Geoscience Reference
In-Depth Information
ant than CO
2
, was found to block radiation in the same way and, therefore, was thought to
be more important.
The Second World War saw a massive improvement in technology and the old measure-
ments of CO
2
radiation interception were revisited. In the original experiments sea-level
pressure was used, but it was found that at the rarefied upper atmosphere pressures the
general absorption did not occur and, therefore, radiation was able to pass through the up-
per atmosphere and into space. This proved that increasing the amount of CO
2
did result
in absorption of more radiation. Moreover, it was found that water vapour absorbed other
types of radiation rather than CO
2
, and to compound it all, it was also discovered that the
stratosphere, the upper atmosphere, was bone dry. This work was brought together in
1955 by the calculations of Gilbert Plass, who concluded that adding more CO
2
to the at-
mosphere would intercept more infrared radiation, preventing it being lost to space and
thus warming the planet.
This still left the argument that the oceans would soak up the extra anthropogenically pro-
duced CO
2
. The first new evidence came in the 1950s and showed that the average life-
time of a CO
2
molecule in the atmosphere before it dissolved in the sea was about ten
years. As the ocean overturning takes several hundreds of years, it was assumed the extra
CO
2
would be safely locked in the oceans. But Roger Revelle, director of Scripps Institute
of Oceanography in California, realized that it was necessary not only to know that a CO
2
molecule was absorbed after ten years but to ask what happened to it after that. Did it stay
there or diffuse back into the atmosphere? How much extra CO
2
could the oceans hold?
Revelle's calculations showed that the complexities of surface ocean chemistry are such
that it returns much of the CO
2
that it absorbs. This was a great revelation, and showed
that because of the peculiarities of ocean chemistry, the oceans would not be the complete
sink for anthropogenic CO
2
that was first thought. This principle still holds true, although
the exact amount of anthropogenic CO
2
taken up per year by the oceans is still in debate,
it is about one-quarter of the annual total anthropogenic production.
Charles Keeling, who was hired by Roger Revelle, produced the next important step for-
ward in the global warming debate. In the late 1950s and early 1960s, Keeling used the
most modern technology available to measure the concentration of atmospheric CO
2
in
Antarctica and Mauna Loa. The resulting Keeling CO
2
curves have continued to climb
ominously each year since the first measurement in 1958 and have become one of the ma-
jor icons of global warming (
Figure 3
).
