The fall of Forest 2006?

Nic Lewis is best known to the sceptic blogosphere as one of the co-authors of the O'Donnell et al paper, which found significant flaws in Steig's paper on Antarctic warming. Lewis has just published an extremely important article about Forest et al 2006, one of the key climate sensitivity papers shown in the IPCC's Fourth Assessment Report. Forest et al found a climate sensitivity of 3°C/doubling, rather higher than many other studies. However, although his research has been hampered by the fact that Forest appears to have lost the raw data (!), Lewis has concluded that there must have been a misprocessing of the figures and that the correct figure for climate sensitivity would be only 1°C/doubling.

If I am right, then correct processing of the data used in Forest 2006 would lead to the conclusion that equilibrium climate sensitivity (to a doubling of CO2 in the atmosphere) is close to 1°C, not 3°C, implying that likely future warming has been grossly overestimated by the IPCC.

It is hard to overstate how important this finding is, if correct.

Read the whole thing.

Comments

[shub]

munroad, thanks for the link to the BMJ article. I remember reading about this in Richard's Smith's "The trouble with medical journals".

I liked this bit.

There is a feeling on the part of the institutions in India, he added, that it is the responsibility of the international journals that have published Singh's work to take action, possibly under the aegis of the World Association of Medical Editors, as it is they who have secured his place in the canon of scientific research.

Lots of small little parallels with the state of climate science data and science.

[tty]

BBD Jun 25, 2012 at 7:19 PM

"However, a misrepresentation is a misrepresentation, and I hope our host will allow a single comment in response."

I see from your somewhat long-winded answer that while you are good att quoting climate-science bullshit you did not bother to actually look up the equation for albedo change that Hansen & Sato used for their paper. I do realize that finding it requires looking up another Hansen & Sato paper (which is only cited in the 2012 paper). Since this might overstrain your powers of scholarship, here it is:

FAlbedo (W/m2) = - 2 (SLS/75 m)4/5 - 3.5 (SLN/105 m)4/5

where SLS and SLN is the sea-level change due to glaciation in the southern and northern hemisphere
respectively. Now exactly how did I misrepresent this by saying that it "assumes that [the albedo change] is negatively proportional to sea-level^0.8"?

[Quid Sapio]

Isn't the real message here that climate sensitivity is almost impossible to measure observationally, and that all the "estimates" on which the current view of catastrophe are based are actually "*guesstimates* on a series of unknown quantities.

I think it's sometimes under-sold to the general public that the most emphasised aspect of CAGW (the C factor) is the one least well supported by data.

[spartacusisfree]

Martin A: 25th June 7.23 pm: 'There seems no doubt that the earth has been far colder in the past, even within the existence of mankind. What changed between then and now? The sun's output?'

The answer is simple: the Earth's albedo changed, a combination of ice caps growing and cloud albedo increasing as far fewer CCN caused droplet coarsening kinetics to accelerate. On Venus, the albedo of 0.9 from the sulphuric acid aerosols in the atmosphere is constant.

Paradoxically, we get the same cloud albedos from convection taking raindrops near the top of cumulus clouds. The physics, a large droplet backscattering process, is the same.

[BBD]

tty

while you are good att quoting climate-science bullshit

The misrepresentation was your claim that:

his estimate of albedo change (a very critical factor) which just assumes that this is negatively proportional to sea-level^0.8, without a shred of justification. He quite simply ignores vegetation changes, changes in snow cover and changes in cloudiness all of which are known to have been very large between the LGM and the present.

The quotes provided show that what you said is a misrepresentation. That is all. I notice you have now shifted ground to venting meaninglessly about something rather different:

Now exactly how did I misrepresent this by saying that it "assumes that [the albedo change] is negatively proportional to sea-level^0.8"?

I'm not going to argue about this with you. It's not worth the bother.

[Martin A]

Jun 26, 2012 at 2:34 PM spartacusisfree
Martin A: 25th June 7.23 pm: 'There seems no doubt that the earth has been far colder in the past, even within the existence of mankind. What changed between then and now? The sun's output?'

The answer is simple: the Earth's albedo changed, a combination of ice caps growing and cloud albedo increasing as far fewer CCN caused droplet coarsening kinetics to accelerate. On Venus, the albedo of 0.9 from the sulphuric acid aerosols in the atmosphere is constant.

Paradoxically, we get the same cloud albedos from convection taking raindrops near the top of cumulus clouds. The physics, a large droplet backscattering process, is the same.

spartacusisfree - thank you. Makes sense to me. I wonder whether HDH would agree.

[tty]

Jun 26, 2012 at 7:02 PM | BBD

"I'm not going to argue about this with you. It's not worth the bother."

For possibly the first time ever, I agree with you!

[Curt]

I find studies that use an estimate/measurement of the overall (average) sensitivity between LGM and Holocene as the present "instantaneous" sensitivity of climate sensitivity in the Holocene to be of no value at all. The implicit assumptions of linearity and constant coefficients seem, even at a casual glance, to be completely unjustified.

Certainly the snow-ice/albedo feedback would be much stronger with glaciers at 45N rather than 75N. In addition, we have to ask why the transition from glacial to interglacial states stops where it does, at similar levels in multiple cycles, and why variation within the Holocene (e.g. Bond events) is so much less that comparable variation (e.g. Dansgaard-Oeschger events) at LGM.

To me, the Holocene climate state bears all the marks of a system with "saturation" somewhere in the dynamic chain, which would dramatically reduce sensitivity. I say this as someone whose academic and professional specialty is feedback control of dynamic systems. I am late to this thread because I am just returning from a conference on the challenges in feedback control to build the next generations of semiconductors, with features below 10 nanometers.

[spartacusisfree]

Martin A: but to accept this idea, you must understand that Carl Sagan's aerosol optical physics which predicts cloud albedo is a monotonic function of optical depth is fundamentally wrong [a second optical process takes over for larger droplets].

This also means ALL satellite data derived from albedo measurements are wrong, some more than others. Climate modelling is in a cul de sac.

[BBD]

Hello Curt

Sorry for not responding sooner - I didn't look at this thread yesterday.

The argument proposed by H&S is that we can investigate climate sensitivity to radiative forcing by taking two near-equilibrium climate states - the LGM and the late Holocene - and quantifying the forcing that maintains the difference between them. Remember that the the process is reversible so it is incorrect to insist that ice albedo feedback at the LGM somehow invalidates the empirical calculation of sensitivity. A reduction of ~6.5W/m2 in net forcings lowers GAT by ~4.5C and gets you from an interglacial back to a glacial. If the process only worked one way, you would have a point.

I found the rest of your comment puzzling:

we have to ask why the transition from glacial to interglacial states stops where it does, at similar levels in multiple cycles

This is all about energy balance. Deglaciation stops once peak orbital forcing is passed. Slight variation in orbital dynamics causes slight differences between interglacial conditions (eg Eemian warmer than Holocene), but that's it.

why variation within the Holocene (e.g. Bond events) is so much less that comparable variation (e.g. Dansgaard-Oeschger events) at LGM.

You are confusing the bundles of DO events within a Bond cycle during the last glacial (MIS3) with the Holocene 'Bond cycle'. The former are thought to be caused by ice sheet dynamics (ice sheet thickness-induced basal melt as the driver of sequences of episodic purges) the latter are more nebulous (Bond himself called them 'enigmatic' and 'at best quasi-periodic'). If there really is a Holocene Bond cycle it is hypothesised to be a response to low frequency solar variability.

To me, the Holocene climate state bears all the marks of a system with "saturation" somewhere in the dynamic chain, which would dramatically reduce sensitivity.

I think there is a danger inherent in applying undoubted expertise in a non-related field to paleoclimate or climatology in general. For example, if the modern climate is insensitive, then how do we explain modern climate variability? If the climate system is sensitive to eg slight changes in RF from solar variability, then it must be equally sensitive to slight changes in RF from the radiating atmosphere. A climate system insensitive to increased RF from CO2 would not exhibit variability such as the MWP, the LIA or the early C20th warming episode. One really cannot have it both ways.

***

'Binge-purge' theory of DO events: MacAyeal (1993a,b); Alley & MacAyeal (1994); Payne & Donglemans (1997).

Holocene 'Bond cycle'?: Bond et al. (1997, 1999, 2001); Sarnthein et al. (2003b); Jennings et al. (2002); Schulz & Paul (2002); Risebrobakken et al. (2003).

[MikeHaseler]

Nic Lewis,

Do you have anything written up on climate forcing we could put on the SCEF site? You can contact me on info2012@scef.org.uk.

Mike