http://www.geocraft.com/WVFossils/PageMill_Images/image277.gif
During the Ordovician, CO2 was more than ten times higher than at present. Global temperatures ranged between very hot and an ice age. We can state with 100% certainty that as CO2 increases, temperatures will either go up, go down, or stay the same.
earth temperature last ice age, geologic co2 record, h h lamb chart, real-science com co2 temp
So, it looks like for the last few million years there’s been barely enough CO2 to keep plants alive.
Exactly where does this chart come from and what is the validity of it?
I heard that H. H. Lamb may have contributed to this graph but it’s over 2 decades old. Has the research ever been updated?
Is this graph peered reviewed in any science journal?
I think you may be thinking of the schematic diagram of the medieval warm period from the first IPCC report (which was actually based on the Central England Temperature data) which was based on a figure from one of Lamb’s papers.
I would also be interested in the origins of this figure. The temperature data is definitely a little odd, I can’t see any good reason for the Earth to have a stable maximum temperature from the Cambrian to the Cretaceous. The idea of a minumum temperature of 0C is alittle odd given that there were global glaciations during the Ordovician, where the global temperature would be well below that.
The argument in the above article is specious though. For a start it assumes that CO2 is the only thing that causes changes in temperature, it isn’t. For a start the sun has been brightening by about 10% per billion years, so it would have been considerably dimmer in the Ordovician than it is now. This leads to the Faint young Sun paradox, i.e. it is difficult to explain why the Earth was so warm in the Cambrian without the greenhouse effect, given that we recieved so much less energy from the Sun.
Dikran – Note the “estimate of uncertainty” on the graph. Also keep in mind plate tectonics and how different quantities and distributions of land masses over the eons can affect climate itself.
Yes, there are big error bars on the CO2 (which appears to be from a reputable source), but none on the temperatures.
Plate tectonics also have a big effect on CO2 as well, as chemical weathering rates increase when the continents are near the equator (as the rocks are warmer, so they react faster with the disolved CO2 in rain IIRC), which tends to reduce atmospheric CO2 levels. This in turn tends to reduce global temperatures (as CO2 is a GHG). This is known as the “chemical weathering thermostat”.
The CO2 data looks like it comes from GEOCARB project (paper here).
Looks like the temperature data is from this paper.
The temperature appears to be based on a plot from that paper, but it isn’t data, it is just a schematic drawing illustrating the approximate timings and temperatures of warm and cold periods. As it isn’t based on proxy data or model data (like the CO2 plot) it isn’t really sensible to try and correllate it with anything (note my comparison with solar activity is just a demonstration that the argument is specious, I am not seriously suggesting that global temperatures are not affected by solar activity!)
To demonstrate why the argument is specious, consider correllating temperatures (according to the figure) and solar activity. The sun has warmed by about 7% since the Ordovician (by comparison the difference between the maximum and minimum of the 11 year solar cycle is a change in TSI of about 0.1%). So has the climate warmed over that period in response to the increase in solar forcing? No.
Following the same logic as that used in the above article “We can state with 100% certainty that as
CO2solar activity increases, temperatures will either go up, go down, or stay the same.” ;o)While I was looking for the data sources, I found this paper
CO2-forced climate thresholds during the Phanerozoic
Dana L. Royer
abstract:The correspondence between atmospheric CO2 concentrations and globally averaged surface temperatures in the recent past suggests that this coupling may be of great antiquity. Here, I compare 490 published proxy records of CO2 spanning the Ordovician to Neogene with records of global cool events to evaluate the strength of CO2-temperature coupling over the Phanerozoic (last 542 my). For periods
with sufficient CO2 coverage, all cool events are associated with CO2 levels below 1000 ppm. A CO2 threshold of below 500 ppm is suggested for the initiation of widespread, continental glaciations, although this threshold was likely higher during the Paleozoic due to a lower solar luminosity at that time. Also, based on data from the Jurassic and Cretaceous, a CO2 threshold of below 1000 ppm is proposed for the initiation of cool non-glacial conditions. A pervasive, tight correlation between CO2 and temperature
is found both at coarse (10 my timescales) and fine resolutions up to the temporal limits of the data set (million-year timescales), indicating that CO2, operating in combination with many other factors such as solar luminosity and paleogeography, has imparted strong control over global temperatures for much of the Phanerozoic.
Note last line of abstract.
So in other words you agree with the graph but not what this webmaster implies.
yes and no. The temperature plot isn’t actually data, just a drawing (from a reputable source) designed to illustrate the existence of warm and cold periods, so I wouldn’t agree that it was in any way a useful quantative description of temperature changes over geological time.
However the main thing I disagree with is that there should be a good correllation between CO2 and temperature over this time scale. This isn’t even true for solar activity, which I would have thought was the dominant climate focing over geological time, so I don’t see why it should be true for CO2.
All temperature plots of anything are “just a drawing”.
Don’t forget, the Earth was a very different place. It was smaller, lower gravity, the moon was much closer and we had shorter days and higher geologic activity. The air was far more dense and CO2 averaging 2kppm, very accessible. The whole globe was warmer but for the hellish cold times like now but I will directly argue with you either way over Solar temperatures because we cannot ascertain where the Earths orbit lay. Only geological warmth.
However, there was no “tipping point” of CO2. It did not burn out all the corals. There is direct evidence that argues with your beliefs over CO2/temperature. Venus and Mars are perfect examples. Gas pressure is a far larger force than radiation. So is the Earth’s magnetosphere on Solar highs.
The lack of tropo heating and what little they can muster in the data is not enough to warm the oceans averaging 3.5 mile deep and a 1000x more specific heat density of air at sea level. The numbers are simply not there!
In the past 5M yr’s there was as much as 15C/century temperature fluctuations. We are still here! This century must be noted as one of the most stable in the known history of man!!!
Your theory is dead.
This answers my question as to where the graph came from. I will ask Scotese about the background.
Both AndyJ and Marsupial have valid points. However the extreme levels of CO2 during the early period of the Earths climate strongly suggests that CO2 forcing has been highly overrated.
And looking at the recent temperature trends from NASA’s own site:
http://www.giss.nasa.gov/research/news/20110113/
Shows that temperature increases prior to the Industrial ramp-up where just as strong as after, showing that human emissions have had little effect on overall climate change. And that’s negating the comment that the temps where ‘adjusted’!
And how can you get accurate surface temps with this business going on:
http://canadafreepress.com/index.php/article/25940
Global Temperature And Data Distortions Continue
http://wattsupwiththat.com/2011/12/05/the-impact-of-urbanization-on-land-temperature-trends/#more-52564
The Impact of Urbanization on Land Temperature Trends
http://icecap.us/index.php/go/joes-blog
Wednesday, November 09, 2011
NCDC Data Shows USA has not Warmed in the Past Decade, Summers are Cooler, Winters Colder
So a so called peer reviewed paper depends on where the authors or author got it’s data from and where it got peer reviewed,….. as many scientists have recently come forth and exposed the ‘pal’ review process of bureaucratic science panels to influence the continuation of grant monies. The climate gate emails are of a prime example of this Pal review process.
So sources are important.