Re: [asa] Limted role for CO2

From: PvM <>
Date: Mon Feb 05 2007 - 12:39:38 EST

Nir has some interesting articles where he admits that the evidence
for CO2 being a causative factor are 'circumstantial' but also argues
that he believes there exists a better explanation namely the sun via
cosmic rays.
Remember that the link between CO2, human contributions and increased
global temperatures is ever increasing but there may always be other
factors which contribute such as the one hypothesized by Nir.

So perhaps Janice can explain to us what Nir Shaviv's arguments
against CO2 and in favor of cosmic radiation are? Preferably in her
own words, as I am hoping that she will do the research to either
support or falsify Nir's claims.

Let me provide you with some references

Shaviv and Veizer (2003) published a paper in the journal GSA Today,
where the authors claimed to establish a correlation between cosmic
ray flux (CRF) and temperature evolution over hundreds of millions of
years, concluding that climate sensitivity to carbon dioxide was much
smaller than currently accepted.

Paper: Celestial driver of Phanerozoic climate?

The paper was accompanied by a press release entitled "Global Warming
not a Man-made Phenomenon", in which Shaviv was quoted as stating,"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". However, in the paper the
authors actually stated that "our conclusion about the dominance of
the CRF over climate variability is valid only on multimillion-year
time scales". Unsurprisingly, there was a public relations offensive
using the seriously flawed conclusions expressed in the press release
to once again try to cast doubt on the scientific consensus that
humans are influencing climate. These claims were subsequently
disputed in an article in Eos (Rahmstorf et al, 2004)

Rahmstorf, S., D. Archer, D.S. Ebel, O. Eugster, J. Jouzel, D. Maraun,
G.A. Schmidt, J. Severinghaus, A.J. Weaver, and J. Zachos 2004. Cosmic
rays, carbon dioxide, and climate. Eos Trans. Amer. Geophys. Union 85,
38, 41.

Several recent papers have applied correlation analysis to
climate-related time series in the hope of finding evidence for causal
relationships. For a critical discussion of correlations between solar
variability, cosmic rays, and cloud cover, see Laut [2003].

A prominent new example is a paper by Shaviv and Veizer[2003], which
claims that fluctuations in cosmic ray flux reaching the Earth can
explain 66% of the temperature variance over the past 520 m.y., and
that the sensitivity of climate to a doubling of CO2 is less than
previously estimated.

Here we present a critical appraisal of the methods and conclusions of
Shaviv and Veizer [2003].</quote>

 by an international team of scientists and geologists (including some
of us here at RealClimate), who suggested that Shaviv and Veizer's
analyses were based on unreliable and poorly replicated estimates,
selective adjustments of the data (shifting the data, in one case by
40 million years) and drew untenable conclusions, particularly with
regard to the influence of anthropogenic greenhouse gas concentrations
on recent warming (see for example the exchange between the two sets
of authors). However, by the time this came out the misleading
conclusions had already been publicized widely.

On 2/5/07, PvM <> wrote:
> If you insist on being skeptical about one side only, you will surely
> find some people who will support you in your quest. However, if you
> are interested in the truth, you need to do the hard work yourself,
> read the relevant papers, research the claims made.

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Received on Mon Feb 5 12:40:14 2007

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