In the new study using samples taken from Xingkai Lake near the Sino-Russian border in Heilongjiang province, researchers have discovered a discrepancy between two dating methods: radiocarbon dating and another method known as optically stimulated luminescence.
C14 dating uses the fact that Carbon in the atmosphere is constantly being bombarded by cosmic rays to create a radiative form which is then absorbed by plants, and then by animals. Because the ratio of the radioactive form of Carbon decays with a half life of 5700 years, the percentage of radioactive carbon can be used to date any organic sample – with the proviso that the amount of cosmic rays is constant, and that large amounts of “fossil carbon” are not being released to the atmosphere.
Optically stimulated luminescence. Uses light to measure the amount of free electrons trapped in quartz. This method relies on the slow accumulation of energy in the quartz, which is then “wiped clean” by exposure to light. So this allowed the team to tell how long the samples had been kept away from sunlight, and therefore estimate when it was that they first fell in the lake.
By comparing results from the two methods, they found that carbon dating became unreliable beyond a range of 30,000 years.
The possible causes of this are:
- An increase in the level of atmospheric C14 due to Cosmic rays (possibly as a result of changes to earth’s magnetic field)
- A constant decrease in the level of atmospheric C14 after this date as more fossil carbon is released (where radioactive forms have already decayed) – this suggests a change from low volcanic activity to high – which fits the Caterpillar theory but suggests modern C14 is repressed (testable)
- A massive “bright light” or some other very unlikely process that changed the quartz. (unlikely and I really just include this as a placeholder as “things which might affect the quartz).
The Caterpillar theory
That the earth will expand as a result of changing temperature at the surface is just common sense physics. So, in this sense the Caterpillar is really just a restatement of fundamental physics: heating and contraction will result in expansion and contraction which will add to the tectonic plate movement. If the heating is large enough and long enough it may be a significant driver and evidence of changing rates of tectonic plate movement corresponding with ice-age cycles is found at the mid ocean ridge.
However, what makes it a theory – is that it predicts subduction and a change in the level of emissions from volcanoes and therefore may well be the reason why CO2 levels fluctuate over an ice-age cycle. However, the last ice-age peaked at 22,000 years ago, whereas this research shows the discrepancy at 30,000 years. As this will be at the limits of sensitivity the difference may not be significant, in which case it could be evidence for a large scale release of volcanic CO2.
Volcanic CO2 – affect on C14 dating
Spurious radiocarbon dates caused by volcanic emanations of radiocarbon-depleted CO2 probably also come under the category of reservoir corrections. Plants which grow in the vicinity of active volcanic fumeroles will yield a radiocarbon age which is too old. Bruns et al. (1980) measured the radioactivity of modern plants growing near hot springs heated by volcanic rocks in western Germany and demonstrated a deficiency in radiocarbon of up to 1500 years through comparison with modern atmospheric radiocarbon levels. Similarly, this effect has been noted for plants in the bay of Palaea Kameni near the prehistoric site of Akrotiri, which was buried by the eruption of the Thera volcano over 3500 years ago (see Weninger, 1989). The effect has been suggested as providing dates in error for the eruption of Thera which has been linked to the demise of the Minoan civilisation in the Aegean. One modern plant growing near the emanations had an apparent age of 1390 yr. The volcanic effect has a limited distance however. Bruns et al. (1980) found that at 200 m away from the source, plants yielded an age in agreement with that expected. They suggested that the influence of depleted CO2 declined rapidly with increasing distance from the source. Radiocarbon discrepancies due to volcanic CO2 emissions are a popular source of ammunition for fundamentalist viewpoints keen to present evidence to show that the radiocarbon method is somehow fundamentally flawed.
CO2 driven by temperature
The honoured Professor Salby impressed me with his research showing that “at least in part” CO2 levels are driven by temperature.
This could mean that “organic carbon” locked up in e.g. peat deposits is being constantly released in the present period thus causing a depression in C14.
However, at least in part, the rise in CO2, must also come from “fossil forms” whether coal, peat or volcanic CO2. And even some academics admit that CO2 has risen as a result of volcanoes:
Prof Jim Zachos of the Univeristy of California said that 55 million years ago volcanic activity caused around 4,500 gigatons of greenhouse gases to be released into the atmosphere over thousands of years. This caused the planet to warm by 6C (source)
The published estimates of the global CO2 emission rate for all degassing subaerial (on land) and submarine volcanoes lie in a range from 0.13 gigaton to 0.44 gigaton per year (Gerlach, 1991; Varekamp et al., 1992; Allard, 1992; Sano and Williams, 1996; Marty and Tolstikhin, 1998). The preferred global estimates of the authors of these studies range from about 0.15 to 0.26 gigaton per year.
However, all of these assume:
- That measurements of obvious CO2 release is an accurate indication of total CO2 release
- That oil is not part of the fossil carbon cycle (which means that all humans are doing is temporarily speeding that cycle up for a few decades).
As such the actual continued release of CO2 from subduction events could be many orders of magnitude larger than academics believe. Indeed, looking at the figure of “4500 gigatonnes over 1000 years”, if the natural release of carbon is 0.2gigatonnes for the last 20,000 years, then there has been 4000 gigatonnes of volcanic CO2.
which if Prof Jim Zachos is right it’s almost the same as the temperature rise at the end of the ice-age … (slaps head) … of course … this looks suspiciously like the old “CO2 rise MUST HAVE caused the end of the ice-age” turned on its head argument.
So let’s ignore what the “scientists” say on volcanic CO2 instead, the best summary comes (as always) from WUWT:
Here’s another, explaining how even obvious sources are being underestimated (but with no figures for actual amount):
This suggest that the estimates of total CO2 release from volcanoes is erupting with 0.1 in 1992, 0.2 around 2000 and latest estimates of 0.6gigatonnes. If the 50% from “inactive” volcanoes is an addition this suggests we are already at 1gigatonne or a 10x increase in 23 years. So it would not be surprising if in 23 years time we were being told volcanic activity was responsible for 10gigatonnes/year nor in 46 years if we then learnt it was closer to 100gigatonnes a year. Needless to say, this is far more than human emissions, although less than the total amount of CO2 from organic decay of plants.
(But what it really shows is that academics have no idea how much CO2 comes from natural volcanic sources)
Looking at the dates, the researchers have dates up to 60-80,000 years. These will be less reliable, but they are suggesting that all dates over 30,000 years are at odds. To me this sounds like a change in production in C14 rather than a “C14 event”. And there are obviously two possible explanations: that C14 was higher in the past, or that C14 is currently lower. So, either more C14 was being produced in the past for some reason. Or we are currently experiencing a period when less C14 is being produced (or C14 is being diluted).
With the last ice-age ending some 22,000 years ago, it seems to me that the two may well be related. This in turns suggests that ice-age may in some way be a result of something that also affects the C14 level. The two obvious choice (for me) are a reduction in cosmic rays or an increase in magnetic field and earth’s shielding – or a change in solar activity which in turn affects the earth’s shielding. Or a change in volcanic activity – so that C14 is now diluted in the atmosphere due to the release of fossil carbon.