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Discussion > Best evidence: The story so far.

What 'coherent body of opinion' would that be?

Jul 25, 2012 at 8:19 PM | Unregistered CommenterBBD

And that's just a daft question.
The debate is going on all around you. The trouble is that you think — no, you can't be that silly: you like to have us think that you believe — that the climate world ends with Hansen and Sato and a few others who may be excellent scientists for all I know but are not infallible.
And there's no point at all in my quoting names to you because you will simply dismiss as of no consequence anyone who disturbs your mindset. You always do.

Jul 25, 2012 at 8:24 PM | Registered CommenterMike Jackson

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?

Jul 25, 2012 at 8:53 PM | Registered Commentermatthu

Mike Jackson

And there's no point at all in my quoting names to you because you will simply dismiss as of no consequence anyone who disturbs your mindset. You always do.

What I do is point out that there is in fact no 'coherent body of opinion' as you suggest. Hence your need to avoid defining it by attribution.

Sceptics are fond of implying that there is doubt and uncertainty - which there is - but not the kind supporting the sceptical position.

I notice that you insinuate that H&S and 'a few others' comprise the mainstream scientific position, but they are simply a part of it. You also imply that this supposedly tiny group of experts might be wrong ('[they] are not infallible'). But you *never* demonstrate any errors.

Jul 25, 2012 at 9:06 PM | Unregistered CommenterBBD


What I need to understand is how climate works if feedbacks aren't positive. You didn't say.

Jul 25, 2012 at 9:11 PM | Unregistered CommenterBBD

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.)

Jul 25, 2012 at 9:26 PM | Registered Commentermatthu


You've said lots of stuff, with no references I can check.

Still, let's look at something straightforward - the divergence between GAT and the PDO.

Doesn't look like the PDO is driving modern warming does it?

Jul 25, 2012 at 9:36 PM | Unregistered CommenterBBD

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

Besides the fact that in order to be truly sceptical you must at least try to understand what it is you are being sceptical about, I don't think you *can* explain known climate variability under small changes in forcings unless feedbacks (including WV) net positive.

I remain very interested to see you try, however.

Jul 25, 2012 at 9:39 PM | Unregistered CommenterBBD

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.

Jul 25, 2012 at 9:41 PM | Registered Commentermatthu

You can't do it, can you?

Jul 25, 2012 at 9:57 PM | Unregistered CommenterBBD

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

Jul 25, 2012 at 10:19 PM | Registered Commentermatthu


The measure of my debate? All I ask is that we address the central question:

If feedbacks net positive, the climate system is correspondingly sensitive to changes in forcings.

If feedbacks net neutral or negative, the climate system is correspondingly insensitive to changes in forcings.

So, how do we explain known climate variability from glacial terminations to the MWP and LIA and early C20th warming?

None were associated with a large change in forcing.

Small push, large response. How can this happen with net neutral feedbacks and the resulting insensitive climate?

Either feedbacks net positive or something very strange is going on.

Jul 25, 2012 at 11:50 PM | Unregistered CommenterBBD

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.

Jul 26, 2012 at 12:08 AM | Registered Commentermatthu

Say what you like, but either feedbacks net positive or something very strange is going on.

Any ideas as to what?

Jul 26, 2012 at 12:23 AM | Unregistered CommenterBBD

"We are not considering whether the PDO or solar effects or orbital variations can explain anything."


One of the warmies' superstition is that every swing of a noisy system with variability at *all timescales* has to be caused (by something).

In reality, a bunch of causes drive the system and each hand off and take hold of the baton one after the other, and all are acting all the time. In such a system, the longest of the long term trends can be 'caused' by an overriding factor and none of the other trends can comfortably be attributed.

Jul 26, 2012 at 12:25 AM | Registered Commentershub

RE: The "best evidence", the so-called attribution studies, models (confer the corresponding points above), and 'metadata'

As far as I understand, there remain some plausible reasons for many trials of members of the general public - and of other interested people - to access and test the ("best evidenced") "data" (that were and are being used incessantly to "inform" the public) in a better way; obviously a lot of trials of "self-help" were in vain, for example, often in cases when models were/are used w.r.t. so-called attribution studies.

There is a considerable amount of seemingly kinda reasonable people who try to monitor especially, for instance, the (quality of the) so-called metadata. Some people want to check, say, certain parametrisations after lots of (e.g. "attributing") climate model runs (which shall compute not only bajillion of years but also, e.g., fantasticatillion other integrated "models"). Please, who is ready to provide the ("best") evidence that, for instance, the parametrisations are (in general?) (sufficiently?) transparent and thus the models in the short- and longterms reliable.

The repeated requests from some inquiring minds include for example also, explicitly, all kind of raw- and un-adjusted data, source code, ("world-class") source-documentation, -history, transparency in replacements of "old" climate modules, explanations for formula changes, metadata for homogenizations etc. Do you think there is some sense in these trials w.r.t. audit either the evidences, the attributions, or the models?

Jul 26, 2012 at 2:01 AM | Unregistered CommenterSeptember 2011

I read this on skepticalscience

It's good to have theories and climate model simulations, but I'm far more interested in observations ...


Jul 26, 2012 at 5:08 AM | Registered Commentershub

Unfortunately there is no practical way in which posters can write joint comments. If there were my name would be attached to matthu's from 8.53 and 9.26 last night.
Precisely which bit of the 8.53 comment did you have difficulty understanding? It seemed to me to be totally straightforward, aligns observations with the known physics of the climate, and suggests that feedbacks are less positive than you would like.
What you do obviously have trouble getting to grips with is that this is a blog and not a climate research project. I do not spend my time reading papers and making copious notes but I do keep an eye on what is being published (both sides of the fence) and make a note of what the conclusions are. So, no I am not going to quote you chapter and verse from every paper that has been published and if you think that being able to challenge your adversaries to do that and claim to have won the argument because they either can't or won't do what you demand then it really is time you either gave up pretending to engage or left the sixth form debating techniques behind.
You may well have a different mental approach to the subject from mine and there is no criticism involved there but I'm afraid I start from the point of view that for a planet that has supported life for as long as this one not to have some built-in thermostat to prevent the runaway warming that the alarmists claim is our destiny is highly unlikely. I will certainly agree that it is possible to distort that thermostat with who knows what result but at the moment there is no evidence that that is happening.
As shub points out there are numerous influences at work and we still do not fully understand the interplay between them which cause multi-decadal, multi-centennial, and multi-millennial peaks and troughs. To say — in essence — "it must be CO2 because we can't think of anything else" simply shows that climatologists have still a lot more work to do.
And to get back to rhoda's point ... I don't see any "best evidence" or indeed any evidence at all that CO2 is causing the atmosphere to heat to a level that will in the foreseeable future be dangerous to mankind or threaten his existence.

PS What is much more likely to threaten his existence would be to deprive him of the ground he needs for food by using it to grow fuel and the materials he needs to make medicines by refusing to allow oil exploration or having him die of cold because fossil fuels produce CO2 and the alternatives don't work.

Jul 26, 2012 at 9:45 AM | Registered CommenterMike Jackson

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).

Jul 26, 2012 at 10:01 AM | Registered Commentermatthu

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.

Jul 26, 2012 at 10:14 AM | Registered Commentermatthu

To be fair to BBD, I don't think he's basing his argument on the models but on his interpretation of the physics. The trouble is that he is falling into the trap (in my opinion) of assuming that CO2 is the main driver and that feedbacks are positive because that is the only way he can see temperature behaving as it does whereas, as shub points out, there are numerous influences in play which I don't think climatologists have even bothered to start researching.
As I see the problem, the global mean temperature (which is a bit if an artificial construct anyway) masks a wide variation in actual temperature readings. When Jones was eventually obliged to release his data we found that about one-third of the stations were actually showing a downward trend while there have been graphs from a variety of sources (some of which I might just agree with BBD are perhaps not as reliable as they might be!) from stations showing no net warming over the last 20, 30 or even 80 years.
Adding in what we now know about ENSO and various oceanic oscillations combined with some (I stress some) of the adjustments that have made over the years and I see a temperature pattern that is all over the place and can hardly be relied on to prove anything very much.
I don't know McKittrick and Vogelsang and I'll chase it up but it's a fair bet that BBD will reject it out of hand simply because of the name McKittrick on it.

Jul 26, 2012 at 11:51 AM | Registered CommenterMike Jackson


We have been banned from the "Climate Communication" thread because we were politically incorrectly communicating about science instead of communicating about communication (it still makes my head hurt hehe). So can you please respond to my last comment on cosmic rays over here so I can continue demolishing your arguments? ^.^

Jul 26, 2012 at 2:55 PM | Registered CommenterDung

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

Jul 26, 2012 at 3:20 PM | Registered Commentermatthu


Hmmm please be honest, is it me who is the problem or is it the subject matter? For me the Svensmark theories are important and are rightly part of any consideration of best evidence.

Jul 26, 2012 at 3:53 PM | Registered CommenterDung

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?

Jul 26, 2012 at 4:10 PM | Registered Commentermatthu