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Atmospheric CO2 Enrichment: Boon or Bane of the Biosphere?

Is the human-induced increase in the atmosphere's carbon dioxide concentration good or bad for the earth and its inhabitants? A number of scientists who base their opinions primarily on the predictions of climate models vociferously claim that it's bad. Other scientists, who base their opinions primarily on real-world weather measurements and historical proxy temperature reconstructions, along with the known positive effects of atmospheric CO2 enrichment on terrestrial plant growth and development, as well as its benign effects on aquatic plants and animals, are equally adamant that it's good.

So who's right? Who has the moral high-ground when it comes to dictating what humanity should or should not be doing about the ongoing rise in the air's CO2 content? The purpose of this brief review of the matter is to answer this most important question.

We begin with the fact that many of the bane-leaning scientists -- together with Pope Francis, who has allowed himself to be tilted in the same direction -- feel so sure about their stance on the issue that they are claiming mankind has a moral imperative to cut CO2 emissions dramatically, and to begin doing so now. But in taking this stringent stance, they ignore a moral imperative that carries even greater weight than what they assign to the issue, which is where we begin our analysis of the subject.

As the world's population continues to climb, there is increasing concern about the sustainability or carrying capacity of the earth; and in making decisions about long-term research and development policies, movers and shakers from many sectors of the global economy need to know if there will be sufficient food some 35 years from now to sustain the projected population of the planet. After all, it is only prudent that we attempt to gain such insight into the human condition, for we all have a stake in the future progression of our species.

Seeking to gain such insight as early as a decade and a half ago, Idso and Idso (2000) developed and analyzed a supply-and-demand scenario for food in the year 2050. Specifically, they identified the plants that currently supply 95% of the world's food needs and projected historical trends in the productivities of these crops fully 50 years into the future. They also evaluated the growth-enhancing effects of atmospheric CO2 enrichment on these plants and made similar yield projections based on the increase in atmospheric CO2 concentration likely to have occurred by that future date.

This work revealed that world population will likely be 51% greater in the year 2050 than it was in 1998, but that world food production will be only 37% greater if its enhanced productivity comes solely as a consequence of anticipated improvements in agricultural technology and expertise. However, they further determined that the consequent shortfall in farm production could be overcome -- but only just barely -- by the additional benefits anticipated to accrue from the aerial fertilization effect of the expected rise in the air's CO2 content, assuming no Kyoto-style cutbacks in anthropogenic CO2 emissions.

In order to avoid the unpalatable consequences of widespread hunger and consequent early deaths in the decades ahead, it would thus appear to be absolutely necessary to allow the air's CO2 concentration to rise at an unrestricted rate. Consequently, efforts designed to discourage CO2 emissions are seen in this light to be inimical to our future well-being, as well as that of generations yet unborn throughout the entire world, which must surely be considered to be immoral.

Around this same time, Wallace (2000) also made some important observations about the state of the earth, leading him to conclude that "the massive and inexorable increase in the number of human beings in the world should be recognized for what it is -- the most important global change facing mankind."

The rationale behind this statement derives from four simple facts. First, the projected increase in the number of people that will have joined our ranks by the year 2050 -- a median best-guess of 3.7 billion from the time of Wallace's publication -- is more sure of occurring than is any other environmental change currently underway or looming on the horizon. Second, these extra people will need a whopping amount of extra food. Third, it will take an equally whopping amount of extra water to grow that extra food. And fourth, there is no extra water.

"Over the entire globe," therefore, Wallace writes that "a staggering 67% of the future population of the world may experience some water stress," which translates into food insufficiency. And food insufficiency results in malnutrition, which in the most extreme cases ultimately leads to starvation.

So what's the solution? There's only one answer, according to Wallace: we must produce much more food per unit of available water, which leads to the most important question of all: How can it be done?

Wallace discusses in some detail what would appear to be the only alternatives. First, he suggests we must greatly augment water conservation measures wherever possible and implement every conceivable efficiency-enhancing procedure in irrigated and rain fed agriculture. Second, we must do everything we can, as he says, "to fix more carbon per unit of water transpired." That is to say, we must strive to dramatically increase plant water use efficiency.

Human ingenuity will surely enable great strides to be made in all of these areas over the coming decades. But will the improvements be large enough to meet the challenges we will face? At the present time, no one can answer this question with any confidence. In fact, pessimism permeates most thinking on the subject; for as Wallace correctly reports, "the global scientific community is not currently giving this area sufficient attention."

And where was our attention focused at the time of his writing? Unfortunately, it was focused on reducing anthropogenic CO2 emissions to the atmosphere, which is truly lamentable; for the continuation of those emissions is, ironically, our only real hope for averting the near-certain future global food shortfall that is destined to occur if the Kyoto Protocol Crowd gets its way with the world.

But how would allowing anthropogenic CO2 emissions to take their natural course help to ameliorate future hunger? The answer resides in the fact that elevated concentrations of atmospheric CO2 tend to reduce plant water loss by transpiration, while simultaneously enhancing plant photosynthesis and biomass production, which two phenomena enable earth's vegetation to produce considerably more food per unit of water used in the food production process.

Literally thousands of laboratory and field experiments -- and that is no exaggeration -- have verified this fact beyond any doubt whatsoever. Indeed, this atmospheric CO2-derived blessing is as sure as death and taxes and as dependable as a mother's love. But what do the climate-alarmist ideologues do about it? They spurn it. They deny it. They try to reverse it, in fact. And they do it to the detriment of all mankind.

Here, then, is the dilemma we face. Many people believe that the potential climate crisis is driven by the increasing greenhouse effect of the ongoing rise in the air's CO2 content, while many others believe that the increasing aerial fertilization and anti-transpiration effects of this phenomenon are the only "extra" things that can help us avert the otherwise near-certain food and water crises looming on the horizon. What is the first group's poison, therefore, is the other group's cure.

So how is this global food and water crisis to be met and overcome? In terms of confronting this daunting challenge, Zhu et al. (2010) state that "meeting future increases in demand will have to come from a near doubling of productivity on a land area basis," and they opine that "a large contribution will have to come from improved photosynthetic conversion efficiency," for which they estimate that "at least a 50% improvement will be required to double global production."

The researchers' reason for focusing on photosynthetic conversion efficiency derives from the experimentally-observed facts that (1) increases in the atmosphere's CO2 concentration increase the photosynthetic rates of nearly all plants, and that (2) those rate increases generally lead to equivalent -- or only slightly smaller -- increases in plant productivity on a land area basis, thereby providing a solid foundation for their enthusiasm in this regard. In their review of the matter, however, they examine the prospects for boosting photosynthetic conversion efficiency in an entirely different way: by doing it genetically and without increasing the air's CO2 content. So what is the likelihood that their goal can be reached via this approach?

"Improving photosynthetic conversion efficiency will require," as the three scientists described it, "a full suite of tools including breeding, gene transfer, and synthetic biology in bringing about the designed alteration to photosynthesis." For some of these "near-term" endeavors, they indicate that "implementation is limited by technical issues that can be overcome by sufficient investment," meaning they can "be bought." But a number of "mid-term" goals could well take 20 years to achieve; and they say that "even when these improvements are achieved, it may take an additional 10-20 years to bring such innovations to farms in commercial cultivars at adequate scale." And if that is not bad enough, they say of still longer-term goals that "too little of the science has been undertaken to identify what needs to be altered to effect an increase in yield," while in some cases they acknowledge that what they envision may not even be possible, as in the case of developing a form of Rubisco that exhibits a significant decrease in oxygenation activity, or in the case of designing C3 crops to utilize the C4 form of photosynthetic metabolism.

Clearly, we do not have the time to blindly gamble on our ability to accomplish what needs to be done in order to forestall massive human starvation of global dimensions within the current century, which suggests to us that in addition to trying to accomplish what Zhu et al. suggest, we must rely on the "tested and true," i.e., the CO2-induced stimulation of plant photosynthesis and crop yield production. And all we need to do to do so, is to not interfere with the natural evolution of the industrial revolution, which is destined to be carried for some time yet on the backs of fossil-fuel-supported enterprises that can provide the atmosphere with the extra carbon dioxide that will be needed to provide the increases in crop growth and water use efficiency that may well mean the difference between global food sufficiency and human starvation on a massive world-wide scale a mere few decades from now.

About this same time, Parry and Hawkesford (2010) introduced their study of the global problem by noting that "food production needs to increase 50% by 2030 and double by 2050 to meet projected demands," and they note that at the same time the demand for food is increasing, production is progressively being limited by "non-food uses of crops and cropland," such as the production of biofuels, stating that in their homeland of the UK, "by 2015 more than a quarter of wheat grain may be destined for bioenergy production," which surely must strike one as both sad and strange, when they also note that "currently, at least one billion people are chronically malnourished and the situation is deteriorating," with more people "hungrier now than at the start of the millennium."

So, what are we to do about it? That is the question the two researchers broach in their review of the sad situation. They begin by describing the all-important process of photosynthesis, by which the earth's plants "convert light energy into chemical energy, which is used in the assimilation of atmospheric CO2 and the formation of sugars that fuel growth and yield," which phenomena make this natural and life-sustaining process, in their words, "a major target for improving crop productivity both via conventional breeding and biotechnology."

Next to a plant's need for carbon dioxide comes its need for water, the availability of which, in the words of Parry and Hawkesford, "is the major constraint on world crop productivity." And they state that "since more than 80% of the [world's] available water is used for agricultural production, there is little opportunity to use additional water for crop production, especially because as populations increase, the demand to use water for other activities also increases." Hence, they rightly conclude that "a real and immediate challenge for agriculture is to increase crop production with less available water."

Enlarging upon this challenge, they give an example of a success story: the Australian wheat variety 'Drysdale', which gained its fame "because it uses water more efficiently." This valued characteristic is achieved "by slightly restricting stomatal aperture and thereby the loss of water from the leaves." They note, however, that this ability "reduces photosynthetic performance slightly under ideal conditions," but they say it enables plants to "have access to water later in the growing season thereby increasing total photosynthesis over the life of the crop."

Of course, Drysdale is but one variety of one crop; and the ideal goal would be to get nearly all varieties of all crops to use water more efficiently. And that goal can actually be reached by doing nothing, except to halt the efforts of radical environmentalists to deny earth's carbon-based life forms (that's all of us and the rest of the earth's plants and animals) the extra carbon we and they need to live our lives to the fullest. This is because allowing the air's CO2 content to rise in response to the burning of fossil fuels naturally causes the vast majority of earth's plants to progressively reduce the apertures of their stomata and thereby lower the rate at which water escapes through them to the air. And the result is even better than that produced by the breeding of Drysdale, because the extra CO2 in the air more than overcomes the photosynthetic reduction that results from the partial closure of plant stomatal apertures, allowing even more yield to be produced per unit of water transpired in the process.

Yet man can make the situation better still, by breeding and selecting crop varieties that perform better under higher atmospheric CO2 concentrations than the varieties we currently rely upon, or he can employ various technological means of altering them to do so. Truly, we can succeed, even where "the United Nations Millennium Development Goal of substantially reducing the world's hungry by 2015 will not be met," as Parry and Hawkesford have written. And this truly seems to us the moral thing to do, when "at least one billion people are chronically malnourished and the situation is deteriorating," with more people "hungrier now than at the start of the millennium."

Two years later in a brief "Perspective" published in Science, Running (2012) resurrected shades of Meadows et al.'s 1972 treatise on The Limits to Growth. Noting that "terrestrial plant production is the foundation of the biospheric carbon cycle" and that "water and atmospheric CO2 are transformed into plant carbohydrate matter with the help of solar energy," he stated that this plant matter "sustains the global food web and becomes the source of food, fiber and fuel for humanity."

A problem that Running saw in these facts, however, was that for more than 30 years, global net primary production (NPP) had "stayed near 53.6 Pg per year, with only ~1 Pg of inter-annual variability," citing two studies of which he was a co-author (Nemani et al., 2003; Zhao and Running, 2010). And he thus went on to speculate that "if global NPP is fixed by planetary constraints, then no substantial increase in plant growth may be possible."

If true, this result would have catastrophic consequences, for it is almost universally agreed, as Running writes, that "the projected 40% increase in human population by 2050 CE, combined with goals to substantially improve standards of living for the poorest 5 billion people on Earth, implies at least a doubling of future resource demand by 2050," the most important of which resources is food.

But is a doubling of food production a mere 38 years from now realistic? Agriculture already was consuming 38% of the world's land surface; and Running reported that "many analyses now conclude that freshwater use for irrigation has already reached a planetary boundary." Furthermore, with "massive river pollution and ocean anaerobic dead zones," he stated that "if anything, future increases in NPP must be achieved with less, not more, irrigation and fertilizer use." And God help us if, as he also noted, "land previously allocated to food production is transformed to bioenergy production, raising food prices for the people who can least afford it," as has been discussed by Tilman et al. (2009).

So, have we really reached the planet's limits to growth? In a paper published in Nature entitled "Increase in observed net carbon dioxide uptake by land and oceans during the past 50 years," Ballantyne et al. (2012) suggested we have not. The five U.S. scientists said their mass balance analysis showed that "net global carbon uptake has increased significantly by about 0.05 billion tonnes of carbon per year and that global carbon uptake doubled, from 2.4 ± 0.8 to 5.0 ± 0.9 billion tonnes per year, between 1960 and 2010." And they thus concluded that "there is no empirical evidence that carbon uptake has started to diminish on the global scale." In fact, as their results clearly indicated, just the opposite appears to be the case, with global carbon uptake actually doubling over the past half-century.

But how can that be? There are many answers: breeding of better crop varieties that are higher-yielding, more competitive with weeds, less tasty to insect pests, more nutritious, more drought resistant, as well as smarter ways of farming, improved technologies, and the worldwide aerial fertilization and transpiration-reducing effects of the historical and still-ongoing rise in the air's CO2 content, which latter phenomena benefit both agriculture and the world of nature at one and the same time.

So rather than allocate precious land and water resources to the production of biofuels, which diminishes our ability to produce the enormous amounts of extra food we will need to feed ourselves every year for the next four decades and beyond, and which drives up the cost of the foods that we are able to produce, we suggest that we concentrate on using our great stores of coal, gas and oil to meet our future fuel needs, as these substances are clearly the least expensive energy sources we currently possess, and the utilization of all of them will result in lower costs of most all of the products and services that small and large businesses alike provide. And perhaps most important of all, more carbon dioxide in the atmosphere will boost the water use efficiencies and yields of essentially all agricultural crops everywhere, as well as the robustness of the entire world of nature.

More recently, Muldowney et al. (2013) introduced their analysis of this issue by writing that "with the human population predicted to reach nine billion by 2050, demand for food is predicted to more than double over this time period." And they go on to say that "in the establishment of the United Nations Framework Convention on Climate Change (UNFCCC), 'ensuring that food production is not threatened' is explicitly mentioned in the objective of the Convention."

Nevertheless, as they continue, they note that "until recent years" this need for a doubling of agricultural output "has had a relatively low profile within the UNFCCC negotiations." And they note that even the IPCC has recognized that "it is necessary to increase agricultural production." Yet the primary efforts of both of these entities have been, and continue to be, directed against that which is most needed to produce the required amount food, as they both argue for reductions in anthropogenic CO2 emissions, which comprise much of the aerial "food" that sustains all of our food crops.

As evidence for this latter contention, we provide a listing of the experimental findings of the vast collection of scientific papers that support this point of view of the subject in the Plant Growth Database of our website ( There, it can be seen that enriching the air with CO2 almost always leads to significant increases in the photosynthetic rates and biomass production of all of the world's major food crops. And as for the highly-unlikely increase in global temperature that the world's climate alarmists predict to result from projected increases in the air's CO2 content, there are also many studies that reveal the positive consequences of warming for agriculture in Earth's cooler high-latitude regions, such as the recent study of Meng et al. (2014) dealing with maize production in the northern reaches of China. And there is also the significant body of work that reveals that as the atmosphere's CO2 concentration rises, the various temperatures at which different plants photosynthesize most proficiently rise right along with it, as we described well over a decade ago in a report entitled The Spector of Species Extinction: Will Global Warming Decimate Earth's Biosphere?

All things considered, therefore -- including the many journal reviews on our website that recount the many failures of the most sophisticated climate models yet developed to replicate real-world past climatic histories in almost all parts of the planet (see Climate Models: Inadequacies in our Subject Index) -- the best thing we could possibly do to assure the production of sufficient food to feed our descendants (as well as many of us) a mere three and a half decades from now would be to stop trying to reduce anthropogenic CO2 emissions!

So we return to the question posed in the introduction to this report: Who stands on the moral high-ground when it comes to dictating what humanity should or should not be doing about the ongoing rise in the air's CO2 content? If you value human life, you must stand with those who support the ongoing increase in the atmosphere's CO2 concentration; for without its ability to enhance crop growth and water use efficiency, it will be impossible to sustain the projected human population of the planet by the midpoint of the current century.

But what about the CO2-induced increase in global temperature that is predicted by climate models? For one thing, the magnitude of the predicted warming is not to be trusted, as the models fail to properly replicate many important characteristics of Clouds, the El Niño-Southern Oscillation, Ice Sheets, Monsoons, Oceans, Permafrost, Precipitation, Radiation, Sea Ice, Soil Moisture and Streamflow, along with a number of other phenomena included within the subject designation of General, all of which may be found in the Subject Index of our website ( under the general heading of Climate Models (Inadequacies).

One thing that we do know about real-world global warming whenever it has occurred in the recent past, however, is that it has typically been characterized by a greater increase in daily minimum temperatures than in daily maximum temperatures, as has been reported by a host of pertinent publications that we have reviewed and described under the general heading of Health Effects (Temperature - Hot vs. Cold Weather) in our website's Subject Index. And the many scientific studies there described have essentially all reported that the number of lives saved by increases in daily minimum temperatures greatly exceeds the number of lives lost as a result of increases in daily maximum temperatures, for a net saving of lives in a warming climate.

One of the most recent of these studies was that of Gasparrini et al. (2015), who analyzed data they obtained from 384 locations scattered around the world, including the countries of Australia, Brazil, Canada, China, Italy, Japan, South Korea, Spain, Sweden, Taiwan, Thailand, the United Kingdom and the United States of America. And by fitting a standard time-series Poisson model to the data obtained for each location, while controlling for trends and day of the week, they estimated temperature-mortality associations with a distributed lag non-linear model with 21 days of lag, after which they pooled the results they obtained in a multivariate meta-regression.

Based on the data they obtained pertaining to a total of 74,225,200 human deaths that occurred between 1985 and 2012, the 23 researchers found that "more temperature-attributable deaths were caused by cold (7.29%) than by heat (0.42%)," which makes cold in excess of seventeen times more deadly than heat.

And so we see that the real-world effects of atmospheric CO2 enrichment are absolutely essential to enable us to adequately feed and sustain the human population of the planet that is expected to inhabit the earth a mere 35 years from now, while at the same time being able to enjoy better health and resultant longevity. Is not this the moral course we all should be pursuing?

Ballantyne, A.P., Alden, C.B., Miller, J.B., Tans, P.P. and White, J.W. 2012. Increase in observed net carbon dioxide uptake by land and oceans during the past 50 years. Nature 488: 70-72.

Gasparrini, A., Guo, Y., Hashizume, M., Lavigne, E., Zanobetti, A., Schwartz, J., Tobias, A., Tong, S., Rocklöv, J., Forsberg, B., Leone, M, De Sario, M., Bell, M.L., Guo, Y.L.L., Wu, C.F., Kan, H., Yi, S.M., de Sousa, Z., Coelho, S. M., Saldiva, P.H., Honda, Y., Kim, H. and Armstrong, B. 2015. Mortality risk attributable to high and low ambient temperature: a multi-country observational study. The Lancet: 10.1016/S0140-6736(14)62114-0.

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Meng, Q., Hou, P., Lobell, D.B., Wang, H., Cui, Z., Zhang, F. and Chen, X. 2014. The benefits of recent warming for maize production in high latitude China. Climatic Change 122: 341-349.

Muldowney, J., Mounsey, J. and Kinsella, L. 2013. Agriculture in the climate change negotiations; ensuring that food production is not threatened. Animal 7:s2: 206-211.

Nemani, R.R., Keeling, C.D., Hashimoto, H., Jolly, W.M., Piper, S.C., Tucker, C.J., Myneni, R.B. and Running. S.W. 2003. Climate-driven increases in global terrestrial net primary production from 1982 to 1999. Science 300: 1560-1563.

Parry, M.A.J. and Hawkesford, M.J. 2010. Food security: increasing yield and improving resource use efficiency. Proceedings of the Nutrition Society 69: 592-600.

Running, S.W. 2012. A measurable planetary boundary for the biosphere. Science 337: 1458-1459.

Tilman, D., Socolow, R., Foley, J.A., Hill, J., Larson, E., Lynd, L., Pacala, S., Reilly, J., Searchinger, T., Somerville, C. and Williams, R. 2009. Beneficial biofuels: The food, energy, and environment trilemma. Science 325: 270-271.

Wallace, J.S. 2000. Increasing agricultural water use efficiency to meet future food production. Agriculture, Ecosystems & Environment 82: 105-119.

Zhao, M. and Running, S.W. 2010. Drought-induced reduction in global terrestrial net primary production from 2000 through 2009. Science 329: 940-943.

Zhu, X.-G., Long, S.P. and Ort, D.R. 2010. Improving photosynthetic efficiency for greater yield. Annual Review of Plant Biology 61: 235-261.

Posted 26 June 2015