Alleged CRU Emails - 25 results below

Original Filename: 839635440.txt | Return to the index page | Permalink | Later Emails

From: John Daly <daly@xxxxxxxxx.xxx>
To: n.nicholls@xxxxxxxxx.xxx
Subject: Re: Climatic warming in Tasmania
Date: Fri, 09 Aug 1996 20:04:00 +1100
Cc: Ed Cook <drdendro@xxxxxxxxx.xxx>, NNU-NB@xxxxxxxxx.xxx, k.briffa@xxxxxxxxx.xxx, Mike Barbetti <mikeb@xxxxxxxxx.xxx>, zetterberg@xxxxxxxxx.xxx, rjf@xxxxxxxxx.xxx

Dear Neville,

You mentioned to me some time ago that in your view, the 11-year solar cycle
did not influence temperature. There have been numerous attempts by
academics to establish a correlation, but each has been shot down on some
ground or other. I remember Barrie Pittock was especially dismissive of
attempts to correlate solar cycle with temperature.

Have you tried this approach?

Load "Mathematica" into your PC and run the following set of instructions -

data = ReadList[ "c:sydney.txt", Number]
dataElements = Length[data]
X = ListPlot[ data, PlotJoined-> True];
fourierTrans = Fourier[data];
ListPlot[Abs[fourierTrans], PlotJoined -> True];

fitfun1 = Fit[data,{1,x,x^2,x^3,Sin[11 2 Pi x/dataElements],
Cos[11 2 Pi x/dataElements]},x];
fittable = Table[N[fitfun1], {x, dataElements}];
Y = ListPlot[fittable, PlotJoined -> True];
Show[X, Y]

The reference to "c:sydney.txt" is a suggested pathname for the following
set of data - which is Sydney's annual mean temperature.

16.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.4
17.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.1
16.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.4
17.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.5
17.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.4
17.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.8
18.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.4
17.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.xxx xxxx xxxx.1
18.6

So Far so good.

"Mathematica" first plots out the data itself (see Atachment 1)

The first part of the instruction set lets "mathematica" do a Fourier Transform
on the data, ie. searching out the periodicities, if there are any. The result is
shown on Attachment 2.

The transform result shows a sharp spike at the 11 year point (I wonder
what is significant about 11 years?). The second part of the instructions
now acts upon this observed spike (the Cos 11 bit), to extract it's
waveform from the rest of the noise. The result is shown as a waveform
in attachment 3, the waves having an 11-year period, with the long-term
Sydney warming easily evident.

Attachment 4 shows the original Sydney data overlaid against the 11-year
periodicity.

It would appear that the solar cycle does indeed affect temperature.

(I tried the same run on the CRU global temperature set. Even though CRU
must be highly smoothed by the time all the averages are worked out, the
11-year pulse is still there, albeit about half the size of Sydneys).

Stay cool.

John Daly http://www.vision.net.au/~daly

Attachment Converted: c:eudoraattachSydney.gif

Attachment Converted: c:eudoraattachFourier.gif

Attachment Converted: c:eudoraattachSolar1.gif

Attachment Converted: c:eudoraattachSolar2.gif

Original Filename: 845217169.txt | Return to the index page | Permalink | Later Emails

From: Fred Pearce <100713.1311@xxxxxxxxx.xxx>
To: keith briffa <k.briffa@xxxxxxxxx.xxx>
Subject: new sciwentist feature
Date: 13 Oct 96 10:32:49 EDT

Keith,

This is my first draft of the dendrochronology feature. I wonder if you have time to go through look. I hope you recognise the quotes, but please makes changes if they think they misrepresent you. And if you can answer any of the questions in square brackets that would be most useful.

Ideally, can you not change the full text but make notes, remarks, answers referring to it.

As ever, haste is of the essence.

Regards

--Fred Pearce

It was one of the largest volcanic eruptions of the past xxx xxxx xxxxyears. Mount Changbai [correct?] in China blasted 50 cubic kilometres of rock into the air and deluged much of the far east with hot pumice. Radiocarbon dated the explosion at early in the 11th century. But it took Keith Briffa, sitting in his office in Norwich and juggling data from tree rings round the world, to pinpoint the precise year: 1032.

Volcanoes scatter the atmosphere with dust that deflects sunlight and cools the world beneath for a year or more. And when the world cools, trees grow less. That year's growth rings are smaller and less dense.

By analysing those rings, Briffa and his colleagues at the Climatic Research Unit in the University of East Anglia have charted these sudden and dramatic shocks to the climate system, from Changbai to Pinatubo in 1991. Larches in the forests of the northern Urals, for instance, have revealed that 1032 was the coldest summer there in a thousand years, more than 6 degrees cooler than the long-term average. Four of the five coldest summers in Europe and North America during the past four centuries (1601, 1641, 1669, and 1912) coincided with known major volcanic events. "We are pretty certain the fifth one, in 1699, did too," says Briffa. "But the geologists haven't found the volcano yet."

It is clever work. But the science of tree-ring analysis, dendrochronology, is more than just a party piece for botanists. Every ring in every tree round the world contains a memory of the climate the year it was formed. Reading these rings holds the potential, Briffa believes, to answer one of the most vital questions of our time: has human activity started to warm the planet?

With colleagues in laboratories and field stations from Dublin to eastern Siberia, he has within the past year [correct?] begun an attempt to construct a history, year by year, of temperatures across northern Europe and Asia over the past xxx xxxx xxxxyears, right back to the waning of the last ice age. The tam, funded by the European Union, hope to help show whether the warming seen across the planet in the past century, and especially since around 1980, is within the limits of normal natural variability, or the start of man-made global warming.

For climatologists, the search for an irrefutable "sign" of anthropogenic warming has assumed an almost Biblical intensity. The leading figures of the UN's Intergovernmental Panel on Climate Change (IPCC), claim that, in all probability, they have seen it. Last summer [ed: 1996], the IPCC's scientific working group, chaired by former UK Meteorological Office boss Sir John Houghton, concluded that "the balance of evidence suggests a discernible human influence on global climate". But it is like the "balance of evidence" suggesting BSE causes CJD. The judgment is far from "beyond reasonable doubt". The case remains "not proven".

Many researchers most intimately involved in the search are still far from sure how the probabilities balance. And some of the sharpest concerns are coming from the places where the original early warnings of global warming emerged in the mid-1980s. Places such as Briffa's base at the Climatic Research Unit in Norwich, and the Scripps Institution of Oceanography in California.

Few investigators doubt that the world has warmed recently. Nor that the enhanced "greenhouse effect" of pollution from gases such as carbon dioxide, will warm the planet. But in the past five years, climate researchers have growing increasingly aware of how little they really know about the natural variability from which they must pick out the "signal" of human influence.

One prominent IPCC researcher concerned about this gap in knowledge is Simon Tett from the Hadley Centre for climate modelling at the Meteorological Office, home to one of the world's five leading global circulation models, capable of recreating a mathematical version of how the atmosphere works and of running simulations of climatic changes over decades or even centuries. He says that "in the past, our estimates of natural variability have been based on climate models." But this autumn [date?], he says, those estimates have been thrown into turmoil by a paper published in the journal The Holocene. In it, Tim Barnett of the Scripps Institution of Oceanography, part of the University of California at San Diego, compared model estimates of natural temperature fluctuations over the past 400 years with the best evidence from the real world -- from instruments in the past century and "proxy data", such as Briffa's tree rings, from before that.

The result was bad news for the modellers. The two models examined -- one German, the other American -- generated a natural variability of around 0.1 degree C per century. This was less than half that revealed in the proxy data. "Of course we don't have to believe the proxy data. They certainly have problems attached to them. But my belief is that they both models, and proxy data too, underestimate real variability," says Barnett

The models' error was not, perhaps, too surprising. As Barnett points out, they do not include vital "forcing" mechanisms that alter temperature, such as solar cycles and volcanic eruptions. Nor can they yet mimic the strength of the largest year-on-year variability in the natural system, the El Nino oscillation in the Pacific Ocean, which has a global impact on climate.

Nonetheless, the findings should serve as a warning, Barnett says, that "the current models cannot be used in rigorous tests for anthropogenic signals in the real world". If they are they "might lead us to believe that an anthropogenic signal had been found when, in fact, that may not be the case."

Barnett knows how easily this can happen. He was a lead author for a critical chapter in the last IPCC scientific assessment, which investigated "the detection of climate change and attribution of causes". It formulated the IPCC case that the evidence points towards a human influence on climate, but it warned repeatedly that great uncertainties remained. "We wrote a long list of caveats in that chapter," says Barnett. "We got a lot of static from within IPCC, from people who wanted to water down and delete some of those caveats. We had to work very hard to keep them all in." Even so, when the findings were first leaked to the New York Times, it was under the headline "Scientists finally confirm human role in global warming".

Suggestive though the evidence may be, Barnett and his co-authors insist that the uncertainties, especially concerning natural variability, have to be answered. And so, suddenly, the modellers are queuing at Briffa's door to find out what his tree-ring data shows about the real world beyond the computer simulations. "Five years ago, climate modellers wanted nothing to do with the palaeo community," says Briffa with a grin. "But now they realise that they need our data. We can help them to define natural variability." He has already collaborated with Barnett. Tett paid his first visit to the dendrochronology lab in November [1996].

And so to the forests of Europe and Asia where, over the next [how many?] years Briffa will coordinate the work of colleagues in a dozen countries who hope to dramatically increase the available proxy data on past climate change. Much of the best data so far has come from the forests round Lake Tornetrask, on the northern border of Sweden, deep inside the Arctic Circle. This is near the northern limit for Scots pine, a place where their growth rate of the trees can be massively altered by small perturbations in summer temperatures. The result is dramatic differences in the thickness and density of tree rings.

The head of this work is Professor W [full first name?] Karlen [ed: acute on e], a geographer at the University of Stockholm, who over many years has taken cores from living trees and from logs and stumps hauled from old peat bogs. Despite the harsh climate, there are living trees here up to 600 years old. And the chronology can be extended ever further by analysing the dead trees. So far the climate reconstruction is complete for more than 1400 years before the present; the aim now is to extent it up to 8000 years.

The best data, says Briffa, comes from analysing both ring width and the maximum density of wood in each ring. By firing X-rays through the wood, researchers can now analyse the density of rings as little as 30 microns across -- the equivalent of a tree's girth growing by a centimetre every century. The growth of cell walls late in the growing season creates the densest wood and, says Briffa, "appears to depend directly on the average mean temperature".

Even so, ring growth is a product of many factors, including the genetics of the tree, past climate, the age of the tree and soil moisture. The relationships between ring growth and summer temperature are not a precise. But comparisons between the recent rings and known climatic data show that the rings can capture at least half of the summer temperature variability.

The temperature graphs produced at Tornetrask show "pronounced variability on all timescales, from year-on-year variations right up to century-on-century," says Briffa. On the longer timescales, for instance, they show 20 major cooling periods during the past two millenia, including long spells between 500 and 850, between 1100 and 1350 and between 1580 and 1750, the little ice age. There were also long warm spells between 900 and 1100, known as the medieval warm period, and 1360 to 1560. [ed: show graph from NERC paper].

Further back, early results suggest a strong warm era from 4000 to 3300 BC, and a cool period ending around 5070 BC. But there are intriguing gaps, for which no tree rings can be found. These, says Briffa, "suggest some major calamity that destroyed trees. Volcanoes, perhaps, or a rapid rise in the water tables." A 19-year gap between 1130 and 1111 BC, for instance, coincides with volcanic ash showing up in Greenland ice.

"What all this means," says Briffa, "is that the old image of the xxx xxxx xxxxyears since the end of the last ice age -- the Holocene era -- as climatically tranquil looks increasingly inaccurate." Hence the intense interest in the EU project, which will attempt to reconstruct those xxx xxxx xxxxyears of climate right across northern Europe and Asia, from Ireland to the Sea of Okhotsk, from the borders of Mongolia to shores of the Arctic Ocean.

During the past summer, helicopters flying low over the tundra have spotted logs in hundreds of small lakes in the Tornetrask region of northern Sweden. Karlen has donned his diving suit to help remove samples of timber from the freezing waters [did he?]. In northern Finland, local diving clubs picked some 3000 samples from lakes.

In the Arctic wastes of northern Siberia, a major survey is being conducted on the Taimyr peninsula, the largest stretch of frozen tundra in Eurasia and far north of today's tree line. There are well-preserved logs buried in river sediments here that grew between 5000 and 8000 years ago. On the Yamal Peninsula, just east of the Ural mountains on the shores of the Arctic Ocean, wood dug from the permafrost grew in conditions so cold that some summers temperatures never exceeded the threshold for growth of about 5 degrees C, so no growth rings formed. Nonetheless Yamal is the only site so far found that yields tree rings right through a gap at 300 BC. "Interestingly, the Yamal rings show this to have been the coldest period in the entire run," says Briffa.

Other, less detailed, surveys are being carried out across the whole of the north of the two continents. And this winter the timber is being analysed at laboratories in Copenhagen and Birmensdorf -- the Swiss home of Fritz Schweingruber, one of the world's top tree-ring analysts. The project will also carry out new analysis on the large numbers of samples of ancient oak already stored in laboratories in Ireland, Britain, Germany, Poland, the Netherlands and Sweden. The oak has been dragged from bogs and river beds, or liberated from archaeological sites and even the beams of old houses over the past 30 years.

"There is a massive amount of data on existing European oak rings. But much of it was done in the 1970s, and then not updated," says Briffa. One of Britain's biggest collections, at Sotterley Park near Lowestoft in Suffolk [Keith: who runs this?], has ring data going back to 1580. "But it stops in the 1980s, missing the recent major droughts. We have got to update that information."

Already, the first long data sets are starting to emerge from Siberia. Last summer [ed: 13 July 1995], Briffa, Schweingruber and Stepan Shiyatov of the Institute of Plant and Animal Ecology at Ekaterunburg in the Russian Urals published a paper on "unusual 20th-century summer warmth in a 1000-year temperature record from Siberia". A complete tree-ring chronology from AD 914, pieced together from larches on the Yamal peninsula, suggested that average summer temperatures since 1901 have been higher than for any similar length of time during the chronology. It estimated that from 1600, the depth of the little ice age, to the present day there has been a 1.14 degrees C warming. The first eight decades of the 20th century were 0.13 degrees C warmer than the next warmest period, nine centuries before in1202-91.

The chronology also showed that Europe's "little ice age" extended east of the Urals, but that the medieval warm period did not. But these long trends disguise sharp short-term anomalies. The 11th century seems to have been a particularly turbulent time in the Urals. 1032, the year of the Changbai eruption, yielded the coldest summer in a thousand years. But the following year was the second warmest of the millenium, at 2.11 degrees above the mean.

Tree rings are not the only source of proxy temperature data. Layers of ice laid down annually in permanent ice sheets, such as those in Greenland and Antarctica, carry a temperature record in the isotopic composition of the ice. Corals also have a temperature imprint, and even sediments on continental shelves can be mined for climate information. The most work, so far, has been done on ice sheets. American and European researchers in the Greenland Ice Sheet Project (GISP), for instance, have drilled for 3 kilometres into the ice pack, going back more than xxx xxxx xxxxyears. Besides plotting the course of the last ice age, they have found evidence of constant climate shifts during the past xxx xxxx xxxxyears.

Briffa says tree rings and ice cores "complement each other, focusing best at different timescales." Tree rings show annual and decade-to-decade variations very clearly. But they do not go back so far, and are not so good at spotting change from millenium to millenium. Ring analysis seems to smooth out long-term trends, probably because trees slowly adapt to these changes, disguising them." On the other hand, ice-core data shows up long-term trends very clearly, but is poor at showing single-year changes. The melting and refreezing of ice in the surface of ice packs means that the ice from individual years tends to mingle together.

The patterns of temperature change revealed by these different methods will probably always remain too fragmented to reveal unambiguous trends in global average temperatures. But this may not matter. "Frankly, global averages are not central to the issue of attributing climate change," says Barnett. "What will ultimately prove whether or not we are altering the climate will be the patterns of temperature change -- geographical patterns, seasonal patterns and vertical patterns." It is not how much it warms, but where, that will be vital.

Under the IPCC umbrella, Barnett and Phil Jones of the CRU have formed a small "detections group", to look for these tell-tale patterns. "We are systematically looking at the patterns, past and present, of all the main forcings on climate," Barnett says. They will investigate how the world's climate systems respond to volcanoes, to changes in the ocean circulation, to solar cycles and so on. "Then we will compare those patterns with what we are seeing today. What we hope is that the current patterns of temperature change prove distinctive, quite different from the patterns of natural variability in the past." And if that turns out to be the case, he says, "we will be able to close down this issue of attribution, perhaps within three to five years."

Here, the climate models will again come into play. If current climate change also accords with what the models predict from global warming, then the "hand of man" will indeed look to be on the planet's thermostat.

The models all suggest that anthropogenic global warming will show a very distinctive pattern. For instance, they predict that anthropogenic warming will be greatest in the northern latitudes of the great continental land masses, such as Eurasia. And that makes the finding of Briffa's team that summer temperatures in northern Siberia are higher than for a millenium potentially extremely important. And the prospect of further data from this region to confirm that finding so intriguing.

Briffa grins at the prospect. "The trend seems to be accelerating. We are getting reports back from Stepan, our man in the Urals, that it was warmer this spring on the Yamal peninsula there than ever before, and tree growth has been absolutely fantastic. It is a major warming, like nothing seen there for a thousand years -- and it is what the climate models predict." Caution prevails, but the elusive pattern of man-made global warming may just be emerging amid the larch groves on the sunny hills of northern Siberia.

ends

Original Filename: 1139847614.txt | Return to the index page | Permalink | Later Emails

From: Anders Levermann <Anders.Levermann@xxxxxxxxx.xxx>
To: Fortunat Joos <joos@xxxxxxxxx.xxx>
Subject: Re: Millennium Simulations
Date: Mon, 13 Feb 2006 11:20:14 +0100
Cc: Jonathan Overpeck <jto@u.arizona.edu>, Stefan Rahmstorf <rahmstorf@xxxxxxxxx.xxx>, Anders Levermann <levermann@xxxxxxxxx.xxx>, Eva Bauer <eva.bauer@xxxxxxxxx.xxx>, plattner@xxxxxxxxx.xxx, Eystein Jansen <eystein.jansen@xxxxxxxxx.xxx>, Keith Briffa <k.briffa@xxxxxxxxx.xxx>

<x-flowed>
Dear all,

here is the data from the Climber-3alpha simulations. I know they are
too late, but
perhaps there is still a way to include them. The structure of the files
is the
same as Eva's. The file names correspond to the ones you gave in the
simulation
protocol.

Cheers,
Anders

Fortunat Joos wrote:

> Dear all,
>
> Please find attached an update of the simulation protocol and input
> data description.
>
> Kasper Plattner pointed out that I forgot the obvious. We need of
> course a control run to correct for potential model drift. The readme
> file has been modified accordingly adding a brief description on how
> the control should be done.
>
> I am looking forward to any additional comments. Hope everything is
> clear.
>
> Kasper is currently working to perform the simulation with the Bern2.5CC.
>
> Regards, Fortunat
>
> Fortunat Joos wrote:
>
>> Dear all,
>>
>> I have now compiled the input data set and written a protocol how to
>> perform the runs. It seems to me that it would make sense if we
>> perform the simulations first with the Bern Model and with the
>> Climber 2 model. We can then still decide if we need Climber 3.
>>
>> Please let me know if there are any questions.
>>
>> I could also provide files where the radiative forcing of solar,
>> volcanoes and non-CO2-anthropogenic has been added together.
>>
>> With best wishes,
>>
>> Fortunat
>>
>>
>>
>> Jonathan Overpeck wrote:
>>
>>> Dear Eva and Fortunat - thanks for working on getting things moving.
>>> It seems that the detailed forcing recommendations laid out below by
>>> Fortunat build nicely on what Eva first suggested, and that going
>>> with the forcing series suggested below by Foortunat (and the 6
>>> simulations) is going to be just right for the IPCC AR4 Chap 6
>>> needs. Does everyone agree?
>>>
>>> Thanks Fortunat for preparing/sharing the standard forcing series.
>>>
>>> Best, peck
>>>
>>>> Dear Eva,
>>>>
>>>> We are working on the forcing series and they should be ready by
>>>> the end of the week. Stefan assured us that you can run this
>>>> within a few hours.
>>>>
>>>> What we are preparing are the following series of radiative forcing
>>>> in W/m2:
>>>>
>>>> a) RF from atmospheric constituents (well-mixed GHGs (CO2, CH4,
>>>> N2O, many Halocarbons) tropo and strato Ozone, various
>>>> anthropogenic aerosols) as used in the Bern CC TAR version and the
>>>> TAR (see Joos et al., GBC, 2001; pdf is on my homepage and TAR
>>>> appendix).
>>>> b) volcanic from Crowley, Sci, 2000
>>>> c) solar based on Lean and Bard et al.
>>>>
>>>> For the solar we will prepare 3 combinations:
>>>>
>>>> c1) original serie from Lean (2005) provided to you already
>>>> c2) Bard et al., Be-10 record linearly scaled to match the Maunder
>>>> Minimum Average of Lean-AR4
>>>> c3) Bard et al., Be-10 scaled to a MM reduction of 0.25 permil,
>>>> i.e. the low case in the Bard et, Tellus, publication corresponding
>>>> to the Lean et al, 1995 scaling
>>>>
>>>> For the RF by atmospheric components two cases are foreseen:
>>>> a1) standard case with reconstructed evolution over past 1150 years
>>>> a2) RF kept at 1765 value after 1765, i.e. a simulation with
>>>> natural forcings only.
>>>>
>>>> This will yield in total 6 simulations 3 over the full length from
>>>> 850 AD to 2000 and 3 brach-off simulatons from 1765 with natural
>>>> only forcing.
>>>>
>>>> An important point in IPCC is that things are published, consistent
>>>> among chapters, and it helps if approaches are tracable to earlier
>>>> accepted and approved IPCC work. The arguments for these series are
>>>> as follows:
>>>>
>>>> a) Considering as many components relevant for RF as possible (more
>>>> than just CO2). The series are fully compatible with TAR and that
>>>> the setup is tracable to the TAR for the industrial era increase.
>>>> The same series will be used in the projection chapter 10 for the
>>>> SRES calculation
>>>>
>>>> b) volcanic: a widely cited record
>>>>
>>>> c) solar: c1) and c3) are published series; c2 follows the same
>>>> approach and spirit as used to derive c3, i.e. scaling the Be-10
>>>> serie linearly with a given Maunder Minimum reduction. The impact
>>>> of the 11-yr solar cycle can be looked at in the original Lean-AR4
>>>> serie.
>>>>
>>>> I hope this help.
>>>>
>>>> With kind regards,
>>>>
>>>> Fortunat
>>>>
>>>> Eva Bauer wrote:
>>>>
>>>>>
>>>>> Dear Jonathan, dear Fortunat:
>>>>>
>>>>> Happy New Year!
>>>>>
>>>>>
>>>>> Stefan, Anders and me just have discussed how to set up our
>>>>> CLIMBER2/3alpha runs, to produce something useful for the IPCC WGI
>>>>> chapter 6. This chapter appears to touch the impact on the NH
>>>>> temperature related to low and high solar forcing.
>>>>>
>>>>> For a reasonable comparison, we think two 1000-year simulations
>>>>> differing only by a low and a high solar forcing, conducted with both
>>>>> CLIMBER models, would be ideal. To do so, we would have to extend the
>>>>> solar forcing time series based on Lean (GRL, 2000) and on Wang et
>>>>> al. (2005) distributed in previous e-mails back to the year 1000.
>>>>> This
>>>>> would require some splicing as was done, for instance, by Crowley.
>>>>>
>>>>> I'm thinking of some scaling applied to a series of Crowley (say the
>>>>> data called Be10/Lean splice in Science, 2000) such that the
>>>>> amplitude
>>>>> of the solar variability from the 11-year cycle is conserved after
>>>>> ~1720. I have to check but it appears that the variation in the TSI
>>>>> due to the 11-year cycle contained in the Crowley series agrees
>>>>> perfectly with the 11yr-cycle data in the file based on Lean (2000).
>>>>> Before starting such an exercise I like to ask you what you think
>>>>> about. We would be happy to receive your response quite soon to be
>>>>> able to finish the calculations with our slow model in time for the
>>>>> IPCC report.
>>>>>
>>>>> Could you please also comment on the other forcings we should
>>>>> include,
>>>>> namely the volcanic forcing and the CO2 forcing. For the present
>>>>> study
>>>>> we suggest to use the forcing as in Bauer et al (2000) but omitting
>>>>> the land-use. This means, using the volcanic forcing from Crowley,
>>>>> 2000 and the CO2 forcing based on Etheridge et al 1996 and Keeling
>>>>> and
>>>>> Whorf, 1996. (If you wish we can distribute these data series.)
>>>>>
>>>>> Also, thinking beyond the IPCC study, the model results may become
>>>>> interesting enough to be discussed in a 3-model comparison study!?
>>>>>
>>>>> Looking forward to your reply.
>>>>>
>>>>> Best wishes
>>>>>
>>>>> Eva
>>>>>
>>>>
>>>> --
>>>>
>>>> Climate and Environmental Physics,
>>>> Physics Institute, University of Bern
>>>> Sidlerstr. 5, CH-3012 Bern
>>>> Phone: ++41(0xxx xxxx xxxx Fax: ++41(0xxx xxxx xxxx
>>>> Internet: http://www.climate.unibe.ch/~joos/
>>>
>>>
>>>
>>>
>>>
>>
>
>------------------------------------------------------------------------
>
>Last Millennium Simulations for IPCC AR4 WG1 Chap 6
>---------------------------------------------------
>
>F. Joos,
>joos@xxxxxxxxx.xxx
>18 Januar 2006
>
>OVERVIEW
>--------
>
>A total of 7 simulations is planned.
>
>A control simulation without any forcing
>
>Two millennium-long simulations with solar forcing following Bard et al. with a Maunder Minimum reduction of 0.08 and 0.25 percent in total irradiance and volcanic and anthropogenic forcing included
>
>A simulation from 1610 to 1998 with solar forcing from Wang et al, 2005 and
>volcanic and anthropogenic forcing included
>
>Three simulations from 1765 to 1998 with only solar and volcanic forcing included, but no anthropogenic forcings. These are branches from the above three simulation.
>
>A range of input data files have been prepeared. Each contains a header with additional descriptions of the data.
>
>Solar irradiance has been taken from Bard et al., Tellus, 1999 and from Wang, Lean, Shirley, JAp, 2005.
>
>It is estimated that the Maunder Minimum irradiance is reduce by 0.08 percent
>relative to today and that the present irradiance is 1366 W/m2 from the Wang et al. data.
>
>A case with a Maunder Minimum reduction of 0.08 percent is calculated from the Bard et al. data by scaling the original Bard series appropriately.
>The original Bard series are offset by 1.3 W/m2 in irradiance to bring them to
>a present irradiance of 1366 W/m2. For this excercise we will utilize a Maunder
>Minimum reduction in irradiance relative to today of 0.08 percent and of 0.25 percent (other cases with high MM reduction are included in the files).
>
>Irradiance has been converted to radiative forcing: RF= (IRR-1366)/4*0.7
>
>Volcanic forcing is from Crowley Science, 2000, with albedo factored in (e.g. as for solar forcing). To avoid a cold start of the model, the serie is extended to 850 AD by mirroring the Crowley data from 1001 to 1150 to the period 850 to 1000.
>
>NonCO2 forcing is following TAR (updated for an error in tropo O3 in the TAR).
>
>CO2 is a spline through the Etheridge, JGR, 97 data and the Siegenthaler, TEllus, 2005 data.
>
>
>INPUT FILES DESCRIPTION:
>-----------------------
>
>It is recommended to linearly interpolate between data points.
>
>A1: Solar irradiance and radiative forcing following Bard from 850 to 2000
>
>(Tag description)
>solBardxxx xxxx xxxx. col: Maunder Minimum reduction of 0.08 percent
>solBardxxx xxxx xxxx. col: Maunder Minimu reduction of 0.25 percent
>
>Note: data from Bard have been linearlz interplated on an annual time step
>
> files:
> bard00tel_solar_RF_IPCC_Chap6_Joos_11jan06.out
> bard00tel_solar_irradiance_offset-13_IPCC_Chap6_Joos_11jan06.out
>
>
>A2: Solar irradiance and radiative forcing following Wang, Lean, Shirley, 2005
> from 1610 to 2004
>
> annual resolution
>
>Tag: WLS-05
>
> files:
> wang05jastr_lean_RF_IPCC_chap6_Joos_11jan06.out
> wang05jastr_lean_irradiance_IPCC_chap6_Joos_11jan06.out
>
>A3: CO2 concentration in ppm from 850 to 2000
>
> annual resolution
>
>Tag: CO2
> file: co2_xxx xxxx xxxx_splined_IPCC_Chap6_Joos_11jan06.out
>
>A4: volcanic forcing after Crowley from 1001 to 1998 AD, extended by artificial
> data from 850 to 1000 AD by mirroring the forcing from 1000 to 1150 to the period 850 to 1000
>
>Tag: volcCrow
>
> annual resolution
>
> file: crowley00sci_RFvolcanic_IPCC_Chap6_Joos_11jan05.out
>
>A5: radiative forcing by non-CO2 agents
>
> annual resolution
>
>Tag: nonco2
>
> files
> rf_nonco2_1yr_1765_2000_individ_IPCC_Chap6_Joos_11jan06.out
> rf_nonco2_1yr_850_2000_IPCC_Chap6_Joos_11jan06.out
>
>
>
>B) SIMULATIONS
>-----------------------
>
>B1. 2 Long simulations from 850 AD to 1998
>
>-------
>
>Simulation B1.1. tag: bard08_volcCrow_CO2_nonCO2_xxx xxxx xxxx
>
>Solar forcing from Bard et al. with MM reduction of 0.08 percent, volcanic forcing and forcing from CO2 and other anthropogenic (non-CO2) agents.
>
>Start of simulation 850 AD
>End of simulation: 1998 AD
>initial condition: model spinup for year 850 (or similiar)
>
>Analysis period: 1001 AD to 1998 AD
>start-up period: 850 to 1000 with artificial volcanic data
>
>--------
>
>Simulation B1.2 tag: bard25_volcCrow_CO2_nonCO2_xxx xxxx xxxx
>
>as B1.1 but with solar forcing from Bard et al. reduced by 0.25 percent for the Maunder Minimum.
>
>Start of simulation 850 AD
>End of simulation: 1998 AD
>initial condition: model spinup for year 850 (or similiar)
>
>Analysis period: 1001 AD to 1998 AD
>start-up period: 850 to 1000 with artificial volcanic data
>
>--------
>
>Simulation B2: A simulation from 1610 to 1998 restarted from bard08_volcCrow_CO2_nonCO2
>
>With solar forcing from Wang et al., 2005, volcanic forci
>ng and forcing from CO2 and other anthropogenic (non-CO2) agents.
>
>B2 tag: WLS-2005_volcCrow_CO2_nonCO2_1xxx xxxx xxxx
>
>Start of simulation: 1610 AD
>End of simulation: 1998 AD
>initial condition: restart from simulation B1.1. bard08_volcCrow_CO2_nonCO2
> at year 1610
>
>Analysis period: 1610 AD to 1998 AD
>
>
>-------
>
>B3: 3 Simulations from 1765 to 1998 with natural forcing only
>
> non-CO2 radiative forcing is kept to zero
> (except for volcanoes and solar)
>
> CO2 is kept at its 1765 value.
>
>Simulation B3.1: tag bard08_volcCrow_1765_1998
>
>Start of simulation: 1765 AD
>End of simulation: 1998 AD
>initial condition: restart from simulation B1.1. bard08_volcCrow_CO2_nonCO2
> at year 1765
>
>Analysis period: 1765 to 1998 AD
>
>-------
>
>Simulation B3.2: tag bard25_volcCrow_1765_1998
>
>Start of simulation: 1765 AD
>End of simulation: 1998 AD
>initial condition: restart from simulation B1.2. bard25_volcCrow_CO2_nonCO2
> at year 1765
>
>Analysis period: 1765 to 1998 AD
>
>-----
>
>Simulation B3.1: tag WLS-2005_volcCrow_1765_1998
>
>Start of simulation: 1765 AD
>End of simulation: 1998 AD
>initial condition: restart from simulation B2. WLS-2005_volcCrow_CO2_nonCO2
> at year 1765
>
>Analysis period: 1765 to 1998 AD
>
>-------
>
>Simulation B4: tag ctrl_xxx xxxx xxxx
>
>Control simulation without any forcing
>
>Start of simulation 850 AD
>End of simulation: 1998 AD
>initial condition: model spinup for year 850 (or similiar)
>
>Analysis period: 850 to 1998
>
>
>OUTPUT
>------
>
>I guess minimal output is global and NH mean surface temperature.
>
>

--
Anders Levermann
phone: xxx xxxx xxxx Potsdam Institute for Climate Impact Research
fax: xxx xxxx xxxx Telegraphenberg A26, 14473 Potsdam, Germany
anders.levermann@xxxxxxxxx.xxx www.pik-potsdam.de/~anders



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Original Filename: 1140009927.txt | Return to the index page | Permalink | Later Emails

From: Fortunat Joos <joos@xxxxxxxxx.xxx>
To: Jonathan Overpeck <jto@u.arizona.edu>
Subject: Re: Fwd: Re: Millennium Simulations
Date: Wed, 15 Feb 2006 08:25:27 +0100
Cc: Tim Osborn <t.osborn@xxxxxxxxx.xxx>, Stefan Rahmstorf <rahmstorf@xxxxxxxxx.xxx>, Anders Levermann <levermann@xxxxxxxxx.xxx>, Eva Bauer <eva.bauer@xxxxxxxxx.xxx>, plattner@xxxxxxxxx.xxx, Eystein Jansen <eystein.jansen@xxxxxxxxx.xxx>, Keith Briffa <k.briffa@xxxxxxxxx.xxx>, oyvind.paasche@xxxxxxxxx.xxx

<x-flowed>
O.k. EMIC caption noted. Can go with the 1xxx xxxx xxxxref period.

Stefan, Anders, and Eva can you provide me the appropriate references
for your models and the official names.

Regards, Fortunat

Jonathan Overpeck wrote:
> Hi Tim and Fortunat: This looks nice (thanks) and my slight bias is that
> we should include the Climber3a results. What do you think, Fortunat? I
> think Stefan likes it based on his email.
>
> Regarding the reference period, I would side w/ Tim and Keith on using
> 1xxx xxxx xxxx. We need to use the same ref period for everything on these
> two figs (obs and forcing/simulations), and I think the EMIC panel still
> convey's the main message. Keith/Tim/Fortunat - we have to resolve this
> FAST, so please weigh in more on this issue. Thanks.
>
> Regarding captions, yes, you should do all but the EMICS, and you should
> make sure you send to Stefan so he can help make sure it makes sense
> (e.g., the red/grey shading). We have asked Fortunat to do the EMIC
> caption. Can you do this Fortunat? Thanks.
>
> Best, Peck
>
>
>
>
>> Dear all,
>>
>> please see the attached diagram (both the same, PDF or GIF) with all
>> three EMICs on now. Climber3a seems to lie between Climber2 and
>> Bern2.5CC mostly. Does it add to the message of the figure to use all
>> three? If so, please use this version from now on, for drafting
>> captions etc.
>>
>> Nobody said much about the previous version, so hopefully this
>> indicates general agreement! I didn't show the "Bard08" runs, because
>> they were so close to the runs I have labelled "WLS", but of course in
>> those runs the pre-1610 solar forcing is Bard08 - so maybe the labels
>> should be altered to somehow indicate them, or this could just be
>> stated in the caption.
>>
>> Am I right that Keith and I need to provide an updated caption for
>> panels (a)-(d), but that someone else will write a caption for the
>> EMIC panel (e)?
>>
>> Cheers
>>
>> Tim
>>
>> At 19:20 13/02/2006, Jonathan Overpeck wrote:
>>
>>> Hi Anders and Tim - It could be too late, but this is up to Tim. Can
>>> you get these data onto the new EMIC panel? I think it'd be worth
>>> it, but only if you and Keith can get everything else done first.
>>> Best make sure you have all the data needed, just in case.
>>>
>>> thanks Anders too.
>>>
>>> best, peck
>>>
>>>> X-Sieve: CMU Sieve 2.2
>>>> Date: Mon, 13 Feb 2006 11:20:14 +0100
>>>> From: Anders Levermann <Anders.Levermann@xxxxxxxxx.xxx>
>>>> Organization: PIK
>>>> X-Accept-Language: en-us, en
>>>> To: Fortunat Joos <joos@xxxxxxxxx.xxx>
>>>> Cc: Jonathan Overpeck <jto@u.arizona.edu>,
>>>> Stefan Rahmstorf <rahmstorf@xxxxxxxxx.xxx>,
>>>> Anders Levermann <levermann@xxxxxxxxx.xxx>,
>>>> Eva Bauer <eva.bauer@xxxxxxxxx.xxx>,
>>>> plattner@xxxxxxxxx.xxx,
>>>> Eystein Jansen <eystein.jansen@xxxxxxxxx.xxx>,
>>>> Keith Briffa <k.briffa@xxxxxxxxx.xxx>
>>>> Subject: Re: Millennium Simulations
>>>>
>>>> Dear all,
>>>>
>>>> here is the data from the Climber-3alpha simulations. I know they
>>>> are too late, but
>>>> perhaps there is still a way to include them. The structure of the
>>>> files is the
>>>> same as Eva's. The file names correspond to the ones you gave in the
>>>> simulation
>>>> protocol.
>>>>
>>>> Cheers,
>>>> Anders
>>>>
>>>> Fortunat Joos wrote:
>>>>
>>>>> Dear all,
>>>>>
>>>>> Please find attached an update of the simulation protocol and input
>>>>> data description.
>>>>>
>>>>> Kasper Plattner pointed out that I forgot the obvious. We need of
>>>>> course a control run to correct for potential model drift. The
>>>>> readme file has been modified accordingly adding a brief
>>>>> description on how the control should be done.
>>>>>
>>>>> I am looking forward to any additional comments. Hope everything is
>>>>> clear.
>>>>>
>>>>> Kasper is currently working to perform the simulation with the
>>>>> Bern2.5CC.
>>>>>
>>>>> Regards, Fortunat
>>>>>
>>>>> Fortunat Joos wrote:
>>>>>
>>>>>> Dear all,
>>>>>>
>>>>>> I have now compiled the input data set and written a protocol how
>>>>>> to perform the runs. It seems to me that it would make sense if we
>>>>>> perform the simulations first with the Bern Model and with the
>>>>>> Climber 2 model. We can then still decide if we need Climber 3.
>>>>>>
>>>>>> Please let me know if there are any questions.
>>>>>>
>>>>>> I could also provide files where the radiative forcing of solar,
>>>>>> volcanoes and non-CO2-anthropogenic has been added together.
>>>>>>
>>>>>> With best wishes,
>>>>>>
>>>>>> Fortunat
>>>>>>
>>>>>>
>>>>>>
>>>>>> Jonathan Overpeck wrote:
>>>>>>
>>>>>>> Dear Eva and Fortunat - thanks for working on getting things
>>>>>>> moving. It seems that the detailed forcing recommendations laid
>>>>>>> out below by Fortunat build nicely on what Eva first suggested,
>>>>>>> and that going with the forcing series suggested below by
>>>>>>> Foortunat (and the 6 simulations) is going to be just right for
>>>>>>> the IPCC AR4 Chap 6 needs. Does everyone agree?
>>>>>>>
>>>>>>> Thanks Fortunat for preparing/sharing the standard forcing series.
>>>>>>>
>>>>>>> Best, peck
>>>>>>>
>>>>>>>> Dear Eva,
>>>>>>>>
>>>>>>>> We are working on the forcing series and they should be ready by
>>>>>>>> the end of the week. Stefan assured us that you can run this
>>>>>>>> within a few hours.
>>>>>>>>
>>>>>>>> What we are preparing are the following series of radiative
>>>>>>>> forcing in W/m2:
>>>>>>>>
>>>>>>>> a) RF from atmospheric constituents (well-mixed GHGs (CO2, CH4,
>>>>>>>> N2O, many Halocarbons) tropo and strato Ozone, various
>>>>>>>> anthropogenic aerosols) as used in the Bern CC TAR version and
>>>>>>>> the TAR (see Joos et al., GBC, 2001; pdf is on my homepage and
>>>>>>>> TAR appendix).
>>>>>>>> b) volcanic from Crowley, Sci, 2000
>>>>>>>> c) solar based on Lean and Bard et al.
>>>>>>>>
>>>>>>>> For the solar we will prepare 3 combinations:
>>>>>>>>
>>>>>>>> c1) original serie from Lean (2005) provided to you already
>>>>>>>> c2) Bard et al., Be-10 record linearly scaled to match the
>>>>>>>> Maunder Minimum Average of Lean-AR4
>>>>>>>> c3) Bard et al., Be-10 scaled to a MM reduction of 0.25 permil,
>>>>>>>> i.e. the low case in the Bard et, Tellus, publication
>>>>>>>> corresponding to the Lean et al, 1995 scaling
>>>>>>>>
>>>>>>>> For the RF by atmospheric components two cases are foreseen:
>>>>>>>> a1) standard case with reconstructed evolution over past 1150 years
>>>>>>>> a2) RF kept at 1765 value after 1765, i.e. a simulation with
>>>>>>>> natural forcings only.
>>>>>>>>
>>>>>>>> This will yield in total 6 simulations 3 over the full length
>>>>>>>> from 850 AD to 2000 and 3 brach-off simulatons from 1765 with
>>>>>>>> natural only forcing.
>>>>>>>>
>>>>>>>> An important point in IPCC is that things are published,
>>>>>>>> consistent among chapters, and it helps if approaches are
>>>>>>>> tracable to earlier accepted and approved IPCC work. The
>>>>>>>> arguments for these series are as follows:
>>>>>>>>
>>>>>>>> a) Considering as many components relevant for RF as possible
>>>>>>>> (more than just CO2). The series are fully compatible with TAR
>>>>>>>> and that the setup is tracable to the TAR for the industrial era
>>>>>>>> increase. The same series will be used in the projection chapter
>>>>>>>> 10 for the SRES calculation
>>>>>>>>
>>>>>>>> b) volcanic: a widely cited record
>>>>>>>>
>>>>>>>> c) solar: c1) and c3) are published series; c2 follows the same
>>>>>>>> approach and spirit as used to derive c3, i.e. scaling the Be-10
>>>>>>>> serie linearly with a given Maunder Minimum reduction. The
>>>>>>>> impact of the 11-yr solar cycle can be looked at in the original
>>>>>>>> Lean-AR4 serie.
>>>>>>>>
>>>>>>>> I hope this help.
>>>>>>>>
>>>>>>>> With kind regards,
>>>>>>>>
>>>>>>>> Fortunat
>>>>>>>>
>>>>>>>> Eva Bauer wrote:
>>>>>>>>
>>>>>>>>>
>>>>>>>>> Dear Jonathan, dear Fortunat:
>>>>>>>>>
>>>>>>>>> Happy New Year!
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> Stefan, Anders and me just have discussed how to set up our
>>>>>>>>> CLIMBER2/3alpha runs, to produce something useful for the IPCC WGI
>>>>>>>>> chapter 6. This chapter appears to touch the impact on the NH
>>>>>>>>> temperature related to low and high solar forcing.
>>>>>>>>>
>>>>>>>>> For a reasonable comparison, we think two 1000-year simulations
>>>>>>>>> differing only by a low and a high solar forcing, conducted
>>>>>>>>> with both
>>>>>>>>> CLIMBER models, would be ideal. To do so, we would have to
>>>>>>>>> extend the
>>>>>>>>> solar forcing time series based on Lean (GRL, 2000) and on Wang et
>>>>>>>>> al. (2005) distributed in previous e-mails back to the year
>>>>>>>>> 1000. This
>>>>>>>>> would require some splicing as was done, for instance, by Crowley.
>>>>>>>>>
>>>>>>>>> I'm thinking of some scaling applied to a series of Crowley
>>>>>>>>> (say the
>>>>>>>>> data called Be10/Lean splice in Science, 2000) such that the
>>>>>>>>> amplitude
>>>>>>>>> of the solar variability from the 11-year cycle is conserved after
>>>>>>>>> ~1720. I have to check but it appears that the variation in the
>>>>>>>>> TSI
>>>>>>>>> due to the 11-year cycle contained in the Crowley series agrees
>>>>>>>>> perfectly with the 11yr-cycle data in the file based on Lean
>>>>>>>>> (2000).
>>>>>>>>> Before starting such an exercise I like to ask you what you think
>>>>>>>>> about. We would be happy to receive your response quite soon to be
>>>>>>>>> able to finish the calculations with our slow model in time for
>>>>>>>>> the
>>>>>>>>> IPCC report.
>>>>>>>>>
>>>>>>>>> Could you please also comment on the other forcings we should
>>>>>>>>> include,
>>>>>>>>> namely the volcanic forcing and the CO2 forcing. For the
>>>>>>>>> present study
>>>>>>>>> we suggest to use the forcing as in Bauer et al (2000) but
>>>>>>>>> omitting
>>>>>>>>> the land-use. This means, using the volcanic forcing from Crowley,
>>>>>>>>> 2000 and the CO2 forcing based on Etheridge et al 1996 and
>>>>>>>>> Keeling and
>>>>>>>>> Whorf, 1996. (If you wish we can distribute these data series.)
>>>>>>>>>
>>>>>>>>> Also, thinking beyond the IPCC study, the model results may become
>>>>>>>>> interesting enough to be discussed in a 3-model comparison study!?
>>>>>>>>>
>>>>>>>>> Looking forward to your reply.
>>>>>>>>>
>>>>>>>>> Best wishes
>>>>>>>>>
>>>>>>>>> Eva
>>>>>>>>
>>>>>>>>
>>>>>>>> --
>>>>>>>>
>>>>>>>> Climate and Environmental Physics,
>>>>>>>> Physics Institute, University of Bern
>>>>>>>> Sidlerstr. 5, CH-3012 Bern
>>>>>>>> Phone: ++41(0xxx xxxx xxxx Fax: ++41(0xxx xxxx xxxx
>>>>>>>> Internet: http://www.climate.unibe.ch/~joos/
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>
>>>>> ------------------------------------------------------------------------
>>>>>
>>>>>
>>>>> Last Millennium Simulations for IPCC AR4 WG1 Chap 6
>>>>> ---------------------------------------------------
>>>>>
>>>>> F. Joos,
>>>>> joos@xxxxxxxxx.xxx
>>>>> 18 Januar 2006
>>>>>
>>>>> OVERVIEW
>>>>> --------
>>>>>
>>>>> A total of 7 simulations is planned.
>>>>> A control simulation without any forcing
>>>>>
>>>>> Two millennium-long simulations with solar forcing following Bard
>>>>> et al. with a Maunder Minimum reduction of 0.08 and 0.25 percent in
>>>>> total irradiance and volcanic and anthropogenic forcing included
>>>>> A simulation from 1610 to 1998 with solar forcing from Wang et al,
>>>>> 2005 and volcanic and anthropogenic forcing included
>>>>>
>>>>> Three simulations from 1765 to 1998 with only solar and volcanic
>>>>> forcing included, but no anthropogenic forcings. These are branches
>>>>> from the above three simulation.
>>>>>
>>>>> A range of input data files have been prepeared. Each contains a
>>>>> header with additional descriptions of the data.
>>>>> Solar irradiance has been taken from Bard et al., Tellus, 1999 and
>>>>> from Wang, Lean, Shirley, JAp, 2005.
>>>>>
>>>>> It is estimated that the Maunder Minimum irradiance is reduce by
>>>>> 0.08 percent
>>>>> relative to today and that the present irradiance is 1366 W/m2 from
>>>>> the Wang et al. data.
>>>>>
>>>>> A case with a Maunder Minimum reduction of 0.08 percent is
>>>>> calculated from the Bard et al. data by scaling the original Bard
>>>>> series appropriately.
>>>>> The original Bard series are offset by 1.3 W/m2 in irradiance to
>>>>> bring them to a present irradiance of 1366 W/m2. For this excercise
>>>>> we will utilize a Maunder
>>>>> Minimum reduction in irradiance relative to today of 0.08 percent
>>>>> and of 0.25 percent (other cases with high MM reduction are
>>>>> included in the files).
>>>>>
>>>>> Irradiance has been converted to radiative forcing: RF=
>>>>> (IRR-1366)/4*0.7
>>>>> Volcanic forcing is from Crowley Science, 2000, with albedo
>>>>> factored in (e.g. as for solar forcing). To avoid a cold start of
>>>>> the model, the serie is extended to 850 AD by mirroring the Crowley
>>>>> data from 1001 to 1150 to the period 850 to 1000.
>>>>> NonCO2 forcing is following TAR (updated for an error in tropo O3
>>>>> in the TAR).
>>>>> CO2 is a spline through the Etheridge, JGR, 97 data and the
>>>>> Siegenthaler, TEllus, 2005 data.
>>>>>
>>>>>
>>>>> INPUT FILES DESCRIPTION:
>>>>> -----------------------
>>>>>
>>>>> It is recommended to linearly interpolate between data points.
>>>>>
>>>>> A1: Solar irradiance and radiative forcing following Bard from 850
>>>>> to 2000
>>>>> (Tag description)
>>>>> solBardxxx xxxx xxxx. col: Maunder Minimum reduction of 0.08 percent
>>>>> solBardxxx xxxx xxxx. col: Maunder Minimu reduction of 0.25 percent
>>>>>
>>>>> Note: data from Bard have been linearlz interplated on an annual
>>>>> time step
>>>>> files:
>>>>> bard00tel_solar_RF_IPCC_Chap6_Joos_11jan06.out
>>>>> bard00tel_solar_irradiance_offset-13_IPCC_Chap6_Joos_11jan06.out
>>>>>
>>>>>
>>>>> A2: Solar irradiance and radiative forcing following Wang, Lean,
>>>>> Shirley, 2005
>>>>> from 1610 to 2xxx xxxx xxxxannual resolution
>>>>> Tag: WLS-05
>>>>>
>>>>> files:
>>>>> wang05jastr_lean_RF_IPCC_chap6_Joos_11jan06.out
>>>>> wang05jastr_lean_irradiance_IPCC_chap6_Joos_11jan06.out
>>>>>
>>>>> A3: CO2 concentration in ppm from 850 to 2000
>>>>>
>>>>> annual resolution
>>>>> Tag: CO2
>>>>> file: co2_xxx xxxx xxxx_splined_IPCC_Chap6_Joos_11jan06.out
>>>>>
>>>>> A4: volcanic forcing after Crowley from 1001 to 1998 AD, extended
>>>>> by artificial
>>>>> data from 850 to 1000 AD by mirroring the forcing from 1000 to
>>>>> 1150 to the period 850 to 1000
>>>>> Tag: volcCrow
>>>>>
>>>>> annual resolution
>>>>> file: crowley00sci_RFvolcanic_IPCC_Chap6_Joos_11jan05.out
>>>>>
>>>>> A5: radiative forcing by non-CO2 agents
>>>>> annual resolution
>>>>> Tag: nonco2
>>>>>
>>>>> files
>>>>> rf_nonco2_1yr_1765_2000_individ_IPCC_Chap6_Joos_11jan06.out
>>>>> rf_nonco2_1yr_850_2000_IPCC_Chap6_Joos_11jan06.out
>>>>>
>>>>>
>>>>>
>>>>> B) SIMULATIONS
>>>>> -----------------------
>>>>>
>>>>> B1. 2 Long simulations from 850 AD to 1998
>>>>>
>>>>> -------
>>>>>
>>>>> Simulation B1.1. tag: bard08_volcCrow_CO2_nonCO2_xxx xxxx xxxx
>>>>>
>>>>> Solar forcing from Bard et al. with MM reduction of 0.08 percent,
>>>>> volcanic forcing and forcing from CO2 and other anthropogenic
>>>>> (non-CO2) agents.
>>>>>
>>>>> Start of simulation 850 AD
>>>>> End of simulation: 1998 AD
>>>>> initial condition: model spinup for year 850 (or similiar)
>>>>>
>>>>> Analysis period: 1001 AD to 1998 AD
>>>>> start-up period: 850 to 1000 with artificial volcanic data
>>>>>
>>>>> --------
>>>>>
>>>>> Simulation B1.2 tag: bard25_volcCrow_CO2_nonCO2_xxx xxxx xxxx
>>>>>
>>>>> as B1.1 but with solar forcing from Bard et al. reduced by 0.25
>>>>> percent for the Maunder Minimum.
>>>>>
>>>>> Start of simulation 850 AD
>>>>> End of simulation: 1998 AD
>>>>> initial condition: model spinup for year 850 (or similiar)
>>>>>
>>>>> Analysis period: 1001 AD to 1998 AD
>>>>> start-up period: 850 to 1000 with artificial volcanic data
>>>>>
>>>>> --------
>>>>>
>>>>> Simulation B2: A simulation from 1610 to 1998 restarted from
>>>>> bard08_volcCrow_CO2_nonCO2
>>>>>
>>>>> With solar forcing from Wang et al., 2005, volcanic forci
>>>>> ng and forcing from CO2 and other anthropogenic (non-CO2) agents.
>>>>>
>>>>> B2 tag: WLS-2005_volcCrow_CO2_nonCO2_1xxx xxxx xxxx
>>>>>
>>>>> Start of simulation: 1610 AD
>>>>> End of simulation: 1998 AD
>>>>> initial condition: restart from simulation B1.1.
>>>>> bard08_volcCrow_CO2_nonCO2
>>>>> at year 1610
>>>>>
>>>>> Analysis period: 1610 AD to 1998 AD
>>>>>
>>>>>
>>>>> -------
>>>>>
>>>>> B3: 3 Simulations from 1765 to 1998 with natural forcing only
>>>>>
>>>>> non-CO2 radiative forcing is kept to zero (except
>>>>> for volcanoes and solar)
>>>>>
>>>>> CO2 is kept at its 1765 value.
>>>>>
>>>>> Simulation B3.1: tag bard08_volcCrow_1765_1998
>>>>>
>>>>> Start of simulation: 1765 AD
>>>>> End of simulation: 1998 AD
>>>>> initial condition: restart from simulation B1.1.
>>>>> bard08_volcCrow_CO2_nonCO2
>>>>> at year 1765
>>>>>
>>>>> Analysis period: 1765 to 1998 AD
>>>>>
>>>>> -------
>>>>>
>>>>> Simulation B3.2: tag bard25_volcCrow_1765_1998
>>>>>
>>>>> Start of simulation: 1765 AD
>>>>> End of simulation: 1998 AD
>>>>> initial condition: restart from simulation B1.2.
>>>>> bard25_volcCrow_CO2_nonCO2
>>>>> at year 1765
>>>>>
>>>>> Analysis period: 1765 to 1998 AD
>>>>>
>>>>> -----
>>>>>
>>>>> Simulation B3.1: tag WLS-2005_volcCrow_1765_1998
>>>>>
>>>>> Start of simulation: 1765 AD
>>>>> End of simulation: 1998 AD
>>>>> initial condition: restart from simulation B2.
>>>>> WLS-2005_volcCrow_CO2_nonCO2
>>>>> at year 1765
>>>>>
>>>>> Analysis period: 1765 to 1998 AD
>>>>>
>>>>> -------
>>>>>
>>>>> Simulation B4: tag ctrl_xxx xxxx xxxx
>>>>>
>>>>> Control simulation without any forcing
>>>>>
>>>>> Start of simulation 850 AD
>>>>> End of simulation: 1998 AD
>>>>> initial condition: model spinup for year 850 (or similiar)
>>>>>
>>>>> Analysis period: 850 to 1998
>>>>>
>>>>>
>>>>> OUTPUT
>>>>> ------
>>>>>
>>>>> I guess minimal output is global and NH mean surface temperature.
>>>>
>>>>
>>>> --
>>>> Anders Levermann
>>>> phone: xxx xxxx xxxxPotsdam Institute for Climate Impact Research
>>>> fax: xxx xxxx xxxxTelegraphenberg A26, 14473 Potsdam, Germany
>>>> anders.levermann@xxxxxxxxx.xxx www.pik-potsdam.de/~anders
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>> --
>>> Jonathan T. Overpeck
>>> Director, Institute for the Study of Planet Earth
>>> Professor, Department of Geosciences
>>> Professor, Department of Atmospheric Sciences
>>>
>>> Mail and Fedex Address:
>>>
>>> Institute for the Study of Planet Earth
>>> 715 N. Park Ave. 2nd Floor
>>> University of Arizona
>>> Tucson, AZ 85721
>>> direct tel: xxx xxxx xxxx
>>> fax: xxx xxxx xxxx
>>> http://www.geo.arizona.edu/
>>> http://www.ispe.arizona.edu/
>>>
>>>
>>>
>>>
>>>
>>
>>
>> Attachment converted: Macintosh HD:modelsE.gif (GIFf/

Original Filename: 1153254016.txt | Return to the index page | Permalink | Later Emails

From: Fortunat Joos <joos@xxxxxxxxx.xxx>
To: Keith Briffa <k.briffa@xxxxxxxxx.xxx>
Subject: Re: new fig 6.14
Date: Tue, 18 Jul 2006 16:20:16 +0200
Cc: Tim Osborn <t.osborn@xxxxxxxxx.xxx>, Jonathan Overpeck <jto@u.arizona.edu>, Eystein Jansen <eystein.jansen@xxxxxxxxx.xxx>

<x-flowed>
Hi Keith,

Thanks.

My concerns comes from the following. I am not convinced that one gets
the same response when forcing a model with smoothed volcanic forcing
instead with the spikes. I suspect that the ocean will gain more heat in
the later case due to the longer time to respond to the forcing.
However, this remains to be tested, but nobody has done this as far as I
know. In other words, postprocessing the output of a model forced with
high resolution data does not necessarily give the same results as
forcing the model with smoothed input. There is a chance to get
different results. That is why I prefer to show the real forcing, i.e.
the volcanic spikes. As long as nobody has done such tests run I would
prefer to be scientifically on the save side with the figure. Sorry, but
this is my modellers view on this.

Forcings do not need to be on the same scale here. We know that
temporarily volcanic forcing, albeit negative, is much larger than
anthropogenic forcing. Why should we hide this well-know fact? Sceptics
my call on this. Readers of our chapter are hopefully able to interpret
the y-axis.

The TS-team (in this case neither me nor Peck) asked us to show the
volcanic spikes.

A point of the figure is to show the implication of low solar forcing
(WLS versus Bard) that is why I prefer to blow the solar panel somewhat
up. We have varied solar forcing between the different runs. Of course
the point about the natural forcing only simulation not able to get the
20th century warming is very important. Indeed, I believe that this
important conclusion is underscoored if we make it very clear that we
have varied solar forcing over a wide range (by a factor of 3).

It would also be nice to show the 11-yr solar cycle that is in the data
(sun spots, but also 14C).

As far as normalisation of the forcing is concerned. I have no strong
opinion. There is a consistency issue with chapter 2 where radiative
forcing is always defined relative to 1750 (1750==0). This point may
especially be important for the TS. There is also the issue about
agreement over recent decades. This is why I slightly prefer to
normalize the forcing to be zero around 1750.

The sulfur figure will show volcanic spikes. We have agreed in Bergen
that we add a sentence to the caption to point out that sulfate
deposition may strongly vary regionally.

I think we have with fig 13 and 14 now the opportunity to convey to the
readers the same information in two different ways. Perhaps, we should
not miss this opportunity. In any case, we will find a solution and then
go forward.

Cheers, Fortunat


Keith Briffa wrote:
> Fortunat et al
> My opinions were consistent with Tim's expression - we discussed his
> response. The importance of consistency between different modelling
> Figures ( time response of filters and in the absolute magnitude of
> forcing scale) are the most important aspects. To start showing
> apparently different volcanic spikes (in the sulphate and EMIC Figure )
> will lead to confusion also. Ultimately we should remember that the
> point of this Figure is to show that you can not get simulated
> temperatures to match observations without anthropogenic forcing - not
> to show proportional responses to different solar or volcanic events.
> cheers
> Keith
>
> At 13:45 18/07/2006, Fortunat Joos wrote:
>
>> Dear Tim,
>>
>> 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 forcing.
>>> I'll hold off from making any more versions till decisions are made
>>> on these issues.
>>> Cheers
>>> Tim
>>> 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
>>>> post-processed.
>>>>
>>>> 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 1xxx xxxx xxxxAD 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,
>>>>
>>>> Fortunat
>>>>
>>>> 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 (xxx xxxx xxxx). 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
>>>
>>>
>>>
>>> Dr Timothy J Osborn, Academic Fellow
>>> Climatic Research Unit
>>> School of Environmental Sciences, University of East Anglia
>>> Norwich NR4 7TJ, UK
>>> e-mail: t.osborn@xxxxxxxxx.xxx
>>> phone: xxx xxxx xxxx
>>> fax: xxx xxxx xxxx
>>> web: http://www.cru.uea.ac.uk/~timo/
>>> sunclock: http://www.cru.uea.ac.uk/~timo/sunclock.htm
>>> **Norwich -- City for Science:
>>> **Hosting the BA Festival 2-9 September 2006
>>
>>
>> --
>>
>> Climate and Environmental Physics,
>> Physics Institute, University of Bern
>> Sidlerstr. 5, CH-3012 Bern
>> Phone: ++41(0xxx xxxx xxxx Fax: ++41(0xxx xxxx xxxx
>> Internet: http://www.climate.unibe.ch/~joos/
>
>
> --
> Professor Keith Briffa,
> Climatic Research Unit
> University of East Anglia
> Norwich, NR4 7TJ, U.K.
>
> Phone: xxx xxxx xxxx
> Fax: xxx xxxx xxxx
>
> http://www.cru.uea.ac.uk/cru/people/briffa/

--

Climate and Environmental Physics,
Physics Institute, University of Bern
Sidlerstr. 5, CH-3012 Bern
Phone: ++41(0xxx xxxx xxxx Fax: ++41(0xxx xxxx xxxx
Internet: http://www.climate.unibe.ch/~joos/

</x-flowed>

Original Filename: 1180342271.txt | Return to the index page | Permalink | Later Emails

From: Gavin Schmidt <gschmidt@xxxxxxxxx.xxx>
To: Phil Jones <p.jones@xxxxxxxxx.xxx>
Subject: Wengen section
Date: Mon, 28 May 2007 04:51:xxx xxxx xxxx(EDT)
Reply-to: gschmidt@xxxxxxxxx.xxx
Cc: mann@xxxxxxxxx.xxx, Caspar Ammann <ammann@xxxxxxxxx.xxx>

<x-flowed>

Hi Phil, sorry for the long delay. But here is a first draft of the
forcings and models section I was supposed to take the lead on. Hopefully,
we can merge that with whatever Caspar has.

Thanks

Gavin

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

4 Forcing (GS/CA/EZxxx xxxx xxxxpp

Histories (CA)
How models see the forcings, especially wrt aerosols/ozone and
increasing model complexities (GS)

An important reason for improving climate reconstructions of the past few
millenia is that these reconstructions can help us both evaluate
climate model responses and sharpen our understanding of important
mechanisms and feedbacks. Therefore, a parallel task to improving
climate reconstructions is to assess and independently constrain
forcings on the climate system over that period.

Forcings can generically be described as external effects on a
specific system. Responses within that system that also themselves
have an impact on its internal state are described as feeebacks. For
the atmosphere, sea surface temperature changes could
therefore be considered a forcing, but in a coupled ocean-atmosphere
model they could be a feedback to another external factor or be
intrinsic to the coupled system. Thus the distinction between forcings and
feedbacks is not defined a priori, but is a function of the scope of
the modelled system. This becomes especially important when dealing
with the bio-geo-chemical processes in climate that effect the
trace gas concentrations (CO2 and CH4) or aerosols. For example, if a
model
contains a carbon cycle, than the CO2 variations as a function of
climate will be a feedback, but for a simpler physical model, CO2 is
often imposed directly as a forcing from observations, regardless of
whether in the real world it was a feedback to another change, or a
result of human industrial activity.

It is useful to consider the pre-industrial period (pre-1850 or so)
seperately from the more recent past, since the human influence on
many aspects of atmospheric composition has increased dramatically in
the 20th Century. In particular, aerosol and land use changes are
poorly constrained prior to the late 20th Century and have large
uncertainties. Note however, there may conceivably be a role for human
activities even prior to the 19th Century due to early argiculatural
activity (Ruddiman, 2003; Goosse et al, 2005).

In pre-industrial periods, forcings can be usefully separated into
purely external changes (variations of solar activity, volcanic
eruptions, orbital variation), and those which are intrinsic to the
Earth system (greenhouse gases, aerosols, vegetation etc.). Those
changes in Earth system elements will occur predominantly as feedbacks
to other changes (whether externally forced or simply as a function of
internal climate 'noise'). In the more recent past, the human role in
affecting atmospheric composition (trace gases and aerosols) and land
use have dominated over natural processes and so these changes can, to
large extent, be considered external forcings as well.

Traditionally, the 'system' that is most usually implied when talking
about forcings and feedbacks are the 'fast' components atmosphere-land
surface-upper ocean system that, not coincidentally, corresponds to
the physics contained within atmospheric general circulation models
(AGCMs)
coupled to a slab ocean. What is not included (and therefore considered as
a
forcing according to our previous definition) are 'slow' changes in
vegetation, ice sheets or the carbon cycle. In the real world these
features will change as a function of other climate changes, and in
fact may do so on relatively 'fast' (i..e multi-decadal)
timescales. Our choice then of the appropriate 'climate system' is
thus slightly arbitrary and does not give a complete picture of the
long term sensitivity of the real climate.

These distinctions become important because the records available for
atmospheric composition do not record the distinction between feedback
or forcing, they simply give, for instance, the history of CO2 and
CH4. Depending on the modelled system, those records will either be a
modelling input, or a modelling target.

While there are good records for some factors (particularly the well
mixed greenhouse gases such as CO2 and CH4), records for others are
either hopelessly incomplete (dust, vegetation) due to poor spatial or
temporal resolution or non-existant (e.g. ozone). Thus estimates of
the magnitude of these forcings can only be made using a model-based
approach. This can be done using GCMs that include more Earth system
components (interactive aerosols, chemistry, dynamic vegetation,
carbon cycles etc.), but these models are still very much a work in
progress and have not been used extensively for paleo-climatic
purposes. Some initial attempts have been made for select feedbacks
and forcings (Gerber et al, 2003; Goosse et al 2006) but a
comprehensive assessment over the millennia prior to the
pre-industrial does not yet exist.

Even for those forcings for which good records exist, there is a
question of they are represented within the models. This is not so
much of an issue for the well-mixed greenhouse gases (CO2, N2O, CH4)
since there is a sophisticated literature and history of including
them within models (IPCC, 2001) though some aspects, such as minor
short-wave absorption effects for CH4 and N2O are still not universally
included
(Collins et al, 2006). However, solar effects have been treated in
quite varied ways.

The most straightforward way of including solar irradiance effects on
climate is to change the solar 'constant' (preferably described as
total solar irradiance - TSI). However, observations show that solar
variability is highly dependent on wavelength with UV bands having
about 10 times as much amplitude of change than TSI over a solar cycle
(Lean, 2000). Thus including this spectral variation for all solar
changes allows for a slightly different behaviour (larger
solar-induced changes in the stratosphere where the UV is mostly
absorbed for instance). Additionally, the changes in UV affect ozone
production in both the stratosphere and troposphere, and this
mechanism has been shown to affect both the total radiative forcing
and dynamical responses (Haigh 1996, Shindell et al 2001;
2006). Within a chemistry climate model this effect would potentially
modify the radiative impact of the original solar forcing, but could also
be included as an additional (parameterised) forcing in standard GCMs.

There is also a potential effect from the indirect effect of solar
magnetic variability on the sheilding of cosmic rays, which have been
theorised to affect the production of cloud condensation nuclei
(Dickinson, 1975). However, there have been no quantitative
calculations of the magnitude of this effect (which would require a
full study of the relevant aerosol and cloud microphysics), and so its
impact on climate is not (yet) been included.

Large volcanic eruptions produce significant amounts of sulpher
dioxide (SO2). If this is injected into the tropical stratosphere
during a particularly explosive eruption, the resulting sulphate can
persist in the atmosphere for a number of years (e.g. Pinatubo in
1991). Less explosive, but more persistent eruptions (e.g. Laki in
1789??) can still affect climate though in a more regional way and for
a shorter term (Oman et al, 2005). These aerosols have both a
shortwave (reflective) and longwave (absorbing) impact on the
radiation and their local impact on stratospheric heating can have
important dynamical effects. It is therefore better to include the
aerosol absorber directly in the radiative transfer code. However, in
less sophisticated models, the impact of the aerosols has been
parameterised as the equivalent decrease in TSI. For extreme eruptions
it has been hypothesised that sulphate production might saturate the
oxidative capacity of the stratosphere leaving significant amounts of
residual SO2. This gas is a greenhouse gas and would have an opposite
effect to the cooling aerosols. This effect however has not yet been
quantified.

Land cover changes have occured both due to deliberate modification by
humans (deforestation, imposed fire regimes, arguculture) as well as a
feedback to climate change (the desertification of the Sahara ca. 5500
yrs ago). Changing vegetation in a standard model affects the seasonal
cycle of albedo, the surface roughness, the impact of snow,
evapotranspiration (through different rooting depths) etc. However,
modelling of the yearly cycle of crops, or incorporating the effects
of large scale irrigation are still very much a work in
progress.

Aerosol changes over the last few milllenia are very poorly constrained
(if at all). These might have arisen from climatically or human driven
changes in dust emissions, ocean biology feedbacks on circulation change,
or climate impacts on the emission volatile organics from plants (which
also have an impact on ozone chemistry). Some work on modelling a subset
of those effects has been done for the last glacial maximum or the 8.2 kyr
event (LeGrande et al, 2006), but there have been no quantitative
estimates for the late Holocene (prior to the industrial period).

Due to the relative expense of doing millennial simulations with
state-of-the-art GCMs, exisiting simulations have generally done the
minimum required to include relevant solar, GHG and volcanic forcings.
Progress can be expected relatively soon on more sophisticated treatments
of those forcings and the first quantitative estimates of additional
effects.

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


*--------------------------------------------------------------------*
| Gavin Schmidt NASA/Goddard Institute for Space Studies |
| 2880 Broadway |
| Tel: (2xxx xxxx xxxx New York, NY 10xxx xxxx xxxx |
| |
| gschmidt@xxxxxxxxx.xxx http://www.giss.nasa.gov/~gavin |
*--------------------------------------------------------------------*

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