Some confusion here over what distinguishes a feedback from a forcing. Both feedbacks and forcings can influence temperature either way, but it's whether or not they are caused BY temperature that determines which name is appropriate. Volcanoes are not affected by atmospheric temperature at all, so a volcano is a forcing. Global water vapour content is affected primarily by atmospheric temperature and so its effect on global temperatures is a feedback effect.

There is a grey area when an influence on global temperatures (such as cloud, appropriately enough) is itself influenced by both global temperature (feedback component) and by other, independent factors (such as the Pacific Decadal Oscillation; forcing component).

It is probably not possible to entirely separate out influences on clouds into temperature and temperature-independent factors. This is bacause temperature changes probably enhance and surpress the influence of what appear to be temperature independent factors. Conversely, temperature-independent factors may moderate (either way) the effects of temperature on clouds.

Not sure about the mechanism, but even if temperature is the only mechanism, that doesn't make your second part valid, or at least what I think you are trying to say.

Let's say clouds are a positive feedback to temperature rise, though back to your other question I think Spencer would call it a forcing here.

So CO2-induced temperature rise would also have a positive cloud feedback mechanism. You are correct on that part.

Here's the problem. We have .8C of temperature rise. Spencer is saying that PDO caused most of this rise, with cloud positive feedback. So that leaves the CO2 rise to be small, so even with cloud positive feedback on this small increase, you are still left with a small climate sensitivity.

Now I haven't followed closely enough, but I think he considers clouds to be both a negative feedback and a positive forcing, with different types of clouds. Or perhaps I am conflating two different skeptics.

According to CERES satellite data clouds are a negative feedback.

Why can't people understand CO2 is saturated, it can absorb no more heat and has very little effect on climate

Both. Singer knows it. Why can't you figure it out?



We're trying to forget man-made CO2 since this is the least forceful of any forcing you are discussing.

CO2 pales in comparison to water vapor as a greenhouse gas.

You warmists have no idea whether human influences have made it cooler or warmer. There is nothing in the temperature record to suggest either scenario.

And if, as Roy Spencer claims, the warming is a result of changes of cloud cover, cause by PDO, by what mechanism, other than temperature, could PDO influence cloud cover?

If the only mechanism by which PDO influences climate is by temperature, then anything which could influence temperature, like volcanoes or the sun could also effect clouds, making them a feedback.

And don't forget man made carbon dioxide.