On 15 Jun 2013, at 16:43, smi...@zonnet.nl wrote:
Not assumed to be caused, but known to be caused.
Hmm.... I agree with the spirit of your post. But we never "known" for
sure, it is still a belief even with serious evidences pointing on
some truth there.
In science we know nothing as such, but some theories are much more
plausible than others, and sometimes they might be true too.
Bruno
The science is clear, it's only that the vast majority of the
population is science illiterate to the point that many people with
university degrees in economics, engineering etc. don't know much
about physics and are susceptible to the same nonsense as most lay
persons.
http://www.sciencemag.org/content/330/6002/356.full
ABSTRACT
Ample physical evidence shows that carbon dioxide (CO2) is the
single most important climate-relevant greenhouse gas in Earth¡¯s
atmosphere. This is because CO2, like ozone, N2O, CH4, and
chlorofluorocarbons, does not condense and precipitate from the
atmosphere at current climate temperatures, whereas water vapor can
and does. Noncondensing greenhouse gases, which account for 25% of
the total terrestrial greenhouse effect, thus serve to provide the
stable temperature structure that sustains the current levels of
atmospheric water vapor and clouds via feedback processes that
account for the remaining 75% of the greenhouse effect. Without the
radiative forcing supplied by CO2 and the other noncondensing
greenhouse gases, the terrestrial greenhouse would collapse,
plunging the global climate into an icebound Earth state.
It often is stated that water vapor is the chief greenhouse gas
(GHG) in the atmosphere. For example, it has been asserted that ¡
°about 98% of the natural greenhouse effect is due to water vapour
and stratiform clouds with CO2 contributing less than 2%¡± (1). If
true, this would imply that changes in atmospheric CO2 are not
important influences on the natural greenhouse capacity of Earth,
and that the continuing increase in CO2 due to human activity is
therefore not relevant to climate change. This misunderstanding is
resolved through simple examination of the terrestrial greenhouse.
The difference between the nominal global mean surface temperature
(TS = 288 K) and the global mean effective temperature (TE = 255 K)
is a common measure of the terrestrial greenhouse effect (GT = TS ¨C
TE = 33 K). Assuming global energy balance, TE is also the Planck
radiation equivalent of the 240 W/m2 of global mean solar radiation
absorbed by Earth.
The Sun is the source of energy that heats Earth. Besides direct
solar heating of the ground, there is also indirect longwave (LW)
warming arising from the thermal radiation that is emitted by the
ground, then absorbed locally within the atmosphere, from which it
is re-emitted in both upward and downward directions, further
heating the ground and maintaining the temperature gradient in the
atmosphere. This radiative interaction is the greenhouse effect,
which was first discovered by Joseph Fourier in 1824 (2),
experimentally verified by John Tyndall in 1863 (3), and quantified
by Svante Arrhenius in 1896 (4). These studies established long ago
that water vapor and CO2 are indeed the principal terrestrial GHGs.
Now, further consideration shows that CO2 is the one that controls
climate change.
CO2 is a well-mixed gas that does not condense or precipitate from
the atmosphere. Water vapor and clouds, on the other hand, are
highly active components of the climate system that respond rapidly
to changes in temperature and air pressure by evaporating,
condensing, and precipitating. This identifies water vapor and
clouds as the fast feedback processes in the climate system.
Radiative forcing experiments assuming doubled CO2 and a 2% increase
in solar irradiance (5) show that water vapor provides the strongest
climate feedback of any of the atmospheric GHGs, but that it is not
the cause (forcing) of global climate change. The response of the
climate system to an applied forcing is determined to be the sum of
the direct (no-feedback) response to the applied forcing and the
induced radiative response that is attributable to the feedback
process contributions. The ratio of the total climate response to
the no-feedback response is commonly known as the feedback factor,
which incorporates all the complexities of the climate system
feedback interactions. For the doubled CO2 and the 2% solar
irradiance forcings, for which the direct no-feedback responses of
the global surface temperature are 1.2¡ã and 1.3¡ãC, respectively,
the ~4¡ãC surface warming implies respective feedback factors of 3.3
and 3.0 (5).
Because the solar-thermal energy balance of Earth [at the top of the
atmosphere (TOA)] is maintained by radiative processes only, and
because all the global net advective energy transports must equal
zero, it follows that the global average surface temperature must be
determined in full by the radiative fluxes arising from the patterns
of temperature and absorption of radiation. This then is the basic
underlying physics that explains the close coupling that exists
between TOA radiative fluxes, the greenhouse effect, and the global
mean surface temperature.
An improved understanding of the relative importance of the
different contributors to the greenhouse effect comes from radiative
flux experiments that we performed using Goddard Institute for Space
Studies (GISS) ModelE (6). Figure 1 depicts the essence of these
calculations, including the separation of the greenhouse
contributors into feedback and forcing categories.
In round numbers, water vapor accounts for about 50% of Earth¡¯s
greenhouse effect, with clouds contributing 25%, CO2 20%, and the
minor GHGs and aerosols accounting for the remaining 5%. Because
CO2, O3, N2O, CH4, and chlorofluorocarbons (CFCs) do not condense
and precipitate, noncondensing GHGs constitute the key 25% of the
radiative forcing that supports and sustains the entire terrestrial
greenhouse effect, the remaining 75% coming as fast feedback
contributions from water vapor and clouds.
We used the GISS 4¡ã ¡Á 5¡ã ModelE to calculate changes in
instantaneous LW TOA flux (annual global averages) in experiments
where atmospheric constituents (including water vapor, clouds, CO2,
O3, N2O, CH4, CFCs, and aerosols) were added to or subtracted from
an equilibrium atmosphere with a given global temperature structure,
one constituent at a time for a 1-year period. Decreases in outgoing
TOA flux for each constituent relative to the empty or the full-
component atmosphere define the bounds for the relative impact on
the total greenhouse effect. Had the overlapping absorption been
negligible, the sum of the flux differences would have been equal to
the LW flux equivalent of the total greenhouse effect (GF = ¦ÒTS^4
¨C ¦ÒTE^4 = 150 W/m2), where ¦Ò is the Stefan-Boltzmann constant. We
found the single-addition flux differences to be overestimated by a
factor of 1.36, whereas in the single-subtraction cases, the sum of
the TOA flux differences was underestimated by a factor of 0.734. By
normalizing these fractional contributions to match the full-
atmosphere value of GF, we obtained the fractional response
contributions shown in Fig. 1.
Because of overlapping absorption, the fractional attribution of the
greenhouse effect is to some extent qualitative (as shown by the
dashed and dotted extremum lines in Fig. 1), even though the
spectral integral is a full and accurate determination of the
atmospheric greenhouse strength for the specified global temperature
structure. Still, the fractional attribution is sufficiently precise
to clearly differentiate the radiative flux contributions due to the
noncondensable GHGs from those arising from the fast feedback
processes. This allows an empirical determination of the climate
feedback factor as the ratio of the total global flux change to the
flux change that is attributable to the radiative forcing due to the
noncondensing GHGs. This empirical determination leads then to a
climate feedback factor of 4, based on the noncondensing GHG forcing
accounting for 25% of the outgoing flux reduction at the TOA for the
full-constituent atmosphere. This implies that Earth¡¯s climate
system operates with strong positive feedback that arises from the
forcing-induced changes in the condensable species.
A direct consequence of this combination of feedback by the
condensable and forcing by the noncondensable constituents of the
atmospheric greenhouse is that the terrestrial greenhouse effect
would collapse were it not for the presence of these noncondensing
GHGs. If the global atmospheric temperatures were to fall to as low
as TS = TE, the Clausius-Clapeyron relation would imply that the
sustainable amount of atmospheric water vapor would become less than
10% of the current atmospheric value. This would result in
(radiative) forcing reduced by ~30 W/m2, causing much of the
remaining water vapor to precipitate, thus enhancing the snow/ice
albedo to further diminish the absorbed solar radiation. Such a
condition would inevitably lead to runaway glaciation, producing an
ice ball Earth.
Claims that removing all CO2 from the atmosphere ¡°would lead to a
1¡ãC decrease in global warming¡± (7), or ¡°by 3.53¡ãC when 40%
cloud cover is assumed¡± [8] are still being heard. A clear
demonstration is needed to show that water vapor and clouds do
indeed behave as fast feedback processes and that their atmospheric
distributions are regulated by the sustained radiative forcing due
to the noncondensing GHGs. To this end, we performed a simple
climate experiment with the GISS 2¡ã ¡Á 2.5¡ã AR5 version of ModelE,
using the Q-flux ocean with a mixed-layer depth of 250 m, zeroing
out all the noncondensing GHGs and aerosols.
The results, summarized in Fig. 2, show unequivocally that the
radiative forcing by noncondensing GHGs is essential to sustain the
atmospheric temperatures that are needed for significant levels of
water vapor and cloud feedback. Without this noncondensable GHG
forcing, the physics of this model send the climate of Earth
plunging rapidly and irrevocably to an icebound state, though
perhaps not to total ocean freezeover.
The scope of the climate impact becomes apparent in just 10 years.
During the first year alone, global mean surface temperature falls
by 4.6¡ãC. After 50 years, the global temperature stands at ¨C21¡ãC,
a decrease of 34.8¡ãC. Atmospheric water vapor is at ~10% of the
control climate value (22.6 to 2.2 mm). Global cloud cover increases
from its 58% control value to more than 75%, and the global sea ice
fraction goes from 4.6% to 46.7%, causing the planetary albedo of
Earth to also increase from ~29% to 41.8%. This has the effect of
reducing the absorbed solar energy to further exacerbate the global
cooling.
After 50 years, a third of the ocean surface still remains ice-free,
even though the global surface temperature is colder than ¨C21¡ãC.
At tropical latitudes, incident solar radiation is sufficient to
keep the ocean from freezing. Although this thermal oasis within an
otherwise icebound Earth appears to be stable, further calculations
with an interactive ocean would be needed to verify the potential
for long-term stability. The surface temperatures in Fig. 3 are only
marginally warmer than 1¡ãC within the remaining low-latitude heat
island.
From the foregoing, it is clear that CO2 is the key atmospheric gas
that exerts principal control over the strength of the terrestrial
greenhouse effect. Water vapor and clouds are fast-acting feedback
effects, and as such are controlled by the radiative forcings
supplied by the noncondensing GHGs. There is telling evidence that
atmospheric CO2 also governs the temperature of Earth on geological
time scales, suggesting the related question of what the geological
processes that control atmospheric CO2 are. The geological evidence
of glaciation at tropical latitudes from 650 to 750 million years
ago supports the snowball Earth hypothesis (9), and by inference,
that escape from the snowball Earth condition is also achievable.
On million-year time scales, volcanoes are the principal source of
atmospheric CO2, and rock weathering is the principal sink, with the
biosphere acting as both source and sink (10). Because the CO2
sources and sinks operate independently, the atmospheric level of
CO2 can fluctuate. If the atmospheric CO2 level were to fall below
its critical value, snowball Earth conditions can result.
Antarctic and Greenland ice core data show atmospheric CO2
fluctuations between 180 to 300 parts per million (ppm) over the
glacial-interglacial cycles during the past 650,000 years (11). The
relevant physical processes that turn the CO2 control knob on
thousand-year time scales between glacial and interglacial extremes
are not fully understood, but appear to involve both the biosphere
and the ocean chemistry, including a significant role for
Milankovitch variations of the Earth-orbital parameters.
Besides CO2, methane is another potent greenhouse control knob,
being implicated in the Paleocene-Eocene thermal maximummass
extinction 55 million years ago, when global warming by up to 5¡ãC
(12) occurred because of a massive release of methane from the
disintegration of seafloor clathrates (13, 14). Methane is the
second most important noncondensing GHG after CO2. Of the 2.9 W/m2
of GHG radiative forcing from 1750 to 2000, CO2 contributed 1.5 W/
m2, methane 0.55 W/m2, and CFCs 0.3 W/m2, with the rest coming from
N2O and ozone (15). All of these increases in noncondensing GHG
forcing are attributable to human activity (16).
Climate control knobs on the solar side of the energy balance ledger
include the steady growth in luminosity since the beginning of the
Solar System (from about 70% of present luminosity, depending on the
postulated early solar mass loss), as hydrogen is consumed in
nuclear reactions in the solar interior (17, 18). Milankovitch
variations of the Earth-orbital parameters, which alter the relative
seasonal distribution as well as the intensity of incident solar
radiation within the polar regions, are another important solar
energy control knob that is intimately associated with glacial-
interglacial cycles of climate change. For solar irradiance changes
over the past several centuries, an increase by about 0.1 W/m2 is
inferred since the time of the Maunder minimum, based on trends in
sunspot activity and other proxies (19).
Of the climate control knobs relevant to current climate, those on
the solar side of the energy balance ledger show only negligible
impact. Several decades of solar irradiance monitoring have not
detected any long-term trends in solar irradiance beyond the 11-year
oscillation associated with the solar sunspot cycle. Large volcanic
eruptions can happen at any time, but no substantial eruptions have
occurred since the eruption of Mt. Pinatubo in the Philippines in
1991.
In a broader perspective, CO2 greenhouses also operate on Mars and
Venus, because both planets possess atmospheres with substantial
amounts of CO2. The atmospheric greenhouse effect requires that a
substantial fraction of the incident solar radiation must be
absorbed at the ground in order to make the indirect greenhouse
heating of the ground surface possible. Greenhouse parameters and
relative surface pressure (PS) for Mars, Earth, and Venus are
summarized in Table 1.
Earth is unique among terrestrial planets in having a greenhouse
effect in which water vapor provides strong amplification of the
heat-trapping action of the CO2 greenhouse. Also, N2 and O2,
although possessing no substantial absorption bands of their own,
are actually important contributors to the total greenhouse effect
because of pressure-broadening of CO2 absorption lines, as well as
by providing the physical structure within which the absorbing gases
can interact with the radiation field.
The anthropogenic radiative forcings that fuel the growing
terrestrial greenhouse effect continue unabated. The continuing high
rate of atmospheric CO2 increase is particularly worrisome, because
the present CO2 level of 390 ppm is far in excess of the 280 ppm
that is more typical for the interglacial maximum, and still the
atmospheric CO2 control knob is now being turned faster than at any
time in the geological record (20). The concern is that we are well
past even the 300- to 350-ppm target level for atmospheric CO2,
beyond which dangerous anthropogenic interference in the climate
system would exceed the 25% risk tolerance for impending degradation
of land and ocean ecosystems, sea-level rise, and inevitable
disruption of socioeconomic and food-producing infrastructure (21,
22). Furthermore, the atmospheric residence time of CO2 is
exceedingly long, being measured in thousands of years (23). This
makes the reduction and control of atmospheric CO2 a serious and
pressing issue, worthy of real-time attention.
Citeren Roger Clough <rclo...@verizon.net>:
On Global Warming----The sun is getting a little hotter
Up to the present day, studies of global warming were
based on CO2 levels in the atmosphere, assumed to be caused by
automobiles (the supposed greenhouse effect).
But more resent studies show that total solar irradiation (TSI) --
solar radiation coming from outside of the atmosphere- not CO2
levels--
is the driving force:
http://wattsupwiththat.com/2012/09/06/soon-and-briggs-global-warming-fanatics-take-note-sunspots-do-impact-climate/
C02 levels are not reliable indicators of what causes surface
temperature warming (the supposed greenhouse effect) ?
.
Why ? Because some of the CO2 in the atmosphere is there because as
the earth warms, the
oceans warm and CO2 gases sare less soluble in warmer water, so
fizle out
into the atmosphere. So it is doubtful to say that current levels
of CO2
are entirely from automobiles.
So current scientific evalutations as in the graph below do not
rely on CO2
measurements, they use solar radiation which is not influenced by
C02 levels
and relate that instead to surface gtemperatures.
The total solar radiation (TSI) is not obtained from measurements
made on earth, so
it isn't supposed to include greenshouse gas effects. It is
measured these days by satellite,
but is reconconstructed from pre-satellite days (<1979 ) based on a
model
based on the number of sunspots.
http://www.aanda.org/index.php?option=com_article&access=standard&Itemid=129&url=/articles/aa/abs/2007/19/aa6725-06/aa6725-06.html
"Reconstruction of solar total irradiance since 1700 from the
surface magnetic flux
N. A. Krivova, L. Balmaceda, and S. K. Solanki
Max-Planck-Institut f? Sonnensystemforschung, Max-Planck-Str. 2,
37191 Katlenburg-Lindau, Germany
e-mail: nata...@mps.mpg.de
(Received 9 November 2006 / Accepted 23 February 2007)
Abstract
Context.Total solar irradiance changes by about 0.1% between solar
activity maximum and minimum. Accurate measurements of this
quantity are only available since 1978 and do not provide
information on longer-term secular trends.
Aims.In order to reliably evaluate the Sun's role in recent global
climate change, longer time series are, however, needed. They can
only be assessed with the help of suitable models.
Methods.The total solar irradiance is reconstructed from the end of
the Maunder minimum to the present based on variations of the
surface distribution of the solar magnetic field. The latter is
calculated from the historical record of the sunspot number using a
simple but consistent physical model.
Results.Our model successfully reproduces three independent data
sets: total solar irradiance measurements available since 1978,
total photospheric magnetic flux since 1974 and the open magnetic
flux since 1868 empirically reconstructed using the geomagnetic aa-
index. The model predicts an increase in the solar total irradiance
since the Maunder minimum of $1.3^{\rm +0.2}_{\rm -0.4}$ Wm-2. "
Dr. Roger Clough NIST (ret.) 3/30/2013
"Coincidences are God's way of remaining anonymous."
- Albert Einstein
____________________________________________________________________
Dr. Roger Clough NIST (ret.) 6/15/2013
See my Leibniz site at
http://team.academia.edu/RogerClough
____________________________________________________________________
DreamMail - The first mail software supporting source tracking
www.dreammail.org
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