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Schwartz on climate sensitivity

Stephen Schwartz et al have published a paper in a journal called Earth's Future that reviews and considers the recent low estimates of climate sensitivity, wondering what the divergence of the different estimates might mean:

Earth's equilibrium climate sensitivity (ECS) and forcing of Earth's climate system over the industrial era have been re-examined in two new assessments: the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change (IPCC), and a study by A. Otto and others (Nature Geosci., 2013). The ranges of these quantities given in these assessments and also in the Fourth (2007) IPCC Assessment are analyzed here within the framework of a planetary energy balance model, taking into account the observed increase in global mean surface temperature over the instrumental record together with best estimates of the rate of increase of planetary heat content. This analysis shows systematic differences among the several assessments and apparent inconsistencies within individual assessments. Importantly, the likely range of ECS to doubled CO2 given in AR5, 1.5 to 4.5 K/(3.7 W m-2) exceeds the range inferred from the assessed likely range of forcing, 1.2 to 2.9 K/(3.7 W m−2), where 3.7 W m−2 denotes the forcing for doubled CO2. Such differences underscore the need to identify their causes and reduce the underlying uncertainties. Explanations might involve underestimated negative aerosol forcing, overestimated total forcing, overestimated climate sensitivity, poorly constrained ocean heating, limitations of the energy balance model, or a combination of effects.

Summary: Recent assessments of Earth's climate sensitivity and forcings over the industrial period, taking into account the observed increase in global mean surface temperature and rate of increase of planetary heat content, exhibit differences and apparent inconsistencies.


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Reader Comments (29)

They forgot the scientific explanation - the climate is insensitive to a doubling of CO2.

Nov 19, 2014 at 9:50 AM | Registered CommenterPhillip Bratby

This analysis shows systematic differences among the several assessments and apparent inconsistencies within individual assessments.
Or put another way we still don't have a clue.
Such differences underscore the need to identify their causes and reduce the underlying uncertainties.
Only if doing so will benefit mankind. Otherwise it's not a "need" merely intellectual curiosity.

Meanwhile, back in the world of mortgages, unemployment, and how to keep the lights on this winter ...

Nov 19, 2014 at 9:53 AM | Registered CommenterMike Jackson

How can "overestimated climate sensitivity" be one of the reasons for an overestimated climate sensitivity?

Nov 19, 2014 at 10:12 AM | Registered Commentersteve ta

The science is settled. Move along now..Nothing to see here.....

Nov 19, 2014 at 10:17 AM | Unregistered CommenterIvor Ward

...wondering what the divergence of the different estimates might mean...

They haven't got a clue?

Nov 19, 2014 at 10:27 AM | Registered CommenterMartin A

The time was when I would comment on all these CS posts saying there ain't no such thing. I have modified my position somewhat on the basis of what I have read here over the years. Currently I'd say that the concept of CS with its immediate and long-term effects is valid for comparison of models including GCMs between themselves and between models and actuals. Or indeed between differing ways of assessing actuals. The concept of CS is limited to this sort of comparison. It is not valid for the purposes of predicting any future climate or global temperature given a change of CO2 concentration. Much of the hot air in this debate is the result of confusion as to when the concept is valid and when it is not.

It's for comparison of models. That's really all it's for.

Nov 19, 2014 at 10:27 AM | Unregistered Commenterrhoda

Perhaps the solution, from the layman's point of view that is, would simply be to cut down on the hot air?
Problem solved and we can all get back to normal.

(Sorry; I think it's the paracetamol getting to me!)

Nov 19, 2014 at 10:51 AM | Registered CommenterMike Jackson

No mention of one of the major uncertainties, the history of the global temperature. Those who claim to know it must believe that most of the early European explorers and colonisers were mainly interested in measuring air and sea surface temperatures with great accuracy.

Nov 19, 2014 at 11:09 AM | Unregistered CommenterMikky

Rhoda, I tend to agree. CS is a creature of the climate models and as these increasingly show themselves to be wrong then CS loses its meaning.

The whole global warming thing is on the verge of collapse and has been for several years. As long as that situation remains unthinkable to mainline climate scientists and the establishment, we shall remain in this limbo. The warming activists keep raising unsubstantiated scare stories to keep the bandwagon moving and this just prolongs the mess.

Everyone can see that there is no correlation between GHG concentration and global temperature but no one is prepared to admit it.

Nov 19, 2014 at 11:29 AM | Unregistered CommenterSchrodinger's Cat

One of the biggest misrepresentations of CS must surely be the IPCC's continued insistence on their high estimates being around 4 - 4.5C. I've followed this debate for years and even as a layman have seen precisely NO real-world evidence to support such a position.

Of course to admit their high-end estimates have been all-but falsified by empirical observations would deliver a hammer-blow to the cause, which means they're deliberately maintaining their stance in-spite of clear evidence to the contrary. Many would call such behaviour fraud.

Nov 19, 2014 at 11:55 AM | Unregistered Commentercheshirered

I quote from the conclusions section of the paper below - and conclude:-

1) Climate sensitivity and model forcings do not match measured temperatures. 2) The factors that influence this are many and varied - the factors cannot be understood or modelled "at this time". 3) Concludes with the "hope" that more work is carried out to understand the reasons for the inconsistencies - so that models of the future better match the measured climate response.

So, not too much to dispute in the conclusions - in a nut shell "we do not understand the factors that influence the climate and the existing models used for climate predictions do not work". Totally amazing that we are spending gazillions of $$££ based on policies driven by the flawed output from the current models.

Quote from the conclusions:-

"In summary, examination of estimates of climate sensitivity and forcing over the twentieth
century in recent assessments in the framework of a global energy balance model shows
apparent inconsistencies relative to measurements of the increase in global mean surface
temperature over this time and the net heat flux into the planet. Potential contributing factors
are underestimated negative aerosol forcing, overestimated total forcing, overestimated
climate sensitivity, poorly constrained ocean heating, and limitations of the energy balance
model. However, determining the contributions of each does not seem possible at present. We
hope that calling attention to these apparent inconsistencies will stimulate investigation of the
reasons for them and, ultimately, their resolution, leading to enhanced confidence in the
quantitative understanding of the response of the climate system to past perturbations and to
estimates of future response to past and prospective future emissions of greenhouse gases and

Nov 19, 2014 at 12:08 PM | Unregistered CommenterRobert Thomson

Lysenko set back Soviet agriculture and genetics for decades. The Greens have done the same for power generation without the threat of Siberia or worse.

Nov 19, 2014 at 12:41 PM | Unregistered Commenterbernie1815

Schrodnger's Cat
You're not wrong but I'll re-quote this from Wirth that I posted earlier today:
"We've got to ride the global warming issue. Even if the theory of global warming is wrong, we will be doing the right thing -- in terms of economic socialism and environmental policy." Timothy Wirth, former U.S. Senator.
"Global warming" is merely the peg. "Economic socialism" (whatever the hell that means) and environmentalism (ditto) are what this is all about.
The more we investigate the supposed interactions between CO2 and climate and climate sensitivity and radiation physics and all the other "results" that the models are telling us about the further we drift from the over-arching fact that this has nothing to do with science (if it ever did).
The loudest mouths are not scientists, not even climate scientists. They are environmental activists with a vision. And it's not a vision that the overwhelming bulk of humanity want to be a part of.

Nov 19, 2014 at 12:55 PM | Registered CommenterMike Jackson

Does any other science use such an emotive term as "forcing"? What was wrong with "coefficient"?

Nov 19, 2014 at 1:23 PM | Unregistered CommenterWJohn

"No mention of one of the major uncertainties, the history of the global temperature" Mikky this is the bit that puzzles me too. Perhaps we're just under-informed? Surely the scientists must know that, say, 19th century temp data is as sparse as it is (un)reliable and, when what matters is changes of a couple of degrees C, the quality of that data is near-useless: given that they do seem to rely on it (that poor quality data) what is it then, that we have missed? Or is it a question of, "thats all we've got so we'll deem it 'good enough' ". Well thats one approach, but I don't see from that approach that one can then scream from the roof tops that the world's ending because we're a couple of degrees above 19th century temps if we don't actually know what 19th century global temp was. Baffling. What book have I failed to read?

Nov 19, 2014 at 1:56 PM | Unregistered Commenterbill

Let me through. I'm a scientist. Climate sensitivity is zero. End of discussion. Clear the area.

Freeman Dyson

But I have studied the climate models and I know what they can do. The models solve the equations of fluid dynamics, and they do a very good job of describing the fluid motions of the atmosphere and the oceans. They do a very poor job of describing the clouds, the dust, the chemistry and the biology of fields and farms and forests. They do not begin to describe the real world that we live in.

The real world is muddy and messy and full of things that we do not yet understand. It is much easier for a scientist to sit in an air-conditioned building and run computer models, than to put on winter clothes and measure what is really happening outside in the swamps and the clouds. That is why the climate model experts end up believing their own models.” –

Hey you with the computer model. Put it down. Now !!

Nov 19, 2014 at 2:26 PM | Unregistered Commenteresmiff

The brilliance of this paper is in exposing the inconsistent choices of aerosol forcing and equilibrium climate sensitivity in AR5. The authors (who include Charlson, the grand old man of atmospheric sciences) show that AR4 and Otto et al produce best estimates of ECS that are completely in line with their choices of aerosol forcing, but that the AR5 range is wildly exaggerated on the upper end. As far as I can tell from their Figure 1, the actual ECS that AR5 should have produced given their choice of aerosol forcing is somewhere around 1.6 or 1.7, barely within their range of 1.5-4.5.

Now I believe I understand why the AR5 seemed to take a bit of a backward step compared to AR4, reducing their lower bound from 2 to 1.5--it's because they KNEW their best estimate would be in this range from 1.5-2. AR5 famously refused to come up with a best estimate, just presenting the range of 1.5 to 4.5, which to most readers would indicate that their best estimate is still around 3 as in all previous IPCC reports.

This is an extraordinarily simple argument, using AR5's own assumptions to fashion a dagger to the heart of AR5.

Nov 19, 2014 at 2:40 PM | Unregistered CommenterLance Wallace

Hara kiri to the gut of the machine. What are they thinking?

Nov 19, 2014 at 3:03 PM | Unregistered Commenterkim

'We know frog all. Maybe they will pith us.'

Nov 19, 2014 at 3:25 PM | Unregistered Commenterkim

"...wondering what the divergence of the different estimates might mean...
They haven't got a clue?"

Nov 19, 2014 at 10:27 AM | Registered CommenterMartin A

Yes, Martin, I have said this for years.
Saying that they know is a premeditated lie, fraud that must be punished with the utmost severity.

Nov 19, 2014 at 5:21 PM | Unregistered CommenterJohn Silver

Mike - your comment reminds me of Lord Donoughhue's post a few days ago. Some people need to be involved in a sort of ideological cause. Rather like religion, it is faith based so the facts don't matter.

Nov 19, 2014 at 5:47 PM | Unregistered CommenterSchrodinger's Cat


Usually, I disagree (violently) with what you say.

If your Nov 19, 2014 at 2:26 p.m. reflects your true thinking - I agree.

Nov 19, 2014 at 8:17 PM | Unregistered CommenterHeretic

I hear you but in my view, religious or not, facts do matter. Though we may well argue what is factual and what isn't.
From where I'm sitting they behave as if they are the true guardians of all the facts which makes them not a religion (which worships a god of some description) but a cult (where divinity is secondary to adoration of the leader of the cult, god being largely irrelevant).
Subtle difference but a difference none the less.

Nov 19, 2014 at 8:17 PM | Registered CommenterMike Jackson

Mike - Yes, I agree, the facts do matter to rational people, but those who keep the global warming scare going at maximum rate are ignoring the facts.

I have not considered whether they are a cult or religion but I don't disagree with the outcome. I shall try not to succumb to further comments about the cults.

Nov 19, 2014 at 9:05 PM | Unregistered CommenterSchrodinger's Cat

WJohn said:

"Does any other science use such an emotive term as "forcing"? What was wrong with "coefficient"?"

Capitalists are forcing the climate to do something it does not want to do. They are using CO2 to bully the global temperatures upward but like all victims the climate is now hiding it down deep where no one will see it as the climate tries to get on with its daily routine. Like all suppressed emotions they will fester until one day everything comes out in a violent explosion that may unintentionally hurt the climate's loved ones.

Once the capitalists bullies have been made to stop by the consensus of climate lovers, the climate may be brought back to the shining path through tough love and re-education.

Nov 19, 2014 at 10:06 PM | Unregistered CommenterJeff Norman

Jeff Norman

So true. At the exact time the little, fraud deniers were in danger of looking like liars, the heat from the bad, bad capitalist pigdogs changed from heating the air to heating the ocean. Intelligent heat. It's a whole new thing.

Nov 19, 2014 at 10:14 PM | Unregistered CommenterE. Smiff

And this "planetary heat content" is arrived at by ...
- model output ?
- the good but relatively insignificant atmospheric data, plus the poor but more significant ocean data ?

Nov 20, 2014 at 12:26 PM | Unregistered CommenterTuppence


You don't need complex models. The basic energy imbalance calculation is surprisingly simple.

There are three main energy sinks in the climate syatem, these are the oceans, the ice and the atmosphere. The pause in air temperatures means that we only need to consider ice and oceans.

Ice volume on land measured by GRACE and Cryosat is decreasing by 500 cubic kilometres per year.

The latent heat of fusion of water is 3.34*10^5 J/kg. 500 cu. Km.of ice is 5*10^14Kg.

The melting ice is therefore absorbing 1.67*10^20J/year.

It takes 360 cubic kilometres of extra volume to raise sea level by 1mm. The melting ice is raising sea level by 1.39mm/year.

Sea level is rising at 3.2+/-0.4 mm/year.Take out the ice- related rise and thermal expansion is causing an increase of 1.81mm/year. This is an expansion of 652

Total volume of the ocean is 1.37*10/9 The thermal expansion coefficient of seawater is ~10^-4/K.

The ocean has expanded by 6.52*10^2 / 1.37*10^9 = 8.9*10^-7. This corresponds to a temperature increase of 8.9*10-7 / 10^-4 = 8.9*10^-3K.

The specific heat of seawater is 3.98*10^3J/Kg/K, 3.98*10^15J/cu. km/K.

To produce the observed rate of sea level rise requires ( 1.37*10^9)*(3.98*10^15)*(8*9*10-3) =4.85*10^22

Total imbalance is 4.85*10^22 + 1.67*10^20, still 4.85*10^22J.

1W = 1J/second, 3.15*10^7J/year.

To produce the imbalance you need an input power of 4.85*10^22 / 3.15*10^7. = 1.54 * 10^15W.

Surface area of the Earth is 5.1*10^14M^2. The imbalance is 1.54*10^15 / 5.1*10^14 = 0.3W/M^2.

The uncertainty in sea level rise is +/- 0.4mm. The uncertainty in energy imbalance is therefore 0.3*( 0.4/3.2) = 0.04.

Stephens et al 2012 gave an imbalance figure at TOA of 0.6+/- 0.4. Nice to see that my own rough amateur estimate is within the uncertainty range of the professional work.


Nov 20, 2014 at 3:41 PM | Unregistered CommenterEntropic man

Thanks Entropic. But
- is the ocean rising any more than before? ie, is there an oceans hockey stick?
- ditto ice.

Nov 22, 2014 at 7:25 AM | Unregistered CommenterKatisha

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