ENVIRON 157 Lecture Notes - Lecture 3: Carbon Cycle, Radiative Forcing, Climate Summit
Course CodeENVIRON 157
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PUB POL 461 Week 1 lect 3
Starts at slide 15
CO2 absorption of sea water was only 10%. The rest was in the atmosphere
The photo in the background shows the Mauna Loa Observatory at dusk (courtesy Forrest Mims). This is
where, in 1958, Charles David Keeling began his now-famous atmospheric carbon dioxide data set –
sometimes called “the Keeling Curve.” The data trend shows carbon dioxide has risen from about 318
parts per million in 1958 to about 388 ppm in 2008. The gray “saw-toothed” line shows actual
measurements and the red line shows the running mean value.
Level of CO2 was constantly increasing since the 1950s
The top trend line shows human population growth from the year 1000 to 2000. The three graphs in the
middle show concentrations in the lower atmosphere of the three most abundant human-emitted
greenhouse gases: carbon dioxide, nitrous oxide, and methane. The purple line in the bottom graph
shows a model prediction of global mean surface temperature, with the light shaded area indicating the
margin of uncertainty. The gray line superimposed beginning in year 1880 shows the observed global
mean surface temperature. Note the very good agreement between the model prediction and
Population doubled & then doubled again over the last century—from 1.65 billion to more than 6 billion
In that same time span, there was a rise in the three most abundant human-emitted greenhouse gases,
mirroring the growth in human population. Isotopic analysis and carbon cycle models established that
the increase in carbon dioxide was due to fossil fuel consumption.
With the rise in those greenhouse gases, Earth experienced an unusually rapid rise in its average
temperature—increasing 0.7°C since 1880.
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