Ant,
You have a huge misconception there. I would think that at least 97% of sceptics fully appreciate that CO2 is a GHG and that it has been proved to be so in lab experiments. The issue for that majority is; what is its NET EFFECT in an extremely complex system? There are small groups that deny GHG warming but mainstream sceptics disagree. (e,g “The Dragonslayers”, Doug Cotton and the gravitational guys like Nikolov and Zeller).

The problem is in the extreme complexity of the system and the fact that in the total thermodynamics and other dynamics such as ocean circulation causing regionalization and whatnot, the proportion of heat transfer via CO2 is tiny (See IPCC/Trenberth Earth Energy Budget above). There are many ‘poorly understood’ phenomena (admitted by the IPCC and other authorities) such as cloud cover and evapotranspiration involving negative feedbacks. That is one reason why thousands of climate scientists are still working on something that paradoxically is claimed to be “debate over”.

You ask for sceptics to produce an experiment to prove that CO2 does not cause warming! That is simply not possible because of the vast complexity of the system. In the same way, climate scientists cannot design an experiment to prove their case either, (and if they could they would become unemployed). There is no significant empirical evidence either. THAT IS WHY they resort to COMPUTER MODELS that involve estimates for ‘poorly understood’ phenomena of great complexity. Unfortunately those models still cover a wide range of predictions and are way-off from the observational trends.

Finally, perhaps you can take comfort that the 2015/16 “Super El Niño” (as described by Kevin Trenberth) which is another ‘poorly understood’ ENTIRELY NATURAL event is declining rapidly (and it is very likely that 2017 will be cooler based on typical past ENSO trends).

PS ‘poorly understood’ is a technical term to describe something that may have well-understood effects but for which the causes are unknown

Can anybody tell me what the negative consequences might be of treating human induced climate change as real, regardless of whether it is or not? In other words, what are the costs associated with taking steps to reduce carbon and other greenhouse gas emissions? Conversely, what are the positive consequences of doing so?

Similarly, what are the relevant negative and positive consequences of treating human induced climate change as not real?

Thanks, I'm sure the people here will have that sort of information at their fingertips.

Craig, Others may wish to respond to you with the actual dollar cost of subsidising, for example, wind energy and in the process forcing up the cost of electricity for all. But I've always been even more concerned about the cumulative costs to societies, families and individuals when we are blind to the truth. Science has always been about getting to the truth of the matter: a byproduct has been the innovative technologies that even enable me to communicate with you (across a great distance and almost instantaneously) via the internet. But now, you are suggesting this truth is irrelevant... indeed it would appear that you, and may others, would like us to adopt a sort of postmodernist approach to science where we accept only that information that supports the utopia you have dreamed of. I would also caution, that you becareful what you wish for.

Jennifer, I'm not sure how you arrived at that rather insulting conclusion from my question. I'm simply trying to understand what the scale of the problem that's being argued over might be, without the rather silly resort to partisan abuse about irrelevancies.

There is and has been an enormous amount of time and energy spent arguing about whether human induced climate change is real or not. It seems reasonable to try to understand whether the game is worth the candle.

You might consider yourself a crusader for truth in science, but I suggest to you that abusing me for asking simple questions that can be very readily addressed scientifically and dispassionately is possibly the most eloquent statement you could have made about the sincerity of your own motives.

El Nino and La Nina, are symptoms of climate change not the root cause! As indeed are the oceanic currents and associated pools of warm or cool water that give rise to this phenomena!

Which seem to be getting progressively stronger or more active? In recent times?

Resulting in the worst most enduring droughts with no comparable example in living memory? And 100 year flood events, manifesting thrice in a single decade?

Yes solar thermal activity creates all our weather along with the aforementioned phenomena! None of which ought to be getting more robust during a solar waning (cooling) phase that kicked in during the mid seventies! (NASA)

Simply put, none of the global weather events cited are the primary product of El Nino or La nina, given they too are impacted positively or negatively by increased trapped solar radiation!

And to put it in a nutshell? the only way to increase solar thermal induced phenomena, when there is less of it! Is to trap more of it!

And to give an allergy that the rubes can understand, greenhouse gas works not unlike double glazing that traps solar thermal output in our homes during the cooler winter months. And more transparent polycarbonate, lets more of it in?

Except, lighter than air methane, traps much more of it a greater altitude than heavier than air Co2. Sometimes referred to as marsh gas, given it seems to find the lowest levels, where it can and does asphyxiate the unwary, which may account for some of the finest fossils found in former marshes?

These Authors and their endless references to El Nino as PRIMARY causative factors in recent record climate events are used, I believe, in the knowledge and understanding that the average rube won't have enough science to question these ill informed conclusions/obtuse obfuscation?
Alan B.

Craig, I am not sure how I insulted you, except to perhaps point out that for me this issue, my article with John Nicol, is all about getting to the truth of the matter and being honest to enlightenment science. Relative to this, the dollar cost of energy is almost irrelevant. Perhaps I did not understand your question: you might rephrase it?