BioGeog Carbon Cycle and Ecosystem Responses L1: The Keeling Curve

What is the Keeling Curve?

A graph that represents the concentration of carbon dioxide (CO2) in Earth's atmosphere since 1958. Meausred at Mauna Loa Observatory.It tells us how the earth is working; the breathing of the earth. It is named after its creator, Dr. Charles David Keeling. It tells us what is happening in the atmosphere, which cannot be cheated.

Before Keeling how much CO2 was in the atmosphere?

0.03% of the content of air. 300ppm.

What percentage of all carbon is made up of carbon isotope 13C?

1%

Why in the early stages of the keeling curve did the southern hemisphere show no seasonal variation? (Keeling, 1960)

There is a lot more land in the northern hemisphere, which is where photosynthesis takes place and so there is a deeper trough in the northern hemisphere.

Why was monitoring allowed to continue?

There was acceleration in CO2 concentration during the 1970s. However these decadal variations could not be attributed to fossil fuel use and were found to be largely driven by ENSO.

What did ENSO show in comparison to CO2?

There was strong correlation between ENSO index and pressure, with records of atmospheric CO2 concentration. However the cause (Oceans/ Tides) was uncertain.

How high was the monitoring station and what significance does this have?

3397 m asl. To get representative values of atmosphere, measurements continued at high altitude in Pacific ocean. Above any possible boundary layer effects. Had to allow for volcanic emissions. These were obvious and so excluded. Active volcano in Hawaii releases a minimal amount of CO2 though may have small effect if wind in right direction.

What forms other than CO2 is carbon exchanged?

CH4, VOCs, and CO, but these will not be considered here as they are small in relation to the C content of vegetation and do not have major consequences for vegetation, although they do for climate.

What did Keeling initially think was the reason for the variability in CO2 concentration? (Pales and Keeling, 1965)

Strong seasonal cycle in oceans.

Why was funding to the keeling curve measurements cut in 1969? (Keeling, 1970)

The rise and cycle was confirmed in 1969. However average annual values appeared to be saturating suggesting that the system is buffered by plants and that an equilibrium will be reached only a little above then levels.

What are some important features of CO2?

Very inert gas so no chemical reactions in the atmosphere. doesn't change or increase without the flux. There is an approximately same level globally as it spreads out. Vegetation has a big effect on long term CO2. The increase of CO2 to the atmosphere is only 50% due to plants and oceans storing it. Not much of air is CO2, but of course is a strong greenhouse gas, shutting one of the few windows left for infra-red radiation to escape to space. Not many areas of electromagnetic spectrum are able to escape through atmosphere with CO2.