Ben Santer's 17 year itch

Rising air temperature: statistically hot or not?

Ben Santer issues a press release on Eurekalert today to “smack down” the non warming we’ve experienced over the last 10-12 years, as I pointed out here for the USA. But the issue goes back further than that. Phil Jones famously said in a Feb 2010 BBC interview:

Do you agree that from 1995 to the present there has been no statistically-significant global warming

Yes, but only just. I also calculated the trend for the period 1995 to 2009. This trend (0.12C per decade) is positive, but not significant at the 95% significance level. The positive trend is quite close to the significance level. Achieving statistical significance in scientific terms is much more likely for longer periods, and much less likely for shorter periods.

MIT Professor Richard Lindzen said something similar in a WUWT guest post:

There has been no warming since 1997 and no

statistically significant warming since 1995.

And, climatologist Pat Michaels said recently in an essay at The GWPF:

“The last ten years of the BEST data indeed show no statistically significant warming trend, no matter how you slice and dice them”. He adds: “Both records are in reasonable agreement about the length of time without a significant warming trend. In the CRU record it is 15.0 years. In the University of Alabama MSU it is 13.9, and in the Remote Sensing Systems version of the MSU it is 15.6 years. “

So with Dr. Ben Santer now solidly defining 17 years as the minimum to determine a climate signal, what happens to the argument when we reach 2013-2014 and there’s still no statistically significant upwards trend?

Separating signal and noise in climate warming

LIVERMORE, Calif. — In order to separate human-caused global warming from the “noise” of purely natural climate fluctuations, temperature records must be at least 17 years long, according to climate scientists.

To address criticism of the reliability of thermometer records of surface warming, Lawrence Livermore National Laboratory scientists analyzed satellite measurements of the temperature of the lower troposphere (the region of the atmosphere from the surface to roughly five miles above) and saw a clear signal of human-induced warming of the planet.

Satellite measurements of atmospheric temperature are made with microwave radiometers, and are completely independent of surface thermometer measurements. The satellite data indicate that the lower troposphere has warmed by roughly 0.9 degrees Fahrenheit since the beginning of satellite temperature records in 1979. This increase is entirely consistent with the warming of Earth’s surface estimated from thermometer records.

Recently, a number of global warming critics have focused attention on the behavior of Earth’s temperature since 1998. They have argued that there has been little or no warming over the last 10 to 12 years, and that computer models of the climate system are not capable of simulating such short “hiatus periods” when models are run with human-caused changes in greenhouse gases.

“Looking at a single, noisy 10-year period is cherry picking, and does not provide reliable information about the presence or absence of human effects on climate,” said Benjamin Santer, a climate scientist and lead author on an article in the Nov. 17 online edition of the Journal of Geophysical Research (Atmospheres).

Many scientific studies have identified a human “fingerprint” in observations of surface and lower tropospheric temperature changes. These detection and attribution studies look at long, multi-decade observational temperature records. Shorter periods generally have small signal to noise ratios, making it difficult to identify an anthropogenic signal with high statistical confidence, Santer said.

“In fingerprinting, we analyze longer, multi-decadal temperature records, and we beat down the large year-to-year temperature variability caused by purely natural phenomena (like El Niños and La Niñas). This makes it easier to identify a slowly-emerging signal arising from gradual, human-caused changes in atmospheric levels of greenhouse gases,” Santer said.

The LLNL-led research shows that climate models can and do simulate short, 10- to 12-year “hiatus periods” with minimal warming, even when the models are run with historical increases in greenhouse gases and sulfate aerosol particles. They find that tropospheric temperature records must be at least 17 years long to discriminate between internal climate noise and the signal of human-caused changes in the chemical composition of the atmosphere.

“One individual short-term trend doesn’t tell you much about long-term climate change,” Santer said. “A single decade of observational temperature data is inadequate for identifying a slowly evolving human-caused warming signal. In both the satellite observations and in computer models, short, 10-year tropospheric temperature trends are strongly influenced by the large noise of year-to-year climate variability.”

The research team is made up of Santer and Livermore colleagues Charles Doutriaux, Peter Caldwell, Peter Gleckler, Detelina Ivanova, and Karl Taylor, and includes collaborators from Remote Sensing Systems, the National Center for Atmospheric Research, the University of Colorado, the Canadian Centre for Climate Modeling and Analysis, the National Oceanic and Atmospheric Administration, the U.K. Meteorology Office Hadley Centre, and Lawrence Berkeley National Laboratory.

###

Source: http://www.llnl.gov/news/newsreleases/2011/Nov/NR-11-11-03.html

Anne M Stark, LLNL, (925) 422-9799, stark8@llnl.gov

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TomRude

1, 2 and 3, all move the goal posts…

Bruce Cobb

What will happen is the new minimum for determining a human influence on climate will be 20 years.

jthomas

[snip. Read the site Policy. ~dbs, mod.]

I wanna beat the crap out of that man.
BTW, whats exactly that human fingerprint? Failed hotspot?

KTWO

One way to win is to define the rules. Then redefine them as needed.
That sounds unfair but it may work, which is why it is sometimes done. So if Santer says 17 now he may say 18 or 19 soon. Or he may not.
We know that at some point rule changes won’t work. But a couple of more years – whether warmer or colder – won’t change many minds.

My experience in metrology, acquired in my career as an Analytical Chemist, is that although there are extremely sophisticated techniques for sorting out a weak signal from strong noise, they involve mathematics – and mathematical assumptions about the nature of the signal and the nature of the noise – that is far beyond the ken of most ‘climatologists.’
The mathematics can involve Fourier Transforms and / or Principle Component Analysis. The assumptions involve assigning characteristics to the signal and the noise, based on *known* mathematical properties of both – characteristics which cannot be justifiably applied in the case of climate.
Other than that, your only resort is to acquire *massive* amounts of data so that the statistical variances in all trends are reduced sufficiently to discriminate between periodic and secular trends.
Until the data has been collected, the problem is very like that of determining “mean sea level” from instantaneous wave height measurments – during a storm.

FergalR

“what happens to the argument when we reach 2013-2014 and there’s still no statistically significant upwards trend?”
IPCC AR6 (2022);
” . . . climate models can and do simulate short-ish, 15- to 17-year “hiatus periods” with minimal warming, even when the models are run with historical increases in greenhouse gases and sulfate aerosol particles. They find that tropospheric temperature records must be at least 25 years long to discriminate between internal climate noise and the signal of human-caused changes”

Pogo

So with Dr. Ben Santer now solidly defining 17 years as the minimum to determine a climate signal, what happens to the argument when we reach 2013-2014 and there’s still no statistically significant upwards trend?
Then Dr Santer will redefine the period to 19 years, or 23, or whatever prime number takes his fancy at the time…

Carl Chapman

Why 17 years? Is it because it’s a prime number? . If so we’ve already had 13 years of no warming, but I guess that was the wrong prime number.
Hansen was happy to announce global warming after 10 years of warming.

D. Cohen

“To address criticism of the reliability of thermometer records of surface warming, Lawrence Livermore National Laboratory scientists analyzed satellite measurements of the temperature of the lower troposphere (the region of the atmosphere from the surface to roughly five miles above) and saw a clear signal of human-induced warming of the planet.”
Wow-wee! Those satellites are sure sophisticated, being able to tell the difference between human-induced warming and just plain warming.

Kaboom

“The positive trend is quite close to the significance level. ”
Fuzzy isn’t part of mathematics.

Interstellar Bill

Somebody should tell these thermodynamically-challenged profs
that their precious forcing is laughably small,
as per the Wikipedia graph so well known here at WUWT:
http://upload.wikimedia.org/wikipedia/commons/9/9c/ModtranRadiativeForcingDoubleCO2.png
It’s easy to calculate that a climatologically undetectable 0.7 deg K
will lift the 600ppm curve up so it has the same integral as the 300ppm curve.
Doesn’t ‘forcing’ seem too muscular a word for such a tiny effect?
Given that the graph is for 50% humidity and no clouds,
the real effect of CO2 should better be called a ‘SUGGESTION’.
Cloud changes… now that’s a forcing,
as shown by the breezes that spring up at the edge of cloud-shadows.
Why should this undetectable temperature rise get catastrophically amplified
when far larger natural fluctuations do not? Truly, CO2 is a magic molecule.
It looks more like there never will be much of a ‘greenhouse signal’,
just as the WWII planes never came for the pathetic Cargo Cultists.
Only this time the Cultists are forcing us to build giant bird-slicers
that cost us far more steel, concrete, rare-earths, and worker deaths
per actual power output than those Eeeville nuclear reactors.
As for any of those stupid obscenities running for 40 years…

Leigh

What a load of crap. We’ve had thirty plus years of their rorting taxpayers moneys around the world for this scam. Now people are starting to wake up to them they’re bleating for more time(taxpayersmoney)
Has any one ever noticed that every time there is a new shampoo add on the box there is a new wonder ingredient that’s just been discovered that will change your hair forever?
These snake oil salesmen are no different.
What is sulfate aerosol particles?
And is this the reason I’m going to be paying a C/2 tax?
Or are there other reasons that the likes of Flannery and co will tell me? I’ve had enough.
I’m all fructosed out.

Give me a day, Anthony, and I’ll have a post comparing 17-year and 30-year trends (running) of models versus observations. The graphs are done. It’ll take a little bit of time to write it up with a introductory-level discussion of what the graphs are showing. As one would expect the models don’t do so good. This Santer post will make a nice lead in.

TomL

“The positive trend is quite close to the significance level. ”
Translation: The positive trend is not significant.

Gary

See William M. Briggs, Statistician, on how his Sample Size Extender™ will provide you a small p-value for any dataset you have: http://wmbriggs.com/blog/?p=4687.

R. Gates

There seems to be some confusion by some about looking for the anthropogenic fingerprint among the natural forcings. This is all about separating the human “signal” from the noise of natural forcings such as from ENSO, solar cycles (long and short), volcanoes, etc. Furthermore, some of that human “fingerprint” runs in opposition to itself (i.e. aerosols versus greenhouse gases, etc.). Finally, the 17 year period is a mininum time required to see the anthropogenic warming signal among the shorter-term noise, but it does not mean that even in that period, it would necessary show net warming. You could very well get a combination of shorter-term “noise” that still masks or counters the warming, but mathematically, 17 years is the minimum to be able to statisically be able to see the anthropogenic warming signal among the noise (even if there was no net warming during that period because the natural factors cancelled out any warming). Here’s an example of how this works: suppose you come home from vacation, and before you left you had turned you thermostat off. Before you left, it had been in the 70’s, but a cold front moved through just before you came home, and the temperature outside now is in the 40’s, and the temperature in your home is in the 50’s. You come home and turn your heater back on and set the thermostat to 70 degrees, and then head out to the store to pick up some groceries. You come back from the store an hour later, expecting to find a nice warm house, but it is still 50 degrees in your home. WUWT you ask yourself. You check your thermostat, and sure enough it is set at 70 degrees. You go downstairs and check your heater and it is running like crazy. Again, WUWT! Then you go upstairs to the top floor of your house and realize while you were gone, your teenager had opened all the windows in to “air out the stuffy house”. How would you have any “proof” that your home heater was working, other than to look at it running if the temperature in the home had stayed the same while you were gone? Only in looking at all the factors going in to the temperature in your house (open windows, temperature outside, heater running), could you come to any conclusioin as to why the temperature of the house is staying at 50 degrees. Related to increases in CO2 and the 17 year period to see the anthropogenic signal, it doesn’t really matter what the temperature does in the 17 year period (the probability is that it would go up, but it could go down as well, depending on other factors), but this is how long it takes to see the signal that the anthropogenic “heater is running”.

Tamino explains it all very well here…

Phil Jones was Wrong
[B]y removing the influence of exogenous factors like el Nino, volcanic eruptions, and solar variation (or at least, approximations of their influence) we can reduce the noise level in temperature time series (and reduce the level of autocorrelation in the process). This enables us to estimate trend rates with greater precision. And when you do so, you find that yes, Virginia, the trend since 1995 is statistically significant.

If you remove all of the annoying bits (exogenous factors), the warming since 1995 magically becomes statistically significant and the cooling since 2001 becomes warming.
The HadCRUT3 cooling trend since 2001 will never become statistically significant. It will be massaged out of the data until we’ve clearly returned to Little Ice Age conditions by the end of this century. By then, the Warmists will have figured out a way to blame capitalism for the even worse climate disruption of global cooling… ;))

John Silver

God (WMO) says 30 years. So there, Santer.
I say 300 years.

HankHenry

“the large noise of year-to-year climate variability”
Why not create a model capable of reproducing year to year variability. It would be interesting to see if the heat involved in El Nino and La Nina is great enough or whether other things must play a part such as average cloud cover or other shifting ocean pools and currents need to be called on to perfect the model.

Rob Z

Santer is pretty proud of “his” fingerprints being all over the IPCC reports and his “signature” work. The warming observed in the “results” does have a human element. This much is true. How much of it is Santer’s remains to be seen. Might be time to have a deeper look into Santer’s stuff.

John Silver

The correct number is of course 42.

keith at hastings uk

Maybe misreading this but isn’t Santer just assuming as a given that any long term (17 yrs (!)) upward signal is human induced ? i.e., no other cause contemplated or allowed? Surely there are longer timescale cyclic events and also the slow uplift post LIA, tho’ no mechanism seems to be posited for that (?)

More Soylent Green!

I read the press release. It does not specify how they measured the human signal. I read implications that known, natural sources were filtered out, so whatever was left must be human.

Frederick Michael

The satellite data shows global temp dropping this year. When this data is folded in to their regressions, the warming won’t be quite so “close” to being significant.

matt v.

Lets not get lost in all this statistics . If the puropose of collecting all this climate data is to make better weather forecasts for the near term first, then waiting for 1 7 years or 30 years to tell the public that the climate cooled or warmed has little value . I see much greater value to the public in more accurately recording and predicting better shorter term and better regional forecats , like seasonal numbers , annual numbers and decadal numbers. Kowledge about short term trends is more imprtant in our daily lives than knowing what the climate will be when none of us will be around . The fact that US has not warmed for 10-15 years is important and we should not wait another 15 [to reachl 30 years ] before we comment publically.It has taken nearly 15 years for the AGW climate scientists to tell the public what is happening and then they cannot even agree what happened , but they claim accuarcy 100 years and some have even tried 1000 years

Dan Pangburn

Think beyond trend lines and other polynomial curve fitting with no predictive ability.
A simple equation based on the physical phenomena involved, with inputs of only sunspot number and ppmv CO2, calculates the average global temperatures (agt) since 1895 (that’s 115 years and counting) with 88.4% accuracy (an insignificantly lower 87.9% if CO2 is assumed to have no influence).
The equation, links to the source data, an eye-opening graph of the results and how they are derived are in the pdfs at http://climaterealists.com/index.php?tid=145&linkbox=true (see especially the pdfs made public on 4/10/10, 3/10/11 and 9/24/11).
As shown in the 9/24/11 pdf, the equation accurately predicted the temperature trends for the last 20 years.
The future average global temperature trend that this equation calculates is down. The huge effective thermal capacitance of the oceans (about 30 times everything else) will cause the decline to be only about 0.13°C per decade. The decline may be as much as 0.22°C per decade if the sun goes really quiet.

Vince Causey

R Gates,
“but mathematically, 17 years is the minimum to be able to statisically be able to see the anthropogenic warming signal among the noise”
Oh come on. This 17 years is just a made up number to buy a few years more time. “Mathematically” indeed!

Given that even warmists concede that an anthropomorphic climate signal is so weak that it takes decades to be identified and quantified, doesn’t this rather undermine the catastrophic tipping point thesis?

Vince Causey

“This makes it easier to identify a slowly-emerging signal arising from gradual, human-caused changes in atmospheric levels of greenhouse gases,” Santer said.”
It’s a slowly-emerging signal now is it, this AGW? Only last week they were shouting about unprecedented rates of warming. It’s funny, this AGW theory. It’s the only theory in science that morphs into a different shape every time it conflicts with real data.

Ben Santer eh? I think this is an opportune time to remind WUWT readers who this Ben Santer is.
The notorious chapter 8 of the 1995 IPCC report included the claim that there was “A discernable human influence on climate.” This claim was added to the report AFTER the meeting of the drafting scientists in Madrid Spain.
Who added the claim? Ben santer.
Where did he get the notion of a discernable human influence? From his own paper which wasn’t even published yet. And in that paper he profoundly cherry picked a time frame of data from sonde balloons.
The full explanation and graphs are at the below link.
http://www.john-daly.com/sonde.htm
This man has the cheek to claim sceptics cherry pick.

janama

OK – let’s look at the past 17 years. (using the satellite figures as it covers the whole planet not just the land)
http://www.woodfortrees.org/plot/uah/from:1994/plot/uah/from:1994/trend
A warming trend of 0.14 per decade or 1.4C over the Century. Nothing significant and not even close to the computer predictions.

R. Gates says:
November 17, 2011 at 12:53 pm
Gates do you actually believe what you wrote? Do you? really do you?

Fred Allen

Ben Santer’s trying to delay that Senate inquiry freight train as long as he possibly can.

Fred Allen

R. Gates…is it difficult trying to justify a lack of warming with a cartload of technogarbage? How’s that consensus holding up?

R. Gates

Vince Causey says:
November 17, 2011 at 1:59 pm
R Gates,
“but mathematically, 17 years is the minimum to be able to statisically be able to see the anthropogenic warming signal among the noise”
Oh come on. This 17 years is just a made up number to buy a few years more time. “Mathematically” indeed!
———–
Wrong. Read the study before mouthing off.

R. Gates

Baa Humbug says:
November 17, 2011 at 2:12 pm
R. Gates says:
November 17, 2011 at 12:53 pm
Gates do you actually believe what you wrote? Do you? really do you?
———-
Tell me where I am in error, and why I shouldn’t.

JimF

The most important aspect of this press release is to identify at least six people to arrest and prosecute for fraud and theft of taxpayer funding immediately, and a whole host of others to begin to investigate for prosecutorial purposes in the long run. It will require that the statutes of limitation be extended to 17 years to bag them all. There’s an entirely new career path for aspiring tort lawyers.

Latitude

“A single decade of observational temperature data is inadequate for identifying a slowly evolving human-caused warming signal”
“by roughly 0.9 degrees Fahrenheit since the beginning of satellite temperature records in 1979”
=============================================================
A full 1/3 of the record shows cooling…..
……and for the math challenged, 17 years is a little more than 1/2 the record, and almost all of that neutral or cooling
Obviously, 30 years is not what they want to see either……….

harry

Climate scientists have argued that satellites have confirmed that the radiation spectrum is showing an increase in energy absorption in the CO2 bands over this period, and that the atmosphere is therefore “trapping” more energy, can they explain where the energy is being diverted to, since it isn’t warming the atmosphere. Claiming that a natural cycle is at play is fine, but the energy is either being held in a large reservoir (which noone has detected or measured any changes in) or it is being expelled from the Earth (and again it appears noone has detected any change). So where is the energy being held since it isn’t showing up in the atmosphere?
I’d argue that the “missing heat” needs to be found or the basic assumption that more energy is being trapped needs to be revisited.

ROM

A year or two ago the Skeptic commentary on WUWT and other skeptical orientated blogs were very defensive of the skeptical arguments regarding the source of the so called AGW and the skepticism that increasing anthropogenic CO2 was the cause of any significant global warming.
In the last year or so and particularly when i read the comments above, the Skeptic commentary has become increasingly derisory of the ever shriller and ever more desperate fear mongering claims of, and to use Richard Bett of the UKMet’s definition, the “climate change scientists” and the self promoting green climate change activists.
Skeptics have recently become increasingly cynical about the suspected and gross ulterior motives driving the claims of so many of the “climate change scientists”, and the shrill howls of outrage from the green lobby as their lavishly funded pet climate projects fall away as a jaded public turn their backs onto their increasingly desperate attempts to install a permanent “climate fear” psychology into the public psyche.
Within the last year the Skeptics have seen an increasing volume of evidence, including much more science based evidence plus ever more extreme quotes from warmists and the green climate activists plus an increasing volume of anti warmist anecdotal evidence from numerous sources to back up and reinforce their skeptiscm.
What a difference a year makes!
And Consensus!
What consensus??
Haven’t heard that word for quite a while now.

Latitude

Baa Humbug says:
November 17, 2011 at 2:12 pm
R. Gates says:
November 17, 2011 at 12:53 pm
Gates do you actually believe what you wrote? Do you? really do you?
==========================================
Of course he does….
He believes that it would have been a lot colder, if it weren’t for “A” global warming….
…so cold, it would have erased all traces of “A” global warming
…and the temperature would be below where it was when we started
😉

Werner Brozek

“See phil Jones’ interview:
http://news.bbc.co.uk/2/hi/science/nature/8511670.stm
A – Do you agree that according to the global temperature record used by the IPCC, the rates of global warming from 1860-1880, 1910-1940 and 1975-1998 were identical?
So, in answer to the question, the warming rates for all 4 periods are similar and not statistically significantly different from each other.
Here are the trends and significances for each period:
Period Length Trend
(Degrees C per decade) Significance
1860-1880 21 0.163 Yes
1910-1940 31 0.15 Yes”
It is generally assumed that CO2 was not a major factor before 1945. So it seems as if nature was quite capable of producing warming trends of 21 and 31 years without any human influence. What am I missing here with regards to Dr. Ben Santer’s 17 years? It seems as if 31 years is not enough. I would suggest we wait 31 years to see if we get a definite signal and not spend a penny in the meantime on things that may not be necessary.

William

The lack of warming for 15 years followed by cooling for the last 7 years supports the assertion that the planet resists climate forcing changes (warming or cooling forcing changes) by increasing or decreasing clouds in the tropical region.
It should be noted that the so called “deniers” quote peer reviewed published paper that support the assertion that the planet’s response to any forcing change is to resist the change (negative feedback) rather than to amplify the forcing change (positive feedback).
The extreme AGW paradigm promoted by the IPCC requires that the planet amplify the CO2 warming forcing. Whether the planet’s response is to resist or amplify the CO2 greenhouse warming is the key fundamental issue.
No one disputes increases in atmospheric CO2 cause some warming.
It is curious that those promoting the extreme AGW do not discuss or acknowledge is a key fundamental scientific issue.

Matt G

Seventeen years is just used to delay the obvious that many of us have known for ages. The goal post keeps changing because a number of alarmists won’t admit defeat, when it is staring them in the face. It is now 17 years because this is the longest period that the scare came about from. The world has only warmed for 17 years over the last 77 years and this cherry picked period is used to predict CAGW alarmist nonsense. When the minimum to determine a climate signal becomes longer than 17 years, no period with a greater length has any credibility because it becomes longer than the scare in the first place. Remember folks the scare first started in the 1980’s after a period of less than a decade of global warming.

RiHo08

Natural variation has currently dwarfed the climate changing CO2 signal. We have seen it before and we are seeing it now. The only problem with this theoretical approach, i.e.. we have had pauses in global warming before, does not address the unprecedented rise in CO2 we humans are causing, especially over the last 10 years. The Earth’s reported fever could be related to just bad surface temperature data; or, that the connection between CO2 and temperature via the trace gas radiative transfer model is…ah…imperfect. Or, and this is my thinking, that what is observed in the wet bench physics lab of CO2 and temperature is irrelevant to global atmosphere and its modulation between air and oceans. Maybe CO2 and temperature just aren’t important; other phenomena play a far larger role. Capricious connected oscillators may rule the day/night/seasons we observe.

Bob

17 years….The goldilocks number.

“In order to separate human-caused global warming from the “noise” of purely natural climate fluctuations, temperature records must be at least 17 years long, according to climate scientists.”
This is simply backward. Natural fluctuations are not noise, it is what it is. The man made signal, if any is the damn noise here. That is why it is so difficult to find. The operative is “if any”.

Gates’ post @12:53 pm is just Gates being Santer’s water boy. And of course, Santer is full of crap. Sixteen years, nine months is too short a time frame, but 17 years is OK?
Ri-i-i-i-i-ght.

Nick in Vancouver

Mr Gates, you are making an assumption that “it”, the anthropogenic signal, is there in the first place. If you cannot see “it” over the last few years you then assume that you need more time to see “it”. Either way AGW as a theory has been falsified. Either “It” is not powerful enough to counteract natural variation, or there are other natural factors now operating that were either ignored or were or are unknown or there are so many unkowns, including “it” that we cannot model climate. Your analogy is amusing but simplistic. Reality is complex and inconveniently unknowable. 2 more years of looking for “it” won’t help IMHO. 2 more years of payroll for Ben, Michael, Phil and Kev however is not amusing.