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4.1.b Paleo-proxy Data and Trends in Carbon Dioxide
For more than a century, scientists have debated how changes in the atmospheric concentrations of greenhouse gases might change climate.
The relationship between greenhouse gases and climate change is strongly supported by evidence from ice samples taken from deep within ice sheets in the Antarctic and Greenland. The smaples provide archives of fossilized air bubbles trapped within the ice over hundreds of thousands of years.
As shown in the figure, over the past 400,000 years there has been a remarkable agreement between changes in regional air temperature in Antarctica (measured from ice chemistry) and the concentrations of carbon dioxide and methane (two key greenhouse gases measured from the air bubbles in the ice).
While other factors, including solar variability and vegetation cover, have also played an important role in the four glacial-interglacial cycles shown in the record, studies indicate that greenhouse gas concentrations were a critical factor.
The highest concentrations of carbon dioxide and methane evident in the 400,000 year record, until the past few centuries, have been less than 300 parts per million for carbon dioxide and 800 parts per billion for methane. These concentrations have consistently occurred only during the warm interglacial periods.
- Describe the pattern. What is the average “repeating” period?
- List the temperature (oC) relative to present climate for each peak high and its C02 concentration (ppmv).
- What is the average high peak correlation? Repeat for the 4 low points.What correlation is there between temperature, carbon dioxide (C02 )and methane (CH4) concentrations?
What do ppmv, ppbv and KyBP mean?