Via Eurekalert and Wiley-Blackwell
The human cause of climate change: Where does the burden of proof lie?
Dr. Kevin Trenberth advocates reversing the ‘null hypothesis’
The debate may largely be drawn along political lines, but the human role in climate change remains one of the most controversial questions in 21st century science. Writing in WIREs Climate Change Dr Kevin Trenberth, from the National Center for Atmospheric Research, argues that the evidence for anthropogenic climate change is now so clear that the burden of proof should lie with research which seeks to disprove the human role.
In response to Trenberth’s argument a second review, by Dr Judith Curry, focuses on the concept of a ‘null hypothesis’ the default position which is taken when research is carried out. Currently the null hypothesis for climate change attribution research is that humans have no influence.
“Humans are changing our climate. There is no doubt whatsoever,” said Trenberth. “Questions remain as to the extent of our collective contribution, but it is clear that the effects are not small and have emerged from the noise of natural variability. So why does the science community continue to do attribution studies and assume that humans have no influence as a null hypothesis?”
To show precedent for his position Trenberth cites the 2007 report by the Intergovernmental Panel on Climate Change which states that global warming is “unequivocal”, and is “very likely” due to human activities.
Trenberth also focused on climate attribution studies which claim the lack of a human component, and suggested that the assumptions distort results in the direction of finding no human influence, resulting in misleading statements about the causes of climate change that can serve to grossly underestimate the role of humans in climate events.
“Scientists must challenge misconceptions in the difference between weather and climate while attribution studies must include a human component,” concluded Trenberth. “The question should no longer be is there a human component, but what is it?”
In a second paper Dr Judith Curry, from the Georgia Institute of Technology, questions this position, but argues that the discussion on the null hypothesis serves to highlight fuzziness surrounding the many hypotheses related to dangerous climate change.
“Regarding attribution studies, rather than trying to reject either hypothesis regardless of which is the null, there should be a debate over the significance of anthropogenic warming relative to forced and unforced natural climate variability,” said Curry.
Curry also suggested that the desire to reverse the null hypothesis may have the goal of seeking to marginalise the climate sceptic movement, a vocal group who have challenged the scientific orthodoxy on climate change.
“The proponents of reversing the null hypothesis should be careful of what they wish for,” concluded Curry. “One consequence may be that the scientific focus, and therefore funding, would also reverse to attempting to disprove dangerous anthropogenic climate change, which has been a position of many sceptics.”
“I doubt Trenberth’s suggestion will find much support in the scientific community,” said Professor Myles Allen from Oxford University, “but Curry’s counter proposal to abandon hypothesis tests is worse. We still have plenty of interesting hypotheses to test: did human influence on climate increase the risk of this event at all? Did it increase it by more than a factor of two?”
All three papers are free online:
Trenberth. K, “Attribution of climate variations and trends to human influences and natural variability”: http://doi.wiley.com/10.1002/wcc.142
Curry. J, “Nullifying the climate null hypothesis”: http://doi.wiley.com/10.1002/wcc.141
Allen. M, “In defense of the traditional null hypothesis: remarks on the Trenberth and Curry opinion articles”: http://doi.wiley.com/10.1002/wcc.145
Trenberth points to two errors with testing for the null hypothesis. Type I is rejecting the null hypothesis in error. Type II is accepting the null hypothesis in error. Matt Ridley’s claim that the there are strong confirmation biases suggests the opposite of Trenberth – that a Type I error is far more likely. This is indicated in the article references. Only one of the papers is outside the subject area of climate science. To justify deviating from normal scientific method Trenberth needs to demonstrate.
1. Why Climate “Science” should be made a special case – with comparisons from other empirical sciences like economics.
2. A strengthening of procedures to help eliminate confirmation bias.
3. Appropriate discussion of the differing perspectives in the philosophy of science and statistical theory.
Kev-in-Uk says:
November 3, 2011 at 3:49 pm
I have a question for those who care to answer:
It is – do any of you discuss the null hypothesis with others?, and I don’t mean others of a scientific bent (who should understand – unless they are called Trenberth!) – I mean more of the typical layperson, kind of in discussion at the pub.
____
By now you should have realized that the average bloke in the pub doesn’t give a rats ass about any of this. We are a “special” breed that frequent here, and while our friends may tolerate our warmist or skeptical rantings, they generally couldn’t care about the details, and they won’t until it hits them in the pocketbook, washes away their house, causes the price of food to skyrocket, or the shelves are simply empty. As long as the shelves at Walmart are full of goodies with “low low prices”, none of this will attract the typical layperson’s attention.
His stated Null hypothesis is wrong and evidence of the fuzziness of the whole field.
Logically, humans MUST have some effect on the environment. There is no chance this is wrong. Zero, zilch, zip, nada!.
It would be like creating a null hypothesis that 1+1 2.
Be careful.
Prior to the posing of the null hypothesis is a process step involving observation of the aspect of nature you want to study.
Prior to that ‘pre null hypothesis’ observation of the aspect of nature you want to study is an even earlier process step involving formulating premises that give you reason to study that aspect of nature.
Prior to the selection of those premises is an even earlier process step of deciding what is objective scientific non-confirmation biased knowledge. How you know what knowledge is.
Leaping to define a null hypothesis without those prior steps leads to the fundamental cause of Trenberth’s epistemologically and metaphysically flawed argument for reversing the null hypothesis. He has an absence of the prerequisite sequential process steps that lead to understanding the proper concept of the null hypothesis in determining objective scientific knowledge.
Do not start incorrectly building the scientific argument at the positing of a null hypothesis; which actually is at the middle of the bridge of scientific knowledge. If you start there in middle without understanding a sequential chain of pre null hypothesis processes then Trenberth’s error will also be yours too.
John
Kev-in-Uk says:
November 3, 2011 at 3:49 pm
I have a question for those who care to answer:
It is – do any of you discuss the null hypothesis with others?, and I don’t mean others of a scientific bent (who should understand – unless they are called Trenberth!) – I mean more of the typical layperson, kind of in discussion at the pub.
————-
Absolutely. Every argument must have a basic premise to start with. When debating any subject “at the pub” my first question will often be, what is your basic first premise. What’s your default position. AKA, what’s your null hypothesis. One cannot have a rational discussion without first stating what one’s position is. Thus it’s used in non-science discussions as a base from which each person bases their argument.
John Whitman says:
November 3, 2011 at 4:54 pm
Be careful.
Prior to the posing of the null hypothesis is a process step involving observation of the aspect of nature you want to study.
Prior to that ‘pre null hypothesis’ observation of the aspect of nature you want to study is an even earlier process step involving formulating premises that give you reason to study that aspect of nature.
Prior to the selection of those premises is an even earlier process step of deciding what is objective scientific non-confirmation biased knowledge. How you know what knowledge is.
Leaping to define a null hypothesis without those prior steps leads to the fundamental cause of Trenberth’s epistemologically and metaphysically flawed argument for reversing the null hypothesis. He has an absence of the prerequisite sequential process steps that lead to understanding the proper concept of the null hypothesis in determining objective scientific knowledge.
Do not start incorrectly building the scientific argument at the positing of a null hypothesis; which actually is at the middle of the bridge of scientific knowledge. If you start there in middle without understanding a sequential chain of pre null hypothesis processes then Trenberth’s error will also be yours too.
John
————
I’m going to disagree with this for the following reason. All other disciplines of science have discovered that the universe works on its own. There is no god twittling knobs, there is no high being on a different plain than the unverse making things happen. Which is what the pre-science era thought about the world. Since all other sciences shows us the universe is quite capable of existing, changing, and functioning all on its own, we can conclude that this includes climate science. Hence it is not unreasonable that when we see events happening in the climate or weather system to conclude that nothing more than natural causes are at work, even if we do not yet understand or event see such causes. Hence the current null hypothesis. Science MUST work on the hypothesis that events we see have natural understandable mechanisms, which if we do not see them now, we will with future research. What Trenberth has essentually claimed is we know everything that can be known about how the climate system works. That is pseudoscience.
Richard Wakefield says:
November 3, 2011 at 5:01 pm
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Richard,
Within a few minutes we posted some similar concepts on what occurs prior to the middle step in the scientific process; the middle step being making the null hypothesis.
John
The null hypothesis is that mankind has a very poor understanding of climate. No one has come close to falsifying it.
Richard Wakefield,
I agree with virtually 100% with what you just said.
Therefore, I am curious how you disagree with what I said.
Appreciate your thoughts.
John
The science is settled, therefore, the null hypothesis is void.
I’m confident that part of the problem is that people like this wish/dream that they were real scientists. For example, in Medicine if you have a known drug that is effective in cancer and would propose another drug is more effective, then you have a control and experimental group…contrasting the effective drug with the maybe more effective drug.
You do this because people will die without any drug. So the null hypothesis is referenced against the known effective drug. There is simply no way that anyone can argue that whatever physics underlie AGW that the certainty is comparable to oncology.
Why is it that the climate communists hippies always regard the negative of anthropogenic influence but never the positive? I mean their idea that man’s influence on climate is negative can be mitigated by man’s influence creating positive, so surely, even in their world, man does positive, like for instance planting trees.
So why is it that only rational capitalists plant trees while the climate communist hippies only plant weeds and windmills? By the very lack of their care of the land weeds take hold and energy companies’s short term strategies destroys forests for a 3-1 return in tax-dollar no matter what.
So, even in their own reality, they’re the bad apples for, climate (windmills apparently change local climate and global climate is just statistics of local climate, but besides every windmill needs a 1:1 existence of coal, gas or nuclear power plant on standby).
“Rob Honeycutt
. Dr Alley has clearly stated on many occasions that the GISP2 data is not a global proxy. It’s a regional proxy of the Greenland summit.”
Just how many global proxies are there?
How does a lay-man differentiate between a global and local proxy?
Why is the ring width of one tree a global proxy of temperature, but one ice core a local proxy?
rk,
Actually, the proven drug is the null hypothesis. The alternate hypothesis is the experimental replacement drug. The analogy to the climate null hypothesis is that the null is the pre-industrial Holocene parameters of temperature, duration, trend, etc., and the alternative hypothesis is CO2=AGW (or any other alternative hypothesis).
The past parameters of the Holocene must be exceeded in order to falsify the null hypothesis. But so far, the change in temperature has been very mild; during the Holocene temperatures have been many degrees above and below today’s temperature, while CO2 remained very low. Therefore the null hypothesis remains unfalsified, which is why Dr. Trenberth is so unhappy.
I agree with virtually 100% with what you just said.
Therefore, I am curious how you disagree with what I said.
Appreciate your thoughts.
John
——–
Guess I misread your post. sorry. Good to always clarify though, LOL.
Piltdown man. All climate scientists junking the null hypothesis are piltdown man makers, the missing no longer link between real scientists and all conmen using language to obfuscate in support of vested interests, their own.
I’m trying to figure out in all this if Trenberth has commited a Type 1 Error (mistaken evidence) or a Type 2 Error (missed the evidence). Let him respond to that–he doesn’t understand corroboration or falsification of a null hypothesis so it’s apparently more basic than that.
This one is ieasy, the Medieval Warm period was just as warm, if not a bit warmer, than now, no SUV’s needed.
My null-null hypothesis, 1000 years ago, mevieval man drove more SUV’s than we do. Makes just as much sense.
One thing, a hypothesis is testable idea, can the idea that man made all the warmth even be tested, on a world where we do not even know how the Medieval Warm Peroid came about, or the following Little Ice Age? Can such an idea be tested when it is being treated as a pseudoscience and thus above testing, when it is considered herisy to even subject it to test?
Rob Honeycutt. . . No, the chart that Gail references from Dr. Spencer is not from Alley’s GISP2 ice core data. It’s from Dr. Spencer’s website & he attributes it to Craig Loehle. It represents 18 non-tree ring proxies throughout the northern hemisphere (Africa, Asia, Europe & North America).
It wasn’t technically a ‘close up of the last 2000 years’ of the VOSTOK Antarctica chart since it was a NH proxy.
“By now you should have realized that the average bloke in the pub doesn’t give a rats ass about any of this. We are a “special” breed that frequent here, and while our friends may tolerate our warmist or skeptical rantings, they generally couldn’t care about the details, and they won’t until it hits them in the pocketbook, washes away their house, causes the price of food to skyrocket, or the shelves are simply empty. As long as the shelves at Walmart are full of goodies with “low low prices”, none of this will attract the typical layperson’s attention.”
—–
I find that to be incredibly snotty and snobbish: Allow me to make the following substitution:
By now you should have realized that the average bloke in the pub doesn’t give a rats ass about any of this. We are a “special” breed that frequent here, and while our friends may tolerate our ****socialist or free-market ****rantings, they generally couldn’t care about the details, and they won’t until it hits them in the pocketbook, washes away their house, causes the price of food to skyrocket, or the shelves are simply empty. As long as the shelves at Walmart are full of goodies with “low low prices”, none of this will attract the typical layperson’s attention.
**********************
Feel free to insert your own phrases. such as “liberal or conservative”, “religious or atheist”, etc.
My point: the American humorist Will Rogers once said, “We’re all ignorant, only on different subjects”.
That applies to you too, R. Gates. ESPECIALLY youl You embody the “progressive” idea that the public is stupid and must be guided (even at the point of a gun) by the Enlightened.
“special breed”, my fundament.
So lets apply the reversal of the null hypothesis to Dr. Kevin Trenberth. He is Head of the Climate Analysis Section at the U.S. National Center for Atmospheric Research in Boulder, Colorado.
JonBenét Ramsey, a six-year-old American girl who had competed in child beauty pageants, was made famous by her Christmastime murder… She was found dead in the basement of her parents’ home in Boulder, Colorado, on December 26, 1996, nearly eight hours after she was reported missing. The official cause of death was asphyxia due to strangulation associated with craniocerebral trauma. After several grand jury hearings, the case is still unsolved….. http://en.wikipedia.org/wiki/List_of_unsolved_deaths
There is an obvious correlation. Both have lived in Boulder, Colorado.
Therefore as a resident of Boulder, Colorado Dr. Kevin Trenberth, is obviously her murderer. It is now up to Dr. Kevin Trenberth to disprove that “Null Hypothesis” /Sarcasm>
Obviously I do not think Dr. Trenberth had anything to do with this little girl’s death just because they both lived in Boulder, Colorado. However Dr. Trenberth is trying to apply a similar type of logic when he tries to blame mankind for harmful “global warming” and then insists we must be disprove his allegation.
I admit I am only a interested observer, trained in Architecture (knows nothing about everything). But even I understand that in order flop the null hypothesis Trenberth must fully describe the new normal. We need an accurate basis describing life, the universe and everything, or at least the climate, in order to see what benefits accrue from all the money spent on saving the climate. Unfortunately Trenberth can’t do that but wants to establish IPCC models as the baseline. When the earth doesn’t warm as expected, the warmists can then claim how well the trillions of everything ($, yen, euro, dracmas) spent have been put to good use.
This is just a second order demonstration of the pathetic state of climate science compared with any other field of applied physics .
My understanding is that the notion of null versus alternate hypotheses came from the statistical testing field where in general a null hypothesis is an assertion that some phenomenon will be constrained to a subset , often a subspace , of the total universe of possible observations . The alternative is that the observations will fall in some disjoint subset . The extent to which observations fall outside either of these two subsets is considered noise . The null hypothesis is rejected if observations fall outside what can be expected even adding noise to the null subset . Generally the test stops there , simply rejecting the null without making any additional assertion with respect to the alternate , eg , 2-tailed tests.
This paradigm , while very useful , is only a tool in the overall enterprise of quantitatively understanding our world .
The real travesty in climate science is that the ubiquitously accepted null hypothesis is that the earth’s spectrum without the greenhouse effect of the atmosphere ( ie , its surface spectrum ) is approximately that of sort of a step function with an ( observed ) albedo of approximately 0.3 with respect to the sun’s spectrum but 0.0 with respect to the approximately 279 kelvin temperature of a gray ( flat spectrum ) ball in our orbit thus producing equilibrium temperature of about 255 kelvin . That’s a little colder than any real ball could be in our orbit .
A more appropriate , 0th order if you will , null hypothesis would be that our mean temperature is simply that of a gray ball in our orbit This is simply the temperature obtained by adding up the energy impinging on a point in our orbit ( essentially all from the sun ) .
This most basic assumption in fact explains 97% , all but about 10 celsius of our approximately 288 observed temperature . Making no assumption about spectrum is 3 times closer to our observed temperature than the hypothesis which confounds spectrum , a specific extreme spectrum , and total irradiance .
This is grossly incompetent physics . I’m not surprised that I have never seen the computations of forcings since whatever is done on the basis of the common 33c null is like trying to understand temperature in terms of celsius instead of kelvin .
“”””” R. Gates says:
November 3, 2011 at 4:28 pm
George E. Smith; says:
November 3, 2011 at 2:04 pm
The hypothesis IS that human influence on the climate has and will continue to drive the climate to a catastrophic state…
_____
Actually, no George, that is not THE hypothesis “””””
Well R, I’m simply using THEIR words; as to catastrophism etc.
So it is entirely moot whether anybody has precisely defined “catastrophe” as it applies to climate change. The fact is that Nobel prize winners; for their climate work, have used precisely that word, in describing the inevitable result of the whole world failing to immediately adopt their Draconian energy curtailment specifications.
So that IS the hypothesis; humans have already damaged the climate environment beyond repair; unless the whole of mankind, adopt their austerity measures.
So if you don’t like the message; get THEM to change it to what YOU believe is more appropriate.
As for me, I’m quite convinced beyond any reasonable doubt, that if we do precisely nothing other than normal attention to our sometimes (real) “polluting behavior”, that this planet will remain quite safely habitable as far into the future as our “intelligence” will allow us to survive as a viable species.
It is the water that is in total feedback (negative) control of the global Temperature; it does that by the surprising, and unlikely mechanism of actually altering the incoming solar energy that drives the climate system; and it can easily eradicate any minor perturbation such as the minor effect on outgoing LWIR because of CO2 or Ozone or other GHGs (other than water).
What a concept; to actually study the feedback correction to the actual real driving input signal, rather than some ancillary energy leakage path; after the incoming energy has been stored.
So if YOU disagree with the term “catastrophic” then take it up with those who introduced it into the “science” discourse; and in IPCC/Gore/Trenberth et al; for it wasn’t me.
I really struggled to bring myself to read this article since I find The Trenberth proposition so depressing. How any scientist could hold such a view (or support such an approach) beggars belief.