Unless there's a physical science basis underlying the mathematical model, there's no good reason to put credence in any specific extrapolation beyond the data used to make the fit. What would be useful, and I'm sure provide suitably dire predictions, would be to model effects the IPCC reports may not include. But there's not particular reason to regard as remotely valid the extrapolation into the future of an essentially arbitrary functional form, simply because you can fit past data reasonably well to an nth order polynomial.

I think the methane release problem is enormous, and could very well moot more efforts to date to address climate change. I just don't think this kind of analysis has any validity. Anyone who really wants to play with the numbers would do well to pick up, say, Pierrehumbert's "Principles of Planetary Climate" and learn the relevant physics.

I'm sure if you asked Sam he might tell you that he's doing just what you're asking for: "to model effects the IPCC reports may not include". You and others might not like trend lines, but as a pedagogical tool to present the effects of BAU and generate a sense of urgency, nothing beats them these days. Any climate or consumption trend-line with a solid R², based on actuals from the last 60 years, is going to scare the shit out of people.

There's a message in there: biophysical trends are going to hell a hell of a lot faster than 99.9999% of the people on the planet can imagine.

Then you do nothing but provide ammunition for the fossil lobby.

People who have no motive to change, don't change. The greatest motivator for change comes not from the intellect but from the emotions, and the strongest of those emotions are fear, guilt and shame.

If there is to be any resolution other than the obvious one suggested by the accumulating data, we need to use every motivational tool at our disposal - including the generation of fact-based fear, guilt and shame.

I mean, you're not even addressing the message of graphics that you acknowledge to be true. You're just indulging in puerile mockery. That tells me your response is driven by emotions and beliefs, rather than by logic and facts. What do you wish to accomplish?

A change in the way the environmentalist movement generates support for its ideas. Only a short time ago I believed that it didn't really matter if we exaggerated things a bit, so long as in the end we accomplished the goal of raising awareness of the issue. I've come to realize that in the long run or perhaps even in the medium term, that tactic is counter productive. If you cannot look at the past 30 years of the environmentalist movement and not see the truth of this, I think you need to look at things from the standpoint of the average person and see things as they do.

Mockery is not helpful. Lead by example.

It was a classic reductio ad absurdum form of responding to your post, and a perfectly acceptable way of pointing out the inconsistencies in another person's position.

I think it works much better to talk about what it has been like historically to live in societies that have outstripped the capacity of their environments to support them. It's easy to dismiss a curve that shoots vertically when you know it's not based on anything more than extrapolation. But it's truly frightening to recognize that a civilization on the brink of collapse looks exactly like one that feels it's at the height of its powers.

I think they can make excellent polemics. i understand your distaste, but I think the circumstances warrant extreme measures. Talking about "what it has been like historically to live in societies that have outstripped the capacity of their environments to support them" doesn't exactly raise the pulse rate, you know?

"if we're in so much trouble, why doesn't it feel like we are?"

I won't deny that poorly-founded extrapolations will have a big immediate effect on some people, but if you choose to present those as forecasts, you open yourself up to charges playing "Chicken Little" when someone comes along and pokes holes in them. As the array of other graphs shows, there's already plenty of scary data out there - there's little need to embellish!

As for the pulse rate, if I imagine being part of, say, the last generation of the Easter Island civilization, knowing there was no reasonable way to get off the island and that there was no real prospect of carrying on... that exercise does affect me! Most people don't have emotional reactions to graphs, but they do respond to stories. We're good at mobilizing against certain kinds of threats, but they tend to be the ones we can react to by going to war and not by changing the way we live, so I recognize it is hard to raise pulse rates regardless of one's rhetorical strategy!

We should not be engaging in it. That is a position I have actually just come around to believing. If you look at the loss of credibility that has occurred on the issue of global warming simply because of not practicing good science, I think its clear that in anything but the very short term we are hurting our efforts, not helping them.

Then again, I can understand why you take this position. It's because:

1) You believe we're doomed no matter what, so it doesn't really matter.
2) Your beliefs do not change in light of new empirical evidence.

They do, but not in the direction your beliefs are forcing you to go.

And hey, how bout those Blackhawks?