Mike,
Sorry for the delay .. in India.
I am afraid I am someone on the "other side" in that I use NWP and climate
models for my living. Thus I can speak as someone who has used them a
lot!
There are good things about climate models as well as bad things. The
fear
I have is that the whole of the IPCC is based on climate models, and that
is the issue. There are huge differences between the poles, and these are
largely ignored. There are other processes which are not replicated in
climate models. Why a double ITCZ? Why little Indian monsoon. One can
explain these features ...
I note the papers, but I am afraid, whether it is 70km mountains on Venus
(as proposed by NASA) history has not looked favourably on those who
ignore the observations, however erratic / unreliable.
Thanks for your comments
Alan
On Wed, 23 Nov 2016, Michael MacCracken
wrote:
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] &
[email protected]
Tel: +44 / 0 775 451 9009
T ---
On 23 Nov 2016, at 15:32, P. Wadhams <[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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Alan Gadian, Senior Scientist, NCAS, Leeds University, LS2 9JT , UK
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