Jonathan Lawhead

“ That is, is the sense in which a human brain is more complex than an ant brain the same sense in which a Mozart concerto is more complex than a folk tune? One way or another, what’s the significance of the answer to that question—if there’s an analogous sense of complexity behind all these cases (and I shall argue that there is, at least in most cases) , what does that mean for the practice of science? What can we learn by looking at disparate examples of complex systems? ”

“ Like the rest of the sciences, molecular biology takes its problems as they come, and does what it can with the resources it has.
If we can't say for any given special science what exactly its domain is, then, perhaps we can say a bit more about what the choice of a domain consists in—that is, what practical activities of working scientists constitute a choice of domain? How do we know when a formerly singular science has diverged into two? Perhaps the most important choice characterizing a particular science's domain is the choice of what measurements to make, and on what parts of the world. ”

“ Since the atmosphere, as we’ve seen, absorbs energy only from the surface of the Earth, but emits energy both back toward the Earth and to space, we have to adjust its surface area accordingly in our model. For the purposes of absorption, we can treat the atmosphere as having twice the area of the surface, since it radiates along both the inside and outside. Just as with the surface of the Earth, the atmosphere radiates energy in accord with the Stefan-Boltzmann law. That is, it radiates energy as a function of its surface area and temperature. ”

“ The demands for more data, better models, further research, a stronger consensus, and so on would be perfectly sensible if we were dealing with predictions about a less complex system. Science is presented to the public--both in primary/secondary education and in most popular journalistic accounts--as aiming at certainty, analytic understanding, and tidy long term predictions: precisely the things that complexity theory often tells us we simply cannot have. Is it any wonder, then, that the general public fails to effectively evaluate the reliability of climate predictions and models? ”

“ Science (to recapitulate the point from above) is hard, and indeed does often fall short of its goal of predicting what will happen in the world. The reasons for these failures are varied and complicated, but Maxwell is surely right to say that some of them have to do with the attitudes of some scientists themselves. With Butterworth, though, I have a hard time seeing the force of the claim that much of the blame for this problem is to be laid at the feet of specialization: the division of scientific labor is a natural, reasonable, and deeply effective response to a messily complex world. ”

“ Given the account of science I developed in Chapter One, though, this is precisely what we should expect out of a concept designed to describe the relationship between how different branches of science view a single physical system. There’s no single correct value for a system’s effective complexity, because there’s no single correct way to carve up a system—no single way to parse it into a string of patterns. ”

“ This is one sense in which the pragmatic idealization approach shares something in common with Norton’s story--when we create any climate model (but especially a CGCM like the GISS) , we have done more than approximate the behavior of the climate system. We’ve created a novel system in its own right: one that we hope we can study as a proxy for the climate itself. The objection that there are aspects of that novel system that have no direct analogue in the global climate itself is as misguided as the objection that no climate model captures every aspect of the climate system. ”

“ The story of science is a story of progress through collaboration. The story of philosophy, on the face of it, is a story of neither: it is an academic cocktail party cliché that when an area of philosophy starts making progress, it’s time to request funds for a new department. If this observation is supposed to be a mark against philosophy, I’m not sure I understand the jibe—surely it’s a compliment to say that so much has sprung from philosophy’s fertile soil, isn’t it? ”

“ In particular, we’ll focus on two aspects of the global climate which, while neither necessary nor sufficient for high dynamical complexity in themselves, are characteristic of complex systems: the presence of non-linear feedback mechanisms, and the presence of chaotic behavior. We’ll think about what it means for a system to be chaotic, and how the presence of feedback mechanisms (which are represented as non-linearities in the mathematics describing the system’s behavior) can contribute to chaos. ”

“ Radiation of a given wavelength may pass almost unimpeded through relatively thick layers of one gas, but be almost totally absorbed by even small amounts of another gas. This is the source of the greenhouse effect: the composition of the atmosphere directly affects how much radiation (and of which wavelengths) is able to escape to space. Recall that the wavelength of the energy radiated by an object depends on its absolute temperature, and that this means that (contrary to the model we’ve been working with so far) , the temperature of the Earth depends on the composition of the atmosphere. ”

“ Given the discussion in Chapter One, there’s another approach that might occur to us: perhaps complexity is a measure of information content or degree of surprise in a system. We can recruit some of the machinery from the last chapter to help make this notion precise. We can think of “information content” as being a fact about how much structure (or lack thereof) exists in a particular system—how much of a pattern there is to be found in the way a system is put together. More formally, we might think of complexity as being a fact about the Shannon entropy [11] in a system. ”

“ Indeed, the evocative idea of the butterfly effect—that idea that the flapping of a butterfly’s wings on one side of the world can lead to a hurricane on the other side of the world days later—has percolated so thoroughly into popular culture that the broad strokes of the concept are familiar even to many laypeople. Still, the specifics of the concept are often misunderstood, even by many philosophers of science. In particular, chaotic systems are sometimes thought to be indeterministic, a mistake which has the potential to create a great deal of confusion. ”

“ In discussing philosophy of science, complexity theory, model-building, and value theory all in a single work, I hope to sketch the general shape that a fully-fledged "philosophy of climate science" literature might take, and to open the door for more systematic contributions to that literature by those who are best equipped to make them. ”