How does rising atmospheric CO2 affect marine organisms?

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Multi-Part Question Submitted by M. Duffin, [with Answers Italicized in Brackets]:

I am a newcomer to your web site and find it both interesting and encouraging, even if I am generally on the other side of the debate.  However, I'm concerned about your editorial admonition to First, Do No Harm! (Vol. 1, No. 6) with respect to the potential regulation of CO2 emissions as expressed in your Vol. 2, No. 11 Editorial Commentary Frog Legs and Climate Change.  You clearly state in this context that we can and should delay action (on restricting CO2 emissions) until we know more.

I am an engineer, not a scientist, and as such I perceive a cause for concern that you apparently don't see.  Looking at the long-term record from the Greenland and Vostok ice cores, and at the records for the past 100 years, there are a few statements that we can make with a high degree of confidence:

1) Average surface temperature and CO2 concentration tend strongly to track over the long run, even if there are phase shifts in the short run.

[Although surface temperature and atmospheric CO2 concentration tend to track rather well over the long run, one must remember that correlation alone does not imply causation.  Consider, for example, our Vol. 2, No. 7 Editorial Commentary CO2 and Temperature: The Great Geophysical Waltz, where we report on a recent study that followed temperature and CO2 concentration back in time for a quarter of a million years.  This landmark investigation revealed that, for three of the most dramatic global warming events ever experienced on earth (the last three ice age terminations), the air's CO2 content did not begin to rise until 400 to 1,000 years after the planet began to warm.  Furthermore, there was a 15,000-year period following the second of the glacial terminations when the air's CO2 content was essentially constant but air temperatures dropped all the way down to values characteristic of glacial times.  And when the air's CO2 content finally did begin to drop after the last ice age was fully established, air temperature either remained fairly constant or actually rose.  Likewise, another recent study cited in that editorial reported finding that, following the termination of the last great ice age, the CO2 content of the air gradually rose by approximately 25 ppm in almost linear fashion between 8,200 and 1,200 years ago, over a period of time that saw a slow but steady decline in global air temperature.  Hence, these recent comprehensive ice core records demonstrate that sometimes CO2 and temperature are totally out of sync with each other, sometimes one is in transit to a higher or lower level while the other is in stasis, and that even when they do move in harmony, temperature seems to take the lead.  And for even more of these types of findings, see our Journal Reviews Nearly Half a Million Years of Climate and CO2 and Miocene Climate and CO2.]

2) There is not enough (or accurate enough) evidence to infer cause and effect.

[How right you are, except for the three great ice age terminations for which we have records.  For these dramatic global warmings, the large rises in temperature appear to trigger large rises in atmospheric CO2 concentration, which is just the opposite of what would be expected if changes in atmospheric CO2 affect climate in the way affirmed by the popular CO2-greenhouse effect theory.]

3) There seem to be long-term upper and lower limits on both temperature and CO2, rather like a process control chart.  This point would seem to be supportive of the idea of homeostasis in the Gaia theory.

[Although there may well be long-term upper and lower limits on temperature that are supportive of a type of homeostasis such as is suggested by Gaian theory, there do not appear to be such limits for CO2.  In the early history of the earth, for example, it is believed that the atmosphere was nearly all carbon dioxide, and the long-term trend of the gas has been basically downhill ever since.  In fact, this inexorable decline in CO2 has been suggested by Lovelock and Whitfield (Nature 296: 561-563) to eventually lead to the demise of the biosphere in the not-too-distant (geologically speaking) future!  For more details on atmospheric CO2 variations over Phanerozoic time, see Carbon Dioxide (History - The Last 4.5 Billion Years).]

4) In the last 150 years the CO2 concentration has a) risen at apparently unprecedented rates, b) risen faster since 1950 than before 1950, c) reached unprecedented levels in the records of the last 250,000 years, and d) appears to be about 20% above the possible "upper control limit."

[When viewed in the larger perspective outlined in our response to point 3 above, the points you raise here lose much of their apparent significance.  Indeed, they can even be turned on their heads; for we could just as well say that the CO2 concentrations of the last 250,000 years have been unprecedented in the level to which they have dropped!  They are clearly not "20% above the possible 'upper control limit'."]

As an engineer, I have to say that when a process variable goes out of control, the result is almost invariably harmful.  Therefore, there is a high probability that we are already doing harm (even if it has not been manifested yet), and that the prudent thing to do would be to try to get back into control, i.e., stop the anthropogenic increase, and if possible reverse it enough to bring the concentration back within the natural (Gaian?) control limit.

[Again, we note that atmospheric CO2 is not "out of control."  In fact, viewed from the perspective of the planet's entire history, one could argue that humanity has finally gotten a grip on the problem of inexorably declining CO2 concentrations and staved off the biospheric death knell that was sounded nearly two decades ago by Lovelock and Whitfield.  As evidence of the validity of this statement, see Growth Response to CO2 and Carbon Dioxide (Seasonal Atmospheric Cycle) in our Subject Index, where we review the evidence that depicts, not an "unmanifested harm," but the demonstrable help that the ongoing rise in the air's CO2 content is providing for the biosphere.]

Normally, when we have not yet been able to determine cause and effect with certainty, thus enabling preventive action, we at least start with containment action while we continue to investigate.  Waiting until we know more, in my experience, has always been a worse choice.

[There is no question that a continuation of the long-term decline in the CO2 content of earth's atmosphere would be disastrous for the planet's biosphere.  Fortunately, the providence that guides the affairs of men and nature has taken the needed "containment action" to arrest this CO2 decline and preserve the planet's plant life and thereby save its animal life as well.  And it has done so at a most opportune time, i.e., "when we have not been able to determine cause and effect with certainty."  Your philosophy is indeed correct when viewed in this larger context.]

The encouraging part of your investigations, for me, is not that higher CO2 and higher temperature promote better plant growth, but that better plant growth causes more rapid carbon fixing, providing a negative or balancing feedback loop.  [We also acknowledge this fact.] Evidently nature has a mechanism for maintaining control.  [We agree.]

However, what if: 1) there is a cause and effect relationship, 2) the cause, increasing CO2, precedes the effect, global warming, by some decades, 3) blowing past the upper control limit and crippling the balancing mechanism, and 4) positive feedback becomes dominant?

[First of all, as we have noted earlier, and as you have also noted, cause and effect, relative to CO2 and global warming, is not always clear.  Second, not only does increasing CO2 not precede global warming, just the opposite relationship seems to prevail in the ice core records.  Third, there is no upper control limit that humans could ever propel the planet's atmospheric CO2 content past.  And fourth, there is no evidence in the geologic record of earth for the operation of a positive feedback mechanism of the type that would turn our planet into a Venus.]

We are already very near the record high temperatures of the last 250,000 years; and while moderate warming may be beneficial, the only model we have for extreme warming is Venus.

[These statements presuppose that increases in the air's CO2 concentration will indeed lead to global warming, when that assumption is currently without proof.  On a dry lifeless planet such as Mars or Venus, this assertion would have some validity; but on a living water-world, there are all sorts of negative feedbacks that can totally negate the primary impetus for warming produced by an increase in the atmosphere's CO2 content.]

In effect, we are conducting a huge uncontrolled and possibly irreversible experiment, and we are locked inside the laboratory.  Prudent scientists never put themselves in such a position.

[Viewed from another perspective, we could just as easily say we are wedded to the earth for as long as we both (us and the earth) shall live.  And fortunately for us, the rising CO2 content of the planet's atmosphere should insure that we live long enough to realize that the huge "experiment" about which we all philosophize has in fact been a means of sustaining us.  What we will call prudent then, when we fully realize the validity of that fact, may well be quite different from what some would call prudent now.]

Apart from missing out on possible augmented plant growth, why would we not want to reverse the trend? [The answer to this question should be clear from what we have written above.]  For sure, reducing anthropogenic CO2 increases is both technologically feasible [possibly] and economically desirable [debatable], regardless of the protestations of the carbon lobby.  We can do economic good and avoid possible environmental harm. [As should be clear from what we have written above, the proposed solutions to this non-problem could do great harm to the environment, allowing the biosphere to continue its long day's journey into night.  And that is much more than mere economic harm.]  So why advocate waiting? [Because of all the reasons we have stated above.]  Why fight nature? [We believe we are not fighting nature; we believe we are helping it.]

[On a personal note, we appreciate your sincerity and willingness to calmly and rationally discuss these important questions.  If everyone - on both sides of the issue - were as civil and as sensible as yourself, it would go a long ways towards enabling us to ultimately achieve an appropriate consensus (which hopefully would also be correct!) about the subject of carbon dioxide and global change.]