Geoscience Reference
In-Depth Information
that geologists estimated had brought about the last Ice Age. His first step was to
develop equations to describe the absorption of heat radiation by water vapor and
CO
2
. To solve them, Arrhenius needed to know how much infrared radiation the
atmosphere absorbs. But no one had yet measured it. Where in the world could he
get the data he needed?
In a flash of scientific insight, Arrhenius realized that he could get the crucial
information not from this world but from the Moon. “The moon-rays have,” he
noted, “as they arrive at the measuring-instruments, passed through layers of car-
bonic acid and of aqueous vapour of different thickness according to the height of
the moon and the humidity of the air” (240).
UsingLangley'smoonlightdataandtheknowntemperature andhumidityatdif-
ferent latitudes, Arrhenius calculated the effect that a change in CO
2
would have
on global temperature for each ten degrees of latitude, for each of the four seasons,
and for each of five scenarios in which CO
2
differed from observed by factors of
0.67, 1.5, 2.0, 2.5, and 3. After a year of “scribbles,” he was ready to report the
results.
9
The work required an estimated ten thousand to one hundred thousand calcula-
divorce, becoming a father, and worrying about the threatened loss of the teaching
position he had won at the Stockholm Högskola.
Arrhenius found that doubling the amount of CO
2
in the atmosphere would
cause temperature to rise 5 or 6°C. Conversely, reducing CO
2
by half would cause
temperature to fall by the same amount. Enough to start an Ice Age.
Arrhenius restated his findings in a popular 1908 topic titled
Worlds in the Mak-
ing: The Evolution of the Universe
.The topic was a tour de force that described the
state of scientific knowledge about astronomy, cosmology, volcanism, and even
the spread of life throughout the universe. It closed with a chapter ominously titled
“The End of the Sun,” which Arrhenius estimated would take place in 150,000 bil-
lion years.
In his 1896 article, Arrhenius had noted that humans were burning 500 million
tons of coal each year. By 1904, the amount had nearly doubled to 900 million tons
and was “rapidly increasing.” He realized that “although the sea, by absorbing car-
bon dioxide, acts as a regulator of huge capacity, which takes up about five-sixths
of the produced carbonic acid . . . the slight percentage of carbonic acid in the at-
mosphere may by the advances of industry be changed to a noticeable degree in
the course of a few centuries.”
11
But as might be expected from a native of Sweden, Arrhenius thought that more
carbondioxideandawarmerEarthwouldbeagoodthing:“Bytheinfluenceofthe
