Environmental Engineering Reference
In-Depth Information
ppm
ppm
400
400
380
380
360
360
340
340
320
320
300
300
280
280
260
260
240
240
220
220
200
200
180
180
160
160
-400,000
-300,000
-200,000
-100,000
0
1000 1200 1400 1600 1800 2000
year
Figure 2.7
Development of carbon dioxide concentration in the atmosphere over the last 400 000
years and in the recent past.
Data: CDIAC, cdiac.ornl.gov.
and the increase in CO
2
. Sources other than the emissions caused by humans were
not considered as reasons for the increase. The models show that the CO
2
concentra-
tion could still more than double, depending on the extent of the future consumption
of coal, oil and natural gas.
This discovery raised another question, namely what the consequences of such
drastic changes would be. In high concentrations carbon dioxide is unhealthy for
humans and can even be life-threatening. However, to reach a level that would
damage the health of humans, the concentration would have to increase a hundred-
fold; to cause the danger of suffocation it would have to increase by a factor of 300.
There is no way that we could reach such levels, even if we were to burn all the
oil, natural gas and coal available. At least any acute danger to the lives of humans
can be ruled out.
Direct measurements of temperature have existed for well over 100 years. A com-
parison of global temperature changes with energy-related CO
2
emissions shows a
signifi cant connection between the two (Figure 2.8). Yet sceptics fi nd fault with this
argument and point out that the temperatures actually fell slightly between the 1940s
and the 1980s. Today there is an explanation for this. Aerosols from high dust and
soot emissions in the burning of fossil energy sources reduce the solar radiation on
earth. They act, so to speak, like sunglasses and thus create a cooling effect. Today
modern fi ltering techniques have eliminated a major proportion of these emissions.
This again decreases the sunglasses effect. However, CO
2
and the associated rise in
temperature have remained.
As wood absorbs carbon dioxide during its growth, its burning is carbon dioxide-
neutral. However, this is only the case if the same quantity of plants is used and
burnt as can grow back again. Tropical rainforests are currently being burnt at a
much faster rate than their rate of regeneration. An area of woodland the size of the
United Kingdom is disappearing every 18 months. Some of the forests being burnt
