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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I’m really not sure what these scientists are doing with this but it certainly ain’t science.
“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.”
Sorry, Trenbersty, old boy, but “very likely” doesn’t hack it, no matter who says it, or how many times.
do people get paid for publishing this stuff?
It amazes me that anyone would still call him a scientist after ejecting that kind of claptrap from his mouth. He doesn’t even have a toe-hold on the principles of his profession anymore.
I propose the mull hypothesis: we should ponder things more, not rush to judgment.
The fundamental question ought (IMO) to be, “Do we have a problem which requires urgent action?” I feel that the “null hypothesis” ought to be “no”, and those whom advocate “urgent action” ought to be the ones to “prove it”.
1) will it get warmer? (due to our activities?)
2) what effect will this have on us?
3) what will be the effect of our proposed responses?
Credit to Dr. J. Scott Armstrong for the “three part forecast”.
Best,
Frank
It seems obvious that since humans of long ago learned to use fire and increase the amount of soot in the air that there has been some impact on climate. The only real question is the degree of that impact. The alarmist view is that impact is substantial and a disaster in the making. The skeptic view is that since there has been no climate change observed that is at odds with historical variability, the alarmist case is not only unproven, but suspect.
I’m afraid Dr Trenberth quoting IPCC 2007 as ‘proof’ of AGW is hogwash. IPCC 2007 is a political document not an experimental research project.
If he can’t summarise in three paragraphs the experiments which prove AGW, then he’s not a scientist of the first rank. This was the hypothesis we tested. This is what we measured. This is what it shows.
He should be challenged to do so and others given the chance to rebut it.
How does this work? The Trenberth gang says AGW is unequivocal, and writes the IPCC reports from that perspective. Then, Dr. Trenberth claims that AGW is unequivocal because the IPCC says so.
Is this circular reasoning, or what?
The scenario-based projections of human-induced (CO2 driven) climate change have been around since the mid 1980s. With 25 years of data acquired through direct observation in the record, it appears the IPCC’s scenarios have no statistical relevance to reality. Even the “best case scenario” postulated by the IPCC was worse than what really transpired. A tremendous sudden warming with rapidly rising sea levels would be required in order to reach the sea level feared by the “climate action plans” so many communities here in California are being forced to mitigate. Yet the global mean sea level fell 6mm last year and is expected to be down again this year.
With so much hard data readily available that contrasts with the fear mongering of the modeled scenarios, why do we have people like Kevin Trenberth insisting, “There is no doubt whatsoever,” to human caused global warming? Why do they fight so tenaciously to avoid discussing the obvious data that contradicts their claims?
Trenberth spews: “So why does the science community continue to do attribution studies and assume that humans have no influence as a null hypothesis?”
Answer: It’s a science thing. You wouldn’t understand.
Seriously, is this clown trying to win a contest for the most unscientific statement made by an alleged scientist?
Valiant effort there, Kev, but your buddy Phil has set the bar pretty high with his classic:
“‘Why should I make the data available to you when your aim is to try and find something wrong with it?”
And they are gonna have to create a whole new category of award for Curry and all of her post normal “Fuzzy Monster” stories.
A new nick for Trenberth: “Bass-ackwards”? His appeals to authority, especially his own, are really offensive.
It was always going to get to this eventually. Stating that it is not legitimate to question AGW implies it has, at the very least, the status of a law placing it alongside those of Kepler and Newton. There is also the whiff of religious fervour. The IPCC’s reports are, therefore, to be considered as holy texts with the chairman and authors having taken the first steps towards beatification.
Of course they need to put the blame on human activity. There is no way they can get a penny out of the sun for its contribution.
Guilty until proven innocent: What a concept!
I’m not a statistician, but my understanding is that in the continuous case, there’s no useful way to reverse the Null Hypothesis, which basically says: Nothing interesting is happening here. I’d be very interested to know William Briggs’ take on that. But to me, it sounds like Trenberth is mathematically illiterate.
Is Trenberth’s latest ex cathedra pronouncement consistent with his famous Climategate email: “The fact is that we can’t account for the lack of warming at the moment and it is a travesty that we can’t.”
Between 2009 and the present, Trenberth has apparently become able to account for the lack of warming, or has acquired putative evidence that the putative warming has resumed. And on top of that, he now has putative evidence for attribution. Is Trenberth taking logic lessons from Muller?
Those darn sceptics. Lets just redefine science to get them out of our hair. But… what’s that about disproving a negative?
“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.”
So we now can elevate a hypothesis to the position of law, without any proof, and with scores of refutations?
What a great man of science! Pointing to the summary for policymakers and not the actual science.
Trenberth has now definitely joined Al Gore and James Hansen in the AGW hall of shame.
He is playing with words. Does he mean if someone proves that anthropogenics only contributes a small percent to climate change, it does not prove the null hypothesis for CAGW? How much of the observed changes above noise is natural, and how much is anthhropogenic? He doesn’t know.
It is complete claptrap of course. Opportunistically, how easy would it be to cherry pick some data that ‘showed’ no human influence? By taking an unlikely outcome as the null hypothesis, it becomes trivial to ‘disprove’ it. So, a safe null hypothesis would be temperature increases linearly with human population. Disprove that and the alarmists are doomed? No?
Its not really a surprise given the ‘Team’ don’t believe in that corner stone of science ‘critical review ‘ and believe that ‘models ‘are more valid than reality . Trenberth problems with the ‘null hypotheses’ as its correctly defined and taught to any undergraduate, is merely part of the ‘Teams’ working approach were anything can be reject if it gets in the way of the ‘greater good ‘ of AGW .
here is a classic example from the alarmists
Assessing the Actual Temperature effect of Man-made CO2
In spite of the IPCC assertions that essentially all the warming since 1850 is wholly due to Man-made CO2 emissions, there is a wider range of published and peer-reviewed opinion that differs on the actual level of the impact of Man-made additions of CO2 to the atmosphere. One well-accepted view is provided by CDIAC, the Carbon Dioxide Information Analysis Centre of the U.S. Department of Energy (DOE) .
The CDIAC figures can be transposed into parts of the 33°C temperature increase, as follows:
Water Vapour ~95% of effect ~31.35°C
Greenhouse Gases ~5% ~1.65°C
Carbon Dioxide at 390 ppmv ~75% ~1.24°C
Natural CO2 ~86% (40% emissions since 1850 Man-made) ~1.09°C
Current 2010 Worldwide Man-made CO2 ~11.28% of 390 ppmv ~0.14°C
Other Greenhouse gases ~25% ~0.41°C
Natural ~0.29°C
Man-made ~0.12°C
The CDIAC figure of ~0.14°C for Man-made influence since 1850 is less than one quarter of the measured temperature rise of 0.66°C since then: it accords well with the notion that roughly 50/50% solar influence and 50/50% natural / Man-made CO2 emissions. The value of the order of 0.14°C for the effect of worldwide emissions to date has been accepted in correspondence with Professor David MacKay, the chief scientific advisor of the UK Department of Energy and Climate Change, DECC.
Another acceptable source from Geocraft published in 2000 show an even lesser amount for additional Man-made CO2. This results in a much lower figure for Man-made influence to 2010 of ~0.039 °C.
On the other hand, Gavin Schmidt of NASA GISS , one of the topmost scientists involved in the Catastrophic Anthropogenic Global Warming cause, in a recent paper clearly asserts that:
• 75% of the Greenhouse effect is attributable to water vapour and clouds
• 100% of the increase in CO2 emissions since 1850 (110 ppmv) is Man-made
Following these numbers through and accounting for the effect of other Greenhouse gases results in a Man-made temperature rise between 1850 and 2010 of 2.21 °C.
As the reported temperature increase since 1850 is only 0.66°C in total, surely that result has to be in error. So this permier scientist supporting the concept of alarming greenhouse warming markedly underestimates the influence of water vapour and clouds. He presumably did not carry out the trivial sums that would have shown that his figures exaggerate Man-made influence on temperature by more than 3 times the actual warming since 1850.
Of course human beings are changing the climate. Anyone with half a brain can see it. It’s especially obvious to me where I live in central Colorado. We plant trees and grass in what was originally semi-desert scrub-land. We plow fields and plant crops where there was nothing but a grassy prairie. We dam rivers and streams, improve ports and harbors, build levees and spillways. THIS IS WHAT IT MEANS TO BE HUMAN: TO ADAPT NATURE TO OUR DESIRES, INSTEAD OF ADAPTING TO NATURE. No other creature on Earth does it to the extent we do. That doesn’t mean we’re “destroying” the Earth.
The hypothesis behind catastrophic anthropogenic global warming is that we’re changing the Earth so fast, we’ll reach a “tipping point” where we’ll destroy the Earth. That’s hogwash. Climate changes constantly, based upon solar dynamics and orbital dynamics of the Earth. It’s changed from having temperatures a dozen degrees warmer and cooler than the current global “average”. Carbon Dioxide has been present in greater and lesser quantities than today, from times when it comprised 30% of the atmosphere to times when it was barely high enough to continue to sustain plant life. We’re currently at a low point in carbon dioxide atmospheric content, gradually recovering from a deep trough.
I can’t help but think of all the CAGW adherents as similar to the cartoons of “prophets” with signs “THE EARTH WILL END TOMORROW”. Every day has a “tomorrow”.
‘Natural variability’ in the North Atlantic suggests rapid cooling:
http://www.vukcevic.talktalk.net/CET-NV.htm
The sad thing about Trenberth’s asshattery is that we still do not have a solid understanding of natural climate variability. The tree-ring circus made a shambles of the paleo proxy field. Cloud behavior is only just starting to be explored. Until this question is resolved, there will be no scientific progress on climate change.
However, the foundations of a dangerous cult have now been completed.