I apologize for "thinking out loud" in your presence, but with my background this note intrigued me:
To the consternation of global warming proponents, the Late Ordovician Period was also an Ice Age, with CO2 concentrations nearly 15 times higher than today-- 5500 ppm. According to greenhouse theory, Earth should have been exceedingly hot. Instead, global temperatures were no warmer than today. Clearly, other factors besides atmospheric carbon influence earth temperatures and global warming.
The reason that I'm thinking out loud is that something we'll return to repeatedly as we consider paleoclimate evidence is the apples-to-oranges comparison trap -- a trap that I'd like to avoid. If we are going to figure out what is happening now and what might happen in the future, we have to make sure that what we are considering is relevant. OK -- there's no doubt that "other factors besides atmospheric carbon [dioxide] influence earth temperatures and global warming". The rate of plate tectonics is a first-order driver over millions of years (something Berner, whom you cite, has studied extensively). But if we are considering climate changes over millenial or shorter timescales, then considering plate tectonic processes is pretty useless. I hope you agree with that.
Having said that, what is known about the Ordovician paleoclimate? Here's a good description, from my Cal-Berkeley friends:
Ordovician: Tectonics and Paleoclimate
Read it at your leisure. Summary: continents were moving around, mountains were rising, ocean currents were totally different tha today, eventually Gondwanaland made it to the South Pole when the Ashgillian glaciation took place. You know how long the Ashgillian was? About 10 million years. All of the Pleistocene glaciations took place in less than 0.5 million years.
So does the fact that CO2 was much, much higher in the Ordovician, when there was an Ice Age, cause me consternation? Not a bit. Because this is an apples-to-oranges comparison; it's virtually meaningless and it does not instruct us regarding processes that are relevant today. Because I know that there are other factors that affect Earth's climate other than CO2, particularly when the timescales under discussion differ by several orders of magnitude. It's also apples-to-oranges in terms of the overall climate setting, i.e., where the continents were, where the ocean currents where, where the continental shelves were, what the ocean chemistry was (note the end of the second paragraph on the linked page), etc.
But there is still an important question regarding whether or not CO2 was a paleoclimate factor. I'll get to that next week. This will be the last post for today and the weekend, but I'll be working on next week's submission in the interim.
The rate of plate tectonics is a first-order driver over millions of years (something Berner, whom you cite, has studied extensively).
That my friend does not account for the total lack of variation in surface temperature with CO2 across paleological time frames.
So does the fact that CO2 was much, much higher in the Ordovician, when there was an Ice Age, cause me consternation? Not a bit.
Look again, remove the decreases to iceage conditions applicable to the Ordovician etc. tectonic movements. Where is the change that should be in place relating to your supposed CO2 driven warming/cooling? please point it out for us, somehow it seems to escape detection.
According to you, and the UN/IPCC modelers you support, a variation in CO2 should induce a commensurate change in global temperatures by a factor of several times the change that would be induce by CO2 alone. Where are these changes in the paleo-climatic record. Please point them out to us.
CO2 across the 500 million year period varied from 7000ppm down to less than 300ppm in an exponential decay, a factor of 35 to 1 that is about 5 doublings.
Look at the temperature line, flat lined except for occasional excursions into iceage conditions spread out along that flat temperature line.
Where is this alleged variation that should be present due to the 35 to 1 variation in CO2 across that geological record? There should be some evidence of that variation superimposed upon any variation you claim to be due to continental drift.
Taking the UN/IPCC's factors for a CO2 doubling of .75C to 4.5 degrees C according to the reported ranges of their models, we should see a decline of 3.75-12.5 degrees C superimposed on the temperature line below.
No such CO2 induced decline is evident, only declines clearly due to other factors than CO2 concentration are apparent in the data with no evidence of any response to changing CO2 concentrations.
Why? because atmospheric water vapor totally overshadows any marginal effects of CO2.
As pointed out the prior replies, atmospheric CO2 concentration has minimal correlation with the earth's surface temperatures and no causal link as is clearly demonstrated in paleo-climate studies and supported in analysis below:
Climate Catastrophe, A spectroscopic Artifact?
"It is hardly to be expected that for CO2 doubling an increment of IR absorption at the 15 µm edges by 0.17% can cause any significant global warming or even a climate catastrophe.
The radiative forcing for doubling can be calculated by using this figure. If we allocate an absorption of 32 W/m2 [14] over 180º steradiant to the total integral (area) of the n3 band as observed from satellite measurements (Hanel et al., 1971) and applied to a standard atmosphere, and take an increment of 0.17%, the absorption is 0.054 W/m2 - and not 4.3 W/m2.
This is roughly 80 times less than IPCC's radiative forcing.
If we allocate 7.2 degC as greenhouse effect for the present CO2 (as asserted by Kondratjew and Moskalenko in J.T. Houghton's book The Global Climate [14]), the doubling effect should be 0.17% which is 0.012 degC only. If we take 1/80 of the 1.2 degC that result from Stefan-Boltzmann's law with a radiative forcing of 4.3 W/m2, we get a similar value of 0.015 degC."
How about looking at the evidence in front of you nose for a change instead of the IPCC hype & flawed computer simulations. There is no CO2 dependant warming crisis.
Having said that, what is known about the Ordovician paleoclimate? Here's a good description, from my Cal-Berkeley friends:
Ordovician: Tectonics and Paleoclimate
Read it at your leisure. Summary: continents were moving around, mountains were rising, ocean currents were totally different tha today, eventually Gondwanaland made it to the South Pole when the Ashgillian glaciation took place. You know how long the Ashgillian was? About 10 million years. All of the Pleistocene glaciations took place in less than 0.5 million years.
Which does not explain the reason for the radical and very rapid GLOBAL cooling at the end of the Ordivician. The article states only that such occurred initiating a mass-extinction.
I suggest you read the following at your leisure which explains not only the rapid onset of the late Ordovician Ice Age, but the distrubution of mass-extinctions that occured as well.
Slow continental drifts do not induce rapid switches into deep iceages from the conditions like that of the Ordovician climate.
Gamma Ray Bursts and other astonomical events involving earths motion through the galaxy offer insight to the Ordovician glaciations and later similar decents in global cooling as well, including the rapid decent into our own Tertiary/Quaternary Ice Age with its repetitive 100kyr interglacial periods with that correlate with earths orbital inclination.
New Scientist article 27 Sept 03: http://www.eurekalert.org/pub_releases/2003-09/ns-dag092403.php
Previous theories blame the two extinctions that occurred in the late Ordovician period on the start and end of an ice age at the time. But it is hard to explain what triggered the ice age itself, which started very suddenly at a time when the climate was quite warm.
Continental changes would have taken too long, and climate models have not been able to replicate the ice age. But a GRB that blocked out the sun could have caused it, points out Pat Brenchley, a retired palaeoecologist from the University of Liverpool, UK, calling the idea" an interesting alternative.
PDF source paper on this subject: Did a gamma-ray burst initiate the late Ordovician mass extinction...,
page 1;
ABSTRACT
At least five times in the history of life, the Earth experienced mass extinctions that
eliminated a large percentage of the biota. Many possible causes have been documented,
and gamma-ray bursts (GRB) may also have contributed. GRB (Mészáros, 2001)
produce a flux of radiation detectable across the observable Universe. A GRB within our
own galaxy could do considerable damage to the Earth's biosphere (Thorsett, 1995;
Scalo & Wheeler, 2002; Dar & DeRújula, 2002). Rate estimates (Thorsett, 1995)
suggest that a number of such GRB may lie within the fossil record. The late Ordovician
mass extinction shows a water-depth dependent extinction pattern that is a natural result
of the attenuation of the strong ultraviolet radiation expected to result from a nearby
GRB. In addition, a GRB would trigger global cooling which is associated with this
mass extinction.
INTRODUCTION AND HYPOTHESIS
As mass extinctions have become well-documented, interest in them has grown, partly
out of concern for our current environmental situation. Extraterrestrial causes have been
more seriously considered in recent years, as the extent of their possible impact becomes
known. It seems likely that a GRB has affected the Earth, and should have had a
substantial effect upon living organisms. We have found patterns of extinction in one
event that match expectations of a GRB-initiated extinction.
*****
page 5;
This extinction has been related to alternating global cooling and warming, each
associated possibly with what may be the two pulses of the late Ordovician mass
extinction (Brenchley et al., 1994; Brenchley et al., 1995; Orth et al., 1986). We do not
dispute the role global cooling may have played in mediating this extinction. Instead, we
emphasize that there is a natural link between GRB and global cooling. There exists a
correlation (Shaviv, 2002) between ice ages and the timing of spiral arm passage, which
has been ascribed to increased cosmic ray flux associated with increased star formation
and supernovae. We note that since GRB probably arise from star-forming regions and
produce opaque nitrogen dioxide in Earth’s atmosphere they provide a mechanism for
global cooling. Paleoclimate modeling (Herrmann and Patzkowsky 2002; Herrmann et
al. 2003) has shown that late Ordovician glaciation would not have proceeded without an
impulse such as reduced solar insolation.
We suggest that the late Ordovician extinction may have been initiated by a GRB. The
oxygen level of the atmosphere was not greatly different from that of the present (Berner
et al., 2003), so that an ozone shield should have been in place. Its destruction would
almost certainly involve similar catastrophic consequences to those observed in modern
organisms (Kiesecker et al., 2001; Hader et al., 2003). A GRB could have triggered the
global cooling, while presenting a host of environmental challenges to life on the planet
through the effects of increased radiation reaching the surface, acid rain, etc., followed
shortly by global cooling; the result: a one, two punch for life on the planet. Notably, the
kind of water depth dependence found in the late Ordovician extinction pattern would
emerge naturally from the attenuation of the UV radiation.
ADDITIONAL ARGUMENT IN SUPPORT OF HYPOTHESIS
Supernovae are known to be correlated, probably going off in chain-reactions of star
formation and detonation, which produce the “superbubbles” found in the interstellar
medium. Given the probable linkage between GRB and supernovae, proximity to one
event would suggest an enhanced probability of a second. The late Ordovician extinction
seems to have occurred in two pulses about 1My apart.
IMPLICATIONS
This hypothesis suggests that a closer look be taken at the geographical distribution of
extinctions in the late Ordovician along the line of what Anstey et al. (2003) have done.
A strong initial muon burst might seriously irradiate only one side of the Earth to
considerable ocean depth, while the other side would mostly be irradiated by post-burst
solar UV due to ozone loss. This suggests an extinction pattern emphasizing depth-dependent
extinction predominantly in one hemisphere, with more complete extinction in
the other hemisphere. We stress however, that such a pattern is likely only if the GRB
emission is isotropic and the event nearby. While at present we only see strong reasons for
associating a GRB with the Ordovician mass extinction, the entire fossil record bears
examination in this light. Given the uncertainty in the evolution of the GRB rate, it is
possible that such events were involved in more than one mass extinction, or that more distant
GRBs could have a stochastic effect, providing small impulses to evolutionScalo & Wheeler, 2002).
A major challenge for astrophysics is to evaluate the likely flux and spectrum of cosmic rays
accompanying a burst.