lrj
Can I conclude from your response that you can provide no counterpoint to Dr Barnett's article? To say that Benny, a social anthropologist is as qualified on climatology as a climatologist, is like saying an historian is as qualified as an oncologist to treat cancer. The claim is simply ludicrous. I'll stick with the expert opinion thanks. There are plenty of well qualified scientists presenting information on climate change at the open democracy website. They even provide a critique of Benny's ideas.
Billy
A few billion years ago the most advanced life was the bacterium. They changed the atmosphere and from them came frogs, Mozart, Beethoven's Fifth, man on the moon and all. Is humanity where it stops?
an interesting article on scientific uncertainty
http://www.opendemocracy.net/globalization-climate_change_debate/globalwarming_2530.jsp
or for a critique of Dr Peiser try
Climate change and science: a response to Benny Peiser
William Connolley
Ray Bradley
Michael Mann
Gavin Schmidt
17 - 5 - 2005
The issues raised in Benny Peiser’s critique of UK chief
scientist David King leave the scientific consensus on the
principal issues of climate change unaffected.
In order to choose policy options wisely, decision-makers
require the most accurate assessment of the relevant
scientific information without having followed every
discussion in the technical literature. To that end,
scientists have a public role in placing new results in
context, distilling the current state of knowledge, and
pointing out where continuing uncertainties and problems lie.
We comment here on scientific content in the submission by
Benny Peiser in openDemocracy’s climate change debate. Any
criticism of his scientific points is however independent of
our opinions concerning his preferred policy options.
Benny Peiser raises two principal issues: continuing
uncertainty in the monitoring of the planet’s albedo (or
reflectivity), and the role of solar-related variability in
forcing the Earth’s climate. We deal with each point in turn.
Albedo (reflectivity) is an important quantity for the energy
balance of the planet. It is affected by the amount of cloud,
snow and ice cover, vegetation and the aerosol content of the
atmosphere. Measuring it directly, however, is very difficult:
it requires instruments to calculate radiation over a huge
range of frequencies, and since it is so locally variable due
to cloud variability, there are significant sampling problems.
Estimates of the planet’s albedo are around 0.3+/-0.01, but
the exact number and its potential variation over time are
highly uncertain. A recent paper (Wielicki et al, Nature 2005)
has produced satellite-based results completely at odds with a
previous study that used Earthshine measurements from the moon
(Palle et al, Nature 2004). Clearly then, changes to the
planet’s albedo are currently unclear.
However, other integrated measures of the Earth’s net energy
balance are available, in particular the changes in ocean heat
content. The increase of energy in the ocean is linked
directly to the energy balance at the top of the atmosphere
because the oceans are by far the biggest repository of heat
in the climate system.
The oceans have been heating up at about 0.6 W/m2 over the
last ten years (Willis et al, Nature 2004) and at a slightly
lower rate since 1950 (Levitus et al, Nature 2000). This can
only have occurred with a net planetary imbalance of radiation
(i.e. the Earth is absorbing more energy than it is giving
out). Thus, regardless of changes in the albedo, the absorbed
solar radiation has been less than the outgoing long-wave
radiation over this period, and in particular over the last
decade.
In addition, climate models driven by our current best guesses
for changes in greenhouse gases, aerosols, and solar forcing
predict a planetary energy imbalance very close to that
deduced from the ocean heat content results (Hansen et al,
Science 2005). Improvements to the albedo record will surely
help further refine climate models, and particular the net
cloud feedbacks, but the current uncertainties do not
undermine the dominant role for greenhouse gases in altering
the present energy balance of the planet.
Solar variability has long been a candidate for causing
climate variations on Earth. Direct measurements of the total
solar irradiance (TSI) have only been available from
satellites since 1979 and even these are subject to
considerable uncertainties. Before then, long-term estimates
have relied on highly uncertain correlations with the sunspot
record and cosmogenic isotopes measured in ice cores. Measured
TSI variations on their own (on the order of ~0.1%) are too
small to have had a large role in recent climate variability;
however, there are indirect effects (such as stratospheric
ozone feedbacks) which can increase the impact of solar
variability.
These effects are included in current climate models but over
the last fifty years or so do not contribute significantly to
the ongoing warming trends. Another postulated effect is the
impact of cosmic rays on cloud nucleation in the atmosphere.
These rays are modulated by solar magnetic activity and thus
also vary in phase with the sunspot cycle. However, this
mechanism remains highly speculative and has not been clearly
demonstrated to occur in the real world.
Regardless of the specifics, though, it should be pointed out
that all solar activity indices (such as sunspots,
helio-magnetic records, cosmic rays) generally peaked in the
late 1950s and have declined or held steady since then. Thus
solar activity is unlikely to be contributing to current
(post-1970) increases in surface temperatures or the planetary
energy imbalance.
In an additional aside, Benny Peiser quotes Jan Vezier’s
statement that "greenhouse gases [act] only as potential
amplifiers". While this might seem to contradict the consensus
position, it is in fact obviously true for changes to
greenhouse gases prior to the industrial era. It is precisely
that amplifying effect that models suggest will lead to
approximately 2-4 degrees Centigrade warming if C02 doubles.
In the current situation where humans have significantly
increased greenhouse gases above background levels, this
amplification is happening in the absence of large external
drivers (whether these are celestial, volcanic, orbital or
tectonic).
We therefore conclude that none of these issues raised by
Benny Peiser have much, if any, implication for the consensus
on the principal climate debate issue: the impact of
anthropogenic greenhouse gases.
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