How does rising atmospheric CO2 affect marine organisms?

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The Fortunate Coupling of Atmospheric CO2 and Temperature Trends Volume 2, Number 20: 15 October 1999

Although there are a number of exceptions to the rule, there has been a general tendency for near-surface air temperature and atmospheric CO2 concentration to vary hand-in-hand across the past half-million or so years that we have been able to reconstruct their temporal histories from analyses of ice core data. Throughout most of the planet's most recent great ice ages, for example, the air's CO2 content has been relatively low; while during the intervening interglacials it has been significantly higher. This is good news, says Sharon A. Cowling of the Institute of Ecology's Climate Impacts Group at Lund University in Sweden; for in the absence of such a relationship, most of earth's plant life would be in a world of hurt during times of global warming.

The reason for her positive assessment is very simple. Most of the planet's vegetation is of what in botanical circles is called the C3 type. In such plants the primary enzyme responsible for carbon fixation or photosynthesis also fixes oxygen in a competitive reaction called photorespiration. Furthermore, increases in temperature and decreases in atmospheric CO2 concentration both tend to favor photorespiration. Hence, if the globe's temperature rises and the air's CO2 content stays the same or falls, the net effect is to significantly reduce the net fixation of carbon, which therefore reduces plant growth. But if the air's CO2 content rises during times of global warming, its anti-photorespiration effect tends to counteract the photorespiration-enhancing effect of the rising temperature; and in experiments where air temperature and atmospheric CO2 concentration have risen together at rates characteristic of current trends, the rising CO2 concentration has been found to be the more powerful of the two phenomena, as demonstrated by the literature review of Idso and Idso (1994).

Based on such experimental data, Cowling has calculated what would likely happen if air temperature and atmospheric CO2 concentration were to rise in accordance with the Intergovernmental Panel on Climate Change's low, intermediate and high estimates of climate warming rates over the 21st century. For the high climate change rate of a 1C rise in temperature in response to a 76 ppm rise in atmospheric CO2, earth's C3 plants - which make up about 95% of the planet's vegetation - experience a 40% increase in net CO2 assimilation (= growth) rate by the time the globe has warmed by 4C. For the intermediate climate change rate of a 1C rise in temperature in response to a 136 ppm rise in CO2, global net assimilation rate rises by approximately 70% by the time the planet has warmed by 4C. And for the low climate change rate of a 1C rise in temperature for a 227 ppm increase in CO2, it rises by nearly 95% by the time the globe has warmed by 4C. What is more, for the scenario in which temperature rises with no change in atmospheric CO2 concentration, by the time the globe has warmed by 4C the net assimilation rate of the planet's C3 vegetation actually falls by something on the order of 10 to 15%.

So what lesson do we draw from this little exercise? It's simple. In the concluding words of Cowling, "maybe we should be less concerned about rising CO2 and rising temperatures and more worried about the possibility that future atmospheric CO2 will suddenly stop increasing, while global temperatures continue rising."

And why not? Cowling's analysis clearly demonstrates that our history of fossil fuel usage over the course of the Industrial Revolution can have done nothing but good for the biosphere, and that continued CO2 emissions - even if they do cause global warming, which is by no means proven - will continue to do nothing but good, driving vegetative productivity upwards by anywhere from 40 to 95% over the course of the next century or so.

Clearly, we have nothing to lose by staying our current course. Indeed, we have much to gain. But full implementation of the Kyoto protocol and its already-anticipated more stringent second and third phase regulations risks the possibility of an actual downturn in global vegetative productivity. And with a continually growing human population, that prospect is a recipe for social and ecological disaster of almost unimaginable magnitude.

What does it take to awake the world to the reality of what is occurring in the rush to impose restrictions on fossil fuel usage? Here sits the answer for all to see; but they apparently will not see. What a tragedy!

Dr. Craig D. Idso
Dr. Keith E. Idso
Vice President

Cowling, S.A. 1999. Plants and temperature - CO2 uncoupling. Science 285: 1500-1501.

Idso, K.E. and Idso, S.B. 1994. Plant responses to atmospheric CO2 enrichment in the face of environmental constraints: A review of the past 10 years' research. Agricultural and Forest Meteorology 69: 153-203.