Wednesday, May 23, 2012

4595.txt

cc: Eystein Jansen <eystein.jansenatXYZxyz.uib.no>, joos <joosatXYZxyzmate.unibe.ch>
date: Mon Jul 17 15:08:48 2006
from: Tim Osborn <t.osbornatXYZxyz.ac.uk>
subject: new fig 6.14
to: Jonathan Overpeck <jtoatXYZxyzrizona.edu>, Keith Briffa <k.briffaatXYZxyz.ac.uk>

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.

Cheers

Tim


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