BDD - By now even you may be beginning to doubt how solid your ground may be when you claim that there is no debate about the level of feedbacks.

Even a small amount of research will reveal that there are a many scientists who point to the relatively stable global temperature and benign climate the earth has enjoyed for billions of years and recognise that this can only have come about by the action of regulating negative feedbacks which balance and neutralize amplifying positive feedbacks. And these scientists do not find it at all difficult to imagine that nature has arranged things in such way that the net climate-driving feedback is negative, slightly stronger than the net positive feedback.

You have already mentioned Lindzen and Spencer. But you could also mention any number of others e.g. Idso Sherwood, Watson and Lovelock, or Douglas and Christie for a start.

And no, I am not going to defend any particular paper as being definitive. I am simply illustrating that contrary to what you say, there certainly is debate out there. And not only is there debate, there is a glaring absence of any obervational evidence. (Even the IPCC assessment reports do not contain any direct observations of the amplification, either by water vapour or the totality of feedbacks, because the IPCC only quotes results from climate simulations.)

So let's look at the facts: most (if not all) mainstream scientists concede that the warming trend expected from CO2 without any feedbacks at all is only about 0.07 ºC per decade.

But what happens when we consider warming since 1979 (when we started measuring temperatures using satellites) and ignore the frequently adjusted and often highly disputed land thermometers? (Douglass and Christy in one of their papers give a good discussion on why UAH is a better data source than RSS, and why both satellites are better than the surface measures.)

What do the satellites tell us?

They tell us that even though most scientists acknowledge the existence of a 60 year cycle of warming and cooling (due to the Pacific Decadal Oscillation) and that the period since 1979 is likely to have included the steepest part of that 60 year cycle (so temperature trends over longer periods are likely to be even smaller) the best available estimate of temperature trends over the period since satellite measurement began is only 0.06±0.01ºC per decade.

But wait - this trend is even smaller than the warming trend expected from CO2 in the absence of any feedbacks. So what does this tell us about the size of all feedbacks over the past 30 years?

Sorry BBD - you've tried that one before and the onus is not on me to explain how the climate works.

May I remind you that the point of this thread is simply to look for the best available evidence - and so far the evidence in support of runaway warming is noticeably lacking.

As I pointed out, the IPCC (which one is being asked to accept represents the views of the vast majority of scientists) quotes absolutely no direct observational evidence about the size of any feedbacks.

Now I have quoted a directly measureable estimate of feedbacks over the past 30 years - and it does not support the view of these being highly positive.

And I have quoted the complete absence of any measureable hotspot (which we had been assured would be a signature trait of highly positive feedbacks).

And I have quoted the directly measureable relationship between surface temperatures and the amount of heat escaping from the earth and the relationship directly contradicts what one would expect if we were to assume the presence of highly positive feedbacks.

Three bits of evidence. Not computer modelling. And all of it contradicts feedbacks being highly positive.

You are right: you do need to understand how climate works in the absence of highly positive feedbacks. (If you need to take a break to do more research - please go right ahead.)

No - let's confine ourelves to the evidence that has already been presented.

And remember that we are considering evidence supporting or undermining the risk of CO2 being a driver for runaway warming. We are not considering whether the PDO or solar effects or orbital variations can explain anything (unless of course they are being used as evidence in support of CO2).

What references are you finding it hard to look up? I assume that you do have Google.

Well, I think others will get the measure of your level of debate. I won't hang around.

I really thought you would have grasped the purpose (or central question?) of this thread, BBD.

Why try to hijack every thread so as to discuss your favoured alternate hypotheses? This thread is intended to discuss *real* evidence in support of or undermining the main hypothesis that CO2 causes runaway global warming.

I have raised three separate pieces of *real* evidence that all undermine the main hypothesis that you are advocating. And you seem strangely reluctant to discuss this evidence.

You seem to think that a failure to identify alternate viable hypotheses somehow strengthens your own hypothesis. Well it doesn't. Your hypothesis needs to stand on its own merit despite the paucity of alternate hypotheses. All you are doing is exposing what else you don't fully understand.

Occasionally the closer you look at some of the more widely accepted evidence - the less it stands up.

Most scientists agree without question that the earth has been warming over the past 50 years and they also accept that CO2 concentrations have been rising in almost linear fashion over this period.

But have temperatures exhibited the same linear trend upwards and can we attribute this rise to CO2?

It turns out that there has been no significant underlying warming trend in any but one of the last 50 years (i.e. over the period studied from 1958 to 2010) and in fact the data is better explained by a small and unusual step change in warming which happened right at the beginning of 1978 (i.e. the world got warmer and somehow the heat was retained, but there was no increase in CO2 in the preceding 12 months so no reason to attribute this jump change to CO2).

So the last 50 years of warming may depend on a single unexplained leap right at the beginning of 1978.

Although this step effect was first noticed by David Stockwell in 2009 it has subsequently been confirmed by McKitrick and Vogelsang who conclude

As our empirical findings show, the detection of a trend in the tropical lower- and mid-troposphere data over the 1958-2010 interval is contingent on the decision of whether or not to include a mean-shift term at January 1978. If the term is included, a time trend regression with error terms robust to autocorrelation of unknown form indicates that the trend observed over the 1958-2010 interval is not statistically significant in either the LT or MT layers. Most climate models predict a larger trend over this interval than is observed in the data. We find a statistically significant mismatch between climate model trends and observational trends whether the meanshift term is included or not. However, with the shift term included the null hypothesis of equal trend is rejected at much smaller significance levels (much more significant).

Perhaps it is worth re-emphasising

We find a statistically significant mismatch between climate model trends and observational trends whether the meanshift term is included or not.

This is direct observational evidence undermining the assumptions in the climate models.

Dung / BBD - or you could simply start your own thread?

I think the full intent of the thread is to search for

the best evidence to support the claim that CO2-caused climate change is actually happening and to what degree

and I have taken the liberty of citing (relatively) uncontestable, observable evidence that measures the extent to which CO2-caused climate change is actually happening (whether that measured extent actually supports the hypothesis of CAGW or not).

I do accept that I have not cited any such evidence that actually supports the hypothesis mainly because such observable evidence is typically associative and not causative.

Equally I wouldn't consider Svensmark's evidence - important though it may turn out to be - to contribute to the debate at this moment as it is more akin to an alternate hypothesis which ought to stand or fall on its own merit? And any effect it may prove to have on CO2-caused climate change is not measurable yet because the relationship is not yet proven?