Geoscience Reference
In-Depth Information
Box 3.1 The greenhouse effect
The greenhouse effect is a naturally occurring process that is responsible for regulating the Earth's
temperature. The greenhouse effect is a product of so-called greenhouse gases (such as carbon
dioxide, methane, water vapour and ozone). It operates on the basis that the Earth's atmosphere
allows solar radiation to pass through and to warm the planet's surface. The infrared radiation (heat)
that is re-emitted by the Earth's surface is then trapped by greenhouses gases enabling the further
heating of the Earth. In essence, greenhouse gases operate like a planetary blanket, which keeps
the planet warm and suitable for life. Without greenhouse gases the Earth's average temperature
would dip to a life constricting
18 degrees Celsius (IPCC, 2007: 97).
to solve the mystery of the onset and retreat of ice
ages, Arrhenius calculated that fluctuations in
gases such as carbon dioxide in the atmosphere
could trigger significant enough shifts in global
temperatures to account for geological forms
of global warming and cooling. Arrhenius had
discovered the greenhouse effect.
Before the work of Charles Keeling there was a
popularly held belief that while greenhouse gases
may regulate global temperatures there was very
little humans could do to significantly disrupt this
global balance and change the planet's climate.
While working at Caltech, Keeling developed the
first reliable instrument that could be used to
accurately measure atmospheric carbon dioxide
(Gillis, 2010). Keeling first used his instrument to
measure atmospheric concentrations of carbon
dioxide in California, but soon relocated his
operation to the Mauna Loa volcano in Hawaii.
Operating at some 3000 metres above sea level,
Keeling used his Hawaiian base to assiduously
monitor atmospheric carbon dioxide levels from
1958 onwards. What Keeling discovered would
radically alter our understanding of what humans
could actually do to global environmental systems,
such as the greenhouse effect.
Keeling's painstaking work in the thin air of
Mauna Loa revealed steadily increasing levels of
carbon dioxide in the atmosphere. (When Keeling
started his study he recorded carbon dioxide at
levels of 310 parts per million, or to put things
another way, every million pints of air in the
atmosphere contained 310 pints of CO
2
. As I write
this chapter reports indicate that we have now
reached the 400 parts per million threshold.)
Collectively, his observations led to the pro-
duction of the now-famous Keeling Curve (see
Figure 3.1)
. This curve shows increasing levels
of atmospheric concentrations of carbon dioxide
over time, with smaller fluctuations of seasonal
Foundation of the US terminated funding for
Keeling's work in the early part of the 1960s (on
the apparent basis that it was 'routine'), over time
scientists and politicians became aware of its
significance.
There are two implications of the Keeling
Curve that have increased in significance during
the final quarter of the twentieth century. Since
the industrial revolution, scientists have been
aware of rising levels of carbon dioxide (and
other greenhouse gases) in the atmosphere (a
consequence of the burning of fossil fuels). Recent
estimates put the aggregate level of carbon that has
entered the Earth's atmosphere since the industrial
revolution at 200 billion tons (Pearce, 2007: 62)
(that is approximately equivalent to the average
weight of 41 billion African elephants!). Prevailing
scientific theories of the time did, however, suggest
that the Earth's oceans and ecosystems would
eagerly absorb this additional carbon dioxide. The
Keeling Curve clearly showed that not all of the
additional CO
2
that was entering the atmosphere
was being reabsorbed into the Earth's biosphere
