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
We now have a banana republic administration, and this seems to go hand-and-hand with that. But what do you call it? Banana republic science isn’t quite right? Sovietized science?
Every square inch of the surface of the Planet Earth, where there is a bit of organic matter, a few bacteria and a temperature a few degrees above your home refrigerator, is undergoing organic decay and emitting CO2. The human addition to this natural activity is piddling.
Trenberth is an idiot!
“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.”
Somehow the word lazy is coming to mind…oh, and how to get more money because the argument should be extended into eternity…. along with the dollars.
“Is this circular reasoning, or what?” Answer: YES plus the Titanic will not sink syndrome.
How entertainingly laughable.
I guess if 100% of my lab’s funding was now contingent on CAGW and the pendulum of public opinion was now swinging the other way I’d start getting desperate too. “T’ hell with the science, we need more true believers for our cause.”
Noise? It’s called “weather”.
It’s OK for me to refer to it as “noise” when comparing climate “scientists” to rock bands of the 1980’s: They both try to make money out of noise. ;:-)
But that’s a joke. Not science. I can tell the difference. Can Kevin?
Any attempt to classify natural variability as noise can only be by imposing an assumed “correct” pattern of behaviour and that one has captured a characteristic pattern. Yet the models, based on that assumed pattern lack forecasting skill. Instead of concluding that the assumptions were wrong, the farce continues. How long before we find that they also lack hindcasting skill when compared to real world data, as opposed to the homogenised data?
Kevin Trenberth: “Noise” is when instruments show what isn’t happening.
Climate change due to GHGs isn’t the kind of issue you fit into a Yes or No box, like a lawyer’s view of black and while, guitly or innocent. Of course GHGs influence and warm the climate. That isn’t the question, although Trenberth wishes it was — because he’d get a “yes” as the answer.
But the real questions are: how much of current warming is due to natural variability, how much to GHGs, how much temperature increase will we have in a century if GHGs double, what good and bad things are likely to happen as a result, and what is the net value of these good and bad things vs. the costs of taking action soon, vs. taking the costs actions a decade or more down the road? That is why Curry is correct here:
“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.
The null hypothesis is for a far simpler scientific issue, such as: “Does this drug cause this cancer to stop growing?” Even there, the null hypothesis is too simplistic, because it might stop tumor growth for 6 months or a year, or only one month. Saving a year of life is a big deal, one month not so much.
When you have huge economic issues and great amounts of uncertainty with regard to things like sensitivity to a doubling of CO2, feedbacks from evaporation (including increases in clouds and their feedbacks), not to mention regarding consequences, then a legalisitic, “does climate change exist or not” approach isn’t the right way to think about the issue.
The argument for the reversal of the null hypothesis stems from a claim that a unique and hither to unseen change in climate is upon us. This is based on several assumptions. First that you need thirty years minimum to separate climate change from the noise of weather. Two that anthropogenic CO2 became a significant variable about 1950. Three that anything outside of the historically normal forcings can be attributed to human produced CO2. And finally the temperature increase from the thirty year period 1970 to 2000 constitutes such an aberrational increase. One caveat it is generally accepted by both believers and skeptics alike, that there has been fairly continuous warming from the Little Ice Age, and that warming in and of itself is not definitive of Anthropogenic effects, but that what we have is natural warming reinforced by Anthropogenic warming and as such constitutes a new and increased warming. Lets look at the Hadcrut global temperature record to see how well these statements stand up to empirical evidence. First the comparison with the most recent thirty year warming period pre AGW 1910 to 1940.
http://www.woodfortrees.org/plot/hadcrut3vgl/from:1910/to:1940/trend/plot/hadcrut3vgl/from:1970/to:2000/trend/plot/hadcrut3vgl/from:1910/to:1940/plot/hadcrut3vgl/from:1970/to:2000
You will note they look remarkably similar though the El Nino of 1998 shows up strongly. Next lets just look at the trend lines to see how much AGW has accelerated the warmth in the second half of the last century.
http://www.woodfortrees.org/plot/hadcrut3vgl/from:1910/to:1940/trend/plot/hadcrut3vgl/from:1970/to:2000/trend
Yes warming has occurred, but no one doubts that we have been more or less continuous warming for far more than a century. The question is the nature of the warming any different than it was in the pre AGW days. What there seems to be no difference. Well if there is no difference, what are we talking about. If there is no difference than it looks to me like the null hypothesis is supported and it is up to those who would promote another interpretation to prove that it is wrong.
“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.”
As chaotic as our climate system is,well, good luck. That is why dooms day science is the new methodology.. “What if” scare mongering.
“However, the foundations of a dangerous cult have now been completed.” Oh so true.
For Dr. Kevin Trenberth to suggest that sceptics of ‘dangerous anthropogenic climate change or otherwise should play along with this psychodrama is an insult to a lot of very intelligent people.
Dr. Kevin Trenberth as a scientist, should have already reversed the ‘null hypothesis particularly on his own research in trying to prove ‘dangerous anthropogenic climate change; and show us all how he can prove that ‘dangerous anthropogenic climate change’ has not or is not occurring.
If Dr. Kevin Trenberth can’t prove that, that it wasn’t or isn’t occurring and why, then he shouldn’t expect anyone to blindly believe that ‘dangerous anthropogenic climate change’ will or is occurring, and is there any such research of role reversal from any of the Anthropogenic climate change enthusiasts, the simplest loudest answer is NO.
So, what is this? Climate Science or psychological warfare? Again, it seems more shameful tactics are being sought and used by anthropogenic climate change alarmists, instead of empirical scientific arguments they have resorted to bright flashing colorful distractions.
http://www.youtube.com/watch?v=_aZ2bdnG97A
To those who are taking up the invitation to visit Dr Trenberth, I greatly admire you. I know that I would struggle to keep my mouth in check were I to be face-to-face with him. His contribution to science and the scientific method would have his peers of bygone years crying into their beers.
The question at this point isn’t whether humans influence climate. The question is: What are ALL the major influences on our climate, and have we discovered all of the major influences. The null hypothesis is that we don’t fully understand the climate. The burden of proof is for theorists to prove that they understand all of the major factors to a quantitatively significant extent. You can’t say that humans have xx.x% impact if you can’t properly attribute all other major competing influences.
Roger Knights says:
November 3, 2011 at 10:27 am
I propose the mull hypothesis
Trenberth prefers the mule hypothesis:
“I don’t care if there are a million travesties; I’m still right. And if anyone says I’m wrong, I’ll thcream and thcream ’till I’m thick.” (snide reference to Violet Elizabeth Bott)
The mullet hypothesis didn’t last. The fish deny swallowing the missing heat.
Kevin Trenberth abandoned science many years ago and its a travesty that people listen to his pseudoscience
A burden of proof and a null hypothesis are not the same thing. Trenberth is just confused.
Forgive my vitriol, but was Trenberth absent the day they covered the scientific method? Climate scientists aren’t special. They don’t get to make up their own rules. They have to follow the scientific method and show their work just like everyone else. Have you ever heard such whining and moaning from other scientists who couldn’t come up with data to support their theories? Instead of changing the scientific burden of proof, these climate fraudsters need to put up or shut up. I’m ashamed that Trenberth, et al. even call themselves ‘scientists’. I call BULL SH*T on this, and urge every scientist and science-minded person to call BULL SH*T on this as well.
Currently the null hypothesis for climate change attribution research is that humans have no influence.
That’s what they say the current definition is? Here I thought it was already established that with black carbon (aka soot) causing up to half of the reported Arctic warming, deforestation (albedo change etc), and other aerosols besides soot (sulfates etc), humans have been show to effect changes in climate. Thus by their specification of the definition, the “current” null hypothesis is already falsified.
The null hypothesis should involve whether humans have made a significant contribution to climate change, the answer being we haven’t.
The initial BEST reports are saying 1/3 of the land stations are showing cooling. That alone should invalidate a major chunk of the (C)AGW orthodoxy as currently reported global warming certainly doesn’t incorporate all of the globe. By the standards of the whining that the Medieval Warm Period wasn’t a global event, the current warming isn’t global either. Of course 70% of the globe is covered in water, we should look for global changes by studying changes in total ocean heat content (TOHC). Given the immense capacity of the oceans for storing heat, and how they release heat that was stored many decades ago, can we mere humans have possibly made a noticeable change in TOHC? Or is “global warming” just a geologically-brief transient change in surface air temperatures on land, where the effects of human influence are most pronounced?
Consider also the time scales involved. There has been warming since the Little Ice Age turned around. Go further back, even to the start of this interglacial, there has been global cooling. Back to more recent times, natural factors like the PDO have a demonstrated huge influence on global temperatures, so large that any possible “human influence” greatly pales in comparison.
Thus the “current definition” of the null hypothesis, for “climate change attribution research,” really should be that the human contribution is negligible.
The new USDA planting zone map is right……because I read it in Readers Digest
….same thing
Instead of showing that human activity has/is changing the climate, just declare it a fact by fiat. Have a vote, like they did when they demoted Pluto to a minor planet.
Once they do that, the answer to AGW skeptics can always be “prove it isn’t true.” Case closed. Party over. Court adjourned.
When did Trenberth stop beating his wife (or mistress or whatever the case may be) and where is the proof?
Old PI says:
November 3, 2011 at 11:00 am
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.
It occurred to me one day, that one main difference between life and not-life, is that life exploits its environment. But when we do it, the greenies tell us it is evil. They must not be in favour of life.
Given all the problems with the IPCC that have come to light, why would anyone cite them as an authority?
“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”
That sentence argues against itself. If the evidence is “so clear”, there is no need to shift the burden of proof.
~~~EXTREME CLIMATE EVENTS IN 2010~~~
When I got to this I had to stop reading.
Is it now we get a daily climate report in the paper !
May I ask, has anyone here read the three papers being discussed? I just did and it seems to me that it’s an interesting set of questions being discussed from several perspectives.
Anyone who quotes the IPCC as a credible source is just pushing a political agenda – it is certainly not science. Donna Laframboise has documented the corruption of the UN and the IPCC in her new book “The Delinquent Teenager” – a must read by anyone who is interested in the inner workings of that organization and how they are trying to defraud the free world.