Bishop Hill Johansen's climate sensitivity estimate
Apr 2, 2015 Climate: sensitivity April 1st is an interesting choice of date on which to release a new paper on climate sensitivity, but nevertheless that is the choice of Nature Climate Change. The new estimate has been produced by a team led a new name in this area: Daniel Johansen of Chalmers University of Technology in Gothenburg. The only member of the team who may be familiar to readers is Claudia Tebaldi.
The article's headline conclusion is that ECS cannot be lower than 2°C.
Here we analyse how estimates of ECS change as observations accumulate over time and estimate the contribution of potential causes to the hiatus. We find that including observations over the hiatus reduces the most likely value for ECS from 2.8 °C to 2.5 °C, but that the lower bound of the 90% range remains stable around 2 °C. We also find that the hiatus is primarily attributable to El Niño/Southern Oscillation-related variability and reduced solar forcing.
And of course with conclusions like that it hasn't taken long to pick up some media attention (Carbon Brief). But of course it's always worth getting another opinion: Nic Lewis has studied the paper and has emailed me some thoughts:
[The study] estimates aerosol forcing using temperature data that is not at all latitudinally-resolved (the data is global only, but with land and ocean values separated – which has little effect). I believe that the use of latitudinally-unresolved data results in the flattening off of the increase in aerosols after the mid 1970s being conflated with the upswing in the Atlantic Multidecadal Oscillation (AMO), resulting in an excessively negative estimate for aerosol forcing. A more negative aerosol forcing estimate inevitably leads to a higher estimate for climate sensitivity.
Good previous studies such as Aldrin et al (2012) used hemisherically-resolved temperature data and, since aerosols are emitted very largely in the northern hemeisphere, were able to do a reasonable job of separating out the influence of aerosols and the AMO, and to arrive a modestly negative estimate for aerosol forcing. By contrast, Johansson obtains a very negative best estimate for aerosol forcing: -1.38 W/m2 including black-carbon-on-snow. This equates to close to -1.50 W/m2 for aerosol forcing alone (taking out BC-on-snow forcing at the AR5 efficacy-adjusted best estimate) as opposed to the AR5 best estimate of -0.9 W/m2 and Bjorn Stevens new estimate of -0.5 W/m2 (all changes since preindustrial).
Additionally, the study uses uniform Bayesian priors for ECS and effective ocean vertical diffusivity (their EVD). Doing so doesn't seem to have a huge effect here, except when using data only to 2001 or earlier. I imagine that is because the study uses low estimates of observational uncertainty, particularly for ocean heat content.
Another, minor, source of bias is that no allowance is made for the ocean being in imbalance in the early part of the 1765-2011 period. The Earth was recovering from the Little Ice Age then and ocean heat uptake was probably not negligible. In conjunction with the high aerosol forcing estimate, this accounts for all or most of the difference between the ECS estimate in this paper and that in Lewis & Curry 2014.
Oh well.
Reader Comments (25)
Hmmm, 2 more C sounds just fine during this cold start to spring, but surely there should be a disclaimer that the figures quoted apply only to Model World.
In what other branch of science are the results of mere models presented as facts?
There were hints from Ringberg of an ECS between 2-5 degrees C., with justification for less than 2 deg. C not being found. Nonetheless, Graeme Stephens ran out of blackboard space and time trying to chalk out cloud feedbacks.
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What about the Forcings of Climate Scientists, trying to make Inconvenient Truths, fit the theory?
Who wrote the headline? Our host? As you clearly state, they give 2C as the 90% lower bound. At least to my understanding, that is very different to 'cannot'.
If you read the paper (absurd, I know) it is clear that the authors understand that not only is this not a hard limit given their method (a 5% chance that ECS is lower), but that it is dependent on their method. For example, some quotes from their paper:
and
I think the Carbon Brief piece gets this point a bit better (although I also think that Carbon Brief misses the real point of the paper). The headline Carbon Brief wrote does not say 'cannot'. It says 'unlikely'. Carbon Brief also quotes Johansson, the lead author of the paper, saying the IPCC was right not to rule out the possibility of lower ECS values:
I have to say that using the word 'cannot' reinforces my impression that many skeptics have difficulty handling uncertainty. In this case, scientists say 'unlikely', and the Bishop seems to hear 'cannot' - or at least thinks that's a useful summary or gloss.
Maybe some in the audience do find 'cannot' a useful summary. I do not. I find it a poor writing style. Simplifying as far as possible is good, but simplifying further than possible is not. You may think only in black and white, that unlikely is the same as cannot. But you need to understand that many people do not. They believe that words such as 'unlikely' do have meaning. There are more possibilities in the world than 'yes', 'no' or 'unknown',
I think there are plenty of problems with alarmist arguments. But in a case like this I get the impression that there's an attempt by the Bishop to avoid the hard argument by creating a bit of a strawman. In this case scientists did not claim that the science is 'settled' or that no discussion is allowed. Some greens have said that. But skeptics have to understand that many - even most - scientists are not saying that.
'JK
But skeptics have to understand that many - even most - scientists are not saying that.'
Sorry but in keeping their mouths shut and failing to call the poor scientific pratice seen so very often in climate 'science' they certainly give no impress at all that they do not agree with the more extreme stances see , especial when they let their professional organisation ,like the RS, lead the shouts of 'we all doomed'
And this before we get to those that have jumped on the CAGW funding bandwagon by linking up research in any way they can to CAGW. Its understandable but not acceptable or others to play the three wise monkeys to 'tricks ' of the Team and friends.
While you are right to say not all of science is 'at it ' , however that all of science will end up carrying the can for those that are is to a large extent becasue of the rest of sciences total failure to call out those which are.
JK, the certainty of global warming and the Hockey Stick graph convinced me.
I started to feel uncertain about it all in 2004/5, but it was not until climategate in 2009, that I realised I was not alone.
The cynic in me suggests that the 97% consensus was fabricated to reduce uncertainty, but the growing number of papers mentioning uncertainty indicates that the distance between the Hockey Stick, common sense and reality is widening.
Sceptics have long understood uncertainty. Climate Alarmists have been forced to accept uncertainty, because nothing they have been certain about, has happened, including , global warming.
I am not sure that ostracism of those expressing scepticism, is normal practise in science. In climate science, it seems to be perfectly acceptable
Looking at the abstract, the chart of p.d.f.s of the ECS as estimated at various points in time shows the latest data (2011) considered by the paper that to this Mk I eyeball has perhaps rather more than 5% of the integral below 2 deg C - and in any event has a very high rate of increase around that value, making any marginal error produce high variations in the probability of ECS<2 deg C.
http://www.nature.com/nclimate/journal/vaop/ncurrent/carousel/nclimate2573-f2.jpg
One can't say there is low solar forcing right now.
TSI from the SORCE/TIM instrument in the last few months has been more-or-less tying the all-time record highs from 1958 and 0.3 W/m2 higher than all the other recent solar cycle peaks except for 1958.
JK Apr 2, 2015 at 10:21 PM
".. my impression that many skeptics have difficulty handling uncertainty."
Putting aside the element of internal contradiction, I think this probably applies to us all.
In this case, journalistic simplification aside, you seem to be bridling against the suggestion that the estimate is significantly wrong because of the unquantified and in some cases unacknowledged uncertainty created by the methods used.
My reaction was different.
It was more "why did they bother?" If they knew the subject well they would have for example known about the limitations created by not testing sensitivity to resolving temp at least at a hemispherical level, particularly since the models they based theirs on seem to give this level of resolution.
The question for JK is whether he/she would have tested for this and reported on it? Or does it feel more comfortable not bothering to try and eliminate that element of uncertainty?
Has anyone looked at the editorial make-up of Nature Climate Change?
Chief Editor: Rory Howlett
Zoology, Oxford, PhD in ecological genetics, Cambridge. He spent three years as Media and Communications Officer at the UK National Oceanography Centre in Southampton, which is a Tyndall Centre, http://www.tyndall.ac.uk/Partner-Institutions/University-Southampton.
Senior Editor: Monica Contestabile, (what a wonderful name!)
"Quantitative economist" PhD in environmental economics. Prior to joining Nature Climate Change, Monica worked with WWF-UK developing research on sustainable consumption. Before that, she was a senior lecturer at the Crichton Carbon Centre in Scotland.
“Top-down, model driven legislation on environmental issues is necessary but not sufficient. We need everyone to be aware of the challenges that we are facing and a recognition of the fact that their individual actions really can make a difference. Making that link is what we do at the Crichton Carbon Centre”
Senior Editor: Bronwyn Wake
PhD in trace element biogeochemistry and first class Honours in Antarctic Studies from the University of Tasmania, Australia. Prior to joining Nature Climate Change, Bronwyn was a postdoctoral researcher at the University of Southampton, UK, (Tyndall again) and European Institute for Marine Studies, Brest, France.
Associate Editor: Alastair Brown
Before joining Nature Climate Change, UK Climate Impacts Programme (UKCIP) at Oxford ECI, Degree in environmental science and Masters in global environmental change, both at the University of Plymouth.
External advisory panel:
Suraje Dessai is Professor of Climate Change Adaptation at the Sustainability Research Institute in the School of Earth and Environment at Leeds. Member of the ESRC Centre for Climate Change Economics and Policy (CCCEP). This is a joint venture with Stern's LSE Grantham outfit and ESRC. The management team includes Simon Dietz and Sam Fankhauser of the Grantham Institute, along with good old Bob Ward. The advisory group has Peter Hoeppe of Munich Re and Corinne Le Quere, Director of Tyndall.
Dessai is a Lead Author on the chapter "Foundations for Decision-making" for the IPCC Working Group 2 (Impacts, Adaptation and Vulnerability) Fifth Assessment Report and also serves on the IPCC's Task Group on Data and Scenario Support for Impact and Climate Analysis (TGICA).
Other names include Riley E. Dunlap http://www.scholarsstrategynetwork.org/scholar-profile/251, co-author of "The Climate Change Denial Campaign" and "Organised Climate Change Denial".
Saleemul Huq, IPCC lead author of the chapter on Adaptation and Sustainable Development in AR3 and was CLA of 'Interrelationships between adaptation and mitigation' in the AR4.
http://www.bcas.net/director-details.php?id=1&&name=Dr.%20Saleemul%20Huq
Diana Liverman
Formerly Oxford Environmental Change Institute, (Myles Allen), Co-Director, Institute for the Environment, University of Arizona, Crispin Tickell is on the Arizona U advisory board.
She is a Senior Fellow, Center for American Progress. This is Obama advisor John Podesta's outfit and it is the parent body of Joe Romm's Climate Progress.
Malte Meinshausen,
University of Melbourne, and Potsdam Institute. Colleague of Stefan Rahmstorf at Potsdam, Former Greenpeace and Climate Action Network. Rahmstorf is lead and co-author with Michael Mann of the current heavily savaged paper about the "slowing of the Gulf Stream".
Can there be any surprise at what is accepted and published in Nature Climate Change?
Good grief, heels within wheels and isn't it a cosy cossetted world these days? Darn it, if I were a cynical type which I am, it would lead me to suggest this latest guff 'Johansen's climate sensitivity estimate' is just so bloody pat, I mean you'd expect them to say the sort of stuff and true to form - they just did!!........................
btw - dennisa good bit of research and thank you - from your link:
"Sustainability Research Institute in the School of Earth and Environment at Leeds" wtf has sustainability research have to do with what was once a smallish but academically tight faculty given to rigorous scientific discipline in the study of geo sciences?......Well actually, I wax rhetorical - answer; politics and academic empire building with half baked courses for a gormless intake - which belong in the abstract pseudo science of the humanities faculties and [not necessarily or] courses for Common Purpose, civil servants, Socialists in general and UN wannabes.
April Fool's dressed up all sciencey. It is hard work to be able to ignore reality, but the loot the climate hypesters draw in sure helps make it worthy while.
"in keeping their mouths shut and failing to call the poor scientific practice seen so very often in climate 'science' "
Yes, what Judith Curry described as the "Deafening Silence" in the aftermath of Climategate. It's not just the few Climategate crooks who were caught, its the tactic approvals of virtually all the others.
More generally, The 97% Deafening Silence ?
Well, so what?
CO2 at present is about 400ppm, and increasing a little under 2ppm per year.
So, if the ECS is 2.5C, in 100 years we might expect to see 1.25C increase. Maybe.
We had around 0.8C increase 1850-1950. Maybe. And no-one noticed.
Most likely, the greening caused by the extra CO2 will act to retard those CO2 level rises anyway, as already seems to be happening.
The sea level rise isn't accelerating, the ice isn't melting (more than usual), there is no tropical tropospheric hot-spot, weather isn't getting more extreme and the millions of climate refugees didn't materialise.
There is plenty of reason to think that 2.5C is still too high, such as Lewis & Curry 2014, but even if it isn't, there is no catastrophe on the way.
Can we all go home now and do some real science?
"I have to say that using the word 'cannot' reinforces my impression that many skeptics have difficulty handling uncertainty. In this case, scientists say 'unlikely', and the Bishop seems to hear 'cannot' - or at least thinks that's a useful summary or gloss."
Considering this is the same scientific community that has all their models predicting higher warming than observational data and still can't accept the hypothesis is dead wrong or needing a major update this analysis is pin gazing.
"If you read the paper (absurd, I know) it is clear that the authors understand that not only is this not a hard limit given their method (a 5% chance that ECS is lower), but that it is dependent on their method."
Actually what the author seems to believe is that the paper says that things won't be as bad as forecast. He's explained to us today that that doesn't mean we can stop trying to de-industrialise the western economies, nor should we withhold reparation payments from India and China for the damage our industrial life has caused. Oh and please ignore the 14% increase in greenery, it's all bad news.
Re Nic Lewis's last remark, Richard Tol tweeted about this paper http://www.voxeu.org/article/myth-europe-s-little-ice-age#.VRZdvxN2x5w.twitter which argues that the Little Ice Age is a statistical artefact resulting from analysing a time series after smoothing it - called the Yule-Slutsky effect apparently. There is a technical paper as well which I have not attempted. The authors are economists. I have always taken the Little Ice Age as given, but now am not so sure.
@ Peter Mott
There's plenty of documentary evidence that the LIA was real. I have no doubt that if you choose your statistical method to obscure, rather than illuminate, reality, that you can make it go away.
The Thames still froze, and the crops still failed, whatever their manipulated numbers say.
I am afriad to say Bish, that any mention of low Solar activity must be banned from entering the discussion regarding the hiatus/pause! It has been repeatedly & consistently stated by the warmisterati, that the Sun has no significant effect upon the Earth's Climate, endored by the UN IPCC. Therefore lower than normal Solar activity "CANNOT" be having an effect upon the Climate, full stop! I am not going to allow these people to claim that the pause is partially as a result of low Solar activity to suit their convenince! AtB
@ Peter Mott
If you want to decide whether or not there was a Little Ice Age, you should check out the chapter on LIA, Brian Fagan,
Floods, Famines, and Emperors: El Niño and the Fate of Civilizations (Basic Books, 1999).
A brief extract:
"Only 150 years ago, Europe came to the end of a 500 year cold snap so severe that thousands of peasants starved. The Little Ice Age changed the course of European history. Dutch canals froze over for months, shipping could not leave port, and glaciers in the Swiss Alps overwhelmed mountain villages. Five hundred years of much colder weather changed European agriculture, helped tip the balance of political power from the Mediterranean states to the north, and contributed to the social unrest that culminated in the French Revolution.
The poor suffered most. They were least able to adjust to changing circumstances and most susceptible to disease and increased mortality. These five centuries of periodic economic and social crisis in a much less densely populated Europe are a haunting reminder of the drastic consequences of even a modest cooling of global temperatures.
The Little Ice Age was the most recent of three relatively long cold snaps during the past ten thousand years. The Younger Dryas that triggered agriculture in southwestern Asia was the most severe, for it brought glacial conditions back to Europe. Another cold snap in about 6200 B.C. lasted four centuries and caused widespread drought. The Little Ice Age had more impact on history than its two predecessors, for it descended on the world after centuries of unusually warm temperatures. One can reasonably call it the mother of all history-changing events.
The colder conditions of the Little Ice Age were not confined to Europe and North America. The world was on average one or two degrees Celsius cooler than it is today (during the late Ice Age it was six-to-nine degrees cooler).
Precisely dated stalagmites from Cold Air Cave as far away as northern South Africa provide evidence of cooler temperatures during the Little Ice Age. Glaciers advanced, tree lines fell, and seas cooled."
Some artifact.....
"I have always taken the Little Ice Age as given, but now am not so sure."
You need to read a bit more, try some reading round - commence with a "known known" - about the Maunder Minimum and take it from there. Solar influence, it means everything to the earth and thus to man - man.
why 90% and not 95 or 99 percent. Are we paying obeisance to the Merchants of doubt wicked "sound like rich"
@ Peter Mott: The assumption that the ocean was in equilibrium at the beginning of modern warming was also disputed in Liang et.al (2015) as they found that there is a current of heat from the abyss to the surface and the abyss is currently cooling . (http://www.mit.edu/~xliang/resources/liang2015a.pdf) . This phenomena is only explainable if one accepts an ocean out of equilibrium in the past, with or without LIA.
The sport of speed skating was well known in East Anglia. From Wikipedia,
But now we read that
So the fens were apparently only iced up because the old London Bridge had too many arches - obvious really.
At Steve Ta
Thank you for your post.
It would be interesting to know whether the tributaries into the Thames, since culverted, also froze over?