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
R. Gates says:
November 17, 2011 at 12:53 pm
—
The problem is that we don’t know what all the natural signals are.
So your claim that the human signal can be detected by subtracting the natural signals is nonsense.
Santer et al base their conclusions upon a psychological theory of how people make decisions under uncertainty; this theory is called “signal detection theory.” As a guide to making policy decisions, signal detection theory suffers from the shortcoming that people are prone to making decisions illogically. Interestingly, logic and Santer et al reach opposing conclusions about the merits of waiting until a period of 17 years has elapsed without significant global warming before concluding that the anthopogenic global warming hypothesis must be rejected.
In logic ( http://judithcurry.com/2011/02/15/the-principles-of-reasoning-part-iii-logic-and-climatology/ ) , a theory is a procedure for making inferences. The task of the theoretician is to build an optimal decoder of a message consisting of the outcomes from a specified sequence of statistically independent statistical events. Each of these events has a duration in time that is identical to the period of waiting. As this period increases, the number of observed statistical events that are available for training the decoder decreases toward 0 and the lack of information provided by the optimal decoder increases toward a maximum. At the maximum, determination of the current state of nature provides no information about the future outcome. For example, determination of the current CO2 level provides no information about the future global surface temperature.
The Hadcrut3 global temperature time series provides us with no more than about 12 observed statistically independent statistical events of 17 year duration but 12 events is by a factor of 10 or more too few for the training and statistical validation of an optimal decoder that provides any information at all about the outcome. The conclusion of Santer et al that there is merit in waiting for a period of 17 years is illogical for if we wait this long we will have no information about the outcomes of our policy decisions.
Pamela Gray,you said
“But a magic number says nothing about what is causing the trend.” You are quite correct . This what I tried to say earlier too. One of the key variables or causes of for the colder climate is the pattern of the amount of colder water in the Northern and eastern Pacific as indicated by PDO. The global cooling of temperatures seems to coincide with the declining PDO levels from peak to trough . The post 1934 , 10-15 cooling period started with dropping PDO levels which went negative by 1944. This was followed by a 30 year global cool period. Currently the post 1998, 10-15 year cooling period coincides also with a declining PDO readings which started its decline in 2003 and went negative in 2007 . Long term cooling of 20 to-30 years may again be indicated .People can wait for 17 years or even 30. To me statistical significance has very little to do with why a cooling trend is most likely indicated as a the key cause or variable better confirms what is probably ahead and there is historical patterns to support this.
A google image search for “Ben Santer” now contains the promo pic for Marilyn Monroe’s “The Seven Year Itch” and a link to this posting.
Congratulations!
It’s on page 2 and isn’t nearly as entertaining as the top line image of a cartoon baby crying its eyes out but still.
http://www.google.com/search?hl=&q=%22ben+santer%22&sourceid=navclient-ff&rlz=1B3GGHP_en___US455&ie=UTF-8&biw=1280&bih=615&sei=LqfGToKBJqOesQKjqvkj&tbm=isch
Santer says:
—–“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……
….. Think of 40 institutes with their Millenium forecast 2001 (TAR +SRES) on rapid global warming of 0.2 C per decade………they included everything in their models, they say….?
Now the newest SREX of Nov 2011, no more global warming for 30 years…..? This is the IPCC latest……what now, yes or no, warming no warming ……
Our models, our wonderful models, believe in the models and in CO2, not in nature, not in reality…..the models are the one and only truth. The AGW alarmists are the true scientists….
the sceptics are the the “anti-science people”…..
matt v. November 17 at 1:44pm
matt v. November 17 at 4:20 pm
matt v. November 18 at 11:00 am
Excellent comments matt. Easy to understand, and esy to remember the main points – in case I decide to honorably steal your comments; with the due credit, of course.
The first warmist commandment remains “Thou shall’t not doubt AGW …..ever”. (Despite any evidence to the contrary by evil AGW deniers) , So it wouldn’t matter if we had 20 years without warming ,these warmists would still be wetting their pants.
Why talk about only 17 years? It is demonstrated that change to the level of atmospheric carbon dioxide has had no significant influence on temperature for at least the last 115 years in the pdf made public 9/24/11 at http://climaterealists.com/index.php?tid=145&linkbox=true
davidmhoffer says:
November 18, 2011 at 5:24 am
“And best of all, he hasn’t said boo about my observation that he only shows up in threads where people like Mann and Santer and Trenberth (especially Trenberth!) are being exposed or questioned in any way.”
_____
I’ve commented more than enough on the points you continually want to bring up. Seems like you’re rather like a broken record. In terms of me “showing up”, I comment when something strikes my interest, but you’d like to read something more into it– which indicates even more to me that you are clearly rather good at fictionalizing reality.
MarkW says:
November 18, 2011 at 9:22 am
The problem is that we don’t know what all the natural signals are.
So your claim that the human signal can be detected by subtracting the natural signals is nonsense.
_____
No, not really. I suggest you read a bit more about global climate models before making such a overly broad statement. These are very sophisticated, and involve extremely detailed knowledge of atmospheric and ocean physics and dynamics. It is true that we don’t know the full details and feedbacks of the natural and anthropogenic signals, and with a dynamical chaotic system, we never will. But we certainly know the major forcing agents. But finding a the human fingerprint on the climate is not simply about subtracting the natural signals and finding out what’s left, but plugging into the models the dynamics and physics of what the human forcings ought to do, and seeing what the fingerprint ought to look like over a given period of time. The “subtracting” that you talk about is really about short-term and medium-term noise filtering (removing the effects of ENSO for example) so that you can see if the pattern the models tell you should be there is actually there.
R. Gates;
Just an observation my friend. If you could point out some threads that you’ve commented on that show otherwise, I’ll be glad to check them out and see if I am wrong or not.
As for commenting “more than enough”, well actually you haven’t. Oh you’ve commented all right, lots and lots of meaningless comments. But it doesn’t matter how much you say if you don’t answer the questions asked of you, or admit when your are wrong. You instead avoid, distract, come up with excuses, post links to immaterial articles, but answer the questions? Nope. Man up to the bet you made? Nope. Admit your errors? Nope.
And this comment is yet another fine example. If you had actually answered the charges I made, you could just cut and paste, or post a link. Instead you imply that you’ve answered when you have not.
Is that not rather disingenuous?
R. Gates says:
November 18, 2011 at 6:27 pm
…plugging into the models the dynamics and physics of what the human forcings ought to do, and seeing what the fingerprint ought to look like over a given period of time.
Ought to do in what environment? And how is that confirmed? Avoid the travesty.
R. Gates:
You talk of models, GCM’s. I can only adivse you to read section of of AR4. Carefully read each subsection, notice the certainty, and then add in the totals to the end product.
With the levels of uncertainty, the end product is really quite worthless.
A glariing example of models uncertainty is the stratosphere. It is not cooling, which indicates something wrong with the calculations of the models.
http://adsabs.harvard.edu/abs/2008AGUFM.A12B..01S
I can only encourage you to read the last line and think about the implications. Some would have you believe that the strat is still cooling. They are in la la land and deny the science.
“The phaseout of chlorofluorocarbons after the 1987 International Montreal Protocol now shows positive effects on ozone in the upper stratosphere. However, due to increasing CO2, the CCMs simulate a continuous linear cooling by 1~K per decade over the entire 1979 to 2010 period. This is not consistent with the near-constant temperatures observed since the late 1980s.”
“
R. Gates,
That is section 8 of AF4.
I wouldn’t want you to miss the opportunity to increase your knowledge.
R. Gates:
One more time I will try and type this correctly:
Section 8 AR4.
I think I got it this time.
R. Gates:
I would also have you note that the time frame of the observations exceeds 17 years. With that in mind, the GCM need to be revised to show the proper responses to the strat concerning the radiative powers of co2. Something is wrong here.
Strat not cooling, longer than 17 years. What else is wrong with the models that is concerning to all?
Camburn,
The pdf made public 8/11/10 at http://climaterealists.com/index.php?tid=145&linkbox=true shows some of what is wrong with the models.
The above seems somewhat related to the following (2009)
http://www.nytimes.com/2009/09/23/science/earth/23cool.html?_r=2
”
Underscoring just how little clarity there is on short-term temperature fluctuations, researchers from Britain’s climate change office, in a paper published in August, projected “an end to this period of relative stability,” with half the years between now and 2015 exceeding the record-setting global temperatures of 1998.
”
[I have not seen the paper itself.]
If we use HadCru3
http://www.cru.uea.ac.uk/cru/data/temperature/hadcrut3gl.txt
then I guess the correct number to use is the last column—annual anomaly-{I think—please correct me if I am wrong}.
For 1998 it is ..548. No number below it is even close (2005 is .482) and it is clear that 2011 will also not be close.
This leaves 4 years 2012-2015 to beat .548 three times. It seems unlikely.
I guess if it does not happen the Hadley center will close its model and announce that all papers based on it are now meaningless :>).
All this fuss about warming is based on SURFACE temperatures (ie: those usually measured about 54 inches above concrete, asphalt, and maybe grass). What about the remaining 99+% of the atmosphere that resides more than 4-1/2 feet above grade? Is it not obvious where the bulk of temperature measurement must be made to get a more representative sampling of the atmosphere’s condition?
In the absence of a quest for such knowledge in this area, one can only conclude that temperatures above the surface DO NOT support global warming theory. If they did, we would not be hearing the end of it.
“rdr200 says:
November 19, 2011 at 10:30 am
This leaves 4 years 2012-2015 to beat .548 three times.”
And if you check the NINO 3.4 Ensemble Forecast on WUWT, it goes to August and the highest one does not even reach 0 in all this time, so if the La Nina persists until then, there is no hope that 2012 will set any record.
Thank you very much for that link where it says:
“the odds of a 15-year pause, they wrote, are only 5 in 100”
If there are no drastic changes, and I do not expect any with the present La Nina forecasts, that point will be reached on HadCrut3 next May.
I wonder if this then means they will be only 5% sure that CO2 causes any warming?
I think some people are missing the point here: If there’s lots of year-to-year variation, as there is with the global average surface temperature (due to El Nino, the solar cycle, volcanic activity etc) then short time series are very unlikely to show statistically significant upward trends in global temperature. That doesn’t mean there isn’t a long-term upward trend, just that the sample size is too small to yield statistical significance. If you include more years in the analysis, the trend becomes statistically significant.
Those who don’t believe that anthrogenic CO2 emissions are causing a rise in global temperatures need to explain what other mechanism has caused the clear rise in global temperature over the last 150 years, and need to put forward sophisticated models with a high degree of predictive skill to back up their arguments. However, they have so far clearly been unable to do either of these things. In contrast, the evidence for anthropogenic global warming is compelling, if you care to read it with an open mind.
Rob Nicholls (Dec. 2, 2011 at 2:22 pm):
One thing we don’t have from the proponents of AGW is “models with a high degree of predictive skill.” The IPCC’s climate models make projections of global temperatures and not predictions. While often confused, projections and predictions are different concepts.
Hi, it has already been done: Transparent calculations for everyone to follow, easy to understand,
never refuted or rebutted, just correct to the last number….. please see booklet ISBN 978-3-86805-604-4, available for 12 EU at the German Amazon. de…… Therefore,
no more ridiculous assumptions please, that skeptics cannot figure out global warming/cooling mechanism. My book even shows how to meticulously calculate the mechanism of “Dansgaard-Oeschger events”,
which is exactly the same warming/cooling mechanism as of today. None of the Warmist bunch with all their recent collutions (Climategate 2) is able to do this…..
The author JS.
As for the “significance level” of any flat or warming or cooling period, the Team keeps (apparently successfully) trying to convince the world that 95%, or in a pinch 90%, confidence levels constitute “statistical significance”. Given the huge zoo of potential biases and contamination of data and analyses, this is outrageous. And given the cornucopia of free (fudgable) parameters in the models, almost certainly also mendacious.