I think "measurable" is a bit of red herring, Roger. To measure something, you have to have a steady state against which to measure it. We can't really measure any effect we migth be having because we don't know what t does normally, we've only been looking a short while.

And to answet the measurable question : yes, I think we are having a marginal yet measurable effect on CO2 levels and possibly the climate (define 'climate' for a start!)

A more realistic questions would be:

"Do you think human activity is having an effect on the climate which moves its parameters out of the bounds of natural variability and its ability to absorb, recover or adapt to it?"

This question takes out of the equation us 97%ers who of course believe there is an effect, the crux of the matter is what that effect means.

They'll need to eat more fair-trade lentils if they want to break my legs :)

Harold, by "climate" I mean the average surface temperature of the Earth. I agree with you about smog, urban heating, etc.

James, you say "We can't really measure any effect we migth be having because we don't know what it does normally, we've only been looking a short while." I respectfully disagree. We have historical records of the LIA (frozen Thames, etc.) and the MWP (dairy farming in Greenland, etc.) so we know that current temperatures are well within the bounds of normality, and no cause for concern.

As for CO2 - I do not trust the ice core methodology (as it disagrees with historical chemical measurements and stomata data), and I would expect outgassing after the LIA. In any event plants evolved with much higher concentrations of CO2, and we need all of the ploant food we can get in order to feed the Earth's teaming billions.

And do't even get me started on the absurdity of GCMs.....

I am proud to be a threepercenter!

It's not about what we believe but what evidence we have, how we can make our case. There is far too much emphasis on belief here without sound evidence or reasoning. It is not only fruitless to debate the consensus, it is wrong. Those who rely on consensus in lieu of a case, on belief instead of facts, are not being scientific.

I say again to the AGW crowd, make your case. If you believe in the absence of good evidence, you are no more than a gnostic, a self-anointed custodian of the arcane secrets.. I am agnostic, and that's how I must remain until someone can answer the questions I've posed here over the months.

The question is a snare, designed to drag us into the warmist camp by moving the goalposts so that we become part of their "concensus". As others have shown above, the trick is to ask one question then present the answers as agreeing to something quite different.

The solution is to take back control of the discussion by rejecting this question which is irrelevant, and instead asking "Is there hard evidence of significant, dangerous effects of AGW?" which is what actually matters.

I think the answer to that would be a lot less than 97% positive - in most cases you would get waffle about models, tipping points, precautionary principle etc.

I wonder how many warmist reports of this survey will mention that it is 97% of 79 people?

NW - surely if it is clear that the "consensus" is so widely drawn that it includes Mr Watts, BH and many people who comment here, then it is clear that the "consensus" is worthless. Then it puts the onus on the guys who think the planet is in danger - the barmists" - to define what makes them different from the normal people.

Harold, there are many reasons why I do not think that anthropogenic CO2 will have any measurable effect on the average temperature of the Earth. I do not use the term "zero", as it does not exist in moderm physics (only the progression towards maximum entropy).

The CAGW hypothesis is based mostly on radiative physics, and the absorbtion bands of CO2. In my opinion (very briefly) this has been incorrectly applied (Holder's Inequality and the inability to model albedo), and furthermore ignores, or minimises, the effects of conduction and convection. The role of water, and its phase changes, has been underestimated, despite evidence of a billion years of life on Earth, which has required relatively stable temperatures. Basically it is a problem of non-equilibrium thermodynamics, applied to a rotating planet, with varying planetary dynamics and insolation.

As such, this describes a "climate attractor" (nothing at all to do with a Lorenz attractor) which must rationally be governed by a negative feedback loop, given the large historical changes in CO2, etc.

A poor explanation (I am tired), but perhaps you can see where I am coming from, when combined with my previous comments?

Roger, your explanation does not rule out humans affecting the climate by adding CO2 to the atmosphere. You are instead arguing for a stable equilibrium in climate, which makes you and I almost completely in agreement. We add a bit of CO2, the temperature may go up a bit in the short term, but some other effect dampens and reverses that change. Over a time period, climate settles back to the same equilibrium that has survived cometary impact, continent-wide vulcanism, glacial ages, etc over millions of years. It's obvious that our climate is pretty much a stable equilibrium, or else the inhospitable universe would have snuffed it out by now simply due to entropy.

You are not one of the 3%. In fact, I would say that the only people in the 3% are the Slayers.

OK James, I can just about live with that - except when I tunnel into the 3% to ensure that I am diametrically opposed to the CAGW fraudsters!

Diogenes, it's a bait - and - switch. The "consensus" presented to us in this thread and which we are invited to join is not what will be presented to the world - see the Obama quote further up the thread for an example. As a regular here you must know that the loudest voices in the warmist game cannot be trusted to behave ethically.

The name of the game is "climate communication"; the next step is "See, we have got them to agree it is happening, now we just need to work on getting them to see how bad it is and what we need to do about it."

Where's Richard Betts? I believe we've established that the deniers aren't denying any human impact. But what is the point of this exercise? During the last year or so I've come around to the belief that a large number of those in the catastrophe tent are, for want of a better word "naive". This has demonstrated itself, to me at least, in three ways. The first is that they assume that we're all pretty dumb and that when it comes to the science they're going to run rings round us viz. Rob Wilson, and in my case Doug McNeall, where they find themselves unable to engage because they hadn't thought of the questions they were going to be asked. The second, and for me the most important, demonstration of their naivety is that the believe we can stop CO2 emissions without destroying the fabric of western industrialised societies. And willingly give sustenance to the environmentalist whose object is to do just that. The third is they seem to believe that if enough scientists support a hypothesis then it must be true, this is in the face of a historical case book a mile high of scientific consensus being wrong.

Now I know Richard is a gentleman, but I have to ask why he bothered to ask the denizens of this blog if they were in the (fictional, by the way) 97% who believed humans caused global warming? Personally I would have thought it obvious that the people on this blog are aware that human activities will affect the climate, you'd have had to have been on a mission to alpha centauri not to understand that. So what's the purpose Richard? You're not John Cook or Lewandowski.

Upton Sinclair: "It is difficult to get a man to understand something, when his salary depends upon his not understanding it"

I think you're doing Richard Betts a slight disservice. I think (hope) the object of the thread was to poke slight fun at the 97% figure, and demonstrate that we shouldn't get upset about it, because we're all part of it. Even amongst skeptics, 97% believe we can and possibly do have some effect on the climate. (Yes, and the 97% figure is completely idiotic, as we all know - just use 'most' from now on)

There's three points here to consider:

First, when extremist AGWers use the 97%, they use it fraudulently. Yes, 'most' people, even sceptics, believe human activity can cause changes to the climate. That doesn't mean that 'most' people agree with their conclusions about the extreme consequences of this. They also don't agree with their proposed solutions. But that is what they claim when they use it - that most people agree with them on the full gamut of their beliefs. This is why we get upset about its use, Richard Betts.

Secondly, the 97% is an opinion poll, not a scientific experiment. The reason we have to go on opinion is because there is insufficient scientific data to base proper scientific conclusions on. The 97% is where the dirty world of politicking and opinion-forming overlaps with the cold, hard realistic world of science and engineering. The most widely misunderstood aspect of the global warming consensus is that the 97% is guessing based on their gut feelings. Not science. The fact that the 97% was borne out of politics poking its nose into science is also why we resent it, Richard Betts.

Lastly, climate science as a 'team' always appear to address the 3% when talking about us or to us. They always take the most extreme silly view (denial) and address that as if it represented all of the sceptic view. Trolls do it here, Mann does it in TV interviews. They refuse to admit that most of the opposition to their activism (about 97% I'd guess) is based on good and reasonable scientific scepticism which they have a scientific duty to address and deal with properly. But they never do. They find it easier to attack the 3% of fringe ridiculous opposition. This is scientific cowardice.

So while I agree that the 97% is nothing to get upset about, it represents a way of thinking that we completely abhor, and encapsulates the cowardly, unscientific way that some AGW proponents think.