Environmental Engineering Reference
In-Depth Information
Yet it is not that long since we have been able to claim with absolute certainty that
the amount of carbon dioxide in the atmosphere is increasing on a yearly basis. The
Mauna Loa Observatory in Hawaii has only been measuring the concentrations of
carbon dioxide continuously since 1958. At that time the concentration amounted
to 315.2 ppm, the following year it was already up to 315.8 ppm. The unit ppm stands
for 'parts per million'. Thus there were 315 parts of carbon dioxide per million parts
of air. The small increase during the fi rst year could also have been caused by a
measurement error or natural fl uctuations. It was not clear until the values began
rising constantly in subsequent years that the amount of carbon dioxide was increas-
ing - and at a growing rate. In 2008 the CO
2
concentration had already risen to
386 ppm.
But, in comparison with the enormous size of the atmosphere, the high carbon
dioxide emissions that occur when fossil fuels are burnt are minute. Furthermore,
some of the carbon dioxide is absorbed again by the oceans and the plants. So the
question is how much our emissions can even change the composition of the
atmosphere.
If we were to produce nitrogen instead of carbon dioxide when we use fossil energy
sources, this would not pose a big problem. The reason is that our air consists of
around 78% nitrogen and 21% oxygen but only 1% other gases - of which carbon
dioxide makes up only a minuscule part. During the course of the earth's history,
the composition of the air has by no means been consistent. However, in the past
few thousand years a balance of less than 300 ppm has established itself. The pro-
portion of carbon dioxide in the atmosphere was thus less than 0.03%. However,
this is also the reason why we can even bring about any relevant changes. Small
quantities can be increased comparatively easily.
A study of the climate of the past few millennia requires a different approach. The
polar and Alpine ice sheets on earth have stored the history of the planet's climate.
In the regions with permanent ice, fresh snow falls on the ice surfaces every year.
Large quantities of air are trapped between the ice crystals. The new snow masses
that form each year alongside the old ones increase the pressure on the old snow
and ultimately press it down into pure ice. In the process the air does not escape
totally but instead remains as small bubbles trapped in the ice. Today these air
bubbles can be examined using modern techniques of analysis. The deposits of snow
and the creation of ice repeat themselves each year with a regularity welcomed by
scientists. All it takes is to drill a hole into the ice and draw up ice samples from
deep down. This provides a silent witness to the past. The deeper one probes into
the ice, the further back in history one is able to look.
Different drill core studies are unanimous in their fi nding that the concentration of
carbon dioxide before the period of industrialization was around 280 ppm (Figure
2.7). But even the theory that high concentrations of carbon dioxide are a recurring
phenomenon could be refuted. The studies showed that the proportion of carbon
dioxide in the atmosphere is higher today than at any other point in the past 650 000
years (Intergovernmental Panel on Climate Change, 2007).
Once it was fi nally proven that carbon dioxide emissions are increasing, climate
models were developed to establish a correlation between the burning of fossil fuels
