You are right, I just realized I never properly addressed this evidence. I appologize that it got lost in the cycle of redundancy. So here I go.
Ice Core Studies Prove CO2 Is Not the Powerful Climate Driver Climate Alarmists Make It Out to Be
Volume 6, Number 26: 25 June 2003
For the past two decades or more, we have heard much about the global warming of the 20th century being caused by the rise in atmospheric carbon dioxide concentration that is generally attributed to anthropogenic CO2 emissions. This story, however, has always been controversial [see Smagorinsky et al. (1982) and Idso (1982) for early pro/con positions on the issue]; and with the retrieval and preliminary analysis of the first long ice core from Vostok, Antarctica -- which provided a 150,000-year history of both surface air temperature and atmospheric CO2 concentration -- the debate became even more intense, as the close associations of the ups and downs of atmospheric CO2 and temperature that were evident during glacial terminations and inceptions in that record, as well as in subsequent records of even greater length, led many climate alarmists to claim that those observations actually proved that anthropogenic CO2 emissions were responsible for 20th-century global warming.
This contention was challenged by Idso (1989), who wrote -- in reference to the very data that were used to support the claim -- that "changes in atmospheric CO2 content never precede changes in air temperature, when going from glacial to interglacial conditions; and when going from interglacial to glacial conditions, the change in CO2 concentration actually lags the change in air temperature (Genthon et al., 1987)." Hence, he concluded that "changes in CO2 concentration cannot be claimed to be the cause of changes in air temperature, for the appropriate sequence of events (temperature change following CO2 change) is not only never present, it is actually violated in [at least] half of the record (Idso, 1988)."
How has our understanding of this issue progressed in the interim? Our website provides several updates.
Petit et al. (1999) reconstructed histories of surface air temperature and atmospheric CO2 concentration from data obtained from a Vostok ice core that covered the prior 420,000 years, determining that during glacial inception "the CO2 decrease lags the temperature decrease by several thousand years" and that "the same sequence of climate forcing operated during each termination." Likewise, working with sections of ice core records from around the times of the last three glacial terminations, Fischer et al. (1999) found that "the time lag of the rise in CO2 concentrations with respect to temperature change is on the order of 400 to 1000 years during all three glacial-interglacial transitions."
On the basis of atmospheric CO2 data obtained from the Antarctic Taylor Dome ice core and temperature data obtained from the Vostok ice core, Indermuhle et al. (2000) studied the relationship between these two parameters over the period 60,000-20,000 years BP (Before Present). One statistical test performed on the data suggested that shifts in the air's CO2 content lagged shifts in air temperature by approximately 900 years, while a second statistical test yielded a mean lag-time of 1200 years. Similarly, in a study of air temperature and CO2 data obtained from Dome Concordia, Antarctica for the period 22,000-9,000 BP -- which time interval includes the most recent glacial-to-interglacial transition -- Monnin et al. (2001) found that the start of the CO2 increase lagged the start of the temperature increase by 800 years. Then, in another study of the 420,000-year Vostok ice-core record, Mudelsee (2001) concluded that variations in atmospheric CO2 concentration lagged variations in air temperature by 1,300 to 5,000 years.
In a somewhat different type of study, Yokoyama et al. (2000) analyzed sediment facies in the tectonically stable Bonaparte Gulf of Australia to determine the timing of the initial melting phase of the last great ice age. In commenting on the results of that study, Clark and Mix (2000) note that the rapid rise in sea level caused by the melting of land-based ice that began approximately 19,000 years ago preceded the post-glacial rise in atmospheric CO2 concentration by about 3,000 years.
So what's the latest on the issue? To our knowledge, the most recent study to broach the subject is that of Caillon et al. (2003), who measured the isotopic composition of argon -- specifically, ð40Ar, which they argue "can be taken as a climate proxy, thus providing constraints about the timing of CO2 and climate change" -- in air bubbles in the Vostok ice core over the period that comprises what is called Glacial Termination III, which occurred about 240,000 years BP. The results of their tedious but meticulous analysis led them to ultimately conclude that "the CO2 increase lagged Antarctic deglacial warming by 800 ± 200 years."
Everything up to this point is OK, basically saying that in the past warming and cooling events, CO2 levels lag behind temperature changes. There is no statement of what causes the warming/cooling. Only repeatedly stating that CO2 lags temperature.
Now comes the red herring:
This finding, in the words of Caillon et al., "confirms that CO2 is not the forcing that initially drives the climatic system during a deglaciation."
Who is saying that CO2 was the forcing that intially drives the climatic system during a deglaciation? Quite the contrary, climate scientists point to a known forcing (changes to Earth's orbit) with a known magnitude that would cause enough warming to trigger CO2 feedbacks. However, that forcing is not strong enough to account for the entire deglaciation event.
Nevertheless, they and many others continue to hold to the view that the subsequent increase in atmospheric CO2 -- which is believed to be due to warming-induced CO2 outgassing from the world's oceans -- serves to amplify the warming that is caused by whatever prompts the temperature to rise in the first place.
This part is nearly accurate, except that "whatever" prompts the temperature to rise is not a whatever... It is a specific phenomena with a specific forcing magnitude (changes in Earth's orbit).
This belief, however, is founded on unproven assumptions about the strength of CO2-induced warming
This is a false accusation:
http://skepticalscience.com/empirical-e ... vanced.htm
The amount of warming caused by the anthropogenic increase in atmospheric CO2 may be one of the most misunderstood subjects in climate science. Many people think the anthropogenic warming can't be quantified, many others think it must be an insignificant amount. However, climate scientists have indeed quantified the anthropogenic contribution to global warming using empirical observations and fundamental physical equations.
And back to your article:
and is applied without any regard for biologically-induced negative climate feedbacks that may occur in response to atmospheric CO2 enrichment. Also, there is no way to objectively determine the strength of the proposed amplification from the ice core data.
CO2 feedback sure fits the data quite well. Has there been any other proposal? This ice core data is not the only indicator that CO2 affects climate (see above quote from skeptical science.)[/quote]
I did not have the time/expertise/resources required to verify the sources in this article. I will have to assume they are fairly reliable.
And the counter argument from climate scientists:
The skeptic argument...
CO2 lags temperature
"An article in Science magazine illustrated that a rise in carbon dioxide did not precede a rise in temperatures, but actually lagged behind temperature rises by 200 to 1000 years. A rise in carbon dioxide levels could not have caused a rise in temperature if it followed the temperature." (Joe Barton)
What the science says...
When the Earth comes out of an ice age, the warming is not initiated by CO2 but by changes in the Earth's orbit. The warming causes the oceans to release CO2. The CO2 amplifies the warming and mixes through the atmosphere, spreading warming throughout the planet. So CO2 causes warming AND rising temperature causes CO2 rise. Overall, about 90% of the global warming occurs after the CO2 increase.
Over the last half million years, our climate has experienced long ice ages regularly punctuated by brief warm periods called interglacials. Atmospheric carbon dioxide closely matches the cycle, increasing by around 80 to 100 parts per million as Antarctic temperatures warm up to 10°C. However, when you look closer, CO2 actually lags Antarctic temperature changes by around 1,000 years. While this result was predicted two decades ago (Lorius 1990), it still surprises and confuses many. Does warming cause CO2 rise or the other way around? In actuality, the answer is both.
Figure 1: Vostok Antarctic ice core records for carbon dioxide concentration (Petit 2000) and temperature change (Barnola 2003).
Interglacials come along approximately every 100,000 years. This is called the Milankovitch cycle, brought on by changes in the Earth's orbit. There are three main changes to the earth's orbit. The shape of the Earth's orbit around the sun (eccentricity) varies between an ellipse to a more circular shape. The earth's axis is tilted relative to the sun at around 23°. This tilt oscillates between 22.5° and 24.5° (oblithis quity). As the earth spins around it's axis, the axis wobbles from pointing towards the North Star to pointing at the star Vega (precession).
Figure 2: The three main orbital variations. Eccentricity: changes in the shape of the Earth’s orbit.Obliquity: changes in the tilt of the Earth’s rotational axis. Precession: wobbles in the Earth’s rotational axis.
The combined effect of these orbital cycles causes long term changes in the amount of sunlight hitting the earth at different seasons, particularly at high latitudes. For example, the orbital cycles triggered warming at high latitutdes approximately 19,000 years ago, causing large amounts of ice to melt, flooding the oceans with fresh water. This influx of fresh water then disrupted the Atlantic meridional overturning circulation (AMOC), in turn causing a seesawing of heat between the hemispheres (Shakun 2012). The Southern Hemisphere and its oceans warmed first, starting about 18,000 years ago. As the Southern Ocean warms, the solubility of CO2 in water falls (Martin 2005). This causes the oceans to give up more CO2, emitting it into the atmosphere. The exact mechanism of how the deep ocean gives up its CO2 is not fully understood but believed to be related to vertical ocean mixing (Toggweiler 1999).
The outgassing of CO2 from the ocean has several effects. The increased CO2 in the atmosphere amplifies the original warming. The relatively weak forcing from Milankovitch cycles is insufficient to cause the dramatic temperature change taking our climate out of an ice age (this period is called a deglaciation). However, the amplifying effect of CO2 is consistent with the observed warming.
CO2 from the Southern Ocean also mixes through the atmosphere, spreading the warming north (Cuffey 2001). Tropical marine sediments record warming in the tropics around 1000 years after Antarctic warming, around the same time as the CO2 rise (Stott 2007). Ice cores in Greenland find that warming in the Northern Hemisphere lags the Antarctic CO2 rise (Caillon 2003).
To claim that the CO2 lag disproves the warming effect of CO2 displays a lack of understanding of the processes that drive Milankovitch cycles. A review of the peer reviewed research into past periods of deglaciation tells us several things:
Deglaciation is not initiated by CO2 but by orbital cycles
CO2 amplifies the warming which cannot be explained by orbital cycles alone
CO2 spreads warming throughout the planet
Overall, more than 90% of the glacial-interglacial warming occurs after the atmospheric CO2 increase (Figure 3).
Figure 3: The global proxy temperature stack (blue) as deviations from the early Holocene (11.5–6.5 kyr ago) mean, an Antarctic ice-core composite temperature record (red), and atmospheric CO2 concentration (yellow dots). The Holocene, Younger Dryas (YD), Bølling–Allerød (B–A), Oldest Dryas (OD) and Last Glacial Maximum (LGM) intervals are indicated. Error bars, 1-sigma; p.p.m.v. = parts per million by volume. Shakun et al. Figure 2a.