphragm in the eye or a camera, to prevent escape of water molecules, while gathering in CO². Increased CO² conserves transpired moisture. Thus, plants, particularly under semi-arid conditions, will fare better with more CO² in the air they “breathe.”  

Landsat (satellite) imagery over the past several decades reveals gradual greening of arid land areas, particularly in equatorial zones of Africa and Asia.

The sub-Saharan Sahel is a belt of semi-arid land stretching from Africa’s Atlantic coast eastward toward the Red Sea. The Sahel is producing more green vegetation (grassland and scrub) to support grazing of livestock and tillage of crops not seen there over the past thousand years.

In addition to modest increases in precipitation over the Sahel, increased CO² is allowing native plants and crops to cope better with scarce soil moisture.

Similar improvements in plant growth are occurring all over the world in response to rising atmospheric CO² concentration. Craig Idso has estimated that we owe about $3.2 trillion in added agricultural production from 1961 to 2011 to it, and that it will generate another $9.8 trillion by 2050.

Policymakers need to know both sides of the story about CO². Agencies that issue alarm-filled reports on the dangers of increasing carbon dioxide are morally bound to consider, in addition to the largely unproven potential negative effects, the already well-documented benefits of higher CO² to agricultural production and human welfare.


William D. Balgord, Ph.D. (Chemistry), is President of Environmental & Resources Technology, Inc., Middleton, WI, and a Contributing Writer for The Cornwall Alliance for the Stewardship of Creation.

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