How reliable is science? new carbon dating problems (The limitations of science)

by David Turell , Wednesday, July 22, 2015, 19:49 (3413 days ago) @ xeno6696

the ratios of C14 and C12 are changed by atom bomb explosions and by C12 deposition as civilization burns more carbon. How to overcome the problem:-http://www.scientificamerican.com/article/fossil-fuel-burning-obscures-radiocarbon-dates/?WT.mc_id=SA_DD_20150722-A T-shirt made in 2050 could look exactly like one worn by William the Conqueror a thousand years earlier to someone using radiocarbon dating if emissions continue under a business-as-usual scenario. By 2100, a dead plant could be almost identical to the Dead Sea scrolls, which are more than 2,000 years old.-These well-known “aging” properties of atmospheric carbon were pinpointed for different emissions scenarios in a paper published in the Proceedings of the National Academy of Sciences yesterday. It describes how fossil fuel emissions will make radiocarbon dating, used to identify archaeological finds, poached ivory or even human corpses, less reliable.-As scrolls, plant-based paints or cotton shirts age over thousands of years, the radioactive carbon-14 that naturally appears in organic objects gradually decays. The amount of carbon-14 decreases relative to the amount of normal carbon. Radiocarbon dating seizes on that fraction, which decreases over time, to estimate age. A lower fraction indicates an older object.-The problem is that the fraction can decrease not only as carbon-14 decays but also as normal carbon increases. That is what is happening with the burning of fossil fuels, which are so old they do not contain any carbon-14. Nonradioactive carbon is now flooding the atmosphere, which creates a dilution effect.-Though this dilution effect is well-known, its precise scale under different emissions scenarios was not, until now. Heather Graven, the atmospheric scientist at the Imperial College London who wrote the paper, was surprised at how much emissions could “age” the atmosphere if pollution continues at its current rate.-***-Physicists and bioengineers seized on this opportunity to study cell regeneration in plants and humans. A cell born after nuclear weapons testing would have a different, higher fraction of carbon-14 to normal carbon than one born several decades earlier. This indicator allows biologists to see which cells turn over and which cells remain the same.-For example, in 2009 scientists revealed in Science that about 0.3 to 1 percent of human cardiac muscle cells regenerated each year. They attributed the discovery to the carbon-14 produced during the Cold War.-Now, however, carbon emissions have risen to the point where they've countered the initial effect of nuclear weapons testing. Graven shows the present-day levels are close to preindustrial.-If the ratio were to remain constant, like in a low-emissions scenario, scientists wouldn't be able to use it to measure the lives of individual cells, a technique that requires a rapidly changing indicator. And a decreasing fraction could start affecting radiocarbon dating by 2020, Graven added.