[colah]

I can't say I've read all (or even most!) of the articles posted on HN about this topic, the ones that I have haven't been climate `denialism' but rather scepticism and more specifically scepticism towards individual claims... There were some people outright rejecting AGW in the comments, but even that wasn't that common.

I'm of the opinion that the AGW hypothesis is correct. I'm very confident of it. (In particular because one can derive a correlation between atmospheric CO2 and average global temperature directly from the properties of CO2.) On the other hand, I'm sure that there are many individual pieces of evidence that are false.

It's good that they're questioned and subjected to rigour. False evidence for a true hypothesis is not something we should accept.

This is how science works and it not a bug but a feature.

The political spin being put on it is a minor irritation that will go away with time.

And be thankful you don't have relatives who tell you that global warming is a government conspiracy to give power to the UN demonstrating that the Antichrist is near. That is really irritating.

[anamax]

> (In particular because one can derive a correlation between atmospheric CO2 and average global temperature directly from the properties of CO2.)

Except that if you actually do the arithmetic, you find that the "heat trapping" properties of atmospheric CO2 concentrations can't produce the claimed temperature increases. That's why the AGW folks talk about the feedback effects, effects which are dependent on other things.

Note that the paleo record shows much higher levels of CO2 in the past (2-10x) with comparable to today temperatures....

[colah]

Well, we're actually in a discussion of the magnitude of its effect at this point... (Which could lead to the discussion of whether there could be multiple causes for climate change rather than _just_ rising CO2...)

Like any chaotic system, it is difficult to predict the outcome, just that temperature is likely to increase. Think about the Mandelbrot set.

In any case, this is where one needs to look at other evidence.

[mnemonicsloth]

but rather scepticism and more specifically scepticism towards individual claims... [although] I'm of the opinion that the AGW hypothesis is correct.

Hats off to you for refusing to poison the debate. I hope you'll read this question in the same spirit.

Have you given any thought to what evidence you'd have to see before changing your position?

[_delirium]

In my case, I'd be more skeptical of AGW if there were better theoretical explanations of how large changes in atmospheric CO2 concentration might not cause macroscopic climate changes. As far as I can tell, most of the debate is over the instrumental record, i.e. an argument that as an empirical fact, warming isn't happening. But we do know that CO2 concentrations have increased (I don't think those measurements are controversial), and as far as I can tell the theoretical understanding is that this ought to produce a warming effect. Are there contrary theoretical models that predict that CO2 levels could increase at magnitudes approximately around those we see and yet not produce a warming effect? (Not a rhetorical question; I'm curious if there are.)

[colah]

Thanks!

It's hard to ask for evidence in advance (and probably mildly contrary to the scientific spirit :) ), but at the very least it will have to explain lots of seemingly contrary evidence (or show flaws in _all_ those studies).

update: I should also mention that I'm fairly trusting of at least some of those studies, since I know some people involved in them and they're both smart and trustworthy... Also, I'd be very surprised if CO2 was completely innocent.

There's actually a theory going around that land use may be a contributing factor to climate change along with CO2: a forest absorbs heat differently than a crop field which is different from a city. This theory demonstrates that CO2-based AGW isn't either-or.