Which is exactly why I said that you were hand-waving away a valid objection. There's a logic fail in using "greenhouse gases contribute a huge amount" to a give a heavy weight to the "minor increase" that has a "huge impact" as you put it.
You can't assume that a tiny contribution to greater whole (like a single vote to an election) has any real impact on its own. And you're ignoring that this is a direct criticism of how many "votes" are really at stake. If Crunch is correct on the impact then the actual reductions in carbon (most policies don't even result in a net carbon reduction, let alone anything that would materially reduce carbon production by humanity) are unlikely to be material. Even if you could eliminate all human caused carbon emissions (literally impossible), you may not see a material impact on climate, but it's certainly questionable whether the percentage decreases contemplated would have any impact, particularly if you don't also include population controls (heck, just increased food production, with irrigation (and evaporation) and methane producing meat sources are probably of greater impact than any potential carbon savings discussed).
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.
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?
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.
Lol. If you have a chart that lays it out for you like that, at best it was written for grade school consumers, and is more propaganda than science. Why don't you go back and find the source and then we can discuss it.
I'll see if I can find it. My copies of the course are buried somewhere...

The evidence that we accurately know on a general basis isn't all that great, we definitely don't know on a specific basis.
Again, credible sources say that we have a pretty good general accuracy.
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? 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? Couldn't you tweek the methane variables, or the HFC variables, or one of the many other variables to account for it, too? If those models are just as good, why hasn't someone done so already?
The group that comes up with a superior climate model gets the accolades and distinction. In Trump words, they are "the winners."

I don't see why they would all play to the same assumption unless it didn't, or more likely couldn't, work without it.
A computer model can not generate a surprise result, everything in it is a forced conclusion.
I still don't know what that means. I am sure most of the early models gave results that were far off the historical record. Some probably predicted that the Earth had a runaway greenhouse effect back in 1970.

Those would be "surprise results." They will work with the program until it conforms to reality, of course, but that is hardly a "forced conclusion." It is goal of the project; to make a model that reflect 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.
How would you do that, with a program that is designed to evaluate the entire surface of the Earth in 110 km square portions and calculate the interactions between these portions?
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."
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.

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.
The impact of carbon is programmed into the models. Therefore increasing or decreasing carbon inputs will cause the model to move in the same direction, you may not see it any single run, but over enough runs that assumption will always cause the same impact. Pretty much the model adds nothing to the debate.
But we
know that CO2 impacts the climate. We know it traps heat. We know how much it should reflect back onto the planet. What we don't know is exactly how that interacts with the rest of the climate, because it is a chaotic system. A small change could cause a large change in another part of the system. Which it could do consistently. And chaotic systems do have "tipping points," where the whole system switches to a new equilibrium. This is why we should worry about a "runaway greenhouse effect." There could a point where everything changes, pretty much permanently.
The models you are familiar with, how many were for chaotic systems?
Our climate doesn't give a damn about its economic impact.
But you should.
I do. If you've noticed, I haven't advocated any particular plan for addressing climate change. I don't think there is only one way to do so. And considering the world's political state, I suspect the solution is going to be more complex than the climate itself.

But, unless we want to deal with the consequences, we must do something. The solution will not be ideal. But neither will not finding a solution.
I never proposed doing nothing. I reject doing the wrong thing.
Agreed.
But doing nothing is also the wrong thing.
So let's so something, even if it is less than ideal, even if it won't completely solve the problem but may only postpone it. Let's do the reasonable things, the Things We Ought To Do Anyway as David Brin says. Let's cut down coal burning for power. Let's use more PV. Let's increase gas mileage on cars. Yes, they will cost us some, but not that much, and they will cut air pollution and decrease our use of foreign oil. And then we can find other ways to address the problem.
But prevention of a problem is always cheaper than mitigation.
And, as AA will tell you, before you can address a problem, you have to admit that it exists.