In my previous two postings, I praised David MacKay's approach to energy analysis in his book, "Sustainable Energy — without the hot air", because he used numbers to put everything into perspective. The problem with numbers is that while they can put the problem into perspective when the numbers are used correctly, the opposite happens when they are not. As the old computer saying goes, "garbage in, garbage out". In general, numbers showing the dependency of one variable (that being measured) with the change of another effectively represent solutions to partial differential equations. In the lab, this is not a problem; most chemists will have done this, assiduously keeping everything except what we wish to relate constant (or at least try to). Unfortunately, for living systems, ecological systems, economic systems, and a number of observational systems, such a separation of the variables can't be done, so elements of significant unreliability creep in.
 
There then arises a consequential problem: you have the numbers, but what do they mean? You believe you have shown something so there is a temptation to take this to an extreme. Worse, in most analyses of complicated topics there is little option but to accept somebody else's numbers for some aspect. Do they really mean what you think they do, or equally importantly, but more difficult to unravel, what the supplier of the numbers thought they meant? In my opinion we need a forum where misinterpretations can be discussed, and if the objections are valid, the conclusions corrected. I do not believe that any single person will have a broad enough and deep enough knowledge of some multi-disciplined problems to get everything right. We need the expertise out there to correct the flaws.
 
An example. In an earlier post I quoted from MacKay as follows: the calculated power available per unit area, in W/m² for pond algae are – 4 (if fed with CO₂) which is an order of magnitude higher than most land based biomass, but then he adds the productivity drops 100 fold without adding CO₂, then he notes that to use the sea, country-sized areas would be required. Does anything about that strike you as odd?
 
My first reaction, perhaps afflicted by living in New Zealand, is that even if country-sized areas of sea are required, so what? Once you fly over the Pacific, it becomes obvious that whatever else we are deficient in, surface area of sea is not one of them. Certainly there are other problems using it, and possibly these will be overwhelming, but let us do some research and find out, and not simply write the possibility off by assumption.
 
My second reaction was to look in disbelief at the two orders of magnitude loss of productivity by not pumping carbon dioxide into the water. The limiting feature of carbon dioxide on photosynthesis will be its solubility in water. However, there are many more factors involved with algal growth. For example, most people have heard of algal blooms. Given the second law of thermodynamics, do we really believe there were suddenly self-assembled massive increases of carbon dioxide that led to them? Or do we accept that the masses of algae in some lakes are actually there because agricultural run-off has delivered the additional nutrients to make this possible? Algal growth is usually limited by nutrients, and not carbon dioxide availability. As an example, one of my first projects in the commercial area was to look at resources for making agar. In the Manakau harbour, Gracilaria chilensis grows at a rate of a few t/ha/y, but we found one pond where, due to the construction of a road and the dumping of gravel, productivity went up to about 110 t/ha/y.  What was different? Gravel for the plants to attach a holdfast, and the pond being close to the effluent from a sewage treatment plant. Such treatments usually discharge high levels of nitrogen compounds and phosphate, which become ideal fertilizers. There was no increase in carbon dioxide levels at this site. Farmers, after millennia of learning, get far better yields than are found in the wild; why should this not happen in the sea? Why do we think we don't have to put any work into making improvements?
 
Yes, I think numbers are important, but only if the appropriate ones are used correctly and their limitations accepted.