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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1, 2 and 3, all move the goal posts…
What will happen is the new minimum for determining a human influence on climate will be 20 years.
[snip. Read the site Policy. ~dbs, mod.]
I wanna beat the crap out of that man.
BTW, whats exactly that human fingerprint? Failed hotspot?
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.
“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”
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…
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.
“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.
“The positive trend is quite close to the significance level. ”
Fuzzy isn’t part of mathematics.
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…
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.
“The positive trend is quite close to the significance level. ”
Translation: The positive trend is not significant.
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.
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…
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… ;))
God (WMO) says 30 years. So there, Santer.
I say 300 years.
“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.
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.
The correct number is of course 42.
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 (?)
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.
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.