Bad Astronomer Phil Plait writes at Slate:
First, it’s true that in the distant past (hundreds of thousands of years ago) a rise in carbon dioxide sometimes did follow a rise in temperature. As Skeptical Science points out, that’s to be expected: If the temperature goes up (which can have a number of initial causes), a lot of CO2 locked up in the oceans gets released. However, this does not mean carbon dioxide doesn’t cause warming; in fact we know an increase in CO2 causes an increase in temperature. That in turn increases the amount of CO2 released from the oceans, further increasing temperature. This is called a positive feedback loop. Happily, in general, positive feedback loops like this tend to flatten out, preventing the heat from cranking up past the point where temperatures become unstable.
It occurs to me that knowledge is a positive feedback loop. As humans understood agriculture and shared that knowledge, we expanded our food supply (and the populations of our domestic animals but that’s another discussion). The expanded food supply facilitated industrial development — even stone tools are a form of industry, let alone metal fabrication.
Each development made the next development possible and each also contributed, until recently at least, to expanding human populations.
Even this cycle seems to have run into a negative feedback, though. Affluent societies have cut back on reproduction considerably. Efficiencies reduce at least the growth rate of resource use per person or resource use per unit of standard of living, if such a metric exists. Perhaps the best version is resource use per dollar of GDP.
If my speculation is meaningful, it seems to represent the smaller positive feedback loop inside a larger negative feedback loop. But now I’m the one feeling loopy so I’ll quit.
My parents traveled to the future and all I’ll get is this lousy T-shirt.
There may be small positive feedback loops in nature, however they are always governed by larger negative feedbacks. That’s why “they tend to flatten” out, as Phil put it. But of course, he doesn’t want to admit that.
Howdy Gene
When I took anatomy and physiology, we learned that most bio processes are negative feedback loops rather than positive. CO2 rises, breathing deepens and speeds up, CO2 blows out of lungs. Blood pressure rises, more fluid in kidneys, kidneys produce more urine (normal conditions, of course). And so on…even food and reproduction seem to be a negative feedback cycle, in that a population will grow until its food supply cuts it back. I’m not aware of any major feedback loops in nature that are positive and wondering how they’d produce a stable system (stable system of moving parts, of course).
Geoff, nature has lots of positive feedback loops, but now that you mention it, I reckon that most of them are contained inside the living part of it.
Nature has very few positive feedback loops. It’s hard to see why this would be one.
In terms of temps and CO2: warming began well before large production of CO2 by humans, depending a lot on where you date the warming from and how much warming you think actually occurred. Given the known lag in previous warming/CO2 rises, it’s possible or even likely that the warming after the end of the LIA caused outgassing of CO2 from the oceans and that humans have had only a slight input into the CO2 level we currently enjoy. Empirically, a rise from 350 to 400 ppm has occurred alongside a standstill in temps.Whatever role CO2 and human production of CO2 may have on temps, it’s very small in the climate system.
If the ocean is absorbing our “missing heat,” it must be releasing CO2. Which would account for about the amount of rise in CO2 they are tallying up. So, we are irrelevant? (That part sounds about right.) And that acidification problem?
Wondering out loud, but I haven’t seen it addressed anywhere. Could oceans absorb heat in connection with releasing CO2 in amounts greater than CO2’s logarithmic forcing vector?
seems like typical institutional gobbledegook
Hmm… so can we now say “runaway global warming” (the positive feedback loop) is a dead letter? It would be nice to be able to move on…