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Monday, May 2, 2011

The Keeling Curve

Take a deep breath.   If you are about as old as I am, every breath you  take now contains about 23% more CO2 than your first breath at birth.   There is a remarkable set of CO2 measurements taken daily on a mountaintop in Hawaii since 1958, termed the Keeling curve.  The data show dispersed CO2 in the Northern Hemisphere, and is taken to represent the rise in global CO2 concentration.   The data shows a seasonal fluctuation (peaking during spring), and an unbroken annual rise in CO2.
 The Keeling Curve, as measured at Mauna Loa, has a seasonal cycle.  Atmospheric CO2 falls in the Northern Hemisphere summer, and rises during the Northern Hemisphere winter.  This is consistent with the absorption of CO2 by plants during the summer growing season, and the return of CO2 to the atmosphere through respiration or oxidation during the rest of the year.

The Keeling Curve at Mauna Loa is only one set of observations, out of a global set of CO2 observations.   There is remarkable consistency of the long-term trend of CO2 across the globe, although details of the cycles differ.  
The amplitude of the cycles varies dramatically by hemisphere and latitude.  The data on this chart are color-coded by monitoring station shown below.
I explore the global data in greater detail in another post, found here: cores from Greenland and Antarctica contain air bubbles preserved in the ice, and forming a continuous record for the past 400,000 years.
We can see from the data that over the last 100 years, the concentration of atmospheric CO2 abruptly increased beyond the levels of the previous 400,000 years.  The causes and the consequences of the rise in CO2 will be the subject of future blog posts.

I have added four additional posts on the topic of global atmospheric CO2, found in the links below.
The Keeling Curve and Seasonal Carbon Cycles
Seasonal Carbon Isotope Cycles
Long-Term Trends in Atmospheric CO2
Modeling Global CO2 Cycles

Source for CO2 data:   Keeling et al,
Source for ice-core data:

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