PCHiway wrote:I suppose, at my core, I still think that humans have a negligible overall effect on the globe's climate.
I'd like to compare notes with you on this, not by way of hostile competition but just out of curiosity. On the subject of AGW I've generally felt, and so admitted on the old site, that I'm inclined to have great faith in the ability of humans to exceed average expectations in this regard. My "core" thinking is certainly conditioned and influenced by having been an earth sciences major in college and in everything I've learned since, but I won't deny that it's also influenced by things I can't show evidence for - by whatever it is that makes me a bit of a misanthrope.
My story many pages back about the Mississippi was an attempt to provide some of the evidence. It's like I'm saying to you, "Look at what humans can do to a natural system as huge and powerful as the Mississippi river and river basin." In a similar vein I'd ask you simply to get on google maps or google earth and fly over the satellite image of the Amazon at a scale where you can see the extent of the deforestation. Also consider this: the ecosystems of large hunks of North America were radically altered four times by humans to the extent that the changes would have been easily visible from the moon: once when ancient humans (in full or part, intentionally or un-) killed off the Pleistocene megafauna, once when Native Americans used fire to clear brush and in other ways manage the ecosystem to meet their needs, once when white men introduced new grazing animals, and once with intensive agriculture. You could probably include city-building as a fifth time. Stay on google a while longer and just fly over the eastern seaboard or Europe, and think about what those regions would have looked like before humans descended from the trees.
There's a natural and understandable tendency to think that anything as BIG as "global climate" must be stable and very tough to alter. But we've long known that climate has changed quite a lot many times during earth's history and we're just now starting to learn that some of these changes took place over surprisingly short time scales. The question that's thus begged is: what does it take to cause a change in climate? Must it be something as huge as the Indian Subcontinent crashing into Asia? Or might it be much smaller "triggering" events? It's here that my thinking is influenced by complexity theory.
Please don't think that I've read math texts about complexity or could expound more than the most rudimentary description of it. No. My understanding of complexity comes from a simple little computer simulation (or game); it comes in several forms but maybe the most common is
WaTor (it's short for water torus). A hypothetical predator-prey system is built of six variables you can control. The idea is to adjust the variables so as to achieve some form of stability. All (?) stable systems show a lot of oscillation/cyclicality (just like the earth's climate). The lessons I've absorbed from killing time with this fun little "game" are these:
• It's hard to achieve stability.
• Stable systems can almost always be destabilized by surprisingly small changes in one or a few of the variables.
• It's not too tough to create conditions that yield what looks to be a stable regime; it runs and runs and runs without much apparent deviation from stability, and then suddenly, for no obvious reason, either wobbles and crashes in the relative blink of an eye, or starts to wobble, then wobbles more, then more, and then crashes. Those second kind are fun to watch because sometimes they manage to "pull themselves together" and "recover" from the brink of disaster. I've had runs where it looks stable, I go eat lunch and it's still running when I come back, and when I check it yet again 20 minutes later it's crashed - it can take that long for instability to express itself.
• No matter what's done to the variables there's always a "seventh" condition that can be critical: the starting position, or where in the cycle the system is when a variable is altered.
Click
HERE and you'll get a running stable (?or is ti?) Java version of the simulation with which you can play. I encourage everyone to first watch the initial simulation for at least a minute to get a feel for it's natural range of variance, and then to start playing with variables.
What I mean by that last bullet point is that it's possible to stop a stable system at point X in time, change a variable, turn it on again, and see almost no change, but do the same thing at point in time X plus a tiny bit and it makes a huge difference - the run spins out of control. So why am I talking about a cute little math game? What relevance can it have? Are these lessons really applicable in the natural world?
One of the second-order lessons to be learned here is about the anthropic principle. At any point in time a natural system (like the earth)
might be stable enough long enough for intelligent life to evolve, and those intelligent beings will see stability as the natural order of things, but in fact stability may be quite illusory. What if the sharks in WaTor were intelligent? Might they not want to alter the "shark breed" variable to what they think is their advantage, or just because they enjoy breeding? What would happen then?
Real-world natural systems display, within the huge range of examples available, both systems that show amazing resilience to perturbation and those that are in precarious balance and easily nudged over a "tipping point". Which type is climate? I don't know, but what I'm impressed by is how quickly we're seeing changes get expressed in some of the fundamental variables of climate. Is this something we'd see no matter what? Is it independent of human influence and just a rare sort of "blip"? Or can the faster-than-geologic-time-scale changes be more rationally explained by the only thing on this planet that has EVER moved faster than geologic - and MUCH faster at that: human culture? I honestly don't know, but the latter explanation doesn't seem improbable to me because humans are incapable of nudging the variables far enough to make a difference. To the contrary, I think we're more than capable.