The Revkin-Gavin debate on lower climate sensitivity

Lower climate sensitivity is getting some mainstream discussion. Last week at WUWT, we had this story: BREAKING: an encouraging admission of lower climate sensitivity by a ‘hockey team’ scientist, along with new problems for the IPCC which is now the most read story on WUWT in the past week.

This morning, WUWT carried this essay from Chip Knappenberger: The yearly lukewarm report which spurred some communication from Andrew Rekvin at NYT about the similar story he just posted today: A Closer Look at Moderating Views of Climate Sensitivity.

Andy just sent me a fascinating exchange from Gavin Schmidt of NASA and the Realcimate blog. Gavin sent sent this note as part of a group e-mail exchange and this is what Revkin forwared to me (and has now posted at Dot Earth):

Andy, I think you may be slightly misrepresenting where the ‘consensus’ on this issue has been. While there have been occasional papers that have shown a large tail, and some arguments that this is stubborn – particular from constraints based on the modern tranisent changes – there has always been substantial evidence to rule these out. Even going back to the 2-11deg C range found in the initial cpdn results in 2005, many people said immediately that the high end was untenable (for instance).

Indeed, the consensus statements in the IPCC reports have remained within the 1.5 – 4.5 range first set by Charney in 1979. James’ work has helped improve the quantifications of the paleo constraints (particular for the LGM), but these have been supported by work from Lorius et al (1991), Kohler et al (2010), etc. and therefore are not particularly radical.

By not reflecting that, you are implying that the wishful thinking of people like Ridley and Lindzen for a climate sensitivity of around 1 deg C is tenable. It is not, and James’ statement was simply alluding to that. For reference, James stated that his favored number was around 2.5 deg C, Jim Hansen in a recent letter to the WSJ quote 2.5-3.5 (based on the recent Palaeosens paper), and for what it’s worth the CMIP5 GISS models have sensitivities of 2.4 to 2.7 deg C. None of this is out of the mainstream.

I sent Schmidt and the group this reply:

In policy circles, including popular calculations of emissions trajectories necessary to avoid a high change of exceeding 2 degrees C. of warming, the hot tail has not been trimmed (unless I’m missing something?).

To me, that says the climate science community — including the Intergovernmental Panel on Climate Change science working group — has not adequately conveyed the reality you state here.

======================================================

Anthony: This essay from Pat Michaels is relevant also:

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leon0112

So…for us beginners…does Gavin think there is a possibility the correct number is less than 2.0 already?

Lonetown

This assumes all warming is due to CO2. Where’s the proof?

Policy Guy

Revkin awakes?

Terry Jackson

Let them debate all they want. The practical impact is along the lines that the WEATHER experienced in Portland OR may move north to Seattle in the worst case. It is well known that Portland has no growing season and is in perpetual drought, right? Good Grief.

Kev-in-Uk

I find it funny that these guys are allowed to ‘favour’ certain values, and that is ok. I personally favour the lower range of CS, probably less than 1.5 – but presume I will now be chastised by others for not backing that up!
Seriously though – the lower range in the first graph looks far more realistic and that is based purely on the fact that earth today ‘may’ have warmed by around 0.5degC since the industrial revolution (and I am not 100 percent convinced of that, due to the vagaries of the station record, etc). Nevertheless, I am still skeptical about the whole CS issue and it being basically ‘assigned’ or ‘correlated’ to being due to CO2.

JC

Wait… Hansen said 2.5-3.5? Where did he say that? That’s incredibly tame compared to his previous statements.
Also, Gavin Schmidt is gabbin’ sh!t as per usual, since he was riding the 3+ train hard until just recently.

Revkin awakes”, the pink slips tend to focus one’s mind

This observation by Revkin is highly significant. This is what I attempted to point out in my reviews of the drafts of the IPCC 2013 report regarding the apparent absence of any visually obvious trend in the latest NVAP-M time series of global water vapor. While the influence of the IPCC has been diminished for all the well known reasons, it’s still relied on by governments around the world. Scientific integrity demands that the IPCC present objective facts untouched by political or other agendas.

JC

Oh, and as a fun side note the global SIA is above baseline for the first time in awhile, which is neat since Gavin, Mikey, and crew love pointing out lows all the time.

Bill Illis

I have my own version of the above chart which shows where the actual observations to date are and that which takes into account Gavin’s comment about the transient warming timeline.
This one goes out to the year 2100 when CO2 will be about 700 ppm and is several years past the time when equilbrium temperatures are reached in the 3.0C per doubling proposition.
http://s3.postimage.org/e3u9d69ub/Zoom_in_RSS_UAH_Hadcrut4_Warming_Dec_12.png

davidmhoffer

Going from memory, the IPCC AR4 estimate was 2.0 to 4.5. I don’t recall an estimate of 1.5 to 4.5.

ThePhysicsGuy

Gavin’s statements:
..“I think you may be slightly misrepresenting where the ‘consensus’ on this issue has been
..the consensus statements in the IPCC reports have been….
Gavin should know better. Climate scientists in general should know better. “Consensus” is not a tenet of the scientific method.
Michael Crichton once stated:
I regard consensus science as an extremely pernicious development that ought to be stopped cold in its tracks. Historically, the claim of consensus has been the first refuge of scoundrels; it is a way to avoid debate by claiming that the matter is already settled. Whenever you hear the consensus of scientists agrees on something or other, reach for your wallet, because you’re being had.
He went on further to say:
Let’s be clear: the work of science has nothing whatever to do with consensus. Consensus is the business of politics. Science, on the contrary, requires only one investigator who happens to be right, which means that he or she has results that are verifiable by reference to the real world. In science consensus is irrelevant. What are relevant are reproducible results. The greatest scientists in history are great precisely because they broke with the consensus. There is no such thing as consensus science. If it’s consensus, it isn’t science. If it’s science, it isn’t consensus. Period.

So…for us beginners…does Gavin think there is a possibility the correct number is less than 2.0 already?
yes. the only people who are certain about the number are the people who think it is certainly below 1.
‘Wait… Hansen said 2.5-3.5? Where did he say that? That’s incredibly tame compared to his previous statements.”
In a new paleo paper. Not sure if it is out there for everyone to read. Its broadly consistent with what he has said before in his LGM work.
There is a debate in climate science. That debate is about sensitivity. If you want to join that debate you can. specifically the debate is over the range of estimates.

All warming before 1950 (including the 5 previous periods of greater warming than now – Holocene Climatic Optimum (9,000 to 5,000 years ago), Egyptian, Minoan, Roman, and Medieval (850 to 1250 AD) was natural, and all warming since was anthropogenic? The Eemian warming 125,000 years ago was natural, and the current warming which is 8 degrees C cooler with sea level 10 meters lower is not? With all the much greater warming of the past obviously due to natural climate change, why is not the current much more moderate warming also a part of that natural cycle? I can’t recall anything special after 1950, although the remarkable cooling through the mid-1970s while CO2 increased steadily triggered the short-lived “Global Cooling” panic. So there it is, the recent history of CO2 driven warming after 1950 – mostly cooling for the first 25 years, then moderate warming, but not as much as fast as in the 1930s, for the next 20 years, and finally no warming for the last 17 years.
“Me thinks global warming panics should be made of sterner stuff.”

Markus

I think Gavin Schmidt is misrepresenting Annan’s estimate.
Annan’s 2.5 deg estimate appears to have been made before including the halt in temperature increase, the reduction of aerosol forcing the increase of black cabon forcing and the discovery of statistics errors in multiple papers.
“Yeah, I should probably have had a tl;dr version, which is that sensitivity is still about 3C.
The discerning reader will already have noted that my previous posts on the matter actually point to a value more likely on the low side of this rather than higher, and were I pressed for a more precise value, 2.5 might have been a better choice even then. But I’d rather be a little conservative than risk being too Pollyanna-ish about it.”
http://www.blogger.com/comment.g?blogID=9959776&postID=1573684829816144955

nvw

When the history of science masquerading as politics is written, this episode will warrant a chapter. That scientific mistakes have been made is not the issue (science is all about identifying mistakes and moving forward), no the more interesting aspect is how and why the known scientific uncertainties were misrepresented to the public. When a scientist involved in the IPCC process calls out his colleagues for lying about inflated climate sensitivities to help motivate political action, that is far more damning than making a simple math-error.

MarkW

I note that they are assuming that 100% of the warming since CO2 was at 270, is due to CO2.

Kev-in-Uk

majormike1 says:
February 4, 2013 at 10:57 am
”All warming before 1950 (including the 5 previous periods of greater warming than now – Holocene Climatic Optimum (9,000 to 5,000 years ago), Egyptian, Minoan, Roman, and Medieval (850 to 1250 AD) was natural, and all warming since was anthropogenic?”
of course! How else can you forcefully describe a CO2 based climate sensitivity and correlate it to human growth/emissions! Thats what I love about the warmists – it’s only natural when it suits them, but anthropogenic at all other times!

It is increasingly clear that the earth has entered a cooling trend which will last until 2030 and probably beyond. It is also clear that the climate sensitivity is below the low end of the model ranges.The models are simply structured incorrectly so that their average range is an average of improperly structured models. For a discussion of this see my post “Global Cooling -Timing and Amount.” on my blog
http://climatesense-norpag.blogspot.com/
an earlier post on that site on 11/18/12 “Global Cooling Climate and Weather forecasting” provides links to the relevant data suggesting cooling.
The best discussion of climate sensitivity is seen in John Kehr’s The Inconvenient SKEPTIC on page 230 he persuasively estimates the sensitivity to a doubling from 380 ppm to be 0.7 degrees. Look at the Eemian Interglacial cooling phase ice core temp v CO2 for example. and also the SST temp trend trend v CO2 for the last ten years which would both produce negative sensitivities. The modellers simply picked a time frame which produced a sensitivity to match their preconceptions.

nvw

I should have added a reference to my post above:
http://julesandjames.blogspot.co.uk/2013/02/a-sensitive-matter.html

Kev-in-Uk

Steven Mosher says:
February 4, 2013 at 10:50 am
>>yes. the only people who are certain about the number are the people who think it is certainly below 1.<<
But logically Steven, and taking the ice core records as 'read' – it must be less than one, possibly even negative! – because CO2 increase always lags the temperature in the ice cores. Until it precedes it (or can be seen to definately accelerate the initial warming, i.e provide a positive AND increasing feedback), logically (on a pure CO2 based CS assumption) actual CS to CO2 must be very small! (and I am ignoring the logarithmic effect of CO2 too!).

Doug Proctor

Absolutely the climate crowd has not rejected the high end of the spectrum. I had a spat with GS in January of 2011 in which I referred to CAGW, which he denied he was saying. But CAGW is the basis of all proposed action, and requires in excess of 3C of heating by 2100. You cannot say that a >3C rise is unrealistic and claim that we have to act now to stop the world from burning up and the biosphere dying.
The alarm coming from >3C of rise is politically and socially useful. If the IPCC and Hansen and Gore had to admit that the chances were slim to none for a big temp rise, all the steam would go out of their whistle, and the monies out of their grants.
Fig. 4 of the draft AR5 report keeps the blue-gray colour around the Scenarios for the same reason, to make the potential disaster still a possiblity with current observational data. It is a visual trick equivalent to Mann’s Nature Trick. It has the same effect as the non-denial of catastrophic temperature rises: it keeps the alarm up.
If the IPCC were forced to drop its Scenario A from AR5, we’d be a long way towards the end of the Global Warming hysteria. That is what would happen if >2.5C were considered unrealistic.
After 25 years you’d think the “scientists” at the IPCC would have to modify their projections. In any business, scientific or otherwise, additional work is used to tighten projections. Apparently climatology is not a business of any kind – but we knew that: it is politics, where nothing that happens is ever different from what you said would happen.

So…for us beginners…does Gavin think there is a possibility the correct number is less than 2.0 already?

It would seem to me that with every passing year that the temperatures don’t rise, their sensitivity numbers have to be adjusted downward. Of course, they could have done that by including the period from 1945 to 1975 in their calculations where temperatures were falling as human CO2 emissions were ramping up.
To my mind their entire notion of climate sensitivity to human CO2 emissions goes right out the window when a few questions are asked:
1. What was responsible for the warming from 1912 to 1940? It clearly could not have been human CO2 emissions. Most of the rural areas of the US weren’t even electrified until the 1930’s and then most of the power was hydro. Why do we have significant warming without significant increases in CO2 emissions?
2. What was responsible for the cooling until the 1940’s to 1970’s when global human CO2 emissions were ramping up? Why do we have significant cooling while we have significant increases in global CO2 emissions?
3. Why have temperatures not risen since 1998 when we have a period of both increased air clarity due to emissions controls across most of the world and CO2 emission rates continuing to increase?
4. Why did the temperatures cool so drastically from the early 14th century to the late 19th century while world population was increasing and our CO2 emissions generally increasing? This is also a period of rather massive deforestation and land use change from forest / plains to agricultural.
5. Why have we still not “recovered” fully to the climate of the Medieval Warm Period despite massive amounts of human CO2 emissions generated since that time?
There is only one roughly 30 year period where temperature rise correlates with CO2 emissions. Why are data changed retroactively in such a way as the trend of the changes (in every database of surface temperatures) always act to validate the AGW hypothesis? Why do we have several hundred years of temperature data that show no correlation of temperature change with atmospheric CO2, one roughly 30 year period when they do correlate, and a global alarm sounded that the CO2 is going to cause grave consequences?
Why are the people sounding the alarm that industrial activity and its requisite energy production will cause temperatures to rise to catastrophic levels the same ones who were claiming in the 1970’s that industrial activity and its requisite energy production was going to trigger another ice age?
From a person on the sidelines looking at what is going on, it appears that the goal is to reduce industrial activity and energy production in certain areas but not other areas and then finding some grave economic consequence in order to justify those policy decisions. In other words, it appears that there is an attempt to develop problems that can be used to justify the desired course of action.

talldave2

It’s the climatology version of the old Jon Stewart “clown nose on, clown nose off” game.
“Look at meeeeee! I turned off the air conditioning at a Senate hearing! I got arrested at a coal plant! I called for war crimes trials for skeptics! I compared coal trains to Auschwitz! Wheee! What fun!”
“Oh, but now I’ve taken off the clown nose, and so I am a Very Serious Person full of Integrity and Reason and Rigorous Intellectual Honesty. I practice Science — and nothing is more important than my work, I’m Saving the World, and so my Gravitas causes the very Earth to shake beneath my irreproachable feet.”

‘But logically Steven, and taking the ice core records as ‘read’ – it must be less than one, possibly even negative! – because CO2 increase always lags the temperature in the ice cores. ”
Nope.cant be less than 1 or you cant get out of an iceball earth.
The lag has nothing to do with it. The lag was predicted before it was discovered and is what one would expect if AGW is true.

pochas

When “sensitivities” get below the “no-feedbacks” sensitivity of 1.2 then that will be a sign that the climate alarm hucksters are beginning to face reality. Convection is a cooling phenomenon with a negative feedback factor on surface heating, a fact which should be blatantly obvious to any qualified scientist. Time to stop the charade.

talldave2

“Also, Gavin Schmidt is gabbin’ sh!t as per usual, since he was riding the 3+ train hard until just recently.”
It’s like how some leaders in the Mideast will release one version of a statement in Arabic and another in English, each telling the audience what it wants to hear, often in direct contradiction.

cui bono

“Isn’t it possible that [the first day] could have been 25 hours? It could have been 30 hours, could have been a week, could have been a month, could have been a year, could have been 100 years, or it could have been ten million years!” – Spencer Tracy in Inherit the Wind.
“Isn’t it possible that [climate sensitivity] could be less than 3 degrees? It could be less than 2.5 degrees with solar influences, could be less than 2 with black carbon, could be less than 1.5 as the years pass with no warming, could be less than 1, could be less than 0.5, could be nothing at all!” – future movie with an alarmist of your choice getting pummelled in a courtroom.

If one is to believe to the Hansens past and present pronouncements , one could conclude that CO2 saved the globe from another Little Ice Age, widely predicted in the late sixties and early seventies, and all due to the CO2 sensitivity of 2, as I demonstrate effortlessly here:
http://www.vukcevic.talktalk.net/00f.htm
🙂

Alex

I smell rats trying to leave the sinking ship in an orderly fashion. They know even the “low” 2 degree is [unsupported] by the evidence. I bet it’s maximum 1.5 and could be lower then 1 at the point where we are now.

talldave2

I have to say though, after reading his blog I quite like this Annan fellow. If only he had Hansen’s job.

Kev in UK.
Let me explain why it cannot be negative.
Definitions:
Sensitivity: the change in temperature per change in Watts.
So, for example if the sun increases by 1 watt, and the earth warms by 1 watt you have a
sensitivity of 1. If the sun goes up by 5 watts and the earth warms by 1 C you have 1/5 or
a sensitivity of .2
By studying the relaxation response to volcanos, for example, you can estimate this to be
lets say .7 +- .3 or .4 to 1. ( just for example ). Note that this estimate has nothing to do
with C02. it describes how the system responds to forcing. This is all definitional work.
More watts = higher C.
The next step is to calculate how many additional watts an increase of C02 will cause.
This is straightforward using known, tested, verified physics.
Watts = 5.35ln(x/y) where x is the concentration after change and y is before the change.
For doubling c02 from pre industrial to today you get around 3.7 watts.
So. If your estimate was .5 for sensitivity ( from your volcano study for example ) you
can then say that doubling C02 from pre industrial to today will get you 3.7* .5 or 1.85C
you cant get negative values unless you deny that c02 blocks IR. Since C02 does block IR, it is a positive forcing.

cui bono

Steven Mosher says (February 4, 2013 at 11:29 am)

(1) The Snowball Earth is a hypothesis.
(2) CO2 concentration posited to exit it has been estimated at 130,000 ppm.
It’s a bit of a stretch to use this as a constraint on sensitivity now.

climatebeagle

How does Gavin’s claim “Indeed, the consensus statements in the IPCC reports have remained within the 1.5 – 4.5 range ”
relate to this from IPCC Fourth Assessment Report: Climate Change 2007?
“Since the TAR, the levels of scientific understanding and confidence in quantitative estimates of equilibrium climate sensitivity have increased substantially. Basing our assessment on a combination of several independent lines of evidence, as summarised in Box 10.2 Figures 1 and 2, including observed climate change and the strength of known feedbacks simulated in GCMs, we conclude that the global mean equilibrium warming for doubling CO2, or ‘equilibrium climate sensitivity’, is likely to lie in the range 2°C to 4.5°C, with a most likely value of about 3°C. Equilibrium climate sensitivity is very likely larger than 1.5°C. ”
http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch10s10-5.html

Seems to me we’ve been over this ground with the Nic Lewis analysis done last December.

Kev-in-Uk

Sorry Steve, had to pop out for a while.
re climate sensitivity – I am referring to it only in relation to CO2 – which is what I thought was usually meant by the figures bounded about? Have I got that wrong? (I am fully aware that it is a generic term for forcing – but in the climate debate it seems exclusively reserved for forcing from CO2). So, in this context, high CS means a large effect from CO2, yes? Low CS means little effect from CO2? By negative, sure – it probably isn’t negative, but it is feasibly as close to 1 as makes it negligible.
re considering forcing from volcanoes, that’s surely comparing apples to oranges in any case? You cannot mix one type of forcing with another IMHO, as the nature of the forcing ‘action’ is different, for any number of reasons, distribution, height in the atmosphere, etc, etc. e.g cloud forcing from high clouds is not the same as cloud forcing from low clouds. My understanding of the CO2 forcing, is that it is an assumed value in all the climate models, and is usually a high value. This is shown clearly wrong from the predictive models themselves!
as for the denying CO2 blocks IR – the experimental work is not the same as the atmosphere (IMHO) – and if you cant have a snowball earth (which as Cui bono correctly says – is a hypothesis anyway) then you equally can’t have earth recovering from the hot temps and high CO2 of the past!
As a geologist I have to stand back and say the CO2 theory for past, present and future warming cannot be reconciled with the geological record, ice cores, etc….

Manfred

Steven Mosher says:
February 4, 2013 at 10:50 am
So…for us beginners…does Gavin think there is a possibility the correct number is less than 2.0 already?
yes. the only people who are certain about the number are the people who think it is certainly below 1
——————————————-
This is another disturbing misrepresentation.
AR4 mainstream position was:
“Equilibrium climate sensitivity is likely to be in the range 2°C to 4.5°C with a most likely value of about 3°C, based upon multiple observational and modelling constraints. It is very unlikely to be less than 1.5°C.”
Lindzen, Spencer and others who computed sensitivites below 1 never expressed certainty and to my knowledge not even likelyhood to the level of the IPCC

Theo Goodwin

cui bono says:
February 4, 2013 at 11:42 am
“Steven Mosher says (February 4, 2013 at 11:29 am)

(1) The Snowball Earth is a hypothesis.
(2) CO2 concentration posited to exit it has been estimated at 130,000 ppm.
It’s a bit of a stretch to use this as a constraint on sensitivity now.”
You fail to understand Mosher. Hypotheses, aka guesses, from CAGW proponents of the consensus count as tested and verified empirical evidence. To him it is all one grand, beautiful narrative that should not be addressed on a hypothesis by hypothesis basis by critics. To do so is to speak with the vulgar.

Rob R

Mosh
I don’t think you can get a 2.5 to 3.5 C climate sensitivity from CO2 from Palaeo evidence unless you assume a large part of the temperature change comming out of the LGM is due to CO2. The evidence that CO2 is the primary or even one of the primary drivers is not entirely convincing.

Bob

Steve Mosher, ” The lag has nothing to do with it. The lag was predicted before it was discovered and is what one would expect if AGW is true.”
Do you have a link or two for this?

Manfred

Steven Mosher says:
Nope.cant be less than 1 or you cant get out of an iceball earth.
————————————–
I think you mean “negative” and not “less than 1”, because less than one is perfectly possible with a solar amplifier and/or exaggerated temperature trends and/or unknown internal climate forcings.

Bob

Steve Mosher, ” Watts = 5.35ln(x/y) where x is the concentration after change and y is before the change.”
X and Y are CO2 concentrations. Since on a molecule for molecule basis, CH4 is ~30 more potent than CO2 (potency=ability to absorb IR, nothing do do with quantity), the same equation cannot be true for CH4, right?

The problem here, isn’t that they were wrong about the sensitivity. Scientists are wrong all the time. The problem is that admitting they were wrong would be politically disastrous. Because CAGW was sold to the wider world on the basis, ‘scientists say this and scientists are always right’.
Otherwise, Gavin is well aware that differences in output from the climate models are just quantified differences in the opinions of the modellers. And the opinions of scientists are only science when they derive from well articulated and falsifiable theories. If they derive from theory, then clearly there is no consensus. If not, then they are just numbers picked out of the air.
And don’t let Mosher mislead you. Sensitivity is net of feedbacks, and we know almost nothing about feedbacks over all timescales.

davidxn

“Nope.cant be less than 1 or you cant get out of an iceball earth.”
Yet Earth has emerged from ice ages where CO2 levels dropped. Try again.

Robuk

Kev-in-Uk says:
February 4, 2013 at 10:29 am
Seriously though – the lower range in the first graph looks far more realistic and that is based purely on the fact that earth today ‘may’ have warmed by around 0.5degC since the industrial revolution (and I am not 100 percent convinced of that, due to the vagaries of the station record, etc).
Proff. Peter Cox below, shows his climate model with CO2 forcing excluded, green line.
Second graph graph shows tree ring study
http://s446.beta.photobucket.com/user/bobclive/media/attenborough_zps1fdbe055.jpg.html?sort=6&o=0
http://s446.beta.photobucket.com/user/bobclive/media/800px-Briffa-tree_ring_density_vs_temperature_1880-2000_zps39423dee.jpg.html?sort=6&o=1
The model without CO2 forcing appears to agree with the tree ring data. does that indicate CO2 forcing is insignificant.
UNEP state,
It is now thought, is that atmospheric carbon dioxide levels have reached levels which are affecting tree growth.
Carbon dioxide acts as a fertiliser to many tree species, making gas concentrations beyond a certain level uncouple the relationship between temperature and tree growth.
Has there been any substantial temperature rise since the 60`s and I thought trees grew more
vigorously with increased CO2.
Can someone explain.

Bart

Anthony Watts says:
February 4, 2013 at 11:34 am
You stole my thunder. There is no reason that the sensitivity would be linear. So, it can heat things up initially, and then lose its potency as an equilibrium with all the other processes going on is established.
Steven Mosher says:
February 4, 2013 at 11:42 am
See above. As the usual disclaimer goes, all things being equal, more CO2 should heat the Earth. But, all things are not equal. Thanks anyway for foregoing your usual driveby style.

@Bill Illis
“I have my own version of the above chart which shows where the actual observations to date are and that which takes into account Gavin’s comment about the transient warming timeline.”
How different would the data be if charted unadjusted?

Alcheson

Steven Mosher says:
February 4, 2013 at 11:29 am
“Nope.cant be less than 1 or you cant get out of an iceball earth”
Steve, tell me then, if the earths warm temps depend so much on CO2 concentration, how come the earth didnt turn into a snowball when recently CO2 was closing in on 200ppm??
.If you dont need CO2 to stay warm, then maybe you DONT need CO2 to get warm.

Richard M

We can always hope the day comes when Mosher reads about unknown unknowns … until then we will probably have to put up with his proclamations.
As for Gavin and company all we need is logic. It is well known that research bias is a given. We all know that the warmists runs climate change research. Hence, it is almost 100% certain that the research is biased to have a higher sensitivity than reality. Every time we see a trimming of the sensitivity we can still be assured they are biased on the warm side.
From this logical viewpoint only it’s looking more and more like the the sensitivity is much less than 2.

Willis Eschenbach

Steven Mosher says:
February 4, 2013 at 11:42 am

Kev in UK.
Let me explain why it cannot be negative.
Definitions:
Sensitivity: the change in temperature per change in Watts.

you cant get negative values unless you deny that c02 blocks IR. Since C02 does block IR, it is a positive forcing.

I see large problems with this interpretation:
1. Climate sensitivity is an inversely proportional function of temperature for several reasons.
• Radiation is a function of T^4.
• Parasitic losses increase with temperature.
• Emergent cooling mechanisms (thunderstorms, dust devils, rain) are temperature based with high numbers above a threshold of emergence.
Clearly, climate sensitivity is inversely proportional to temperature, falling as temperature rises.
2. Climate sensitivity varies over both space and time. In the early morning in the all-critical tropics where the energy enters the planet-sized heat engine we call “climate”, the temperature rises rapidly because of the lack of clouds—a high change in temperature per change in watts (high sensitivity). In the late morning the watts are still rising but the clouds greatly reduce the temperature rise—smaller change in temperature per change in watts (low sensitivity). And indeed, certain areas at certain times can show negative sensitivity, and some areas of the planet are not sensitive to the forcing at all.
Now, the global average climate sensitivity that Steven is discussing is no more than the average of these highly varying sensitivities. But the average is greatly misleading, because it is taken as constant or semi-constant. In the real world, however, climate sensitivity not constant in any sense. It is both inversely proportional to temperature and highly non-linear.
As a result you can’t just say well, because the global average surface temperature doesn’t vary much, we can treat it as a constant. The average is not real, it is a mathematical chimera. In the real world, we don’t see an average temperature. If the “average temperature” goes up by one degree, and it happens to be evenly spread out, let’s say the morning temperature goes from say 7°C to 8°C, while the afternoon goes from 22°C to 23°C.
But both the climate sensitivity, and the change in climate sensitivity with temperature, are very, very different in the two temperature regimes of morning and afternoon. It takes much, much more energy to go from 22°C to 23°C than it does to go from 7°C to 8°C. So while the average temperature doesn’t change much, that is highly deceptive. In reality, the dependence of sensitivity on temperature makes a huge difference in how the system actually reacts to changes in forcing.
Regards to all,
w.