In regards to land use, two factors are the most significant: deforestation and urbanization. Deforestation causes an increase of thermal contrasts in the lowest layer of the atmosphere and a decrease in the amount of water vapour in the atmosphere. By changing the ground roughness the process of deforestation leads to an increase of the wind speeds, which lowers the humidity of air and increases evaporation of water. In the last 15 years (from 1975) the total surface of forests increased slightly (by 1.7%). However in some voivodships (Czestochowa, Jelenia Gora, Kielce, Cracow, Legnica, Leszno, Lublin and in a few others in the southern and western Poland), as well as per capita, the surface of the forests decreased.
Urbanization increases air temperature (so called urban heat islands), lowers the amplitude of temperatures, weakens the
inflow of solar radiation and changes the precipitation system.
Air pollution disturbs the balance of solar radiation by increasing the atmospheric obscurity, changing the chemical composition of the atmosphere and of the drops of water that are in the atmosphere (acid rains), increasing the ozone concentration in the troposphere * decreasing it in the stratosphere **, and delivering additional amounts of thermal energy to the atmosphere which changes its thermal structure.
A systematic increase of ozone concentration in the troposphere in the highly industrialized regions has been observed. Ozone is a result of photo-oxidation of carbon monoxide, methane and other volatile organic compounds in the presence of sulphur dioxide or nitrogen oxides. Because of the short lifespan of ozone in the lowest layers of the atmosphere it does not have a large influence on climatic conditions, but it is a deterrent to living organisms.
According to international scientific institutions, the changes in the global climate result from the emission of gases into
the atmosphere which cause the greenhouse effect. These emissions result from human activities. The most important
greenhouse gases are: carbon dioxide, methane, nitrous oxide and chlorofluorocarbons
(freon gases). Freon gases have a
great heat capacity and are used for, among other things, cooling (GRAPHS illustrating changes in concentration of greenhouse gases in the atmosphere).
A growing concentration of greenhouse gases in the atmosphere causes the global warming of temperatures in the lowest layers
of the atmosphere (GRAPH illustrating the deviation from mean
air temperature in the near-ground layer of the earth).
Poland mainly emits carbon dioxide and methane. In 1988 the emissions of carbon dioxide totalled
about 480 mln tonnes, while emissions of methane amounted to 2.7 mln tonnes.
The main source of carbon dioxide was emission from the power-generating sector (about 57.5%), and then: agriculture and public utilities (23.5%),
industry (11%) and transportation (8%). Methane emissions come from coal mines (38%), agriculture and animal breeding
(35%), landfill sites (13%), natural emissions from swamps (9%) and extraction of natural gas (5%).
The increase of temperature and lowering of precipitation in Poland is also related to the rising trend in the global
temperatures (See graph). The average annual air temperature in Poland has risen from the end of the 1960’s to the 1990’s
by about 0.5oC and average annual precipitation has fallen by about 70 mm.
One of the problems of a global concern is the destruction of the ozone layer in the stratosphere due to the emission of freon gases (chlorofluorocarbons, or CFCs). Ozone has a very important and beneficial function in the stratosphere – it absorbs ultraviolet radiation that is harmful to living organisms. Freon gases, which in the lowest layers of the atmosphere act as greenhouse gases, decompose in the stratosphere freeing atoms of chlorine, fluor or bromine, which cause the brake-up of ozone particles (See graph).
 |
 |
 |
 |
 |
 |
| Chapter Homepage |
SOE Homepage |
GRID-Warsaw Homepage |
MEP Homepage |