Transcript Folie 1 - hvonstorch.de

Reconstruction of historical
temperatures during the last
millennium
- analysis of methods
- significance for detection of
anthropogenic climate change
Hans von Storch & Eduardo Zorita
Institute for Coastal Research
GKSS Research Center, Germany
Fidel González-Rouco,
Universidad Complutense, Madrid, Spain
Meeting #1 Open Session of Committee on Surface Temperature Reconstructions for the past 1,000-2,000
Years: Synthesis of Current Understanding and Challenges for the Future, Washington, 2.3.2006
Our results indicate …
The temperature variations during the
preindustrial times (1000-1850) are
likely considerably larger than shown by
the “shaft” of the “hockeystick”.
The significance of the “blade” for
detecting ongoing anthropogenic climate
change is not compromised by the choice
of the various historical reconstructions.
The debate has been
unfortunate as …
• Premature declaration
of validity of a
knowledge claim;
• Critique stifled
instead of
encouraging debate
and discussion to get
a full airy for concern
of misuse in the
political process;
IPCC chairmann Pachauri
in “nature”, 2005
Major conclusions should be
1. Peer review process: no
publication without
reproducible description of
complex methodology;
2. IPCC and related
processes: Have
independent scientists
doing the review; not the
key authors in the field.
3. Data access: Relevant data
and details of algorithms
need to be made public
even to “adversaries”.
"We have 25 or so years
invested in the work.
Why should I make the
data available to you,
when your aim is to try
and find something
wrong with it." (Jones'
reply to Warwick
Hughes, 21. Februar
2005; confirmed by P.
Jones)
Our work
• Are the methods suggested by MBH98 and
by Moberg 2005 reliable in returning
unbiased estimates of low-frequency
temperature variations?
• How good is the method of inverting
terrestrial borehole temperature profiles?
• This is tested in the laboratory of a 1000
year simulation exposed to estimated natural
and anthropogenic forcings.
Relevant new publications from our
international and interdisciplinary group
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Zorita, E., and H. von Storch, 2005: Methodical
aspects of reconstructing non-local historical
temperatures, Memorie della Società Astronomica
Italia 76, p.794ff
González-Rouco, J.F., H. Beltrami, E. Zorita, and H.
von Storch, 2006: Simulation and inversion of
borehole temperature profiles in surrogate climates:
spatial distribution and surface coupling. Geophys.
Res. Letters 33, doi:10.1029/2005GL024693
Rybski, D., A. Bunde, S. Havlin,and H. von Storch,
2006: Long-term persistence in climate and the
detection problem. Geophys Res. Lett. (in press)
Recent "global" near-surface air temperature anomalies
Courtesy of Philip Brohan, Hadley Centre
Comparison between simulations and real reconstructions
Not a specific
result of ECHO-G
For the purpose of testing
reconstruction methods, it does not
really matter how „good“ the historical
climate is reproduced by a millennial
simulation.
Such model data provide a laboratory
to test MBH, Moberg, borehole
inversion and other methods as well as
hypothesis like “McMc”.
Training with trend
• In our test of MBH in science
(2004), the trend in the
calibration period was taken out.
• When the trend during the
calibration period is used as a
critical factor in the empirical
reconstruction model, then the
contamination of the proxy trend
by non-climatic signals must be
mimicked.
• Thus, we introduced an error on
the centennial time scale as red
noise.
• Here: 50% centennial,
75% year-to-year.
• Again heavy underestimation of
long-term variability.
Claim: MBH
was not built
for such
large
variations as
in Erik-I
But – the
same
phenomenon
emerges in a
control run.
Using trends
in statistical
modelling …
Testing
Moberg’s
method
CPS: simple average of normalized proxies,
then rescale to instrumental NHT variance
Testing the Moberg method
in the laboratory of ECHO-G.
The inflation is done using
80-year filtered data.
Solid: Northern Hemisphere
temperature simulated in
ECHO-G
Light: Several
reconstructions obtained
when feeding Moberg's
method with local
temperature records, which
have been contaminated with
centennial noise (signal-tonoise ratio: 1)
González-Rouco et al.,
2006, GRL
Forward model simulations of borehole
temperature profiles with SAT at all
NH grid points (light shading) and at
selected borehole grid points.
Testing the method of inverting
borehole temps
21 year low pass filter of SAT and
inverted (forward modelled) borehole
temperatures
We conclude
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MBH98 underestimates low-frequency
variability.
Moberg does a reasonable job (maybe
fortuitously).
Borehole temperatures reconstructions
provide reasonable estimates, albeit
heavily smoothed.
Does the controversy about the methodology in reconstructing
historical temperature variations have a bearing on the claims
that an anthropogenic signal is detectable in the recent
temperature change?
NO
No sulfate aerosols
Historical Reconstructions –
their significance for “detection”
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- Statistics of ΔTL,m, which is the
difference of two m-year temperature
means separated by L years.
- Temperature variations are modelled as
Gaussian long-memory process, fitted to
the various reconstructions.
Rybski, D., A. Bunde, S. Havlin,and H. von Storch, 2006: Long-term
persistence in climate and the detection problem. Geophys Res. Lett. (in
press)
Temporal development of
Ti(m,L) = Ti(m) – Ti-L(m)
divided by the standard
deviation (m,L) of the
considered reconstructed
temp record
for m=5 and L=20 (top), and
for m=30 and L=100 years.
The thresholds R = 2, 2.5 and
3 are given as dashed lines.
Bunde et al., GRL, 2006, in press
The mystery of the
expected error
of reconstruction
From Gerber, Joos, Brügger, Stocker, Mann,
Sitch and Scholze, Climate Dynamics, 2003
From IPCC TAR (2001)
Rep. Boehlerts questions:
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What is the current scientific
consensus on the temperature record
of the last 1,000 or 2,000 years?
What are the main areas of uncertainty
and how significant are they?
What is the current scientific
consensus on the conclusions reached
by Drs. Mann, Bradley and Hughes?
What are principal scientific criticism
of their work and how significant are
they?
Has the information needed to
replicate their work been available?
Have other scientists been able to
replicate their work?
How central is the debate over the
paleoclimate temperature record to the
overall consensus on global climate
change?
How central is the work of Drs. Mann,
Bradley and Hughes to the consensus
on the temperature record?
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There is consensus on the “blade”, but the claimed
smoothness of the shaft is likely false.
The main problem is the loss of information encoded
in the proxy data and the shortness of the
instrumental record for training the statistical models.
There is no consensus on the claims (which?) made
by MBH. The main critique is that the method is
suffering from a too large loss of variability on long
time scales.
No, the information required for replication was not
made available in a suitable manner. The original
publication in “nature” did not provide this
information and was obviously published without
careful review of the methodology.
Yes, the details of the method were finally
determined, among others by Bürger et al., who
checked a wide range of combinations of details –
which all gave widely different results.
The main conclusions about “detection and
attribution” are drawn from the instrumental record
and models; the different reconstructions do not
contradict “detection”.
The MBH work is widely accepted as truth outside of
people directly engaged in the issue, because of a less
than satisfactory marketing by the IPCC.
Additional relevant literature
Bürger, G., I. Fast, and U. Cubasch, 2006:
Climate reconstruction by regression - 32
variations on a theme, Tellus 58A, 227235.
Bürger, G., and U. Cubasch, 2005: Are
multiproxy climate reconstructions
robust? Geophs. Res. Lett. 32, L23711,
doi:10.1029/2005GL024155
See also,
von Storch, H. and N. Stehr 2005:
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A Climate of Staged Angst,
http://sciencepolicy.colorado.edu/prometheus/archives/
climate_change/000343a_climate_of_staged_.html
Et klima af iscenesat frygt. Vejret 10, 39-42
Geënsceneerede klimaatangst. Natuur, Wetenschap &
Techniek 73, 44-46
Klima inszenierter Angst. SPIEGEL 4/2005, 160-161
Reserve
GCM: ECHO-G
Model description
Atmospheric component
(MPI Rep. 218, 1996)
•ECMWFMPI
•~ECHAM3
+ fresh water on glaciers
+ river runnoff + partial ice cover
•T30 ~ 3.75 x 3.75 ºlat x ºlon
•19 vertical levels:
Highest: 10 hPa~ 30 km
Lowest:~ 30 m
Ocean component
(DKRZ Rep. 13, 1997)
•Prim. Eq. & Thermodyn.
+ sea ice model with snow cover
•Gauss. T42 ~ 2.8 x 2.8 ºlat x ºlon
0.5 ºlat x ºlon Equator
•20 levels
Coupler
(CERFACS Rep. CMGC/98-05, 1998)
•Coupling: 1 day
•Atm  Oce: Heat, fresh watter,
momentum fluxes
•Oce  Atm: Surface conditions
•Grid interpolation
GCM: ECHO-G
Land-Sea Mask
T30 resolution
Soil model
Extension of
Warrilow et al., 1986 Met. Off. Tech. Note, 38.
Z=0 m
Soil processes:
T1=
T(z) soil
T2=
Snow pack
T3=
Soil hidrology
0.065 m
0.319 m
1.232 m
T 4=
4.134 m
T 5=
9.834 m
• Forcing is not
particularly strong
• Sensitivity of ECHOG about 2.5K
Different reconstructions of
solar irradiance
ECHO-G
simulations
„Erik den
Røde” (10001990)
and
“Christoph
Columbus”
(1550-1990)
with
estimated
volcanic,
GHG and
solar forcing
Man et al, 2005
Remind: only coarse stratosphere,
no ozone (ECHO-G)
Discussion
Trend –
does it really
help ?