@Shub Nov 11, 2011 at 3:49 AM

Just love the statistically ignorant ranting on this thread.

Shub, I'm disappointed! You seem to have missed the appeals to the self-declared authority of our favourite "it's all about me 'n whatever question I posed, whenever I might have posed it" zealot.

Or are you going to carry your denial of the obvious to ever-more farcical extremes?

Nice bit of displacement activity, there, BBD. If in doubt move the goalposts and throw in an insult.
Simple question: Is the temperature trend for 1970-2000 almost identical to the temperature trend for 1910-1940 ay ~0.15c per decade? Yes or no.
If your answer is 'yes' then go to the next stage of our discussion (wherever that might be leading).
If your answer is 'no' then please explain in what way it differs.

Simples.

Mike

Care to explain the centennial trend? You know, the one caused by increased RF from CO2 warming the climate system... The one steepening post-1975 as CO2 begins to emerge as the dominant forcing...

Just pointing to 1910 - 1940 and saying 'same trend' is meaningless. Look at the centennial context.

Explain that.

Shub

You have exactly zero scientific or statistical knowledge, so stop posturing. It's grotesque.

matthu

"Most of the impact is likely caused by CO2 emissions, and the effect will steadily intensify over time"

BBD - this is your belief - but certainly not the scientific consensus. And I gave Richard every opportunity to correct me here.

It is the scientific consensus.

I don't usually link to Wikipedia, but the relevant article there contains an exhaustive list of national academies of science (32 in all, I think) endorsing this scientific consensus. Do take a long look.

Your reflexive denial that CO2 is a serious problem going forward is the problem with this conversation. As is the case with Shub, Hilary, Mike and others.

That and the collective refusal of people here to question their own assumptions, read widely with an open mind and generally think clearly.

matthu

Some diligent soul has provided a hyperlinked reference to the worldwide scientific consensus here. It fits with the Wiki article well, and can be used as a fact-checker if you wish.

BBD - this is the statement made by the Royal Society:

There is strong evidence that the warming of the Earth over the last half-century has been caused largely by human activity, such as the burning of fossil fuels and changes in land use, including agriculture and deforestation. The size of future temperature increases and other aspects of climate change, especially at the regional scale, are still subject to uncertainty. Nevertheless, the risks associated with some of these changes are substantial. It is important that decision makers have access to climate science of the highest quality, and can take account of its findings in formulating appropriate responses.

http://royalsociety.org/policy/publications/2010/climate-change-summary-science/

Now why do you try to distort this very clear statement to meet your own beliefs?
Or is the RS distorting the consensus?

You're changing the rules again, BBD. You were the one that claimed an increasing trend for the last warming period. I'm just pointing out that the trend was the same as the previous warming period (1940-1970) and not dissimilar to the one before that (1880-1910). And I will continue to claim that to compare a warming period of 30 years with an overall 100+ years of warming and cooling and use that as the basis for an argument is cheating.
There is no "steepening trend" post 1975. The 1970-2000 trend is ~0.16 per decade; the 1910-1940 trend is ~0.15 per decade. The centennial figure (which includes the warming periods and the cooling periods) is ~0.08 per decade which accords with the projected 0.9C per century.
http://tinyurl.com/7g235r4 (sorry about this, but every time I try to embed a link I manage to get it wrong!) is quite clear, at least to my mind, and also shows the trend for the last 10 years which, as you can see, could be interpreted as suggesting that the this 30-year warming cycle has ended. Now I wouldn't dream of claiming any such thing for at least another couple of years but then neither would I dismiss the idea out of hand.

BBD -

Compare the RS statement with my own version:

1) global warming is real (whatever that means)
2) man is having an impact
3) at least some of the impact is likely caused by CO2 emissions

I asked Richard Betts whether there was another similarly brief way of expressing the totality of the consensus and he replied

Nov 9, 2011 at 10:39 PM | matthu

Thanks - yes, to my mind that pretty well captures the bits that virtually everyone who knows about the science can agree on.

Anything beyond that (what the impacts will be, and how we should respond) become highly uncertain and down to value judgements and attitude to risk.

and Tamsin Edwards replied

I agree with Richard.

so you appear to be out on a limb here. Not for the first time.

matthu

Nope.

The effects of LUC are real, but the effects of RF from CO2 are larger, ongoing, increasing and will persist far into the future. Which is why CO2 is the principle concern, not a secondary one as you would have it.

As is overwhelmingly evident from the mass of endorsements of the scientific consensus I link to above.

A partial, biased reading does not constitute an argument.

I am likely to be without any net connectivity now until tomorrow at least. (The only reason I am telling you this is so that you don't construe my absence as being in any way silent acquiescence with any response you may make to what I have just said!)

Cheers.

My very last comment:

All the endorsements linked to above are simply that - they are a collection of statements, some very old, not a cconsensus. In fact the link they give to the RS no longer exists. It has been superseded by the statement I linked to above.

But, BBD, you must be right - because you say so. And your view always trumps the view of the Royal Society and that of the Head of Climate Impacts at the Met Office.

It is just a pity that your view is not consensually held.

Mike

You are just going back over old ground. In response to your dogged refusal to accept the in-context trend analysis, We looked at 10 year means yesterday. Remember? These show an unequivocal acceleration of warming:

CRUTEM3 land and BEST 1900 - present, common 1981 - 2000 baseline, 10 year means

You did not respond to that comment and have simply waited 245 hours and re-appeared with an argument which has already been addressed.

Even the annual mean reveals an acceleration in warming:

BEST 1900 - 2010.2 annual mean

The five year mean reveals the invalidity of the comparison you strive to make with the 1910 - 1940 warming even more clearly:

BEST 1900 - 2010.2 five year mean

When are you going to accept that you are mistaken?

matthu

I'm simply saying that the scientific consensus places far more weight on the role of CO2 than you admit.

And I'm backing that up in detail. You are nit-picking because you know that you are mistaken and it's now impossible to convincingly pretend otherwise.

You did not answer my earlier question:

What is the statistical test/s to determine outliers?

Next statistics question:

What is/are the name of the statistical test/s to determine differences between trends?

Again, no googling. Hint: It is not called 'intellectual honesty'.

I'm afraid, for too long now, we have been taken for a ride by a person not from a science discipline, ranting but about science papers.

Shub

I'm afraid that for too long, readers here have been taken in by you.

Rather than attempt to obfuscate the very clear issue here (see Nov 11, 2011 at 4:18 PM), why don't you actually address what is obvious from the data?

Allow me to supply the answer, since I know you aren't honest enough to do so yourself:

You can't. Not without admitting that the degree and rate of warming require an accumulation of energy in the climate system over the C20th that can only adequately be explained by increased RF from CO2.

So instead, you continue your endless attempts to delegitimise me and muddy the waters.

You can posture and rant and claim whatever you like about my level of knowledge, but you cannot get around this.

And the beauty of it is, you are just smart enough to recognise the fact.

Yes, BBD, very clever.
You can make the figures prove what you want and I can make them prove what I want. There is no meeting of minds here so we'll call it a day.
It's not a question of my refusing to accept that I'm mistaken; it's a question of interpretation. Equally it's a matter of your refusing to accept that the 1970-2000 trend is an artefact. If you are going to take a centennial trend and then overlay it with a bit of itself you are going to get a distorted result and if you can't see that then I don't see any point in trying to convince you further.
And neither is this anything to do with "waiting 245 hours (or even 24 hours!) and then re-appearing". Weird as it may seem, I do have other things to do with my life and I didn't see your reply until this morning.
After which I thought you deserved a considered response, which you got.
Obviously I needn't have wasted my time.

?

and

any thoughts?

Mike

You can make the figures prove what you want and I can make them prove what I want. There is no meeting of minds here so we'll call it a day.
It's not a question of my refusing to accept that I'm mistaken; it's a question of interpretation. Equally it's a matter of your refusing to accept that the 1970-2000 trend is an artefact.

The 1970 - 2000 trend is not an 'artefact'. It exists in its own right.

Be that as it may, using 10 year means avoids the problem you are fixated on. It also confirms what I have maintained from the outset: the rate of warming has increased over the C20th. Accept this graciously. I have spent long enough trying to point out your errors. And I too, have better things to do.

Philip

I've just got back from a school fireworks display (yes, I thought it was last weekend too). Need to speak to Mrs BBD, who I have seen little of this week, then I will read these papers (or at least skim them) and respond.

Philip

Sorry for the delay, but I hadn't read either of these studies. Both interesting - thanks for the links.

Federov et al. (2006) shows that the Early Pliocene climate was dominated by a perennial El Nino and the absence of large NH ice sheets/polar cap. The gradual Cenozoic cooling had not yet reached the point where the latter could form and provide the ice-albedo feedback mechanism that apparently amplifies Milankovitch forcing sufficent to trigger glacial terminations.

The warming effect of the perennial El Nino is suggested to arise from high atmospheric water vapour content and positive stratospheric cloud albedo feedback:

Persistent El Niño conditions would have had a huge impact on the global climate given that, today, even brief El Niño episodes can have a large influence. The reasons are evident in fig. 2 which shows a remarkably high correlation between tropical sea surface temperature and rainfall patterns. Tall, rain-bearing, convective clouds cover the warmest waters but highly reflective stratus decks that produce little rain cover the cold waters. During El Niño, the warming of the eastern equatorial Pacific reduces the area covered by stratus clouds thus decreasing the albedo of the planet, while the atmospheric concentration of the powerful greenhouse gas, water vapor, increases. Calculations with a General Circulation Model of the atmosphere indicate that this happened during the
early Pliocene and contributed significantly to the warm conditions at that time.

SSTs began to fall ~3Ma, and an alternating ENSO replaced the perennial EN. I assume you are familiar with the hypothesised causes suggested by the authors, so I won't summarise them here.

The Discussion opens with this caution:

A major factor in the warmth of the early Pliocene was the persistence of El Niño in the Pacific; it contributed to global warming by causing the absence of stratus clouds from the eastern equatorial Pacific, thus lowering the planetary albedo, and by increasing the atmospheric concentration of water vapor, a powerful greenhouse gas.Today the atmospheric concentration of another greenhouse gas, carbon dioxide, is comparable to what it was in the early Pliocene, but the climate of the planet is not yet in equilibrium with those high values. It is possible that a persistence of high carbon dioxide concentrations could result in a return to a globally warm world if it were to melt glaciers and increase temperatures in high latitudes, and as a consequence cause the tropical thermocline to deepen by a modest amount, a few tens of meters. (Near the date line at the equator the thermocline is already so deep that its vertical excursions leave surface temperatures unaffected.)

While this is clearly not intended as a prediction of imminent doom, it is a sobering conjecture.

Zaliapin & Ghil (2010) is harder to parse. In fact I wish I'd read it first while I was still half-awake. Let me look over it again.

Philip

Zaliapin & Ghil (2010) my emphasis:

In a truly nonlinear setting, indeterminacy in the size of the response [to normally distributed feedback forcing] is observed only in the vicinity of tipping points. We show, in fact, that small disturbances cannot result in a large-amplitude response, unless the system is at or near such a point. We discuss briefly how the distance to the bifurcation may be related to the strength of Earth’s ice-albedo feedback.

My understanding is that glacial climate states are unstable because the dominant positive feedback maintaining low GAT is ice-albedo. Ice sheet dynamics apparently result in cascading collapse initiated by regional change in RF without significant global change in RF (Milankovitch ~100Ka cycle). This is amplified by diminishing ice-albedo feedback and Bob's your interglacial.

Z&G:

This S-shaped curve nevertheless reveals the existence of sensitive dependence of Earth’s temperature on insolation changes, or on other changes in Earth’s net radiation budget, such as may be caused by increasing levels of greenhouse gases, on the one hand, or of aerosols, on the other.

And:

The GCM simulations of Wetherald and Manabe (1975) (see again their Fig. 5) suggest that this point might lie no farther than 5% below the current value of the solar constant. At the same time, the Sun has been much fainter 4 Gyr ago (by approximatyely 25–30%) than today, without the Earth ending up in a deep freeze, except possibly much later. So how close are we to this tipping point? Figure 6 here shows stable and unstable equilibrium solutions for different profiles of the ice-albedo feedback,  = (T ; ); this profile is determined by the value of the steepness parameter  (cf. Fig. 3a). The figure suggests that the steeper the ramp of the ice-albedo feedback function, i.e. the larger , the further away the bifurcation might lie.

[Formatting mash-up: see p8 - 9 of pdf for correct notation]

So, while this study asks pertinent questions about the methodology and conculsions of another paper (Roe & Baker 2007), it does not suggest that the climate system is insensitive.

I'm very interested as to your readings of both these papers, especially if you are proposing a synthetic interpretation.

Let's have it!

Thanks for your thoughtful comments BBD, and sorry if I kept you away from your Zzzzs. I agree: these papers don't provide quantitative answers about sensitivity, but I think they do suggest a conceptual picture of the kind of behaviour we might expect. I think the Z&G picture reflects reality. They consider a single variable (T) and three processes (sunshine, greenhouse and ice albedo) and find in that a combination of gradual and sudden changes. In real reality, there must be many variables of interest and many many processes that can affect them; the variables vary not only in time but also in position.

Imagine the surface drawn out as these variables change under the influence of the processes. It seems plausible it will contain kinks and folds (like Z&G's S) at many different scales and positions. If so, then as the various processes play out, it is possible to encounter numerous sudden changes in the variables or their derivatives; it may be possible to avoid jumps by taking routes around the side; it may be possible to reach a given state by many different routes; and so on. Movement on the surface is caused by real physical processes; the kinks and folds arise from the earth's response to these processes.

The suggestion is that not only does snowball/hothouse correspond to jumps and round-the-side routes on this surface; the Fedorov et al finding of different T for the same sunshine, geography and CO2, corresponds to taking different routes; sudden changes at glacial->interglacial etc correspond to taking a jump rather than an easy route; the Cenozoic change from gradual erratic cooling to wild oscillation corresponds to a movement into a more folded part of the surface; the step discernible in UAH/RSS corresponds to a jump; as do the discontinuities in slope discernible in the HADCRUT record.

Further aspects of my confusion arise from wondering about this, this and this. At the very least, I think it might be worthwhile dipping a toe into what appears to be an enormous literature, the tip of which can be seen both at the first two links and in Z&G.