At 06:05 PM 1/16/2007, PvM wrote:
>So much can be learned by reading.
@ Isn't that the truth. :) ~ Janice
IPCC and Solar Correlations
http://www.climateaudit.org/?p=1079#comment-78077
By Steve McIntyre
Here’s a post which I wrote last June but didn’t
post up at the time because the NAS Panel report
came out and I had other pressing matters to
comment on. My post as then drafted started:
Last week, through Chefen, Jean S and myself,
<http://www.climateaudit.org/?p=690>here
<http://www.climateaudit.org/?p=689>here
<http://www.climateaudit.org/?p=685>here and
<http://www.climateaudit.org/?p=692>here , we
showed that MBH98 contained questionable
statistical methodology for assessing the
relative contribution of solar and greenhouse
gases to increased warming and outright false
claims about the robustness- the falseness of
which was easily determined, making it remarkable
that they’ve remained undetected so long.
Now one of the things that we know about the
Hockey Team is that most things have a purpose.
It may not be obvious and it may not be stated.
(I don’t think that one can properly understand
the MBH98 reconstruction and its rapid inhaling
into policy other than in the context that the
IPCC wanted to “get rid of the MWP”.) So what was
the purpose of MBH98 Figure 7 in the context of
the times? What scores were they trying to
settle? What was the pre-MBH98 status of attempts
to correlate forcings and temperature?
IPCC reports prior to TAR are usually a good
place to start. Here are some notes, which (I
think) place MBH98 Figure 7 in context and which,
in turn, provide some very interesting leads to
follow up on, now that Figure 7 has been overturned.
The rest of my notes follow only slightly
modified. I’ll try to post up some notes at some
point on the work of Reid 1991 and White et al
(JGR 1997) on correlations between solar and tropical SST.
IPCC 1992. (p 65)
IPCC 1992 referred to then recent results from
Reid (1991) which they acknowledged as yielding
“strong visual correspondence between solar cycle
changes and temperature”, but pointed out
concerns from Kelly and Wigley related to the
reconciliation of solar and greenhouse forcing.
Also note the last sentence of the first
paragraph, which I’ll comment on below.
These [airborne] show an apparent change of
irradiance between the late 1960s and the late
1970s of around 0.4%. There is considerable doubt
however about the representativeness of these
values (measured over the time-scales of a day)
and about the absolute accuracy of the
instruments used to obtain them (Lean 1991).
Although Reid (1991) argues against these
problems, it is clearly difficult to identify a
long-term trend using extremely noisy daily data
from instruments of uncertain accuracy.
Apart from these measurements, there are no
useful direct irradiance measurements prior to
1978 so various authors have tried to deduce
irradiance forcing indirectly. For example Reid
(1991) has suggested that low-frequency
irradiance changes in parallel to the envelope of
sunspot activity which shows quasi-cyclic
behavior with a roughly 80-year period and
Friis-Christensen and Lessen 1991 have
hypothesized that low-frequency irradiance
changes are related to changes in the length of
the solar cycle. In both cases, there is a strong
visual correspondence between temperature changes
over the past 100 years – see Section C4.2.1.
These results are intriguing but they have yet to
be fully evaluated in terms of implied changes in
solar forcing compared to greenhouse forcing (Kelly and Wigley 1990).
I don’t disagree with the bolded comment in the
first paragraph, but do observe that this bit of
prudence has not been consistently applied by
IPCC e.g. no such comment was later made about MBH.
The bolded comment in the 2nd paragraph refers to
the issue that a physical interpretation linking
solar changes to temperature changes requires a
greater sensitivity of temperature to solar
forcing than to greenhouse forcing. As an
editorial aside, I don’t like seeing Wigley cited
so often as an omnibus authority to support IPCC,
ranging from statistic significance to glaciers
in the Holocene Optimum to solar forcing. Given
this over-exposure, one needs to see an authority
other than Wigley to substantiate a claim for
reliance in public documents. (2007 - I also note
that the Friis-Christensen results have been
criticized by Damon and Laut (as noted by Lee on an another thread).
IPCC 1994 p 191-2
IPCC 1994 re-visited the issue of solar
correlation devoting an entire subsection devoted
to the topic. Again they noted a seemingly
compelling statistical relationship, but argued
that (1) the relationship was dubious on
statistical grounds and, as bolded below, (2)
that the relationship was inconsistent with then
current ideas of climate sensitivity, which held
that climate sensitivity to solar forcing was not
greater than climate sensitivity to forcing from
additional CO2. Anyway here’s IPCC:
4.5.3 Correlations between Climate and Solar Variability
“Suggestive correlative evidence for an enhanced
role of the Sun in forcing climate has been
presented by many authors including Labitzke and
Van Loon 1993 and references, Reid 1991,
Friis-Christensen and Lassen 1991 and Tinsley and
Heelis 1993, In these studies the correlations
between solar indices such as sunspots and solar
cycle length and observed characteristics of the
atmosphere (e.g. temperature at particular
locations, global average SST etc) are examined.
Some authors have questions the usefulness of
solar-cycle correlation studies noting that
undersampling and/or aliasing of other periodic
atmospheric phenomena could lead to spurious
results (Teitelbaum and Bauer 1990, Salby and
Shea 1991, Dunkerton and Baldwin 1992)….
Labitzke and von Loon 1993 noted remarkably high
correlations between stratospheric temperatures
and solar indices (such as solar emissions at a
wavelength of 10.7 cm) as well as an apparent net
propagation of such correlations in the form of
planetary scale temperature patterns throughout
the troposphere with amplitudes exceeding 1 deg C
in some cases. Kodera 1993 showed by examining
running correlations that undersampling is not
the origin of the Labitzke/van Loon oscillations.
However it is clear that large changes in
temperature noted by Labitzke and Van Loon 1993
and others are inconsistent with observed changes
in the radiative forcing associated with the
well-documented total solar irradiance
fluctuations of the past decade and very probably
the last century…These wavelengths( UV) are all
absorbed well above the tropopause. If this
forcing resulted in only local stratospheric
temperature changes, then there would be little
direct impact on surface climate. .
Friis-Christensen and Lassen 1991 found a high
correlation between solar cycle length and NH
land temperatures. Hoyt and Schatten used solar
cycle length as one of their parameters in
deducing a quantitative variation in solar output
over recent centuries. Hoyt and Schatten 1993
also found a good correlation between solar
output and NH surface temperatures over the past
century. However, these results imply that a
0.14% increase in solar output (equivalent to a
forcing of 0.34 wm-2) causes a surface warming of
0.5 deg C; this is a high climate sensitivity
which, if applied to the 4 wm-2 forcing
associated with doubling the concentration of
CO2, would result in a warming of about 6 deg C.
Thus the hypothesis that variability in solar
irradiance explains the observed temperature
variations over the past century is inconsistent
with our current understanding of climate
sensitivity and would require a dramatically
different forcing-response relationship for solar
forcing than for other forcing mechanisms; there
is no known physical mechanism and no modeling
evidence to support such a difference, *****
Studies using limited records indicate
correlations of winds and temperatures with the
solar cycle. However their interpretation remains
controversial on statistical grounds. No physical
mechanism has been proposed that is
quantitatively consistent with the relationships implied by the correlations.
Again, as an editorial point, “efficacy” seems to
me like a large and interesting question: it does
not seem at all axiomatic that equal wm-2 of
high-energy short-wavelength solar forcing at
surface should have the same impact on surface
temnperature as low-energy long wavelength
infrared forcing at high altitudes from
additional CO2. The supposed equivalence is
relied on but not demonstrated; and continues to
be relied on a virtual axoim (See HAnsen et al
2005). In addition,
<http://strat-www.met.fu-berlin.de/labitzke/moreqbo/MZ-Labitzke-et-al-2006.pdf>Labitzke,
2006, with the benefit of a nearly douled amount
of data, denied that the validity of the above criticism:
Several publications criticized the short data
record and suggested that the correlations are
due to aliasing caused by dividing the data
according to the phase of the QBO (e.g.,
Teitelbaum and Bauer, 1990; Salby and Shea,
1991). But even when 20 more years of data became
available, the correlations remained stable, see Table 1 (Labitzke, 2006).
IPCC TAR, 2001
IPCC TAR’s treatment of solar correlations is
reduced from 1994, with Reid 1991 dropping off
the radar screen altogether. In their handling of
solar correlations, as Jean S observed,
<http://www.grida.no/climate/ipcc_tar/wg1/450.htm>IPCC
got “punk’d” by MBH98, which included both
misrepresentations and incorrect statistical
handling of solar correlations. An amusing
statement in IPCC TAR, relying on MBH98, was that
the use of “multiple correlations avoided the
possibility of spuriously high correlations” to
solar. It’s hard to believe that something
reviewed by entire stadiums of scientists could
say something like this, but here it is:
A number of authors have correlated solar forcing
and volcanic forcing with hemispheric and global
mean temperature time-series from instrumental
and palaeo-data (Lean et al., 1995; Briffa et
al., 1998; Lean and Rind, 1998; Mann et al.,
1998) and found statistically significant
correlations. Others have compared the simulated
response, rather than the forcing, with
observations and found qualitative evidence for
the influence of natural forcing on climate
(e.g., Crowley and Kim, 1996; Overpeck et al.,
1997; Wigley et al., 1997; Bertrand et al., 1999)
or significant correlations (e.g., Schönwiese et
al., 1997; Free and Robock, 1999; Grieser and
Schönwiese, 2001). Such a comparison is
preferable as the climate response may differ
substantially from the forcing. The results
suggest that global scale low-frequency
temperature variations are influenced by
variations in known natural forcings. However,
these results show that the late 20th century
surface warming cannot be well represented by
natural forcing (solar and volcanic individually
or in combination) alone (for example Figures
12.6, 12.7; Lean and Rind, 1998; Free and Robock,
1999; Crowley, 2000; Tett et al., 2000; Thejll and Lassen, 2000).
Mann et al. (1998, 2000) used a multi-correlation
technique and found significant correlations with
solar and, less so, with the volcanic forcing
over parts of the palaeo-record. The authors
concluded that natural forcings have been
important on decadal-to-century time-scales, but
that the dramatic warming of the 20th century
correlates best and very significantly with
greenhouse gas forcing. The use of multiple
correlations avoids the possibility of spuriously
high correlations due to the common trend in the
solar and temperature time-series (Laut and
Gunderman, 1998). Attempts to estimate the
contributions of natural and anthropogenic
forcing to 20th century temperature evolution
simultaneously are discussed in Section 12.4.
The discussion in
<http://www.grida.no/climate/ipcc_tar/wg1/245.htm>Section
12.4 include the following mention of Reid (together with Soon) as follows:
An alternative approach which has been used to
reconstruct TSI (Reid, 1997; Soon et al., 1996)
is to assume that time variations in global
surface temperature are due to a combination of
the effects of solar variability and enhanced
greenhouse gas concentrations and to find that
combination of these two forcings which best
combine to simulate surface temperature
measurements. However, these authors did not take
natural climatic variability into account and a
TSI series derived by such methods could not be
used as an independent measure of radiative forcing of climate….
However, because of the large uncertainty in the
absolute value of TSI and the reconstruction
methods our assessment of the “level of
scientific understanding” is “very low”.
At this point, we know that the MBH98 claims in
respect to solar correlations cannot be relied on
(for quite distinct reasons than principal
components or bristlecones - see links at top of
post). The dismissal of Reid 1997 here does not
include any peer-reviewed citation, and, to that
extent, is merely an editorial opinion of the
section authors - and these are the same authors
who made the silly comment about multiple regression.
Conclusion:
At this point, I’m far from arguing that anyone
has established a connection between solar
irradiance changes and temperature changes.
However, it is incorrect to say that no
statistical correlations between solar irradiance
changes and temperature changes (in this case, to
tropical SST in particular) have been observed.
Whether those correlations are valid is a
different issue. IPCC relied to some extent on
MBH98 in dismissing these supposed relationships,
but, given the defects in this specific area of
MBH98 (as well as more general problems),
alternative grounds for dismissal have to be
sought if one repudiates MBH98. I’m not saying
that such alternative grounds are not possible -
merely that it is not prudent to rely on MBH98 in
respect to taking a position on solar
correlations. The other large issue is whether
there are physical reasons why the efficacy of
solar forcing (high-energy low-entropy at
surface) might differ from the efficacy of
additional CO2 forcing (low-energy high-entropy
at altitude). I am not in a position to make
statements one way or the other, but merely
observe that I see no reason why this should be
an axiom and that establishing differing efficacy
would be a necessary aspect of research for
anyone seeking to argue an increased role for
solar forcing in temperature change.
References:
Labitzke website
http://strat-www.met.fu-berlin.de/publications/publications_90s.html
K. Labitzke and H. van Loon 1993Some recent
studies of probable connections between solar and
atmospheric variability Ann. Geophysicae, 11, 1084-1094, 1993
Reid, George. “Solar variability and climate
change on the time scale of decades to centuries,” Eos, 69:18, 567, 1988.
Reid, George. “Solar total irradiance variability
and global ocean temperature variations.” Eos, 73:14 supplement, 244, 1992.
Reid, GC 1991. Solar total irradiance variations
and the global sea surface temperature record.
Journal of Geophysical Research 96: 2835-2844.
Reid, G.C. 1997. Solar forcing of global climate
change since the 17th century. Climatic Change 37: 391-405.
Reid, G.C. 1999. Solar variability and its
implications for the human environment. Journal
of Atmospheric and Solar-Terrestrial Physics 61(1-2): 3-14.
Reid, G.C. 2000. Solar variability and the
Earth’s climate: introduction and overview. Space
Science Reviews 94(1-2): 1-11.
http://www.agu.org/revgeophys/reid00/node2.html
http://www.agu.org/pubs/crossref/1991/90JD02774.shtml
4 Responses to “IPCC and Solar Correlations” so far:
1
<http://www.geocities.com/uc_edit/>UC says:
January 16th, 2007 at 12:13 pm
The use of multiple correlations avoids the
possibility of spuriously high correlations due
to the common trend in the solar and temperature
time-series (Laut and Gunderman, 1998)
LOL! And what about the common trend in CO2 and
Solar, no multicollinearity problems?
2
jae says:
January 16th, 2007 at 12:17 pm
it is clearly difficult to identify a long-term
trend using extremely noisy daily data from instruments of uncertain accuracy.
LOL. As if tree rings were a more accurate “instrument?”
Great post!
3
Francois Ouellette says:
January 16th, 2007 at 12:35 pm
Steve,
I’ve noted before, and elsewhere, that, from what
I’ve learned about the so-called “feedback”
effect to the CO2 forcing, it applies equally
well to other types of radiative forcings. I
don’t like the word feedback because in my
opinion it’s just an amplifying factor (IOW the
additional warming does not cause more CO2 in the
atmosphere). (As an aside, this is an important
distinction for a laser physicist like me, as
lasers rely on both feedback AND amplification).
The “amplification” comes from the fact that a
warm surface generates more water vapor, which in
turn warms the atmosphere. The net effect, as I
see it, is in the lapse rate. But if, for
example, less clouds are formed because of a lack
of cosmic rays, the additional warming of the
surface will also result in more water vapor and
a warmer atmosphere. This is all in the case of a
“clear” atmosphere, ie. without clouds. As far as
I can tell, the value of any sort of “feedback”
or “amplification” when clouds are present is
still a major unknown, and depends on a number of
factors (ie. low clouds vs high clouds etc.).
Since it is presumed by the “cosmic ray”
hypothesis that these also affect cloud
formation, the net result is…, well, you guess is
as good as mine. We don’t know and it could take a while to decipher.
So, in conclusion, there is nothing to preclude
“amplifying” factors to the solar (direct or
indirect) forcing. That we know little about them
is merely the result of the emphasis placed on
GHG’s over the last 20 years. When more research
effort is devoted to a better understanding of
the sun-climate connection instead of trying to
publicly discredit the few researchers who are
working in that area, then we might make progress.
4
<http://>Steve McIntyre says:
January 16th, 2007 at 1:17 pm
#1. UC, I thought that you’d like this quote. Can
you imagine what a prof would say in a 2nd-year
statistics class to someone saying this in a presentation.
I hadn’t thought about this before, but I guess
that the Laut here is from Damon and Laut. I
hadn’t noticed this at the time. So the reference
is not to a real statistics text. Typical.
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Received on Tue Jan 16 18:43:01 2007
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