[gwright]

No one is making the claim that "change isn't happening". The skeptical view point isn't even "warming isn't happening". The skeptical view is that catastrophic warming isn't an accurate prediction of future temperature trends.

I believe the primary difference between the "consensus crowd" and the "skeptic crowd" is that the consensus crowd is confident in the predictive value of models that have a net positive feedback sensitivity to temperature increase while the skeptics argue that we don't actually know what the feedback mechanisms well enough to be confident in the models and in fact basic physical principles argue for a negative net feedback to temperature increases (to avoid runaway warming).

As for possibile negative feedback loops, increased CO2 might increase clouds, which increases the earth's albedo resulting in less energy input from the sun, which reduces temperature.

[Oletros]

> The skeptical view point isn't even "warming isn't happening".

What the heck?

[gwright]

Let me clarify. There is a difference between warming and catastrophic warming. Serious skeptics are arguing against catastrophic warming as predicted by the models.

There is another level of debate, less foundational, regarding the quality of our temperature observations and the amount of warming (not catastrophic warming) that is a result of natural variation, human activity, measurement errors, data adjustments and the like.

Observational warming has in general been less than that predicted by the models suggesting that the extrapolation into the future by the models may not be accurate.

[Oletros]

> Serious skeptics are arguing against catastrophic warming as predicted by the models.

What catastrophic warming? Or better, define catastrophic warming

And by the way, 90% of skeptics still say that there is no warming.

> Observational warming has in general been less than that predicted by the models suggesting that the extrapolation into the future by the models may not be accurate.

Source for that?

[gwright]

I'm using the phrase 'catastrophic warming' to refer to the warming predicted by climate models as opposed to the warming directly observed today and in the historical record.

Anthropomorphic global warming theory is roughly two connected claims. 1) rising CO2 levels caused by human activity results in a rise in the average global temperature and 2) the climate system has a feedback mechanism (sensitivity) that magnifies this CO2 induced warming.

Basic physics can be used to determine the warming caused by increased CO2. There are no serious skeptics in regards to these physical properties of CO2. My understanding is that the IPCC reports have consistently reported this warming as 1-1.5 degrees for every doubling of CO2 concentration in the atmosphere.

But that temperature rise isn't enough to create the catastrophic side effects that you see reported. That rise has to be magnified by the climate system through a variety of feedback mechanisms. This magnification/sensitivity can't be measured. It is the output of the climate models not one of the input parameters. Credible skeptics argue that a positive sensitivity is incorrect and that the climate system (as with most natural systems) has a negative sensitivity.

Here is what seems to be a reasonable review of predictions vs observations using a variety of methodologies most showing observations trending towards the lower half of the predicted ranges of the models (as opposed to trending toward the center line of the predictions): https://judithcurry.com/2017/09/26/are-climate-models-overst...