WUWT readers may recall this chart which clearly illustrates just how uncertain climate science really is.
It seems that some climate academics are a bit embarrassed that they haven’t been able to pin down climate sensitivity. From EU Horizon Magazine
Climate sensitivity – reducing the uncertainty of uncertainty
by Jon Cartwright
A study published in January 2018 claims to halve the uncertainty around how much our planet’s temperature will change in response to rising carbon dioxide (CO2) levels, potentially giving governments more confidence to prepare for the future.
The results suggest that, when it comes to the climate, both the doom-mongers and optimists are wrong. On the other hand, they have prompted a heated debate over how certain you can be about uncertainty.
‘People are quite rightly looking at what we’ve done, because we’re claiming quite a big reduction in uncertainty, based on a pretty simple analysis,’ said lead author Professor Peter Cox of the University of Exeter in the UK.
The climate is a complex beast. To make predictions about how much temperatures will rise in the future, scientists employ hugely detailed computer simulations, which rely on swathes of experimental data as input.
But there is a big unknown in these simulations: how much warming do you get for a certain amount of CO2? This simple parameter is known as the climate’s sensitivity, and it dominates our uncertainty about future global warming.
Normally, climate sensitivity is estimated by looking at historical data on temperature and greenhouse gases – either measurements of global warming or records of past climates, such as ice cores and tree rings. Given a rise in CO2 and a concurrent rise in temperature, scientists can judge how much the former affects the latter.
Big range
For the past 25 years or so, studies based on this method have led the Intergovernmental Panel on Climate Change (IPCC) to conclude that the sensitivity of the Earth to a doubling in CO2 falls in a ‘likely’ range of 1.5°C to 4.5°C, with a central estimate of 3°C.
Prof. Cox believes this degree of uncertainty isn’t good enough. ‘I think it’s slightly embarrassing that we’ve had a range that is so large for so long,’ he said.
‘I think it’s slightly embarrassing that we’ve had a range that is so large for so long.’ – Prof. Peter Cox, University of Exeter, UK
To avoid this problem, Prof. Cox and colleagues ignore the historical warming trend altogether, and instead picture the climate as a spring. The length of the spring is the global temperature, and the weights on the end are the net heating due to CO2 and aerosols.
Crucially, to work out the sensitivity using this new method, Cox and his co-authors don’t actually need to know how much weight there is. All they need to do is measure the spring’s stiffness, and this is betrayed by how quickly the spring oscillates – or in real terms, how much temperatures have varied from year to year.
A ‘stiff’ climate equals a small sensitivity, while a ‘slack’ climate equals a big sensitivity. In their paper published in the journal Nature, Prof. Cox and colleagues estimate the sensitivity to be in the ‘likely’ range of 2.2°C to 3.4°C – less than half the range given by the IPCC.
Sensitive figures
To be clear, this range is not necessarily how much warming anyone should expect. It only reflects how much warming there would be for a doubling of CO2 levels since the baseline period of pre-industrialisation – although we’re about halfway to that threshold already.
Nevertheless, the researchers’ results appear to simultaneously exclude the very worst- and best-case scenarios. ‘I sort of see this as good news, in that our range says values above 4°C are unlikely, and so we’re not yet too late to avoid the 2oC limit set by the Paris Agreement,’ said Prof. Cox.
But not everyone is on board with the new statistics. Climate scientist Professor Tapio Schneider of Caltech in California, US, believes the researchers have mistakenly assumed that their springy relationship is linear, when it could be more complicated.
This view is not shared by Dr James Annan of Blue Skies Research in the UK. On his blog he describes himself as a ‘fan’ of the new approach, albeit ‘not uncritically’.
Professor Reto Knutti of ETH Zürich in Switzerland points out that Prof. Cox and colleagues are not the first to try an alternative method to cut the uncertainty surrounding climate sensitivity, and ‘it’s not obvious why theirs should be much better than others’.
‘So while I do find those emergent constraints promising, and I hope we will be able to narrow the range eventually, there is a danger of finding spurious and not robust correlations – the result being that error bars are too small,’ he added.
Prof. Cox admits that his group’s results will probably not be the last word, but he is hopeful that they can move the science of climate uncertainty forwards, beyond the IPCC range.
‘I think there’s good reason to believe climate scientists are now ready to reduce the long-standing uncertainty in ECS (equilibrium climate sensitivity). It is high-time that we did that,’ he said.
###
The study: https://www.nature.com/articles/nature25450
Emergent constraint on equilibrium climate sensitivity from global temperature variability
Abstract
Equilibrium climate sensitivity (ECS) remains one of the most important unknowns in climate change science. ECS is defined as the global mean warming that would occur if the atmospheric carbon dioxide (CO2) concentration were instantly doubled and the climate were then brought to equilibrium with that new level of CO2. Despite its rather idealized definition, ECS has continuing relevance for international climate change agreements, which are often framed in terms of stabilization of global warming relative to the pre-industrial climate. However, the ‘likely’ range of ECS as stated by the Intergovernmental Panel on Climate Change (IPCC) has remained at 1.5–4.5 degrees Celsius for more than 25 years1. The possibility of a value of ECS towards the upper end of this range reduces the feasibility of avoiding 2 degrees Celsius of global warming, as required by the Paris Agreement. Here we present a new emergent constraint on ECS that yields a central estimate of 2.8 degrees Celsius with 66 per cent confidence limits (equivalent to the IPCC ‘likely’ range) of 2.2–3.4 degrees Celsius. Our approach is to focus on the variability of temperature about long-term historical warming, rather than on the warming trend itself. We use an ensemble of climate models to define an emergent relationship2between ECS and a theoretically informed metric of global temperature variability. This metric of variability can also be calculated from observational records of global warming3, which enables tighter constraints to be placed on ECS, reducing the probability of ECS being less than 1.5 degrees Celsius to less than 3 per cent, and the probability of ECS exceeding 4.5 degrees Celsius to less than 1 per cent.
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
The science shows it is maybe 1 degree, most likely less and could even be negative. That is not catastrophic and will not fund any new studies. Thus, the only answers that are fiscally possible to put forward have to have larger, much larger numbers.
I was not aware the following has ever happened.
When you are continually adjusting the temperature records, and often just making up temperatures by homogenising huge areas of the Earth, the result will be impossibly large ranges of uncertainty, as anything is now possible.
adjustments cool the record.
ecs is higher with raw data.
Except that most of the cooling is in the past, which increases the slope.
But the science is settled!!! Heretic!!
the science that co2 is a ghg is settled
how much warming?
uncertain but estimatable
would you then mind responding to this comment, in detail?
willhaas March 16, 2018 at 4:15 pm
Steven,
Stop telling half-truths if you want to be taken seriously.
The problem isn’t that CO2 is a GHG, or that absent feedbacks, CO2 forcing would otherwise drive the troposphere temperatures up. Modeling the physics without feedback makes that clear, which is why the models produce a tropospheric hotspot in the tropical latitudes.
The huge problem for climate science is the model-predicted (CO2-only theory predicted) tropospheric hotspot has not been detected in observation by satellites or balloons.
The modellers simply make the feedback positive with parameter tunings to double to triple the the CO2 only sensitivity. Their need for confirmation bias is abetted by poorly constrained observational limits on many of the model parameters that deal with water and the consequences of its phase changes.
But the inconvenient reality for them is the sign (+ or -) of the feedback is not known. If it is negative, a CO2 sensitivity of 1.0-2.5 deg C so be easily cancelled out to well less than 1.0 deg C by higher precipitation rates or cloud albedo in the future.
CO2 science on the part of alarmist scientists is settled in their own mind, but not with real science.
One simple question. If you had “66 per cent confidence limits” that the bridge would hold your weight would you carry a bag of rocks across for me? Are You 66% confident in the 66% confidence level? Okay, that is two simple questions but It seems to me any degree of confidence is really no confidence at all. That is about the point I have reached in respect to scientists (the climate brand), governments, and bureaucracy.
that is why its wise to decrease emmissions.
Decreasing emissions of plant food is wholly and completely unnecessary, what is needed is to repair the Carbon Sinks AKA forests of fast growing large leaf trees and rain forests.
Tell that to the volcanoes and ocean vents.
No, you need to take into account of the price in lives, money of the decrease compared to not decreasing emissions. OTOH there are some marginal emissions that can be cut without a high price. But, theyre marginal so probably cutting them won’t make other than marginal changes. Going full nuclear takes a century and new reactor types. Wind and solar will just get us annoyed. So we’re stuck.
According to Steven, we should never do anything until after science has proven that it is 100% safe. At a minimum.
When you can show me why 500ppm is a danger, when 5000ppm wasn’t, I’ll listen to your predictions of doom.
MarkW, there was no agriculture or humans for that matter when CO2 levels were that high. Luckily we won’t witness that kind of a scientific experiment. Currently I find it improbable the humanity would ever reach 2xCO2, let alone this or the next generation.
Steven,
When the cost of insurance exceeds the cost of damages, you don’t insure. The effects of varying ECS is even more murky and subject to hysteria than the value of ECS.
test
http://wps.prenhall.com/wps/media/objects/3026/3098843/water_vapor_capacity_%20graph_PH.jpg
Is it a coincidence that Earth’s atmospheric temperatures center around the apex of this curve?
I don’t think anything is by accident. Philosophically. But I know it is rather difficult to define how you could recognize an accident. We could theoretically live in a simulation that has no accidents whatsoever. Or it could be everything is indeterministic.
To the topic. I guess the apex helps stabilize the climate, but I don’t immediately see why a planet should be 15C warm. So it is an accident, but still anthropic-argument forced.
Thanks Hugs – “… I guess the apex helps stabilize the climate …”
That’s what I think we should explore, it sure looks like a self-correcting force. If there is a force driving from either end towards the apex, would this force then determine the temperature?
Thomas Homer March 17, 2018 at 6:20 am
I don’t understand this. The average earth surface temperature is on the order of 15°C … hardly the “apex of this curve” …
w.
One should never be embarrassed when they fail to do the impossible. One should be embarrassed that they even thought they could! (Especially when they continue to ignore the huge amount of evidence that falls under the category of natural climate variability.)
C. Paul Pierett
March 16, 2018 at 5:33 pm: It gets tiresome seeing folk use the warm end of a cycle as if it proves anything about the whole. The AMOC is switching so learn from the next 20-30 years please.
Which MODEL are you using for the AMOC?
…
I could care less what your MODEL predicts for the next 20-30 years, all I’m telling you is that it doesn’t explain the past 150 years or anything else for that matter.
…
Do you run your AMOC modell on super computers?
do you get paid for this?
You would not believe me if my response was either affirmative or negative.
It really is fascinating how trolls can no longer tell the difference between models and reality.
But the troll is right. You can’t know what AMOC will do without a model. I admit I have a tendency to use linear trends and cycles,which is just guesswork in the end.
Does anyone want to bet on the September Arctic ice minimum 15% extent?
c.paul pieret. given your ramblings i have to think you may not be here long. however ,as is my custom when i read any arctic alarmism my first response is the offer of a bet regarding what year arctic sea will disappear in summer. the word “disappear” is like many words used by alarmists, its standard meaning does not apply.
as you will know “disappear” in arctic alarmism terms actually means 1 million square kilometres of sea ice. would you like to have a bet on when this threshold will be reached and if so how much. i have a few charities close to my heart and they always welcome donations from people that lose bets with me :).
The good professor is ‘slightly’ embarrassed after Billion$ and Billion$ spent over 30 years yield no change to ECS uncertainty range in the proclaimed settled science? He should be more than embarrassed! He should be re-assessing his dogged determination to an increasingly unsupportable hypothesis. He should be profoundly concerned about his participation in this profligate waste, fr@ud, and abuse of taxpayer dollars.
From the article: “But there is a big unknown in these simulations: how much warming do you get for a certain amount of CO2?”
There is the heart of the matter. A VERY BIG unknown.
How much warming do you get from CO2? This fella doesn’t know and noone else does either. Yet the Alarmists continually make all sorts of wild, unsupported claims about the future, based on the assumption that they *do* know how much warming we get from a certain amount of CO2. All of them are guessing. Their studies are guesses without foundation because they are based on a VERY BIG unknown.
This is Climate Science today: Speculation, speculation, speculation. No evidence.
The physics and data are unambiguously clear that the climate sensitivity is somewhere between the sensitivity of an ideal BB at 255K and one at 288K, or between about 0,2C per W/m^2 and 0.3C per Wm^2 and no where near tthe 0.4C-1.2C per W/m^2 initially claimed in AR1 where its only requirement was that it be large enough to justify the formation of the IPCC and UNFCCC.
Prof. Cox
Your paper is wrong on two counts:
1) A spring follows Hooke’s law:
F = k x
Where: F is force applied, k is string constant (or stiffness), x is displacement or change in length
It’s a linear relationship. You double the force, the displacement also doubles.
Temperature sensitivity to CO2 is not linear but logarithmic
2) Following your spring analogy, the weight on top of the spring is not only CO2 forcing but also other forces and there is a hand holding the weight and you don’t know if the hand is pushing down or pulling up the weight. You only know the net weight after the “hand effect.” The hand is the feedback: push down is positive and pull up is negative
More importantly, the temperature sensitivity to forcing is not linear or even approximately linear across the range of temperatures found on the planet. The temperature sensitivity to forcing is a function of 1/T^3. The IPCC’s self serving consensus’s assumption that this is approximately linear is one of the biggest mistakes ever made in climate science (the relevance of Bode’s LINEAR feedback amplifier analysis being another that was layered on top of it).
Far too many are misled by the many levels of misdirection, misrepresentation and obfuscation related to how the sensitivity is quantified. Worst of all is moving the uncertainty from that of the sensitivity itself to that related to uncertainty about how much CO2 we emit relative to the various bogus RCP scenarios.
I’m noticing quite a few more alarmists on this site. I expect to see more as the lipstick on the CAGW pig washes off. Is the current saturation a cyclical uptick or is this trend abnormal?
when a group of people with faith in a position have that faith shaken to the core the first stage of grief appears to be “denial”, then comes anger. it would appear alarmists are fluctuating between the two and lashing out wherever they can. expect more of this in years to come.
a similar thing can be witnessed in the brexit debate in the uk and with trump in the usa.
It’s a wild circus right now, in’it?
I assume most people don’t pay attention to my comments since it’s more politically (globalism, individual rather than collective type comments) based rather than scientific, but I’ll repeat that I am voluntaryist in my worldview. I have no skin in the politics arena. That being said, I’ve never noticed the Left so incensed and childish. Maybe because in my 20’s I leaned to that emotional low hanging fruit but goodness, these anti Trump, pro nanny statists are a circus until themselves.
It’s quite disturbing
It’s just another insignificant trend in an ambiguous anomaly.
Total waste of ink.There is nothing new. Aerosols effects have been over weighted prec8sely to maintain a higher than reasonable ECS. This is exactly what they should be embarrassed about! They make it sound like there has been genuine efforts to constrain ECS by alarmists.
The Pause caused there to be narrower and lower estimates made by sceptics and this was resisted when it was clear that if the ECS was in the lower range indicated, then there was no need to worry about the modest future warming. This would not do!
It is also disingenuous to assume that aerosols are the only negative feedback. Clouds/albedo, phase change of water in which incident energy is absorbed without manifesting itself in temperature rise, and the greening of the planet which ties up atmospheric sourced CO2, is exothermic (cooling) and exponential. Recent estimates are an over 15% increase in forest cover in 35 years. This makes a 2.2-3.4 ECS too high and more reasonable recently published levels support the idea that business as usual emissions still wouldn’t cause a rise of more than 1.5C limits hoped for by IPCC.
rather “endothermic’
Knutti and the Editor of Nature say that the ECS is dead because of uncertainty and that it should be trashed and replaced with Carbon Climate Response aka Transient Climate Response to Cumulative Emissions. (CCR/TCRE)
More here ….
https://ssrn.com/abstract=3142525
to a point .with such uncertainty what exactly is a climate sceptic? The funny thing is i firmly believe that most climate scientists think actual uncertainty is larger…
“All they need to do is measure the spring’s stiffness, and this is betrayed by how quickly the spring oscillates – or in real terms, how much temperatures have varied from year to year.”
Except that the fact that the climate is a complex, coupled, multi-variate system means this is not an apt comparison. Springs have a purely negative feedback which is, per Hooke’s Law, roughly linear and dependent only on the extension. Climate is almost exactly not like that.
What type of scientist continues to promote a major hypothesis that has failed the first, fundamental, most critical part? How can you have a global warming hypothesis based on CO2 when you cannot display a causal relation between CO2 and warming?
These turkeys wonder why experienced scientists laugh at them. Geoff.
CO2 sensitivity is 0.0C per doubling. CO2 is a resultant, not a driver function!
The real embarrassment should be that the two most (2017) papers have very tight error limits — which don’t overlap at all, with more than a degree C difference between their ranges.
“ECS is defined as the global mean warming that would occur if the atmospheric carbon dioxide (CO2) concentration were instantly doubled and the climate were then brought to equilibrium with that new level” This is a double impossibility. As such, it entitles the pseudo scientific ex falso, quodlibet, to ‘prove’ anything you want to ‘prove’.
“scientists employ hugely detailed computer simulations.”
Well at least they admit they are “simulations” and not physical models.
It can all be described succinctly in two words – Horse Hockey.
MWP was global and warmer than now with CO2 lower than now.
https://www.google.com/maps/d/viewer?mid=1akI_yGSUlO_qEvrmrIYv9kHknq4&ll=-0.10986313704833135%2C64.45953365000003&z=3
Horse Hockey? Don’t you Brits call that Polo?
There is no scientific proof that any
warming has been caused by CO2.
The warming between 1975 and 2000,
claimed to be caused by CO2,
is similar to the warming from 1910 to 1940,
claimed to be natural.
There is no logical reason to ASSUME
the 1975 to 2000 warming was NOT
natural warming.
And there is no explanation
for why 4.5 billion years of natural
climate change would suddenly stop
in 1975, and man made CO2
would suddenly start “controlling”
the average temperature.
The climate sensitivity to CO2 doubling,
net of feedbacks,
could be too small to measure.
But if you attribute ALL the warming
in the weather satellite era,
(they are only GLOBAL measurements,
that are not mainly wild guess infilling),
then the WORST CASE climate sensitivity
is about +1 degree C. per doubling of CO2.
Whether near zero, or +1 degree C,
THERE IS NO CO2 CRISIS.
In fact, adding CO2 to the air has been
the BEST thing humans have even done
to improve the planet, inadvertently
boosting CO2 levels that were too low
for optimum plant growth.
Slightly warmer nights
in cool, dry northern latitudes
have also been good news,
whether caused by CO2, or not.
My climate blog for people with common sense.
Leftists please stay away !
Over 15,000 page views so far:
http://www.elOnionBloggle.Blogspot.com