Drs. Shaviv and Veizer have now responded to the statement of the 14 scientists on their GSA Today paper. Their responses are reproduced below, with our comments added.
Response by Dr. Nir Shaviv (bold) with our comments (normal):
> I carefully read the letter written by the
cosigners and was quite bewildered by it. First, it is strange that
they decided to hold a scientific debate by press releases. While I am
sure that this debate is of interest to the general public, the nature
of the medium allows them to bring forth accusations without actually
presenting any supporting evidence. This is hardly a scientific
approach, made even worse with general claims, such as "methodically
very doubtful". To counter such a claim, we would have to show that all
the steps we have taken were done carefully. Obviously I cannot
condense about 75 journal pages of detailed analysis, published in 6
articles, and reviewed by 10 referees. I will, however, show how
specific concerns are invalid.
We agree that a proper
scientific discussion needs to take place in the scientific journals,
and to our knowledge one such journal article has been submitted and a
second one is in preparation. As you know, such articles take many
months to appear in print. We took the decision to make a public
statement after careful consideration, because strong political claims
were being made based on your publication.
We would like to point
out that you published a media release yourself on 12 August, titled
"Global warming not a man-made phenomenon". This starts as follows:
"Global warming will not be helped much by efforts to reduce carbon
dioxide emission into the atmosphere, say two scientists who have
studied the matter". You are cited as saying: "The operative
significance of our research is that a significant reduction of the
release of greenhouse gases will not significantly lower the global
temperature, since only about a third of the warming over the past
century should be attributed to man."
Even if your scientific
analysis were completely correct, your paper would have merely provided
one intriguing piece of evidence pitted against many other studies that
come to a different conclusion, and it would have been irresponsible to
publish such a far-reaching statement in a press release, especially
since your paper does not study 20th Century warming. After making such
a strong claim about the "operative significance" of your work in the
media, you can hardly be surprised that this will be scrutinised and
criticised also in the public arena.
> For example,
the statement that "The reconstruction of the cosmic radiation is based
only on 42 meteorite finds, which are interpreted differently by other
experts" demonstrates the above. First, the reconstruction is based on
50 not 42 meteorites. This is a minor point, but it demonstrates that
they read only the first analysis published in a short letter and not
the 30 page subsequent paper detailing the cosmic ray flux
reconstruction. Second, they failed to mention that the same
periodicity and phase is obtained in a totally independent way using
astronomical observations on galactic spiral arm dynamics. One can thus
throw away the meteoritic data altogether, yet still reach the same
conclusion. This makes the cosmic ray flux reconstruction quite robust
since it is based on two independent methods. Third, if there are
"completely different interpretations by other experts", why have they
not been published in the scientific media (or non-scientific for that
matter). Apparently, no other consistent explanation of the data
actually exists.
We wished to point out that the
meteorite data on which the cosmic ray flux curve is based are
relatively few and uncertain, especially considering that it is an
indirect inference based on apparent age clustering of the meteorites
that is used to construct this curve. Other specialists on meteorite
research working on cosmic-ray effects interpret the clustering of CRE
ages as the result of break-up processes on parent asteroids, Mars and
Moon, where large numbers of meteorites were ejected. The models of
galactic spiral arm dynamics are also rather uncertain and do not
directly provide data on cosmic ray flux. For the lay-person newspaper
reader, it is important to point out that your data may be sufficient
to put forward a speculative new hypothesis about cosmic ray variations
(which we welcome), but they are not sufficient to overrule conclusions
based on the much more abundant and accurate climate data from the more
recent past, let alone to call for policy revisions. We expect you will
agree on this point.
> As another example, writing
that "The two curves show a statistic connection only because the time
scale of the cosmic data was stretched arbitrarily in such a way, until
an agreement arises", is simply wrong. The cosmic ray flux
reconstruction gives a periodicity of 143 +/-10 Myr. Since the
reconstructed tropical temperature shows a periodicity of 135 +/-9 Myr,
the two signals are consistent with each other, without a needless
"arbitrary stretching". Interestingly, also, the phases of the signals
are consistent to within the measurement error.
Here
you state that the periods and phase found in the two data sets are
similar. We do not disagree with that statement. We do disagree with
the much further reaching claim in your paper, namely that the two data
sets show a statistically significant correlation which can explain 66%
of the temperature variance. Our calculations show that your original
data sets show no significant correlation; this only arises after you
artificially enhanced the correlation by stretching the time scale
(transforming the blue curve into the red curve in the upper panel of
your Fig. 2). We note that you do not dispute this.
>
And a last example, writing that "Even if it were material, this cycle
(with three degrees of warming over 70 million years) would cause a
warming of around a millionth degree in 20 years" simply is not
relevant. What we strived to demonstrate is that the cosmic rays appear
to affect climate on geological time scales as a result of the changing
galactic "geography". If the result is correct, then the implication to
global warming is not through the slowly changing flux outside the
solar system, but arises from modulations by the solar wind, which is
known to affect the cosmic ray flux reaching Earth. In particular, the
increased solar activity over the past century should have translated
into a quick rise in global temperature, explaining more than half of
the observed global warming.
We understand the
mechanism that you propose. Our statement cited above explicitely
refers not to your paper but to a newspaper article by Edgar Gärtner.
This article states that your work explains why global temperature has
been rising over the past 20 years even though solar activity has not;
it claims that this is due to diminishing cosmic ray flux as the Earth
is leaving the Saggitarius-Carina spiral arm. We think that we all
agree this is nonsense; we cited this as an example for the exaggerated
media claims that were made in conjunction with your paper, and which
required a response (especially given that this particular claim was
even debated in the German parliament, the Bundestag).
We would like
to ask you in which scientific publication we can verify your claim
made above, that increased solar activity should explain more than half
of the observed 20th Century warming.
> I could
continue, but I think I have made my point. An avid reader should not
take for granted a single word that I or the cosigners write in
non-scientific media. Instead, he/she should take a look at the
scientific articles and counter-articles and judge with a critical
mind. One should always look also at the error quoted in these
scientific articles. It may prove illuminating. The cosigners write
that the doubling of CO2 in IPCC models would result in a "1.5 to 4.5
deg Celsius" rise in temperature. In our paper, we find that the upper
limit (at 90% confidence) for the doubling CO2 is about 1.5 degs (at
least on the geological time scales). Our results are thus inconsistent
only with the upper range of the IPCC claims.
You refer
here to "IPCC models" and "IPCC claims". We would like to point out
that the IPCC does not run models, but that it publishes reports that
are reviews of the published scientific literature. It does that after
an extremely thorough and open process of discussion, drafting, peer
review and revision of the individual chapters, involving hundreds of
scientists. This process exists to provide policy makers and the public
with a balanced overview of the state of knowledge, and to avoid that
individual and exaggerated claims, such as those in your press release,
unduly influence the public or policy.
Your estimate of the
effect of doubling CO2 is in fact the main point of critique in our
statement, since the method by which you arrived at it is flawed. You
arrive at this by a regression analysis of temperature and CO2 time
series. Climatologists have long known that this is not feasible, which
is why they have not applied this simple analysis to the existing
other, more reliable time series of temperature and CO2, such as those
from Antarctic ice cores. One reason is that other forcing factors vary
in a statistically not independent manner with temperature and CO2, so
that the basic precondition for a meaningful regression is not
fulfilled.
Imagine performing your regression analysis to the Vostok
data, to determine the relative roles of insolation variations (due to
orbital cycles) and CO2 variations on glacial cycles. The result would
yield almost no role of orbital cycles, yet an effect of CO2 that is
far too large. This is because other factors (e.g., the growth of ice
sheets with their albedo, as well as methane variations) covary with
CO2 and cause a large part of the temperature response, but these
factors are irrelevant to the question of CO2 doubling on a time scale
of decades. Only when these factors are carefully considered, as in the
article of Lorius et al. (Nature 1990), can an estimate of climate
sensitivity be derived from paleodata. Lorius et al. concluded from the
Vostok data that the climate sensitivity to CO2 doubling is 3-4 ºC, in
line with independent estimates based on the known radiative forcing of
CO2 and the physical understanding of feedbacks as coded in climate
models.
Your analysis applies to the hundred-million-year time scale
and to a climate that for most of the time has far higher CO2 values
than at present (between twice and ten times present levels). The
position of continents also differs from the present. As is the case
for the Vostok data, processes that operate on such time scales and at
such high CO2 values will differ from those of interest for present
climate. There are reasons to believe that the climate response could
be much weaker than that to a CO2 doubling from current values. For
example, due to the lack of ice, the ice-albedo feedback, one of the
strongest amplifiers of climate change in a CO2 doubling scenario,
would be much weaker for higher CO2 values.
We note that you did not respond to this fundamental issue, although this is the central point of our statement.
Response by Prof. Veizer (bold) with our comments (normal):
> In a press release of October 24
(http://idw-online.de/public/zeige_pm.html?pmid=71073), a group of
scientists denounced our publication in GSA Today (July 1) as
"wissenschaftlich nich haltbar" and based "auf aeusserst fragwuerdigen
Methoden" that should "in keiner Weise in Frage stellen" the "fundierte
Wissen" about anthropogenic climate impact.
It concerns me that the
debate stooped to this level, but it is symptomatic of the general
atmosphere surrounding the climate change issues. A recent personal
attack by the PIK cosigner on other scientists in Die Zeit is another
example. I strive to refrain from the divisive public discussion of
political ramifications (Kyoto) and would not conceive of attacking the
scientific integrity of the IPCC-supporting scientists, despite the
fact that these models too have a plethora of weak points (clouds,
biology...) and yield predictions that are inconsistent with reality
(balloons and satellites show no tropospheric temperature rise, the
Antarctic and Greenland are mostly cooling...).
We
would like to point out that we made no personal attacks. We only put
forward strictly scientific arguments, which we believe are correct
also after considering your response. We deemed it necessary to present
these scientific arguments after exaggerated and irresponsible
political claims were repeatedly being made with reference to your
work. We would have much preferred it if you had made it clear yourself
in public that your paper should not be used to draw political
conclusions about the Kyoto protocol or other climate policy measures.
We
would also like to point out again that the IPCC is a body which
summarises published journal articles; its conclusions are based on all
published work including yours and including all work in
paleoclimatology and data analysis, not specifically on modeling work.
>
Note also that in the Antarctic ice cores, cited by the signatories as
the prime confirmation of the greenhouse theory, the CO2 commences to
rise only centuries after the temperature has risen. Nonetheless, in
the GSA article we still treated this cause/effect issue as an open
question, striving not to belittle the research that attributes climate
change to greenhouse gases. Regrettably, such is often the treatment of
ideas exploring alternative scenarios.
We did not cite
the Antarctic ice cores as the prime confirmation of greenhouse theory
- we cited these ice cores as an illustration of why the kind of
regression analysis performed in your paper does not yield correct
results. We are not aware of any research that would suggest that
greenhouse gases are the prime cause of the glacial cycles (or of
shorter-term, millennial climate variations) seen in these ice cores.
There is a wide consensus amongst climatologists that the glacial
cycles are primarily caused by insolation variations due to orbital
variations, which are amplified by various feedbacks including the
build-up of continental ice sheets. It is hence to be expected that CO2
follows these temperature variations with a time lag that depends on
the response time of the carbon cycle. None of this yields direct
information on the feedback effect of these CO2 variations on climate.
>
Arguing that our research is being "misused" by others is hardly a
justification for personal attack on our scientific integrity. After
all, is not the research of the signatories utilised in exactly the
same way, albeit for an alternative view?
Far from
attacking anyone on a personal level, we only criticise a few specific
statements in one publication, and with good reason. Any scientist who
makes such high-profile statements and operates as a public figure in
the media can be expected to accept reasoned scientific criticism of
their statements, not just in scientific journals but also in public
discourse. We are subject to that as well.
Whenever our own research
is misused for ill-founded or exaggerated claims in the public, in one
sense or the opposite, we protest and try to rectify the matter. We
believe it is very important that the public perception of science
reflects in the most accurate and balanced way possible the actual
state of knowledge, discussion and uncertainty that exists within the
scientific community. That is why we deemed a public statement
necessary in this case.
> My coauthor, Dr Shaviv, has
responded to the points that concern the astrophysical issues. As for
the geological part, it involved years of data gathering by many
researchers, financed mostly by the Leibniz prize of the DFG, and the
curve is based on about 4500 hard won measurements. Moreover, ours is
the only comprehensive Phanerozoic database presently available,
yielding a result in good agreement with the actual climate patterns
deduced from sediments (see www.scotese.com/climate.htm). In contrast,
the CO2 model (IPCC, page 40, figure 10e,f) is completely at odds with
actual observations. Yet, it is the thousands of measurements
corroborated by observations that are "fragwuerdig", while the
theoretical construct that is at odds with reality merits inclusion in
the IPCC summary chapter.
In our statement we merely
point out that CO2 reconstructions so far back in time are still highly
uncertain. You state this yourself in your paper, and you include three
very different CO2 reconstructions in your Fig. 1. Hence we think we
can agree on this point.
> The insinuation that our curves were shifted around until a fit was obtained is just that, unfounded insinuation.
As
discussed above, we refer to the shift in curves from your blue to your
red cosmic ray curve, which you describe as "fine tuning to best fit
the low latitude temperature anomaly" in the caption to your Fig. 2.
Without this "fine tuning", which shifts the oldest peak by about 20
million years, there is no significant correlation.
>
Dr Shaviv and ourselves published our research and curves independently
in top refereed journals, totally ignorant of each other's work. As for
the rest, I invite the readers to peruse our publication and decide for
themselves what we have actually claimed, and what is being imputed to
us by the cosigners.
As scientists, we are not infallible and may
eventually be proven wrong, but this should be done by factual science
and not by denunciation of our scientific integrity in press releases.
As
scientists, we are indeed not infallible. Hence, a thorough and open
process of discussion and review of all relevant results needs to be
performed; only the conclusions that stand up to such debate and
scrutiny should be used to inform public policy. Such a process is
facilitated by the IPCC. We believe that an individual publication,
especially if it is at odds with the work of many other scientists,
should not have been launched with a press release that suggests
immediate policy implications. Nevertheless, we refrained from
criticising such personal behaviour. Our statement focussed entirely on
scientific arguments, since what ultimately counts is the science.
The
original statement, signed by 14 scientists from Switzerland and
Germany, can be found at http://www.pik-potsdam.de/news/archive/archiv-2004-2005/pm_Shaviv_Veizer_e.html
