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« Cook's progress | Main | Robbins in the minefield »
Friday
Sep202013

Speccy on AR5

The Spectator has a leader article on the Fifth Assessment Report today, and pretty much nails it:

Next week, those who made dire predictions of ruinous climate change face their own inconvenient truth.  The summary of the fifth assessment report by the Intergovernmental Panel on Climate Change (IPCC) will be published, showing that global temperatures are refusing to follow the path which was predicted for them by almost all climatic models. Since its first report in 1990, the IPCC has been predicting that global temperatures would be rising at an average of 0.2° Celsius per decade. Now, the IPCC acknowledges that there has been no statistically significant rise at all over the past 16 years.

And the outlook seems to be upbeat too:

As things have worked out, carbon emissions in the rich world have been falling anyway — not due to green taxes but to better technology, like fracking. Global warming is still a monumental challenge, but one that does not necessarily have to be met by taxing the poor off the roads and out of the sky. Sanity is returning to the environmental debate. Let us hope that, before too long, it also returns to British energy policy.

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Reader Comments (138)

"Now, the IPCC acknowledges that there has been no statistically significant rise at all over the past 16 years"

Straw man walking.

Even at the 1970-2000 warming rate there would still have been no statistically significant warming in 16 years. How many times does this have to be repeated? You need around 20 years of data before you can significantly separate the warming signal from the noise.

Sep 20, 2013 at 1:03 PM | Unregistered Commenterentropic man

There’s a very definite feeling in the air that the IPCC is having a final solitary drink in the Last Chance Saloon, before riding out to be permanently swallowed up by the bad lands outside town. The previous report got torn to pieces by the skeptics and this one, judging by the commentary on leaks of it from various quarters, won’t fare much better.

http://thepointman.wordpress.com/2013/09/20/armageddon-report-no-5/

Pointman

Sep 20, 2013 at 1:07 PM | Unregistered CommenterPointman

You mean nothing much is happening so you can't see the signal? That's what I've been trying to tell you. Nothing much is happening, and if anything is, it is doing so slowly enough that we can adapt to what comes. Until the ice age returns, which is the only real climate catastrophe which is really a threat.

Sep 20, 2013 at 1:07 PM | Unregistered Commenterrhoda

'Sanity is returning to the environmental debate. Let us hope that, before too long, it also returns to British energy policy.'

Some hopes - with the likes of Ed Davey in charge...

Sep 20, 2013 at 1:07 PM | Unregistered CommenterSherlock1

Sep 20, 2013 at 1:03 PM | Unregistered Commenterentropic man

[Manners] Go hide in your little dark corner and weep by yourself. OH, and it has to be repeated until people such as you come to understand it's significance relative to the useless models you sooooo admire.

Sep 20, 2013 at 1:10 PM | Unregistered CommenterStephen Richards

But it shows how the Greenshirts have completely implanted their vicious meme even in the heart of Conservative land.

"Global warming is still a monumental challenge, but one that does not necessarily have to be met by taxing the poor off the roads and out of the sky."

Really? 0.1 degree Celsius per decade!!!!

Sep 20, 2013 at 1:16 PM | Unregistered CommenterStuck-Record

In 1981, Hansen relied on 15 years of temperature change as his ‘dramatic evidence’ of global warming- "They have found that the Earth's average temperature rose 0.2 degrees Centigrade from the mid-1960s to 1980."- Eleanor Randolph, in The Pittsburgh Press, August 15, 1981

There are several problems with this. For example, from 1965 to 1980, HadCRUT now gives 0.06C rise, GISS now gives 0.12C rise and HadSST now gives 0.02C DROP for this time period. So, Hansen hung his hat on a temperature increase that has disappeared in a cloud of data tampering.

Of course, some will screech- what difference does it make now?

We now have 15 years of no temperature increase, while annual CO2 emissions are 2.5 times higher than in 1980.

Sep 20, 2013 at 1:22 PM | Unregistered Commenterchris y

It's all over and has been for a while.

Have the climate sceptics really won?

http://www.theguardian.com/science/political-science/2013/may/24/climate-sceptics-winning-science-policy

Sep 20, 2013 at 1:23 PM | Unregistered CommentereSmiff

I have to say I think that entropic man deserves a better response here.

Surely skeptics have seen enough slippery statements and misunderstood qualifiers coming from the greens to know the importance of clarity.

(Let us set aside the difficulties of defining statistical significance, although personally I think the debate that Doug Keenan has raised here and elsewhere highlights that this is not the clearest way to try to think about what is happening.)

Can we estimate what proportion of the Spectator's readership will, when they read "no statistically significant rise at all" think to themselves something like "most likely no rise at all"? I suspect it is a large fraction, over 90%, although I admit that this is just a ballpark guess based on intuition.

The editorial writer can of course reply - "I told the truth, I never said no warming, I said no no statistically significant rise".

Whose responsibility is it if they are misunderstood? What counts as poor journalism? Do different standards apply to different sides of the debate?

Sep 20, 2013 at 1:49 PM | Unregistered CommenterJK

Good God Bish, don't link to articles like that without a clear warning. Not being familiar with Speccy, I was confronted by a cartoon face which at first glance looked horribly like George Monbiot, and that's not good for anyone's health.

Sep 20, 2013 at 1:57 PM | Unregistered CommenterJohn B

@entropic man

" You need around 20 years of data before you can significantly separate the warming signal from the noise."

Do you have a source with 97% consensus for that allegation?

Sep 20, 2013 at 1:59 PM | Unregistered CommenterJoe Public

We all know that if the trend had been upwards, and even if you want to accept 20 years* as some magic period, phrases like "indicators are", "consistent with", "likely due to" would have been pouring forth from every climate "scientist", and media "expert".

*If the trend would be up the 20 years would shrink, if the trend is no change or down, the 20 years would grow. The magic of climate "science".

Sep 20, 2013 at 2:00 PM | Unregistered CommenterJiminy Cricket

This is what I think of EM and his science. This is the best ever article on the Greens. It is worth reading every hilarious word.


Monbiot’s metamorphosis - Brendan O'Neil


George Monbiot, the Guardian columnist and predictor of the world’s end, has undergone a metamorphosis of Kafkaesque proportions in recent years. Never mind poor Gregor Samsa, who awoke one morning to find himself transmogrified into a monstrous insect; Monbiot has made an even more remarkable cross-species leap. Some time during the past five years he went to bed an hysteric, the closest thing Britain had to a nutty Nostradamus, and awoke to find himself labelled a man of reason, a ‘defender of truth’ no less, who is praised on the dust-jacket of his latest book for possessing a ‘dazzling command of science’ (only by Naomi Klein, admittedly, but still).

How has this happened? How is it that Monbiot, who still writes the same old apocalyptic nonsense (think Book of Revelations but without the hot pokers or sex), can now pose – more than that, be hailed – as a scientific visionary? His metamorphosis from green-tinted despiser of all things modern to man with a dazzling command of science reveals a great deal about the politics of environmentalism, and how it has added a gloss of ‘scientific fact’ to long-standing middle-class prejudices against mass modern society.

http://www.spiked-online.com/index.php?/site/article/5479/

Sep 20, 2013 at 2:15 PM | Unregistered CommentereSmiff

Trends do not matter, statistical significance is not relevant, the IPCC judged that CO2 was the main driver of temperature and the settled science and the models all derive from that. Remember that they said natural variations were less powerful than CO2. There is nothing therefore that they can pull out of their bag of tricks to explain even one year of no warming, let alone 15. CLEARLY CO2 is NOT the main driver of temperature because we have been chucking ever greater amounts of the stuff up there for all those 15 years.

Sep 20, 2013 at 2:33 PM | Registered CommenterDung

Slowly but surely, the unintended consequences of green policies are beginning to emerge,
not only in the UK but also in Germany and Spain.
The leaderless resistance to CAGW is having an increasing impact on the debate and has likely
lead to the alleged toning down of the latest IPCC Opus Magnum.
It's time perhaps for the consensus to familiarise itself with the word "Presage"

Sep 20, 2013 at 2:46 PM | Unregistered Commenterpesadia

How you can have the nerve to tax climate change when there is no empirical proof that recent climate change is not purely natural. Stupidity abounds.

Sep 20, 2013 at 2:47 PM | Unregistered CommenterJohn Marshall

OT:

Request Initiative, the FOI bureau for green organisations run by Brendan Montague, has been gazetted.

Gazetting is the first step you take in closing down a company. You basically publish in the London Gazette that you intend to shut down. Six months later you shut down.

Sep 20, 2013 at 2:53 PM | Registered CommenterTerryS

Sep 20, 2013 at 1:03 PM | Unregistered Commenter entropic man


Classic warm-mongery: Making up the rules as you go along.

Sep 20, 2013 at 3:18 PM | Unregistered CommenterJimmy Haigh

entropic man -
"Even at the 1970-2000 warming rate there would still have been no statistically significant warming in 16 years."

Are you sure of that? I just ran the HadCRUT4 annual figures from 1997-2012 inclusive (16 years of data). Result: OLS trend = 0.0047 K/yr, upper 95% level = 0.0135 K/yr. In other words, the uncertainty in trend for such a short period is +/-0.0088 K/yr. The 1970-2000 OLS trend, from the same dataset, is 0.0164 K/yr, clearly above the significance level.

However, the more relevant question is not whether or not warming is statistically distinguishable from zero -- because few are advancing that hypothesis -- but whether observed warming is statistically distinguishable from the AR4 multi-model mean of ~0.022 K/yr -- which people *are* using to justify policy. And it is.

Sep 20, 2013 at 3:22 PM | Registered CommenterHaroldW

" You need around 20 years of data before you can significantly separate the warming signal from the noise."

Good point.

1980 to 1998 = 18 years. The IPCC should have taken your advice.

Sep 20, 2013 at 3:24 PM | Unregistered CommenterBruce

"Global warming is still a monumental challenge"

No, it isn't.

Sep 20, 2013 at 3:40 PM | Unregistered CommenterRoger Longstaff

You need around 20 years of data before you can significantly separate the warming signal from the noise.

Says who?

Sep 20, 2013 at 4:24 PM | Unregistered CommenterJustice4Rinka

The other day, I read either here, or perhaps another blog, that Julia Slingo said they used the same models for climate change as they do for weather forecasting.

I just had a look at the BBC weather (in association with the Met Office) for next week. Their forecast max temperatures for a week Sunday (29th) ranges between 11/23 C. If they can't forecast 9 days ahead with an accuracy better than 12.0 C how do they honestly expect us to believe them when they say the science is settled on a rise of 0.2 C/decade?

http://www.bbc.co.uk/weather/2634569

Sep 20, 2013 at 4:44 PM | Unregistered CommenterNeilC

Boris Johnson was writing in the Sun this week saying Wind Turbines cant pull the skin off a Rice Pudding and lets go for a new generation of Nuclear Stations and Shale Gas

Suppose if Boris don't make leader of the Conservative party he can always have his old job back.

Sep 20, 2013 at 4:53 PM | Unregistered Commenterjamspid

Harold W

Nice figures.

Before anyone else jumps in, they also show slower warming for the post 1997 period and a lower rate of warming than AR4 predicted. I'm quite happy to agree on that.

This is where most of the research on short term changes are now focused.

Is the slowdown

1) because the energy is still coming in, but warming the ocean and the ice, rather than the atmosphere?

2) because there is less energy coming in, due to increased albedo from clouds, aerosols, reduced insolation etc?

3) because the warming trend is genuinely stopping for the long term?

oe indeed some combination.

The underlying question is more like " Is this period going to behave like 1880-1910 and 1940-1970?".

http://data.giss.nasa.gov/gistemp/graphs_v3/Fig.A2.gif

Both were extended periods with 30 years of static or cooling temperatures which ended with further warming.

I look forward to AR5's discussion of these possibilities.

In the meantime all the "you're a poo-head" deniers are jumping on option 3 without any proper evidence and insulting me for raining on their parade.

Sep 20, 2013 at 4:56 PM | Unregistered Commenterentropic man

EM, we don't need to wring our hands over what is causing the observations to not match the models and the AR4 figures. It is not the sceptics who need to provide an explanation or wonder whether heat is suddenly, not to say miraculously, disappearing into the ocean or whatever. It is for the modellers and the IPCC to alter their predictions/projections in the light of reality. Some of us wonder whether they cannot do so because it means letting go of the certainty of disaster, in which case we don't need to bother with them as their minds are closed. It is for them to make their figures right, not us.

Sep 20, 2013 at 5:06 PM | Unregistered Commenterrhoda

NeilC

That's the difference between weather and climate. Weather is short term questions, such as whether there will be high pressure over the UK next weekend, which would give high temperatures.

9 days out that is impossible to answer with present technology.

Cimate is the long term behaviour of the system, with such very short term variability averaged out.

Sep 20, 2013 at 5:09 PM | Unregistered Commenterentropic man

Entropic.

The null hypothesis has to be that observations throughout the period are the result of natural variation. It is not up to me (or anyone else here) to prove that - it is up to Mann, Hansen, Briffa, Jones (et al) to prove otherwise. You don't get to assume either of your first alternatives without proof - and the recent lack of warming is making that proof somewhat elusive. Your second alternative would seem to undermine the assumption that CO2 is the primary driver of climate, since other factors - including a major negative feedback from clouds - are operating to maintain the temperature at a lower point than predicted by CO2 modeling. You might note that the likelihood of strong negative feedbacks in the climate system is a point much more acknowledged by sceptics than by the cAGW-promoting crowd, and tends towards the conclusion that nothing need be done to address the purported problem.

Sep 20, 2013 at 5:14 PM | Unregistered Commenterdcardno

Sep 20, 2013 at 1:03 PM | Unregistered Commenterentropic man

[Manners] Go hide in your little dark corner and weep by yourself. OH, and it has to be repeated until people such as you come to understand it's significance relative to the useless models you sooooo admire.

Sep 20, 2013 at 1:10 PM | Unregistered CommenterStephen Richards

Bish LoL. :))

Sep 20, 2013 at 5:15 PM | Unregistered CommenterStephen Richards

"It is for the modellers and the IPCC to alter their predictions/projections in the light of reality."

rhoda

That's what I expect to see more of in AR5.

I read somewhere that 2% of climate model runs do show the pattern we've been seeing recently, so its a low probability outcome, not an impossible one.

Thas is the reality, outside your window. Feel free to believe it has stabilised. I, and others, doubt it, on evidence we've discussed many times.

Sep 20, 2013 at 5:20 PM | Unregistered Commenterentropic man

EM
This is a genuine question, do you know if any of the reasons you have listed are being incorporated into the models?

1) because the energy is still coming in, but warming the ocean and the ice, rather than the atmosphere?

2) because there is less energy coming in, due to increased albedo from clouds, aerosols, reduced insolation etc?

3) because the warming trend is genuinely stopping for the long term?

Having a test engineering background I would change the model one variable at a time, at then compare the results with reality.

Sep 20, 2013 at 5:21 PM | Unregistered CommenterSandyS

entropic man
Even at the 1970-2000 warming rate there would still have been no statistically significant warming in 16 years. How many times does this have to be repeated? You need around 20 years of data before you can significantly separate the warming signal from the noise.

-------------

So if after another 3 cold years we get one hot year you wont be crowing your head off that theres been significant warming over the last 20 years?

Do me a favour! Stop kicking the can down the street - you're going to have to pick it up and throw it in the rubbish eventually - why not now?

Sep 20, 2013 at 5:27 PM | Unregistered Commenterduncan

"Having a test engineering background I would change the model one variable at a time, at then compare the results with reality."

SandyS

That's how you use a model, and that's where a lot of research effort is going at present. Make multiple runs using different emission scenarios and different figures for climate variables like cloud production . You may also be familiar with Monte Carlo methods, in which random variations are introduced into the starting data to assess the model's, and the system's, sensitivity to such variations.

The AR4 forecasts were made in this way, using mostly 20th century data. Since they ran the models, reality has changed the projected solar insolation, aerosol and ocean heat absorbtion values on which their projections were based.

Think of being asked to design and run a finite element model to test the behaviour of a structure. You are then blamed for the differences between the behaviour of the model and the final build, after someone changed the spec and failed to inform you.

I know that the sceptical empiricists would like us to have duplicate planets to run all the possible scenarios, but with only one planet it becoms difficult to change one variable at a time. Models are imperfect, but the least worst option for now.

Sep 20, 2013 at 5:47 PM | Unregistered Commenterentropic man

"Do me a favour! Stop kicking the can down the street - you're going to have to pick it up and throw it in the rubbish eventually - why not now?"

duncan

With pleasure, as soon as you show me proper evidence that the long term trend will be flat.

Sep 20, 2013 at 5:55 PM | Unregistered Commenterentropic man

EM, finite element analysis?

Ignoring the fancy maths, Young's modulus forms the core of such an analysis. A figure which is derived directly from empirical measurement. Finite element analysis saves lives. Proven thousands of times. People trust it.

Climate modelling? Do me a favour.

Perhaps you should have chosen fluid dynamics? Where there the laws are clear. Yet despite all the investment and empirical testing, is still imperfect modelling.

Climate science doesn't even the base laws of fluid dynamics.

Sep 20, 2013 at 6:11 PM | Unregistered CommenterJiminy Cricket

entropic man (5:20 PM)
" [Quoting rhoda:] 'It is for the modellers and the IPCC to alter their predictions/projections in the light of reality.'
That's what I expect to see more of in AR5."
I disagree. The CMIP5 models have similar climate sensitivity as the CMIP3 ensemble. As far as I can tell, the modelers have further developed their models without any substantive effort at conformance with observations.

It is certainly not an easy task -- while we here in the peanut gallery may tend to focus on a summary indicator such as global average temperature or OHC, the modelers must deal with trying to match spatial patterns as well, and other aspects such as precipitation, cloudiness, storm frequency, etc. All under the condition that the observations have a certain amount of randomness which the models are not expected to replicate exactly but only statistically (e.g., ENSO). And of course the statistics only become more evident with more data, which requires the passage of time. Unlike other fields where controlled experiments can be run, multiplying the data available. I emphathize with the modelers, but I note that the policy problem exists primarily because the models have been oversold. [With a definite assist from those pushing their own commercial or political interests.]

Sep 20, 2013 at 6:24 PM | Registered CommenterHaroldW

EM
I suspect that Climate Scientists would like multiple planets to test theories too! We know that the AR4 predictions were way off the mark no matter how many times the simulations were run. You have listed a few of the things they got wrong.

If our test programs failed to identify field failures then we spent much time and effort identifying why. Usually because every test is a compromise of cost vs efficiency then we couldn't cover all conditions met in the field so frequently we'd have to try and duplicate the field which wasn't easy. Until we'd got a program which could identify 100% of the field failures then it was regarded as the not fit for purpose and system test would be used instead (the rule of 10 applying to costs). This would put annual pay rises and bonuses in jeopardy. Rather than having the same pressure Climate Scientists seem to get paid more and more for producing more and excuses.

So in this particular instance I'd say we can't tell how good the modified models are until they have been compared with reality for 20 years (your preferred period).

You say to me Since they ran the models, reality has changed the projected solar insolation, aerosol and ocean heat absorbtion values on which their projections were based.
and
Models are imperfect, but the least worst option for now.

and to duncan

With pleasure, as soon as you show me proper evidence that the long term trend will be flat.

So you can't, as you've admitted, do what you've asked of Duncan. So why do you take what the models predict so seriously?

Sep 20, 2013 at 6:32 PM | Unregistered CommenterSandyS

What is the IPCC to do, now? Blush and say, "Oopsie?" No matter what they do, we mustn't lose sight of the club in their back pocket and the fact that they had (and still have) the intent to use it on the entire world. Read the original draft Copenhagen agreement. This is a long way from over.

Sep 20, 2013 at 6:33 PM | Unregistered Commenterjorgekafkazar

Global warming is still a monumental challenge…

It is? Why? What Crystal Ball of Doom do these people peer into? How on earth can anyone be so adamant that any further increase in global temperatures is going to be a Bad Thing?

By inference, they are all saying that Global Cooling is what we want – return us to the Ice Ages; things were so much better then!

EM (Sep 20, 2013 at 1:03 PM): why is the 15/16/17 (“cherry pick” pick your preferred year) year claimed pause in warming less significant than the 15/16/17 (“cherry pick” pick your preferred year) year increase in warming prior to that year (following the alarm of us heading into another Ice Age)? You find a 30-year rise, and I have little doubt that there will be a 30-year fall close by.

Sep 20, 2013 at 6:49 PM | Unregistered CommenterRadical Rodent

i haven't read this thread, I've just logged on, I've got to say, the Speccie does well - until this; "Global warming is still a monumental challenge"

Global warming [natural background warming] is incontrovertible, it is a boon and most welcome.

All of mankind are lucky - we are all lucky to be the recipients of a period of beneficial warming - this warming when compared to periods such as the Minoan epoch, it is not extraordinary but since the mid C18th enlightenment and then the industrial revolution entwined - atmospheric warming has heralded an unprecedented economic and technological human rennaissance.

Global warming presents no challenge to mankind, indeed on the contrary - global warming: it is our ally.

Sep 20, 2013 at 7:02 PM | Unregistered CommenterAthelstan.

Harold W,SandyS

I take the models seriously because the limited output of the models matches a warming world less badly than any of the alternatives. To force them to produce a flat long term trend you have to input unrealistic physics. Incidentally, climate semsitivity is not an input parameter, it emerges from the physical processes modelled.

If someone of the calibre of Pielke or Curry could produce a good physical model which projected a flat 21st century under current emission scenarios I would take the sceptics a lot more seriously. Unfortunately nothing like it has yet appeared.

I know that GISS and the Met Office make all their data and code available under license. Fancy a try?

Regarding policy, that is a matter for political debate. Part of the problem of politics is its tendency to polarise into all-or-nothing camps, which obscures the nuances of the argument.

Sep 20, 2013 at 7:11 PM | Unregistered Commenterentropic man

eSmiff (Sep 20, 2013 at 1:23 PM): Is it really about winning and losing? How sad – James Hansen: “…the sceptics "have been winning the public debate with the help of tremendous resources."
Resources like, errr, the truth? Certainly the warmists have far greater financial resources, with the ever-bountiful public teat to suck upon. Seeking the truth is not about winners and losers, surely – it has to be about the truth! Let the truth be the only winner.

Sep 20, 2013 at 7:13 PM | Unregistered CommenterRadical Rodent

Yes, Athelstan, those were my thoughts. A good article, but he fell at the last. Two degrees per century, or 0.2 degrees per decade, was the nominal (if somewhat arbitrary) number by which means the IPCC can be hoist on its own petard, and scrapped. Then we can just get on with trying to make the world a better place, instead of inventing new crises.

It goes without saying that some individuals and institutions feel threatened by the prospect of the world warming at less than this rate.

Sep 20, 2013 at 7:20 PM | Unregistered Commentermichael hart

Radical Rodent - the truth is paid for in the world today.

They lost because

1. They lied over and over again. I have no confidence in the global temperature for 1995 never mind 1195, never mind models.

2. They are too stupid to get away with lying.

3. No one believed them. They lied about the polls and when they hit single figures, they stopped publishing them. We all basically knew it was a lie. No one demonstrated. Even Bono kept his mouth shut.

4. They sold their souls to big oil. Whatever anyone here thinks, the biggest propaganda campaign in history wasn't funded by Friends of the Earth. It was funded by carbon trading money.


cheers.

Sep 20, 2013 at 7:40 PM | Unregistered CommentereSmiff

"It goes without saying that some individuals and institutions feel threatened by the prospect of the world warming at less than this rate."

Indeed Michael, yes indeed.

Sep 20, 2013 at 7:48 PM | Unregistered CommenterAthelstan.

entropic man:
"I take the models seriously because the limited output of the models matches a warming world less badly than any of the alternatives. To force them to produce a flat long term trend you have to input unrealistic physics. Incidentally, climate sensitivity is not an input parameter, it emerges from the physical processes modelled."
First, I agree that climate sensitivity emerges from GCMs, and is not directly programmed. Nevertheless, it is a direct result of other choices of parameter settings in the models, plus the choice of which processes are modelled. While all GCMs include some sort of model of atmospheric and oceanic circulation, not all include e.g. biological effects. Some models produce a significantly lower sensitivity than the mean.

Second, nobody should be trying to force a flat long term trend. That does not appear to be an accurate summary of the observations. My conclusion (and I don't think this is an unusual one) is that there is a smaller long-term trend (perhaps 0.1 K/decade) superposed on a slow natural oscillation of amplitude about +/- 0.1 K. I've got no idea if any of the GCMs replicate that oscillation, and given its long period and the relatively short period of precision observations, I don't think it can even be very accurately characterized. I think you're getting unduly hung up on "no warming since XXX" -- the conclusion which I have drawn is that whatever natural factors are now counteracting greenhouse forcing to cause the Pause, may well have been operating to augment greenhouse forcing in the 80s. If one assumes symmetry (not a given by any means), then it is not unreasonable to suggest that the forced response to GHG's is only about half of what we experienced then. [Hence my stab at 0.1 K/decade as the long-term trend, which is also close to the observed trend from 1950-today.]

Sep 20, 2013 at 7:59 PM | Registered CommenterHaroldW

Radical Rodent

I'll try a somewhat simplified answer, with no formulae, though Harold W would do it better. Forgive me for reverting to teaching mode. Oh for a blackboard! :-)

You might like to print out this graph.

http://data.giss.nasa.gov/gistemp/graphs_v3/Fig.A2.gif

For simplicity, tale the period from 1970 to 2000. Think of it as a band containing all the individual points.

Draw three parallel slopes. one up the middle of the band, one at the upper edge of the band and one at the lower edge of the band. The upper and lower slopes should just enclose all the points.

The middle slope is the mean, the average temperature trend. The upper and lower slopes indicate how far individual years tend to vary from the trend, warmer or cooler. Variations between closely spaced years can be due to weather, events or whatever and would be expected whatever the long term trend.

Now for the long term trends. Draw a vertical line through the point where the mean slope reaches 2000. Draw horizontal lines where the vertical crosses the lower slope and the upper slope. These bounds approximately defines the uncertainty in the actual value of the 2000 temperature.

Do the same for 1970.

There is a gap between the upper bound line for 1970 and the lower bound line for 2000. This indicates that the difference between the two years is larger than the uncertainties and you can be confident that there is a real, a significant difference between them.

If the lower 2000 bound and the upper 1970 bound overlapped there would be no significant difference and no evidence for a trend.

Look across the lower 2000 bound and it crosses the upper slope above the 1982 mean, on my graph. This is the upper bound for 1982 and the earliest year for which a significant difference from 2000 can be claimed.

In this case the gap is 18 years.

If the slope were flatter the minimum gap between significantly different years would be longer. If the slope were steeper the gap would be shorter.

Sep 20, 2013 at 8:05 PM | Unregistered Commenterentropic man

EM
Who and what are the alternatives to the models and modeler? I don't think there is much else other than those who say that solar cycles have an influence which isn't much use as solar cycle prediction isn't that good. Milankovitch cycles aren't much use either. Ocean oscillations aren't that well understood so we can't use them.

Isn't what you're saying we don't understand anything about the climate but these models can be made to predict the past after a fashion so mthey are the best we've got, damned by faint praise?.

I think that I'm of the view that something that matches a warming world less badly than any of the alternatives. isn't worth taking notice of in terms of spending trillions of pounds and putting up the cost of energy beyond the reach of a large chunk of the population.

Sep 20, 2013 at 8:09 PM | Unregistered CommenterSandyS

EM I'm sorry, you can't get away with that. By their own criteria, not mine, the models quite simply do not match the world temperature over the last 10-15 years. They had a good fit before then, but then they would, as like von Neumann's elephant they had enough parameters to tweak that they were bound to. Nowadays a warming trend of about 0.06ºc per decade with a sine curve overlaid is a far better fit to global temperatures; of course there is no physical basis for selecting it, but then there is precious little for using the models which by their own admission fail to take into account significant elements of global temperature, particularly the poorly-understood effect of changes in cloud cover.

Of course climate sensitivity is not an input parameter, but it is a direct function of the parameters themselves which were selected because, as I said, they made the models a good fit for the reference period of say 1980-1995 when there was an exceptional but not unprecedented spell of warming, exacerbated by some well-documented tweaking of the record (see New Zealand, Darwin or GISS with their mysteriously changing historical data for instance.)

Vast sums of money have been poured into producing physical models that may at some stage tell us something about climate, but at present are not fit for purpose. The fact that cleverer people than Phil (Mr Excel) Jones cannot build models that work does not mean we are doomed to use ones that don't, less still believe their output when it is palpably wrong and base our economic and energy policies on them. It may just mean that with the current state of knowledge of the highly complex and chaotic weather system, the integral of which over time is climate, we do not have the means to build useable models, and scientists should stop lying to politicians about it.

Sep 20, 2013 at 8:09 PM | Unregistered CommenterDavid S

I take the models seriously because the limited output of the models matches a warming world less badly than any of the alternatives.

Sep 20, 2013 at 7:11 PM | Unregistered Commenterentropic man


There is nobody else trying to predict the future, there are no alternative models because rational people understand that we do not know enough about climate to even try.

The only truth in this whole sorry mess is that climate can not yet be predicted and that therefore (as others have said) the idiot energy policies based on the idiot models should be scrapped.

Sep 20, 2013 at 8:11 PM | Registered CommenterDung

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