There is a small amount of radioactive carbon-14 in all living organisms because it enters the food chain.
Once an organism dies, it stops taking in carbon-14.
The results showed that Ötzi died over 5000 years ago, sometime between 33 BC. It is found in the air in carbon dioxide molecules.
The amount of carbon-14 in the air has stayed the same for thousands of years.
Slices of ice core, drilled from the depths of the Earth’s ice sheets, reveal details of the planet’s past climate.
Research teams from the United States, the Soviet Union, Denmark, and France have bored holes over a mile deep into the ice near the poles and removed samples for analysis in their laboratories.Most ice core records come from Antarctica and Greenland, and the longest ice cores extend to 3km in depth.The oldest continuous ice core records to date extend 123,000 years in Greenland and 800,000 years in Antarctica.In an Antarctic core (Law Dome) with a very high snowfall rate, it has been possible to measure concentrations in air from as recently as the 1980s that is already enclosed in bubbles within the ice.Comparison with measurements made at South Pole station show that the ice core acts as a faithful recorder of atmospheric concentrations (see Fig.