OK, let me define my term here.
When I say "huge impact," I mean that the CO2 level itself leads to a change in temperature that impacts our ability to live, such as sea level rises, desertification, acidification of the oceans, etc. I don't care how big a temperature change it is nor how big a percentage it is to the total effect. If that change leads to a significant reduction in my, and the rest of humanity's, ability to survive, then it is a "huge impact."
Everything else is just hand-waving.
Again what you did is hand-waving. The specific point is that your claim that the change in CO2 leads to a "huge impact" is what is disputed. Claiming that it has a huge impact definitionally doesn't fix that problem.
But, from what I understand, the contention is that CO2 is not having a huge impact now because it had a large impact in the past. Specifically, since Crunch said that there is a huge impact between 0 - 20 ppm, it is having only a minor, negligible impact now.
And he has a point, since the CO2 had 25 times the effect from going from 10 ppm to 20 ppm than it does today (if my calculations are correct).
But that is just saying it does not have a huge impact
compared to the past. It really doesn't matter how big an impact it had between 10 and 20 ppm, since we pasted those concentrations a long, long, LONG time ago. We are only worried about the impact that a 10 ppm change has to the system today. And how CO2 influenced the climate at 20 ppm is irrelevant to that.
I don't agree that you've shown any reason to believe that a 4 degree C change (what is that almost 7 F) is even on the table. Certainly, I see no possibility that any now existing or currently proposed environmental legislation could even in theory cause that large of an impact.
Credible sources say it is an extremely likely outcome. Why don't you see it as a possibility?
I literally don't believe you have cited credible sources, and I'm questioning what your basis for determining the credibility of a source is.
This chart was presented by a professor at U.C. San Diego, who studied climate, and participated in gathering and evaluating studies for inclusion in the IPCC.
Unfortunately, I have not yet found his source for these numbers. But I ask, what would you consider a credible source?
What I want is proposals that are balanced and have a real meaningful impact. Environmental legislation that doesn't help the environment but rewards bad environmental actors like China is a complete waste of time. Rules that impose massive costs for marginal benefits are just stupid.
Great. So does everyone else. But we can't agree to start looking at them until we agree that there is an actual problem for them to address. Work with those who acknowledge the problem to come up with such proposals, and oppose those who say that the problem doesn't even exist.
We actually don't have to agree here to make progress. Virtually all pollutants have actual provable health impacts and other societal costs (even if its just loss of green space). Many things can be addressed rationally and collectively, however, when you're trying to make an argument from authority and demanding solutions that don't even plausibly relate to your claims I'm gonna fight that.
I remind you again, I have not "demanded" any specific solutions.
One of the assumptions HAS to be that CO2 causes increases in global temperature. There is no legitimate way to exclude that, which doesn't mean it's correct, just that it reflects our best guess of how carbon works in an open system from our observations of it in a closed system.
How would you program that? I mean, with dozens of systems being modeled, from solar input to convection currents to ocean absorption to cloud cover to methane levels, how to you program that the main cause HAS to be CO2?
I don't know where to begin, it almost sounds like you have no idea what a "model" is. You do understand that every single rule of the model is selected by a human being? The impact of CO2 is literally programmed into the model by the researchers, failing to include it's expected impact would literally be scientific malpractice, which means it's not possible for the model not to show increases of carbon increasing global temperature.Yes, you have to include the basic amount of energy absorption by CO2 into the model. But if something else is causing the warming that we are seeing, how do you make sure that the CO2 is THE culprit?
There is no way for a model to do this.
Data analysis based on properly constructed studies can lead to such a conclusion. If you have real experimental data (which we don't because n=1) you can do that analysis. We use models to generate data to do an analysis, but there is a fatal flaw to modeled data, the analysis can only show you what the model requires. For a complex system you may get a result you didn't expect but you can't get a result that wasn't a necessary conclusion of the rules you put in. You can get any number of Queen takes King results, but your chess model will never return Snake Eyes as an answer.
Crunching modeled data does nothing but return the modeled rules.
OK, I think I see where our disagreement comes from. You originally said, "which doesn't mean it's correct, just that it reflects our best guess of how carbon works in an open system..."
The closed-system experiments showed how CO2 interacts with infrared light. How it absorbs it, then emits it, sending some back as a "reflection." This is a property of CO2 that is assumed true whether it is in a closed system or not.
It is assumed true because we could not make any conclusions about the universe otherwise.
If CO2 acted differently in this respect in an open system (which the Earth may or may not be--we would have to discuss exactly what you mean by that), then we could make no assumptions about CO2 outside of it being in a closed container.

Which means we would have to throw out
everything we know about the universe outside of the laboratory.
For instance, how do we know how an airplane wing works? Sure, we have all this theoretical stuff about fluid dynamics we know, but those are based on laboratory experiments. Sure, we have tests in wind tunnels, but those are enclosed, "closed" systems. Sure, we have thousands of airplanes flying, but since they are actually outside in the world, we cannot say that what we tested in the lab applies to them. They may be staying up the air for other reasons, reasons we don't know, reasons we cannot predict...
You see how it snowballs?
CO2 works the same way trapping heat in our atmosphere as it does in a closed system in the lab. The way it absorbs and re-emits the light is the same. Otherwise, we don't need to bother with models at all. We could never be sure that any of them worked the way we think they do. It would only be sheer luck that any of them work. As would any of our understandings of reality.
Once you've done that, then you can analyze what factors created this conclusion, but it is hardly a foregone conclusion. It's just too complex for that. Otherwise, they wouldn't be using supercomputers to run the models.
Unless they add "random" to their models the results are largely a foregoing conclusion, and adding "random" is a highly questionable thing to do. What part of nature do you derive the "random" from?
In the case of a chaotic system, the initial conditions would be considered "random" since we don't know precisely what they were.
What program do you think could do that? We don't have data in those packets. If you have generated data for them, you've effected played make believe.
According to my notes, that is the computational resolution of T106 L56 Atmospheric GCM, created by Center for Climate System Research (CCSR), National Institute for Environmental Studies (NIES) and Frontier Research Center for Global Change (FRCGC). Certainly they do not have unique measurement for every one of those grids, but they are not complete unknowns, either. (You can't have hurricane-force winds in one grid and calm in the adjacent grid, for instance.) Estimates are far from "make believe."
Considering that hurricanes have eyes, you literally could not have picked a worse example for your point.
I'd doubt that less than 60% of those grids have any direct measurement, when you think through the polar caps and ocean regions. I'd doubt that more than 5% have regular measurements and even less have measurements that meet any kind of reasonable quality controls (for instance its questionable if there are quality measurements for most of Asia or Africa).
OK, you got me with the hurricane eye.

But I think you see the larger point.
We can make good estimates of the data changes between grids. Not perfect, of course. Which would be another good reason to multiple runs, with each run having slightly different values for the grids to see how sensitive the model is to changes. But there is a range we can work with. So you just can't ignore the entire model when it has covered just about all the possibilities.
It appears to create significance by running multiple iterations, but all it will ever do is regress to the mean of the pre-programmed results.
Sure, but the results may be wildly different than what you expected. Just ask any beginning programmer. 
Completely missing the point. Not understanding a forced conclusion of your assumptions doesn't mean it isn't a forced conclusion.
But if your assumptions are wrong, unless you are very lucky, the conclusions will be wrong. So then you re-examine your assumptions and try to find better ones, with the hope that one day your assumptions will be correct, or at least close enough to not matter.
From what I understand, the different iterations don't "regress" in any way. They run independent of the other iteration. One might follow the average of the runs, the next might be wildly different. If there is a path, yes, it is a result of the programming. But the idea is to make a program that works the same way the climate does.
Yes, I agree you don't understand what is going on. A single iteration can't regress. But just like if you flip a coin enough times the percentage you get the coin to turn up heads regresses to 50%, the "sophisticated" climate models have to do the same.
Yes, we only have one coin that is flipped--Earth. (Assuming you ignore the other planets in our solar system which have been modeled in a similar way.) But it is hardly a single flip, since the results change from day to day. We have far more data than a single flip of a coin.
Also, we run the models multiple times to make sure they follow the known path as well as it can. So rather than having multiple flips of the coin, we have to settle with multiple tries of the model.
What we don't know is exactly how that interacts with the rest of the climate, because it is a chaotic system.
No, just no. Whether or not its chaotic has nothing to do with why we don't know how it interacts exactly.[/quote]
To repeat, it is a basic assumption of science that what is measured in the lab--a closed system--applies to the rest of the universe. Our knowledge about how infrared light interacts with CO2 is true in the atmosphere as well as in the container. Otherwise, we don't need to discuss anything, because everything is ultimately unknowable.

But prevention of a problem is always cheaper than mitigation.
This is literally not true. There are plenty of problems that are cheaper to treat than to prevent.
OK, there are exceptions.

But when you are dealing with gigatons of CO2, I can't imagine how this would be one of them.
