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
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One has nothing to do with the other so what is the purpose of tying them together?
Look at it from the converse. Assume there is no human impact, that none was ever suspected to begin with and our endeavor was purely to understand what the optimum conditions are. Imagine how much more efficacious the research could be if no one had a political cross to bear in regard to human ‘blame’ which seems to be the real ‘crux of the matter’ right now – a borderline mass psychosis I’d say.
When the real possibilities are that we are changing our climate a lot or not much at all, talk of null hypotheses either way is utter nonsense. The issue is quantification of the amount of change. If it is a lot then some action should soberly considered. If it is a little then maybe we live with it and try to trim our emissions over time in a rational manner. To postulate a null hypothesis is to set it up to fail as there will almost certainly be some at least arguable AGW. To set up a ‘reverse null hypothesis’ is to set it to be all but impossible to refute. ANd this is the level of debate by our appernently finest minds. Good Grief!!
I’ve just completed an analysis to determine what fraction of the atmospheric CO2 is anthropogenic and what is natural. click on my name for details.
and with attention to spelling the last bit reads
And this is the level of debate by our apparently finest minds. Good Grief!!
Dr. Trenberth is as fine a practicing scientist as Dr. Trofim Lysenko; the out come of following the the ‘science’ of either leads to the death of tens of millions.
AGW is real and has been since the first human killed the first methane belching herbivor.
Saying AGW is real as if it were some kind of argument is ludicrous beyond words.
Since no-one has actually proven with empirical data that humans are causing significant change, why should anyone even bother with proving the opposite?
Roy Spencer might be on to something Gail – maybe the Vikings somehow managed to trigger the Little Ice Age? Then they were actually the first humans to cause climate change and now we’re just slowly clawing our way back from all the trouble they caused?
I like it! Let’s get some more money to research that theory too; just put it on the charge card.
Russ he claims the missing heat is on vacation in the deep ocean where it’s usefully hard to measure and even better it seems to have got there by avoiding the upper layers where there are measurements, lucky that !
Unbelievable. I read Trenberth’s “paper” and i wanted to puke. What a pile of BS from first letter to last period. And this passes as science? How sad it has become. I, non-scientist, could write pages showing the assumptions, lack of logic, and pure speculative arguments in his paper. Take this:
“The times when extremes break records are especially the cases when natural variability, such as El Niño, is working in the same direction as human-induced warming”
Breaking records? Does he not understand that our record system is puny? It’s barely 100 years old, and old records which are thin and sporatic. Take temperatures. When records started to be taken EVERYDAY was a record breaker! As time goes on, and more records accumnulate, the number of record breaking temperature days drops in a decay curve. This is because slots of what the temperature can be start to get filled in. For example. If the temperature of July 1 of any year can be no lower than 20c and no higher than 40c, with 0.1c slots, how many years would it take to fill them all? That’s 200 slots to fill!! In only 100 years? Please…
I decided to test how long it would take to fill all the slots with a simple simulation. If you just use a random number generator, I fould that it would take some 1000 years to fill all the slots. If you use a gausian curve to add probability for any given slot (higher/lower range temps the least likely), then it would take some 6000 years to fill all the slots!! Record breaking days is an accounting issue, not a indicator of changing temps.
The FACT is, for Canada and a few other locations I have checked, the VAST majority of record summer high temps were BEFORE the 1950’s.
His Fig 1 is also grossly misleading because there is no time frame. One assumes that, if temperature is used, that the “normal” was from 1945-1975 and the “abnormal” shifted curve is 1975 to 2000. Hence using that as the dataset for comparison is missing a major property of the climate system — oscillations. What if the apex of the curve vibrates with a frequency of more than 30 years? All Trenberth is doing is showing some portion of that vibration.
Of course the most rediculous comment in his paper was: “Besides, there is no other viable explanation to the observed temperature changes.” Is he a god of some kind? Geeze!! Classic god of the gaps. “Just because we don’t know a natural cause means it MUST be a human cause.” And this is science? Please…
I think everyone is missing the point.
Trenberth and the AGW faithful are clearly unable to prove/demonstrate that man’s production of CO2 causes global warming. So, as a clear admission of failure, he turns the question around.
That’s smart reasoning, political reasoning – and most important of all, it could just keep the grants coming for a few months longer.
The activities of Man undoubtedly affect the climate at local level and possibly a little at the global level. However, soot (an activity of Man) is probably a far greater cause of glacier and Arctic ice melting than CO2, but that kind of reasoning cuts the grants’ umbilical cord.
Soot causing glacier and Arctic ice melting is simply not a scary story, and without scary stories the funding of the AGW cult through grants will come to a grinding halt.
Trenberth is admitting failure – he just may not realise it yet.
“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.”
Anthony, I would love to see a sidebar link to Donna Laframboise’s book. This should be required reading.
Gail Combs… Actually the chart you’re attributing to Dr Spencer is the GISP2 ice core data and should be properly attributed to Dr Richard Alley. 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.
That’s the problem with Post Modernist Science, it’s not scientific enough to give definite answers, only vague opinions and beliefs.
When you dedicate a large part of your working life to a theory and it all goes pear shaped it is difficult to admit you are wrong. So Trenberth and friends hang on to their lunacy but only get away with it because the politicians and the media have dug an even bigger hole than the scientists. It beggars belief…but just remember that 1.5b on this planet have no access to fresh, clean drinking water, sanitation and power….and it is the likes of Tenberth that keep these poor souls in this misery. Technology in it’s various forms should be for the benefit of all mankind.
OMG, this is truly “crack-pottery”.
In classic debate, the rules of rhetoric specify a variety of sins and logical fallacies that are regularly attempted by one side or the other, and are either disallowed on the spot, or are pointed out by one’s opponent when it’s his turn to stand up and reply.
One such major sin goes by the not so obscure Latin name of a “petitio.” Which refers literally to an act of “begging.” Just as Trenberth is essentially “begging” that the rules of the argument be modified in such a way as to grant him, as already proven, the terms of the debate itself. As in: “AGW should now be assumed as fact before we go any further, even though no completely conclusive evidence has been introduced to prove it, because…”
“Well…because it makes it a whole lot easier for me to prove that AGW is the correct hypothesis if we do that..” Just go ahead and assume that AGW is the correct hypothesis and it has already been magically demonstrated as such. Of course Trenberth wants to dress it up in scientific language a bit by identifying it as a simple procedural change in the “Null Hypothesis,” but begging is what he’s doing, begging that we grant him his argument as a condition for continuing to participate in the argument itself.
This begging aspect, or petitio, is what is known in formal rhetoric and debate as the sin of “begging the question.” That’s what the term “begging the question” properly refers to. It’s a forensic term used in debate in the English speaking world to designate that specific (attempted) sin. It’s very useful.
Somewhere sometime a few years back, some quarter-educated journalist, probably just out of a privately endowed educational institution, overheard two or more older and smart-type people discussing an issue in the form of a polite argument, or casual debate, and he heard one of them respond with, “No wait, that begs the question.” And then he made the regrettable assumption that he knew what was being said – that the smart type person must have meant something like “No wait, that just forces me to ask you this, then: blah-blah-blah…”
And regrettably the kid started misusing the term down at the local boozer to impress his similarly quarter-educated date and friends. All of whom, including himself, carried it off to work with them the next day and started trying it on all and sundry, in writing articles, interviews, etc. on TV, over and over until it became a veritable virus among those too lazy to look it up. While thinking themselves hugely sophisticated while doing it. You hear it all the time now.
And we have all been the poorer for it.
It drives me nuts, because a lazy, casual vandalism of the English language is far worse than vandalism against, say, a restroom mirror or a toilet stall. It takes a lot of bright people several thousand years longer to build a language and its tools than it takes to build a toilet stall, for one thing.
Trenbeth,
Show that the current mild warming is not due to natural variation? Go on, do it.
I’m waiting … where’s the power-point presentation, the Nobel prize?
Oh, wait, you cannot show that the current mild warming is not due to natural variation, can you?
Largely off topic but maybe relevant:
From some recent reading I have done, I understand that in the BC era Spain, Italy, and Greece were heavily forested and vegetated, and had a wet sub tropical climate.
With the advent of growing human population and associated demand for wood (Ie: fueling the Roman baths and ship building), these forests were clear felled.
As a consequence the climate of both Italy and Spain changed to what is now known as “The Mediterranean Climate”.
Is this scenario historically accurate? Would this not be compelling evidence for human influence on climate?
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. How many of you have taken any time to explain this or indeed the scientific method to someone prepared to listen? just curious – because I find that as soon as big words get mentioned, many lay folk just lay off!
Boy ‘O boy are these people dangerous?!?!?! They’re going to push this to the point of civil conflict maybe even international.
Beesamen, the key feature of Post-Modern Science is that there is no objectivity, all viewpoints are equally valid, as knowledge is a social construct. Thus there is feminist, islamic, or even gay science. The objectivity of science is dismissed as being a white male (and by insinuation, oppressive) construct.
I deny, detest and reject this crap, but you gotta know your enemies.
Although we build with concrete and steel leading to an UHI effect, mans nett effect on temperatures is that of a moderation.
The vast areas of irrigation and dams and levees add to the hydrological cycle leading to regional moderation (lower daytime highs, higher night time lows).
However in the greater scheme of things (ice ages coming and going) mans influence amounts to about a poofteenth of a tenth.
“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. ”
###
What a hack. We would not even talking about this nonsense if it were not being used as a hook to snooker people into giving away their freedoms so that the great socialist utopia can be established.
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, that is just ONE hypothesis, and only one of many related to the human influence on climate. Furthermore, in that one hypothesis, the term “catastrophic” has never been very well defined. Even melting ice and rising oceans, while inconveniences, are not catastrophic, and humans are pretty adaptable creatures and could probably adapt to even to those circumstances just fine.