Dear Alan--When observationalists are clear the observations of ice
thinning and retreat are right, and the modelers are insisting that the
physics is the model is properly constructed and correct, then, if there
are inconsistencies between the two, what needs to be looked at very
carefully is the forcing, or more specifically, the changes in the
forcing over time. Specifically, there have been changes over time in
the sulfate and black carbon forcing that affect the solar radiation
budget and also cloud albedo, and there have been changes in the
tropospheric ozone concentration (as well of the greenhouse gases, which
need to be treated specifically and not using CO2e). I'd suggest that
all it would take are some relatively modest problems in some of these
forcings as the region has gone through the issue of Arctic springtime
haze and the its "clean up" as SO2 emissions in Europe and North America
grew and then cleaned up much of the SO2 emissions, as the black carbon
loadings changed as growth of diesel emissions of black carbon changed
and were somewhat reduced, and then as China has grown. Calculations in
Navarro et al, 2016 make clear that changes in forcing can influence the
Arctic. I'd just suggest that a hypothesis that I think likely needs
some exploration is that it is the time history of the forcings that
could explain the difference between the observations and the models,
and that it might be more productive to look at this alternative
hypothesis as a way of explaining their differences.
I'd also note that I suggest this as only one alternative
hypothesis--there may well be others. In any case, I'd suggest finding
some possible explanation(s) for the differences and to get working on
reconciling and understanding the reasons for the differences--which is
what science generally aims at doing rather than simply blaming the
other side.
Best, Mike MacCracken
On 11/23/16 1:50 PM, Alan Gadian wrote:
Reto and Peter,
ECMWF is the best forecast model in the world. If you had attended
the change of directorship last Spring, you would have heard them say
that the ice model predictions ( and they have the HIGHEST resolution
forecasting model) are terrible, do not predict changes and have
little connection with reality. My climate model has taken 250 days
on 12,000 cray cores and I only achieve 20km resolution. ( I
estimate I used about 2 million dollars of electricity in the end, as
some of the model is at 2-3km resolution. It has possibly been one of
the biggest projects on ARCHER.
ECMWF can run globally at 2-4km resolution. How is it also that
Martin Miller , who masterminded much of the ECMWF model said of AR5 ,
that the clouds were so badly predicted that the radiative balance is
not correct, and the climate models could not be trusted for clouds
and radiation? He was one of the worlds best experts,but ignored.
Also then, How is it that then the climate models can do so much
better than the best weather prediction models in the world? When
the data evidence of the HUGE changes in ice volume and extent, are so
apparent, so much so that by the time AR5 went to press , six months
after writing, the ar5 ice extent predictions were outside the
predicted range for the worst scenario, how can the ar5 community
still try to sell the story? Maybe Trump took his lead from the
climate modellors?
I have had endless arguments with Piers Forster , another lead author
on ar5 about this. scientists who know about modelling the weather
have been ignored. You do not get papers published which day that
models are wrong, only when you say how great they are.
In essence ,after AR3, it has become a gravy train for academic
careers based largely on CXXP models. In a short time these models
will be shown to be catestrophically wrong, and all that is done is to
pillory those who try to point out the true science.
Regards
Alan.
T ---
Alan Gadian, NCAS, UK.
Email: [email protected] <mailto:[email protected]> &
[email protected] <mailto:[email protected]>
Tel: +44 / 0 775 451 9009
T ---
On 23 Nov 2016, at 15:32, P. Wadhams <[email protected]
<mailto:[email protected]>> wrote:
Dear Dr Knutti, I would like to intervene in this seemingly
interminable thread to draw attention to errors which you have made
when you mention my work.
1. " But the natural variability is very large (e.g. Kay 2011,
Swart 2015, Screen 2013, 2016). There is no reason why short term
trends could simply be extrapolated, and the predictions by Peter
Wadhams of sea ice disappearing by today have not happened so far"
a) I completely agree that natural variability is very large and
stress this in my book "A Farewell to Ice" which I suspect you have
not read. In the book I stress that it is the TREND which is rapidly
downwards towards zero, not that every successive year features a
monotonic decrease in summer ice volume. And, despite the newspaper
reports which seems to constitute your reading matter on my work, I
do NOT forecast that the ice volume will go to zero in a specific
year (like this year), only that it will go to zero in a very small
window of years (of which this year forms one) as opposed to the
decades which are still forecast by the worst of the current models.
You might also care to glance at the current NSIDC charts for ice
volume (Arctic and Antarctic) which show an extraordinary turndown
since September suggesting that the co-operative collapse which I
have long projected through my thickness measurements is now
happening. b) Why can't short term trends be extrapolated? Firstly,
they are not short term - they date back to the 1980s when
observations began. And secondly, please name the magical effect
which will cause the trend to become invalid and the ice volume to
pick up again.
2. > Maybe the models are missing something, but it's just as
plausible (and
in most scientist's view more likely) that the models are largely
consistent with observations within natural variability.
Your idea of "most scientists" is an odd one. When the observations
show a rapid declining trend leading to zero very soon, how can
models (which predict decades of continued summer sea ice) be
consistent with these observations? They are simply not consistent,
and it is clear that by "most scientists" you mean "many modellers",
some of whom have never seen sea ice.
3. I'm not
downplaying the strong changes in the Arctic, but the science
suggests a fairly linear (and reversible) relationship between
Arctic sea ice and temperature with large variability superimposed.
In my view they do not support a "death spiral".
Well, it's obvious that there is a linear relationship between air
temperature history and sea ice thickness. The "degree days of cold"
analysis dates back to the 1950s and was amplified by Maykut and
Untersteiner's analysis in 1971. But if air temperature is increasing
rapidly, as it is, then thickness will decline just as rapidly,
leading to a period in summer with zero thickness, in other words, a
"death spiral" QED.
To paraphrase Captain Scott, I don't think I need say more,
Best wishes
Peter Wadhams
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