Yesterday at 05:45 PM Hank said this in Post #31
Thank, as always the patient teacher in the forum. 
Thank you.
Would Ice-ages not indicate drastic changes in the atmosphere? What I am getting at is that the last one started 70k years ago and ended 10k years ago. Certain amount of earth was covered by ice. Vegetation did not flourish there and probably neither would the CO2 cycle have been balanced. If the CO2 is not balanced why would C-14 be absorbed at a constant rate by living entities?
Where to start in this paragraph?
1. The CO2 balance we are talking about is formation of C14 from N14 and the radioactive decay of C14, so that the amount of C14 stays constant. That wouldn't be affected by climate. It depends on the amount of gamma radiation received, nitrogen content of the atmospher, and decay rate of C14. None of those get affected by climate.
2. The biochemistry of an
individual plant is not influenced by an ice age. In the tropical rainforests life went on as before: the extent of the rainforest was just a little less. Plants living next to the glacier are the ones adapted to living in cold climates, so their metabolism doesn't change in an ice age. Now they simply live further south than they used to. To grow a plant needs to absorb a fixed amount of CO2 to convert to glucose by photosynthesis. After all, the plant requires a certain number of glucose molecules to go on living. Once those are absorbed, a fixed percentage will be C14O2 and you can then measure the ratio of C14 to C12.
3. An ice age does not change the ratio of isotopes or major elements in the atmosphere. Instead, the mean temperature of the earth depends on a balance of heat coming in from radiation from the sun, heat lost thru re-radiation from the surface of the planet, and the amount of that re-radiation trapped by so-called greenhouse gasses in the atmosphere. You don't have to change those greenhouse gases by more than a couple of hundred or thousand parts per
million (0.02% to 0.2%) to change the temperature of the atmosphere. Now, 0.02 to 0.2% is far below the margin of error in C14 measurements anyway. These are at 1-5%. So even changing the amounts of CO2 enough to give an ice age isn't going to change the C14 absorbed enough to change the dating significantly.
Now, radiation absorbed by the earth depends on how much is reflected, which is the albedo. Raise the albedo and more is reflected and the temperature of the earth drops. Ice, of course, has a high albedo. So do clouds. OTOH, CO2, methane, and some other gasses reabsorb heat given off by the earth at night. Most of the methane in the atmosphere comes from the intestines of large animals (farts) and comes to a truly staggering total in pounds per day. If for some reason the number of large animals declines, there goes the greenhouse gas and the temperature drops.
Or, as the first of your websites states, perhaps the earth's orbit changed slightly and the amount of solar radiation dropped. One theory that was popular a while back was having an open ocean at the north pole to provide moisture for clouds and snow.
http://www.ngdc.noaa.gov/cgi-bin/paleo/peltice.pl
You should give this site to JohnR7 so he can check the extent of the ice sheets against his hypothesis that they all melted 12,000 years ago and how far they extended.
Studying the magnetic ages of lake sediments indicates a variation of the C-14 content of about 10% for the period of 20k years. If I allow for another drop of -10% for the next -20k years C-14 becomes unreliable at age -40k. There a plus/minus 20% works out to 4k year fluctuation, or ten percent of the date. This is based on actually accepting lake dating as accurate.
For a biological process, a margin of error of 10% is pretty good. Of course, you have an "if" in there that is not documented. Notice none of this is going to get you to less than 20,000 years, much less 6,000.
If I where a creationist, my next question would be:
Do plants actually absorb C-14 at a rate relative to the presence of C-14, or do they have a "mind" on there own?
I have seen no data where receptors on the relevant proteins can distinguish the difference in nuclear weight. Receptors work on the shape of the molecule, which depends on the electron shell, not the nucleus. Have you ever seen space-filling models of chemicals? They represent the electron shells. The isotope of the element doesn't register at all.
