Bonmot, I think the temperature increase is likely to be less than 3%. Most of the warming we are going to see from CO2 has already occurred because of its logarithmic reaction to infra-red radiation. The only way models get it as high as they do is by postulating positive feedbacks from water vapour, but the experimental evidence says that this is overstated - this is the importance of the failure to find the tropospheric hotspot.

So, another 1 to 2 degrees is not only tolerable but probably beneficial, which is why I am quite relaxed about CO2 emissions.

I think Amicus' reference to whether 2010 would be the hottest ever was probably a reference to the predictions by BOMA and I think NASA before 2010 was even half over that it would be the hottest ever. This was off the back of the El Nino at the time, but now we are in La Nina territory I suspect the annual temperature will not be as high as 1998. Makes you wonder what sort of a person makes predictions when less than half the data is in, and why.

Raycom,
I provided a link to a round-up site and suggested you google a bit to read outside the denialist literature. For me, the main thing is, frankly, the consensus.No matter what Michael Chrichton said, is precisely how science works. Scientific consensus is good enough for me on atomic theory, gravity, relativity, particle/wave duality, evolution and heliocentrism. Why would it suddenly not be good enough on this one area?

Debate and eventual consensus is the heart of science. Even after consensus is reached, there will naturally be debate continuing. This is used by the Young Earth Creationists to try to rubbish evolution, and it's used by people like Chrichton or Monckton to rubbish climate science. Eventually, unless you have the appropriate degrees and experience, it comes down to trusting one pack of experts or another. I've put my lot in with the scientists -- the group for whom debunking majority views is a fast-track to fame. These aren't people who form consensus easily.

GrahamY,
That's the first time I've seen information about the temperature limits from CO2 being limited. I did a quick google and found a couple of things, but couldn't follow what they were saying. That goes against my knowledge of the field, though; in the deep past, despite having a sun much weaker than today's, massive CO2 concentrations managed to lead to temperatures far higher than we have now. I'm really not sure that the logarithmic limit on CO2 absorbtion is something to rely on.

Graham, on a “global” scale you may be right (for the wrong reason) that the “global” temperature increase by 2100 will be less than 3 degrees C. However, my point was that some regions will experience (much) higher increases, some less. The IPCC’s AR5 should make it clearer as to what different regions should expect – increased data and computing technology will enable this.

Think of the troposphere as the planet’s lungs, it can expand and it can contract – what you say about the “logarithmic reaction to infra-red radiation” would be true if the tropopause was ‘fixed’ and/or the concentration of CO2 beneath it were at saturation levels – it’s not and it isn’t, far from it. Therefore, 3 degrees C (+/-) per doubling of [CO2] is established in the literature (Lord Christopher Monckton would disagree :) This century or next is neither here nor there.

As to water vapour, positive and negative feedbacks – it all depends (though “overstated” does seem somewhat harsh insofar that real scientific studies cater for uncertainties). Roy Spencer is doing some good work on the “negative” side of things, but that is largely unproven and less robust that the “positive” side of things.

Raising the tropospheric hot-spot in the same sentence (as you do) does conflate and confuse the issue for many who might be reading this. Perhaps readers with a bent for techno-stuff should have a peak at this:

http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch9s9-2-2.html

then this: http://www.skepticalscience.com/tropospheric-hot-spot.htm

As to CO2 emissions, I would be more relaxed if we focussed on the way we use and utilise our energy resources, there are better ways than just burning fossil fuels. Having said that, coal will be around for sometime yet.

BOM (and NASA) report their “predictions” with caveats and/or in probabilistic terms. People really should understand the significance of "uncertainty", most don't. To see a climate ‘trend’, you have to be able to filter out the ‘noise’ (natural variability) e.g. ENSO, Sun cycles, etc.

James, I suspect most people who get involved in this debate don't understand that the relationship between CO2 and heat is logarithmic, not a straight line. But it is, and you need to get your head around that, because that is where the whole genuine debate is.

Interesting that you obviously read blog sites by proponents of the catastrophic theory and haven't picked that fact up, because it's part of the consensus. It's just easier for them not to talk about it, because then the focus gets thrown onto the high uncertainties in modelling water vapour.

Bonmot, one of the things everyone agrees on is that the models aren't very good at regional forecasts. We do know that the heating tends to be more at the poles, which is one reason that we are likely to have less severe storms with global warming because it decreases the energy differential in the system and therefore decreasing the strength of energy flows.

Your comment about the logarithmic effect of CO2 depending on whether it is saturated or not says you need to do more research in this area. As it reaches saturation it reaches a point where it reradiates nothing, but that doesn't mean that the effect doesn't occur at all levels.

The Skeptical Science blog post is a bit of disinformation. The issue isn't whether CO2 causes the hot spot, but whether the modelling of water in the models is accurate. The recent Royal Society statement concedes that there are issues here.

The probabilities that scientists assign to some of these things are just guesses (unlike probabilities that can be assigned to statistical measurements).

Dear Graham,
I've been looking over old threads looking for inconsistencies in your stand on this issue. But though they're bound to be there, in some degree, you do seem by and large to be consistent; that a little more Co2 is not a bad thing and may even be salubrious. you base this stand on your faith (presumably you're not a scientist) that warming wont exceed three degrees "because of its logarithmic reaction to infra-red radiation".
I'd remind you that Co2 is not the only greenhouse gas and water vapour not the only possible positive-feedback--we are in unprecedented territory after all. Indeed, as I'm sure you'll acknowledge, the science is very complex indeed, ergo I side with raycom in deferring to the experts; surely scientific consensus (overwhelming) should decide how we deal with the issue. Which brings us to the conspiracy hypothesis. It seems to me then that the most pressing considerations for this or another thread are a) is Co2 in the atmosphere self-inhibiting? and b) is there a world-wide conspiracy abroad, and if so what is its aim?

haha Looks like James Carman bought the bridge.

So after all the sanctimonious little lectures and finger wagging about "denialist" sites, you don't even understand what this is all about? Talk about a true believer indulging in blind faith.

So, hey James, hey .. here you go

"You need to read outside the BELIEVER literature and their favorite strawmen. I can state confidently that you haven't, because you wouldn't have said something like that if you had."

There you go, fixed ..

You've swallowed the whole consensus thing without having realized what the whole skeptical side of the "debate" is about - which is, now I'm sure this will be new to you ..

Skeptics doubt that increasing CO2 leads to increasing temperature, there is no proof that it does, but the "consensus" comes out of the modeling (which cannot be easily disproved as most scientists, can hide the decline! Or tweak temperature measurements, till they fit .. now that's real science son. It's a trick evidently). Al Gore misused graphs to show CO2 led temp, but it turns out temp leads CO2 by hundreds of years .. anyway enough .. you need to go do some reading haha!

Oh that's made my day.. thanks.