Start Relative dating vs numerical dating

Relative dating vs numerical dating

INTRODUCTION Anyone who has spent any amount of time reviewing climate science literature has probably seen variations of the following chart…

The age of the layers of ice can be fairly easily and accurately determined. I am very surprised the scientific community does not have a very warm welcome for new innovative techniques when those techniques put question marks at established ideas.., I always learned that these discussions are the fundamental backbone for science… Because the ice core temperature and CO2 time series have vastly different resolutions.

The age of the air trapped in the ice is not so easily or accurately determined. therefore my hope that climate science will ever become a fullgrown scientific discipline is lost as long as politics (read funding) keeps intermingling Tom van Hoof on January 11, 2011 at am To come back on questions about the validity of Stomatal index (read, NOT stomatal density) as a CO2 proxy… It is physically impossible for Law Dome to have a resolution better than 60 years.

Currently the most common method for aging the air is through the use of “firn densification models” (FDM). We use an index value between the number of leaf stomata and the number of epidermis cells called the stomatal index instead of just the number of stomata per leafarea as some people tned to do, the reason for thsi is that indeed drought can have an influence on stomatal density, but only through the mechanism on epidermal cell expansion… The differential between the ice age and gas age is at least 30 years…

A recent study (Van Hoof et al., 2005) demonstrated that the ice core CO2 data essentially represent a low-frequency, century to multi-century moving average of past atmospheric CO2 levels. A period where both methods consistently provide evidence for natural CO2 changes is during the 13th century AD. Highly variable Northern Hemisphere temperatures reconstructed from low- and high-resolution proxy data. The mean air age is thus aa = ai δa = ai Ts – Td where ages are dates A. Mixing of air from the ice sheet surface to the sealing depth is primarily by molecular diffusion.

It appears that the ice core data represent a long-term, low-frequency moving average of the atmospheric CO2 concentration; while the stomata yield a high frequency component. The results of the two independent methods differ significantly in the amplitude of the estimated CO2 changes (10 ppmv ice versus 34 ppmv stomatal frequency). doi:10.1073/pnas.0805721105 Mc Elwain et al., 2001. Stomatal evidence for a decline in atmospheric CO2 concentration during the Younger Dryas stadial: a comparison with Antarctic ice core records. The rate of air mixing by diffusion in the firn decreases as the density increases and the open porosity decreases with depth. (1996) determined the sealing depth at DE08 to be 72 m where the age of the ice is 40±1 years; at DE08-2 to be 72 m depth and 40 years; and at DSS to be 66 m depth and 68 years.

Stomatal density can be empirically tested and calibrated to CO2 changes over the last 60 years in living plants. IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series #2004-013. Tom van Hoof on December 28, 2010 at am As one of the “stomata: people and author ofd the cited Tellus paper, I want to draw attention to one of the most interesting outcomes of our research. The natural source-sink ratio is far more variable than indicated by the ice cores.

The advantage to the stomatal data is that the relationship of the Stomatal Index and atmospheric CO2 can be empirically demonstrated… NOAA/NGDC Paleoclimatology Program, Boulder CO, USA. That is that for the past thousand years the stomata records seem to match with respect to timing to two Antarctic ice core records which are not often cited…. This was occurring long before man ever discovered how to burn things. 33–36…The discrepancies between the ice-core and stomatal reconstructions may partially be explained by varying age distributions of the air in the bubbles because of the enclosure time in the firn-ice transition zone.

I somehow doubt that the air at a depth of 99 meters is last year’s air. In contrast to conventional ice core estimates of 270 to 280 parts per million by volume (ppmv), the stomatal frequency signal suggests that early Holocene carbon dioxide concentrations were well above 300 ppmv. This effect creates a site-specific smoothing of the signal (decades for Dome Summit South [DSS], Law Dome, even more for ice cores at low accumulation sites), as well as a difference in age between the air and surrounding ice, hampering the construction of well-constrained time scales (Trudinger et al., 2003). Agreed, but the bubble enclosure period in the high accumulation Law Dome cores is only 8 years starting at 72 m depth.