cc: Jonathan Overpeck <jtoatXYZxyzrizona.edu>, Keith Briffa <k.briffaatXYZxyz.ac.uk>, Eystein Jansen <eystein.jansenatXYZxyz.uib.no>
date: Tue, 18 Jul 2006 14:45:32 +0200
from: Fortunat Joos <joosatXYZxyzmate.unibe.ch>
subject: Re: new fig 6.14
to: Tim Osborn <t.osbornatXYZxyz.ac.uk>
Sorry, that was a very careless and a totally inappropriate choice of
words. I seriously apologize. Of course smoothing is not dishonest (I do
it also all the time). To the contrary, I very much apreciate all your
hard work to do these figures. I know that it is very time consuming
from own experience ... (that is perhaps why I did not reflect on my
wording when writing the e-mail). What I wanted to say is that if one
has the opportunity to show directly what forcing was used by the model
than I very much prefer to do so. I hope there remains no
misunderstanding. I realize now that I should have used more modest
wording at various places.
Let us see what Eystein, Peck and Keith are thinking about it.
With best wishes, Fortunat
Tim Osborn wrote:
> Hi all,
> thanks for the responses, Peck and Fortunat.
> I drafted the new figure 6.14 following as closely as possible the
> approach used for the original forcing/simulation figure (now 6.13).
> This is why I smoothed all series and used a common anomalisation period
> for all curves across all panels. It can greatly help to interpret why
> the simulated temperature responds in the way it does, because the zero
> (or "normal" level) is comparable across plots and because the strengths
> of different forcings can be compared *on the same timescale* as the
> simulated temperatures are shown. And, for 6.13, with so many different
> forcings and models shown, it would have been impossible to use
> unsmoothed series without making the individual curves indistinguishable
> (or indeed fitting them into such a compact figure).
> Now that the EMIC panels are separate from the original 6.13, we do have
> the opportunity to make different presentational choices. But I think,
> nevertheless, that some of the reasons for (i) proportional scaling,
> (ii) common anomalisation period; and (iii) smoothing to achieve
> presentation on comparable time scales, that held for 6.13 probably also
> hold in 6.14.
> However, I also appreciate the points raised by Fortunat, specifically
> that (i) it is nice to be able to compare the magnitude of the 11-yr
> solar cycles with the magnitude of the low-frequency solar variations;
> and (ii) that using a modern reference period removes the interpretation
> that we don't even know the forcing today.
> So we have various advantages and disadvantages of different
> presentational choices, and no set of choices will satisfy all these
> competing demands.
> One thing that I am particularly perturbed about is Fortunat's
> implication that to show smoothed forcings would be scientifically
> dishonest. I disagree (and I was also upset by your choice of
> wording). If it were dishonest to show smoothed data, then presumably
> the same holds for 6.13 (but its impossible to distinguish all the
> different volcanic forcings if shown unsmoothed), but also to every
> other graphic... should I be showing the EMIC simulated temperatures
> without smoothing too, so you can see the individual yearly responses to
> the volcanic spikes? But annual means are formed from the temperatures
> simulated on the model timesteps, so we still wouldn't be showing
> results that had not been post-processed. Most climate models, even
> GCMs, respond in a quasi-linear way, such that the smoothed response to
> unsmooth forcing is very similar to the response to smooth forcing. So
> if we are interested in the temperature response on time scales of 30
> years and longer, it seems entirely appropriate (and better for
> interpretation/comparison of forcings) to show the forcings on this time
> scale too, because the forcing variations on those time scales are the
> ones that are driving the temperature response (even though the forcing
> may be intermittent like volcanoes or have 11-yr cycles like solar).
> The choice of smoothing / no smoothing is not, therefore, anything to do
> with honesty/dishonesty, but is purely a presentational choice that can
> made accordingly to what the purpose of the figure is. Here our purpose
> seems to be long-term climate changes, rather than response to
> individual volcanoes or to the 11-yr solar cycle.
> So the position is:
> (1) smoothing or no smoothing: there are arguments for both choices,
> though clearly I prefer smoothing and Fortunat prefers no smoothing. I
> could make a figure which kept the smooth lines but put the raw annual
> histogram volcanic spikes underneath in pale grey, as Peck requested
> anyway (and possibly put the 11-yr solar cycles in pale brown underneath
> the smoothed brown solar series). This would be a compromise but the
> main problem is that the scale of the largest volcanic spikes would far
> exceed the scale I am using to show the smoothed series (so the panel is
> not large enough to do this)!
> (2) pre-industrial or present-day anomalisation reference period: again
> there are arguments for both choices. Whatever we choose, I firmly
> believe it should be the same for *all* curves in this figure (which can
> make a dramatic difference).
> (3) exaggeration of solar scale or proportional vertical scales: this is
> the one that I have the firmest opinion about. I see no reason to
> exaggerate the scale of the solar forcings relative to volcanic or
> anthropogenic forcings. The difference between the forcings looks clear
> enough in the version of the figure that I made. Exaggerating it will
> wrongly make the Bard 2.5% case look (at first glance) bigger than the
> anthropogenic forcing, and make it look more important than volcanic
> I'll hold off from making any more versions till decisions are made on
> these issues.
> At 09:01 18/07/2006, Fortunat Joos wrote:
>> Hi Tim and co,
>> Thanks for the figure. I like the figure showing the model results and
>> the general outline/graphic style.
>> However, I am concerned about what is shown in the forcing figure.
>> 1) Volcanic panel: I strongly believe that we should show what was
>> used by the model and not some 40 year smoothed curves for volcanic
>> forcing or any other forcing. So please use the original data file.
>> Scientific honesty demands to show what was used and not something
>> 2) solar panel:
>> 2a) We must show the Wang-Lean-Shirley data on the original resolution
>> as used to drive the models. In this way, we also illustrate the
>> magnitude of the 11-yr annual cycle in comparison with the background
>> trend. The record being flat, apart from the 11-yr cycle, during the
>> last decades is a reality.
>> 2b) Do not apply any smooting to the Bard data. Just use them as they
>> are and how they were published by Bard and used in the model.
>> 2c) It is fine to supress the Bard 0.08 case after 1610 (not done in
>> my figure version)
>> 2d) the emphasis of the figure is on the solar forcing differences.
>> So, please show solar somewhat overproportional in comparison to
>> volcanic and other forcings.
>> 3) other forcings: again no smoothing needed here. It would be hard to
>> defend a double smoothing.
>> 4)- normalisation of solar forcing to some period mean. If the
>> different solar forcings disagree for today as in your option, we may
>> send the signal that we do not even know solar forcing today.
>> Thus, I slightly prefer to have the same mean forcing values for all
>> solar records during the last few decades as shown in the attached
>> version. However, I also can see some arguments for other normalisations.
>> To illustrate points 1 to 4, I have prepared and attached a version of
>> the forcing panel.
>> other points
>> - Your choice of colors is fine
>> - time range 1000-2000 AD is fine
>> - suggest to remove the text from the y-labels except the units W/m2.
>> Sorry for this additional comments coming a bit late. However, I did
>> not realise that you planned to smoothed the model input data in any way.
>> With best wishes,
>> Tim Osborn wrote:
>>> Hi Peck, Eystein and Fortunat,
>>> I've drafted two versions of the new fig 6.14, comprising a new panel
>>> showing the forcing used in the EMIC runs, plus the old fig 6.13e
>>> panel showing the EMIC simulated NH temperatures. Keith has seen
>>> them already.
>>> First you should know what I did, so that you (especially Fortunat)
>>> can check that what I did was appropriate:
>>> (1) For the volcanic forcing, I simply took the volcanic RF forcing
>>> from Fortunat's file and applied the 30-year smoothing before
>>> plotting it.
>>> (2) For the solar forcing there are 2 curves. For the first, I took
>>> the Bard 0.25% column from Fortunat's RF file. For the second, I
>>> took the Bard 0.08% column from Fortunat's RF file from 1001 to 1609,
>>> and then appended the WLS RF forcing from 1610 to 1998. Then I
>>> smoothed the combined record. NOTE that for the Bard0.25%, the line
>>> is flat from 1961 onwards which probably isn't realistic, even though
>>> that is what was used in the model runs.
>>> (3) For the "all other forcings" there are 2 curves. For the first,
>>> I took the CO2 concentrations provided by Fortunat, then used the
>>> "standard" IPCC formula from the TAR (in fact the first of the three
>>> options for CO2 in IPCC TAR Table 6.2) to convert this to a radiative
>>> forcing. I then added this to the non-CO2 radiative forcings data
>>> from Fortunat's file, to get the total radiative forcing. For the
>>> second, I replaced all values after 1765 with the 1765 value (for the
>>> natural forcings case). Then I smoothed the combined record (as in
>>> fig 6.13c, I only applied a 10-year smoothing when plotting the "all
>>> other forcings", because it is fairly smooth anyway and using a high
>>> smoothing results in lower final values when there is a strong trend
>>> at the end of a time series).
>>> Now, some comments on the figures themselves (please print them and
>>> refer to them when reading this):
>>> (1) File 'chap6_f6.14_option1.pdf' is strongly preferred by Keith and
>>> me. This shows the three forcing components separately, which helps
>>> with understanding the individual causes of specific warming and
>>> cooling periods. I have managed to reduce the size of this
>>> considerably, compared to the equivalent panel in fig 6.13, because
>>> with only a few series on it I could squeeze them together more and
>>> also reduce the range of the vertical axes.
>>> (2) Although we don't prefer it, I have also made
>>> 'chap6_f6.14_option2.pdf' which is even smaller by only showing the
>>> sum of all the forcings in the top panel.
>>> Which version do you prefer? Please let me know so I can make final
>>> changes only to the preferred version.
>>> Some more comments:
>>> (1) Fig 6.14b was originally Fig 6.13e. When it was part of that
>>> figure, the colour bar showing the shades of grey used to depict the
>>> overlapping ranges of the published temperature reconstructions was
>>> only on Fig 6.13d. Do you think I should now also add it to the EMIC
>>> panel (6.14b), now that it is in a separate figure? It will be a bit
>>> of a squeeze because of the legend that is already in 6.14b.
>>> (2) Another carry over from when 6.14b was part of 6.13, is that the
>>> time range of all panels had to match (900-2010). Now that the EMICs
>>> are in a separate figure, I could start them in year 1000, which is
>>> when the forcing and simulations begin. Unless you want 6.13 and
>>> 6.14 to remain comparable? Again please comment/decide.
>>> (3) I wasn't sure what colours to use for the forcing series. In
>>> option 1, the volcanic and other forcings apply to all runs, so I
>>> chose black (with thick/thin used to distinguish the "all" forcings
>>> from the "natural-only" forcings (basically the thin flat line in
>>> "all other forcings). The cyan-green-blue runs used strong solar
>>> forcing, so I used blue for that forcing. The red-orange-brown runs
>>> used weak solar forcing, so I used brown for that forcing. Sound ok?
>>> Sorry for the long email, but I wanted to get everything explained to
>>> avoid too many iterations.
>>> Please let me know your decisions/comments on these questions, or on
>>> any other aspects of the new figure.
> Dr Timothy J Osborn, Academic Fellow
> Climatic Research Unit
> School of Environmental Sciences, University of East Anglia
> Norwich NR4 7TJ, UK
> e-mail: t.osbornatXYZxyz.ac.uk
> phone: +44 1603 592089
> fax: +44 1603 507784
> web: http://www.cru.uea.ac.uk/~timo/
> sunclock: http://www.cru.uea.ac.uk/~timo/sunclock.htm
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