Environmental Engineering Reference
today are densely populated would have been covered with thick layers of ice. And
during the hottest periods in our climate's history our coastal cities would have been
sunk metres deep below the ocean. If major changes to climatic conditions occur,
they will undoubtedly have an even stronger impact on the face of the earth and our
current conditions of life than any of the most dramatic historical events of the last
Observed Climate Changes (Intergovernmental Panel on
Climate Change, 2007)
■ The global surface temperature rose by 0.74 °C between 1906 and 2005.
■ Eleven of the last 12 years have been the warmest since records were kept.
■ The increase in temperature during the last 50 years was twice as high as during the
last 100 years. The warming of the Arctic has been twice as fast.
■ The temperatures of the last 50 years have probably been higher than at any time in
the last 1300 years.
■ Glaciers are shrinking worldwide, as are the ice sheets on Greenland and
Since 1993 the sea level has risen an average of 3.1 mm per year; during the 20th
century this amounted to a total of 17 cm. More than half of this is due to the thermal
expansion of the oceans, about 25% to the melting of mountain glaciers and around
15% to the melting of the arctic ice sheets.
The frequency of heavy precipitation has increased.
The frequency and intensity of droughts has increased since the 1970s.
The frequency of extreme temperatures has increased.
Tropical cyclones have become much more intense since the 1970s.
During the past 100 years the average temperature on earth has increased by a good
0.7 ° C. At fi rst glance this does not seem like much. However, this warming is not
occurring at a uniform rate in all regions and is also not constant throughout the
year. If temperatures fall into a normal range for ten months, then two months can
follow at more than 4 °C above the average. In some regions of the world the tem-
perature is already higher by 2 °C as an annual average (Figure 2.1).
As a result of global warming, the water in the oceans expands. Due to the rise in
temperatures, more and more Arctic ice and the permanent ice of the glaciers also
melt. As a result, the sea levels rise even higher.
The temperatures in the polar region rise even more quickly than in the rest of the
world. The ice coverage in the Arctic has decreased by about 10 to 15% within 20
years (Figure 2.2). Along with the ice masses of the Arctic, many glaciers are also
melting at a fast rate. The largest glacier in the world, the Bering Glacier in the
Arctic region of Canada, has shrunk by more than 10 km during the past century.