Climate Change and the European Water Dimension - Agri ...

Other causes
Other causes of climate change include: deforestation and other changes in land-use
that enhance surface albedo. The largest effect is believed to be at high latitudes,
where snow-covered fields with high albedo have replaced snow-covered forest with
lower albedo. Warming due to increasing solar irradiance change has been taking
place mainly in the first half of the 20 th century. Other mechanisms by which
emissions from the sun may influence climate have been proposed, but the IPCC has
not found that they have a sufficiently rigorous scientific basis. Stratospheric aerosols
from explosive volcanic eruptions (e.g. Pinatubo) in lead to cooling that lasts a few
years.
I.G. Global Greenhouse Gas Emissions
The majority of the important greenhouse gases are compounds that are chemically
inert or only slowly degraded by chemical reactions in the atmosphere. These gases
tend to become well mixed in the atmosphere because of their long residence times.
The most important example of such a greenhouse gas is CO2.
The concentration of CO2 in the atmosphere remained stable at 280±10 ppmV for
several thousand years until the beginning of the Industrial Era in the middle of
the18 th century. Since then CO2 concentrations have been steadily increasing to
reach a level of 367 ppmV in 1999. The Mauna Loa record depicts an 18.8%
increase in the mean annual CO2 concentration, from 315.98 ppmv in 1959 to
375.64 ppmv in 2003 (Figure I.3 ). The 1997-98 increase in the annual growth rate of
2.87 ppmv represents the largest single yearly jump since the Mauna record began in
1958 Three quarters of the present atmospheric increase is caused by fossil fuel
burning while the last quarter is caused by land use changes (mainly deforestation).
These emissions are partially compensated by
Figure I.3. CO2 Concentrations at Mauno Loa since 1958 (through
Nov., 2004). (74Hhttp://cdiac.esd.ornl.gov/trends/co2/sio-mlo.htm).
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