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« Quote of the day, Lewandowsky edition | Main | Letts laugh at the BBC »
Saturday
Dec052015

Is underlying warming only 0.8 degrees per century?

A new paper by Craig Loehle tries to address an area that has frequently been the cause of criticism of mainstream climate science -namely the blind eye it tends to turn to questions of natural variability. It's not online, but here's the abstract.

Multidecadal climate variability has proven difficult to deal with when estimating temperature trends. This possible unforced internal oscillation of the climate system provides an opportunity to correct temperature trends. The Atlantic Multidecadal Oscillation (AMO) is proposed as a potential index for this unforced variability. The AMO pattern does not appear to correspond to forcing histories used by the IPCC. Subtracting a scaled version of the AMO from the Hadley global temperature data produced damped decadal-scale fluctuations in the temperature data. The adjusted dataset is highly correlated with the anthropogenic forcing history from IPCC AR5. The linear post-1970 temperature trend is 0.83°C/century vs. 1.63°C/century for the raw data. Thus almost exactly half of the post-1970 warming is possibly natural. The use of the AMO as an index of unforced variability is supported by the fact that subtracting it simplifies the temperature response by damping the peaks and troughs consistently.

 In the main text, Loehle says that these results imply estimates for ECS of 1.5 and for TCR of 1.21.

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Reader Comments (47)

Dear BBC. My question to Roger Harrabin about climate change is this.


Who owns the thermometer that measures global temperature and where is it kept ?

Dec 5, 2015 at 11:25 AM | Unregistered Commenteresmiff

It would be interesting to see the paper, but my understanding is that it is quite likely that some of the AMO is forced. Consequently, simply removing the AMO from the temperature record and arguing that what is left is the forced response may well under-estimate the forced response and produce an estimate for climate sensitivity that is too low. Admittedly, one could argue that this is a decent estimate for the lowest possible TCR and ECS :-)

Dec 5, 2015 at 11:42 AM | Unregistered Commenter...and Then There's Physics

It is my understanding that the proposed external forcing is solar and volcanic*.

* Knudsen, M. F. et al. Evidence for external forcing of the Atlantic Multidecadal Oscillation since termination of the Little Ice Age. Nat. Commun. 5:3323 doi: 10.1038/ncomms4323 (2014)

Dec 5, 2015 at 11:58 AM | Unregistered CommenterTerryS

This is Pielke Sr. country and here is something of his I read a long time ago (2009) about human forcing of climate which he re-twittered the other day.. Hint. It's more complimikated than we thought.


https://pielkeclimatesci.files.wordpress.com/2009/12/r-354.pdf

Dec 5, 2015 at 11:59 AM | Unregistered Commenteresmiff

Terry,
I'm not aware of how the system can respond to volcanic and solar forcing, but not to anthropogenic forcings.

Dec 5, 2015 at 12:04 PM | Unregistered Commenter...and Then There's Physics

I'm not aware of how != does not

That is the problem with complex systems. You don’t always know the "how"

Dec 5, 2015 at 12:19 PM | Unregistered CommenterTerryS

Terry,
Okay, I'll phrase it differently. It is extremely unlikely that the system will respond very differently to volcanic and solar forcings, as it does to anthropogenic ones. Of course, there are some difference in that the solar forcing is distributed differently to other forcings, but if the AMO is forced by solar and volcanoes, it probably also responds to anthropogenic forcings. Hence, simply removing the AMO and assuming that the remaining temperature signal reflects the full forced response probably under-estimates the forced response. However, as I said above, this might be a reasonable way to estimate the lowest possible TCR/ECS values.

Dec 5, 2015 at 12:23 PM | Unregistered Commenter...and Then There's Physics

'Thus almost exactly half of the post-1970 warming is possibly natural.'

Or almost exactly ALL of the post-1970 warming is possibly natural.

Dec 5, 2015 at 12:41 PM | Unregistered CommenterGamecock

Re: ATTP

1. The mechanism by which the AMO is forced is currently unknown. It may or may not be influenced by small changes in a trace gas.

2. If solar and volcanic account for any external forcing then any possible effect of a change in a trace gas is negligible.

As an example, dropping a cabinet on my foot* will account for all the injuries. If the draws were still in the cabinet then any possible effect due to the draws being present is negligible.


* Do not try this at home. It is painful.

Dec 5, 2015 at 12:45 PM | Unregistered CommenterTerryS

Gamecock

The problems go back even closer to the source, what was the temperature increase ? Hence my question to Sir Roger Harrabin at the start of this thread.


Deep ecology nut James Hansen and his team of gremlins at NASA have been fiddling the figures so much, no-one has any idea what is going on. This is not the only source. It's been highlighted before.


It Was All a Lie! German Scientist Confirms NASA Fiddled with Climate Data

http://www.thegatewaypundit.com/2015/11/it-was-all-a-lie-german-scientist-confirms-nasa-fiddled-with-climate-data/


"German professor Dr. Friedrich Karl Ewert confirmed what other previously reported, NASA fiddled with global warming data to push global warming.

Ewert is not the first scientist to make this discovery. British scientists called the fiddling of climate data the biggest science scandal ever in February."


The fiddling with temperature data is the biggest science scandal ever

http://www.telegraph.co.uk/news/earth/environment/globalwarming/11395516/The-fiddling-with-temperature-data-is-the-biggest-science-scandal-ever.html

Dec 5, 2015 at 1:15 PM | Unregistered Commenteresmiff

ATTP, If I understood what you say above, the system response would not be different for different forcings. This seems counterintuitive. Could you expand on this a bit?

Dec 5, 2015 at 1:15 PM | Unregistered Commenterjferguson

jferguson,
A forcing is essentially defined as a changes in the top-of-the-atmosphere energy balance in the absence of any other changes in response to that change (although, technically, it is sometimes defined as being the TOA change after the stratosphere has adjusted). Hence in the simplest sense, if solar forcing increases by 0,5W/m^2 then it means that we are now gaining 0.5 Joules per square metre per second due to this change. Similarly if anthropogenic forcings increase by 0.5W/m^2 it means the same thing. Therefore, on average, we would expect the response to be similar - if we are receiving more energy than we are losing, we will warm until we are back in energy balance and how much we warm will depend largely on the change in forcing. The same applies if the change in forcing is negative, but then we would cool.

Of course, there are some complexities in that the distribution of the forcings can be different and hence the details of the response will be different. However, we still expect that the responses will be similar, if not the exactly the same. So, if the AMO responds to changes in volcanic and solar forcing, it would be extremely surprising if it somehow didn't resond to changes in anthropogenic forcings.

Dec 5, 2015 at 1:35 PM | Unregistered Commenter...and Then There's Physics

Hi ATTP,
I think I went wrong here by assuming that "forcing" meant the entire process, not simply the effect which modifies the TOA energy balance. My misunderstanding might have owed to the assumption that feedback mechanisms which involved the energy balance might also have been driven by other aspects of the process driving the forcing. i don't think it unreasonable to suppose that different processes would provoke different feedbacks. Maybe that is outside the topic under discussion.

Your last sentence wonders (?) how anyone could think the AMO might not be responsive to Anthropogenic effects. Is anyone actually suggesting that?

Dec 5, 2015 at 2:53 PM | Unregistered Commenterjferguson

jferguson,


i don't think it unreasonable to suppose that different processes would provoke different feedbacks.

Given that a change in forcing is essentially a change in energy balance, it's hard to see why the feedbacks would be wildly different. Typically the fast ones are water vapour, lapse rate and clouds. It can depend on how the forcing is distributed (given that the land and oceans are not evenly distributed across the planet) but I don't think there is some kind of different physical process that will operate when the change in forcing is solar, rather than anthropogenic.


Is anyone actually suggesting that?

Based on the abstract of Loehle's paper, that is in the post above, then it does seem so. If his analysis removes the AMO signal and assumes that what is left is the forced response, then that's essentially what he is doing.

Dec 5, 2015 at 3:09 PM | Unregistered Commenter...and Then There's Physics

ATTP,
Thanks for this. My problem is probably with the nomenclature, my ignorance.

Dec 5, 2015 at 3:22 PM | Unregistered Commenterjferguson

Bish, please provide more details about the paper, e.g. journal and date, if available.

Dec 5, 2015 at 3:31 PM | Registered CommenterHaroldW

The paper is actually available free
http://www.hrpub.org/download/20151130/UJG1-13905038.pdf

Thanks Bish for posting this.
Craig

Dec 5, 2015 at 3:35 PM | Unregistered CommenterCraig Loehle

Craig,
Since you're here, what about the possibilty that the AMO is partly (or wholly) forced, in which case your analysis will potentially under-estimate the forced response.

Dec 5, 2015 at 3:44 PM | Unregistered Commenter...and Then There's Physics

Craig,
Many thanks for providing the paper.

In it, you write "The optimal scaling for the AMO index to convert it to comparable °C was 0.625." Can you please elaborate on the method used to arrive at this coefficient, or indicate the criterion being optimized?

Dec 5, 2015 at 3:55 PM | Registered CommenterHaroldW

There is no such thing as a "forcing". It is all part of the climate change scam. It is dreamed up by climate "scientists" to try and persuade the layman that there is some actual physics behind the "atmospheric greenhouse effect" scam.

Dec 5, 2015 at 3:58 PM | Registered CommenterPhillip Bratby

Philip.
You really should avoid projecting your ignorance into others. If you were right, then there would be no way to change the energy balance of the planet, which is clearly utter nonsense. Also, it is comments like yours - that largely go unchallenged here - that makes me regard this site as a site that promotes science denial

Dec 5, 2015 at 4:05 PM | Unregistered Commenter...and Then There's Physics

ATTP: Likewise, you talk a complete load of nonsense and show a denial of real science. The Earth's climate is a straightforward but complex problem of heat transfer and fluid flow. There is no need to introduce meaningless things like "forcings".

Dec 5, 2015 at 4:19 PM | Registered CommenterPhillip Bratby

Philip,
A forcing is simply defined as a change in energy balance. You may want to define it some other way, or choose to give it a different name, but that does not mean that changes cannot influence the energy balance. Suggesting otherwise is bizarrely ignorant. On the other hand, you do seem to think that Salby's ideas may have merit, so I probably shouldn't be surprised.

Dec 5, 2015 at 4:22 PM | Unregistered Commenter...and Then There's Physics

...and Then There's Physics

You are a man who appears highly motivated to challenge climate windmills wherever they appear. The question is why you waste your time skiddling about on internet forums when you could be exploring the mysteries of the cosmos or fighting real poltergeist like the late, great Archie Roy (astronomy, Glasgow).


I asked the same question of Peter Sinclair (greenman3610) who makes the sneering climate videos on Youtube. He wouldn't answer the question. My assumption about him was dodgy eco politics like Hansen and his team, Paul Ehrlich, Mike Hulme and many others. It's a strange kind of hobby for a physicist.

Dec 5, 2015 at 4:37 PM | Unregistered Commenteresmiff

There you go. There is no need to use this made-up term if it is just a change in energy balance. Of course the climate is in energy balance - what comes in goes out. In years of involvement of heat transfer and fluid flow and using standard textbooks, there was never the mention of this artificial term. Who invented the term and why?

Dec 5, 2015 at 4:38 PM | Registered CommenterPhillip Bratby

esmiff,


The question is why you waste your time skiddling about on internet forums

A very good question. I do not have a good answer.

Philip,


There is no need to use this made-up term if it is just a change in energy balance. Of course the climate is in energy balance - what comes in goes out.

Except it is not always in energy balance. If the Sun gets brighter it will produce a positive forcing change and will cause the surface temperatures to go up. If it gets fainter, we will cool. Similarly there are other things - like GHGs - that can also produce a change in the energy balance. Volcanoes are another. We simply call the resulting energy imbalance a change in forcings. There's nothing particularly special about this. It's perfectly normal to have some word that describes something. Of course, we will tend towards a state of energy balance, but that does not mean that we are always in energy balance.

Dec 5, 2015 at 4:43 PM | Unregistered Commenter...and Then There's Physics

My statement about the AMO not being forced is to say it has no secular trend--it is a trendless index. If it is forced by solar or something, it is not related to CO2.

The optimal scaling for subtracting the AMO was the scaling that reduced the variance in the result the most.

Dec 5, 2015 at 4:44 PM | Unregistered CommenterCraig Loehle

Craig,
Expect that it may be partly anthropogenically forced, hence your analysis will potentially under-estimate the forced response.

Dec 5, 2015 at 4:53 PM | Unregistered Commenter...and Then There's Physics

Craig: "The optimal scaling for subtracting the AMO was the scaling that reduced the variance in the result the most."
Thanks! I see that I missed this in my first skim of the paper: "The AMO data were scaled vertically to minimize the variance in the (temperature – AMO) data." My bad.

Dec 5, 2015 at 5:11 PM | Registered CommenterHaroldW

If we sceptics decline to believe other attempts to do the attribution trick, we can't believe Craig's attempt is any better just because we like the answer.

( I don't buy forced/unforced. Everything has a reason. Oh, and the idea of forcings being somehow capable of being summed arithmetically to give a valid resultant is a stretch for me. It suggests a methodology chosen to give a slick explanation and a desired result for those who use it. If it was right, we wouldn't need climate models.)

Dec 5, 2015 at 5:43 PM | Unregistered Commenterrhoda

ATTP

"if solar forcing increases by 0,5W/m^2 then it means that we are now gaining 0.5 Joules per square metre per second due to this change. Similarly if anthropogenic forcings increase by 0.5W/m^2 it means the same thing. Therefore, on average, we would expect the response to be similar ec 5, 2015 at 1:35 PM | Unregistered Commenter...and Then There's Physics" Per: Dec 5, 2015 at 1:35 PM | Unregistered Commenter...and Then There's Physics
//////

I do not understand why anyone would consider the response to be similar.

The ocean is opaque to DWLWIR; and given the omni-directional nature of DWLWIR, it can at most penetrate the ocean by 4 or 5 microns!!!

Whereas the ocean is substantially transparent to solar with solar irradiance penetrating upwards of a 100 metres, albeit that the majority of solar irradiance is fully absorbed within the top 3 or 4 metres of the ocean.

Given this very substantial difference, why would anyone consider that the ocean's response would be similar.

It is likely that one (solar) can slowly warm the ocean and warm it to depth, whereas the other can simply drive evaporation given that there is no effective mechanism whereby DWLWIR energy fully absorbed in the top 3 or 4 MICRONS can be sequestered to depth and hence dissipated at a rate faster than the DWLWIR would energize and drive evaporation for the very surface of the ocean.


As we know the ocean surface skin is cooler than the the top few Millimetres, so energy in the top MICRONS cannot be conducted to depth, ocean overturning is a diurnal phenomena so does not operate for half the day, and the action of the wind and swell is a slow mechanical process, and in any event would be wholly in effective in conditions of say BF3 or less

As you no doubt know, the average wind conditions over the oceans is just over BF4, so it follows that there are vast swathes of the ocean where prevailing conditions must be less than BF3 to average out all those storms.

Perhaps you will further explain why you consider it reasonable to consider that the response to solar and DWLWIR would be the same given the very different absorption characteristics of the relevant EMR spectrum in water/the oceans.

Dec 5, 2015 at 5:48 PM | Unregistered Commenterrichard verney

ATTP: the pattern of the AMO does not match any individual forcing nor total forcing of the IPCC compilation appendix, which is why I suggest it is an index of internal oscillations. I cite several papers justifying my supposition.

rhoda: no, you should not accept my results just because you like the answer. Instead you should read it and see if it makes sense.

Dec 5, 2015 at 6:19 PM | Unregistered CommenterCraig Loehle

Craig: I think you are very tolerant. You take the trouble to spend - however long- time on producing a paper with detailed argument, and some arrogant, self-proclaimed, tax-payer-employed 'physicist' tells you that, even though he has not bothered to read your paper he can tell you where you've gone wrong. And yet, and yet, you take the extra time to engage with said arrogant abstinent pillock. Well done you.

Dec 5, 2015 at 7:41 PM | Unregistered CommenterHarry Passfield

“Thus almost exactly half of the post-1970 warming is possibly natural …”.
========================
Professor Ole Humlum @ climate4you says:
“… the total global cloud cover reached a maximum of about 69 percent in 1987 and a minimum of about 64 percent in 2000 (see diagram above), a decrease of about 5 percent. This decrease roughly corresponds to a radiative net change of about 0.9 W/m2 within a period of only 13 years, which may be compared with the total net change from 1750 to 2006 of 1.6 W/m2 of all climatic drivers as estimated in the IPCC 2007 report, including release of greenhouse gasses from the burning of fossil fuels. These observations leave little doubt that cloud cover variations may have a profound effect on global climate and meteorology on almost any time scale considered …”.
During the 80s and 90s tropical cloud cover and global surface temperature appear to be correlated:
http://www.climate4you.com/images/HadCRUT3 and TropicalCloudCoverISCCP.gif

Dec 5, 2015 at 8:05 PM | Unregistered CommenterChristopher Hanley

The dishonesty of the thread subject:
"Is underlying warming only 0.8 degrees per century?"
So what exactly are we expected to understand as 'underlying warming'? Is it the warming for which we understand the causes or the warming that occurs in addition to the 'understood' warming or is it the current trend in global warming? Once you have answered that then which warming are we talking about? Is it the figure after adjustment by NASA/NOAA, or before adjustment or is it the satellite figure and are any of them reliable?

Then we get to the abstract (after reading the abstract I have no desire to read the whole thing).
"This possible unforced internal oscillation of the climate system provides an opportunity to correct temperature trends."
So would that be changes to the climate system which have no causes? Systems can change without internal or external action upon them?
"Thus almost exactly half of the post-1970 warming is possibly natural." Please explain natural variation or is this just another collective term for variation you can not explain?

Dec 5, 2015 at 9:02 PM | Registered CommenterDung

dung: without reading the paper how do you expect to understand it? "underlying warming" is the warming NOT due to natural fluctuations. It is postulated that ocean circulation can create natural oscillations such as El nino--you've heard of el nino, AMO, PDO, right? So yes, a system with ocean circulation can change without external forces acting on them. It does not generate energy but can circulate heat in and out of the atmosphere over time.

Dec 5, 2015 at 9:33 PM | Unregistered CommenterCraig Loehle

There was a letter in the Irish Times today that read
" This risible pseudo-science can only survive with a regular,
- self replenishing supply of gullible, exploitable fools who
are happy to disregard logic in favour of unverifiable nonsense".

It was only when I looked at the headline that I realised the writer
was referring to astrology rather than climate alarmism!

Dec 5, 2015 at 9:34 PM | Unregistered CommenterSpectator

Dec 5, 2015 at 9:33 PM | Unregistered CommenterCraig Loehle

Craig I tried to make clear that I was commenting only on the thread title and the abstract.
NOTHING changes without a cause. All of the ocean circulations are the product of the forces acting upon them and unless those forces change then the circulations will not change. All effects have a cause and the fact that we do not understand all the causes does not change that.
You do not know what all the natural variations are and how they change and yet you act as though you do.

Dec 5, 2015 at 10:16 PM | Registered CommenterDung

Dung: you clearly did not read the paper (and I did not choose the blog post title here). I do not act as though I know what all the natural variations are: I proposed that the AMO might (might) capture part of it and it does appear to do so by reducing the variability in the resultant record.
As to everything having a cause: I did not say the AMO is "uncaused" but that it might be internal to the Earth system rather than being strictly forced externally. There is a body of work out there on ocean circulations that shows how complex they are. Once initiated, they continue as part of the heat dissipation network of the Earth system. Warm water flows north and ocean currents are driven by trade winds (etc). All of this has nothing to do with CO2 and thus is "unforced" variability and does not necessarily respond in a clear way even to solar changes.
I hope this clears it up for you.

Dec 6, 2015 at 12:13 AM | Unregistered CommenterCraig Loehle

"Warm water flows north..."
Such Northern-Hemisphere-ism! Every hemisphere is special in its own way. We must embrace a diversity of hemispheres.

Dec 6, 2015 at 3:44 AM | Registered CommenterHaroldW

Craig

I am unimportant and not worth wasting your time on and I seriously have no problem with you as a person.
However although there is a lot of "possibly", "could have", "might", "estimating", "imply",
your paper produces a figure for Equilibrium Climate Sensitivity of 1.5.
The idea that the Earth has a CO2 'climate sensitivity' at all is a joke. I would compare 'climate sensitivity' to CO2 with the importance of a screw in the construction of an aircraft carrier.
The only reason climate sensitivity gets an airing at the moment is because the more recent papers give figures that imply CO2 is less important than the alarmists have told us.

Dec 6, 2015 at 3:57 AM | Registered CommenterDung

Has anyone any ideas about this paper by Hermann Harde?

http://www.scipublish.com/journals/ACC/papers/846

He claims:

The short- and long-wave absorption of the most important greenhouse gases water vapour, carbon dioxide, methane and ozone are derived from line-by-line calculations based on the HITRAN08-databasis and are integrated in the model. Simulations including an increased solar activity over the last century give a CO2 initiated warming of 0.2 ̊ C and a solar influence of 0.54 ̊ C over this period, corresponding to a CO2 climate sensitivity of 0.6 ̊ C (doubling of CO2) and a solar sensitivity of 0.5 ̊ C (0.1 % increase of the solar constant).

Dec 6, 2015 at 10:41 AM | Unregistered CommenterHans Labohm

Hans Labohm
I don't have an opinion on the Harde paper but I can give you the official view.

If what Harde says is correct, then all the 40,000 people in Paris at COP21 are wasting their time.
All those who making millions throught their hedge funds or tens of thousands in fat sinecures in ivory towers could find the winter wind round their unclothed backsides very cold indeed.
The BBC, MSM, NGOs and other lying spongers would be found out.

It must therefore be the case that this Harde character doesn't know what he is talking about and his conclusions are rubbish.

* Note to Harvard-Smithsonian: Check and see if there is any conceivable chance this guy could be right. If there is, you know what to do.

Dec 6, 2015 at 11:28 AM | Registered CommenterMike Jackson

As I understand it, the problem with Harde's calculation is the he has a vertical water vapour profile that is simply at odds with what is actually observed. Hence, he is over-estimating the significance of water vapour, and - as a consequence - under-estimating the significance of CO2. You can read about it here.

Dec 6, 2015 at 1:01 PM | Unregistered Commenter...and Then There's Physics

ATTP
Rabett quotes Pierrehumbert:

Water vapor is removed either by condensation or by diffusion into a neighboring drier air parcel.
which is fair enough but Pierrehumbert then goes on to say
Let us suppose for the moment that diffusivity is so low that the latter mechanism is unimportant.
which is where the cynic in me kicks in because he then explains at length what happens "if that diffusivity is so low that the latter mechanism is unimportant."
Watch for the pea under the thimble!
I don't have a problem with anyone debunking anyone else's theories, hypotheses, guesses, hunches. That is (as I understand it) is what science is all about. But at least do it openly and honestly which that isn't.
Where does Harde stand if diffusivity is not "so low that the latter mechanism is unimportant."?
Perhaps this can help you understand why we are not as trustful of climate scientists as we might be. ☺

Dec 6, 2015 at 1:21 PM | Registered CommenterMike Jackson

Check ot this week's More or Less broadcast on BBC 4:

Ruth Alexander investigates claims climate change has contributed to the war in Syria, and with the climate change summit COP21 underway in Paris, we answer listener’s climate change number questions.

Dismantles the statistics of Global Warming.

Dec 6, 2015 at 3:51 PM | Unregistered CommenterDoug Elliot

How the five times multiplication of the sun?
================

Dec 6, 2015 at 8:12 PM | Unregistered Commenterkim

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