Māris kļaviņŠ, azamat azizov, JĀnis zaļoksnis environment, pollution, development: the case of uzbekistan

Figure 4.16. 
Earth’s 
energy balance

---

62 
ENVIRONMENT, POLLUTION, DEVELOPMENT:  THE CASE OF UZBEKISTAN
surface mostly emits infrared radiation that can interact with atmo-
spheric gases.
Several of these gases can intensively absorb infrared radiation. 
These gases are carbon dioxide (CO
2
), methane (CH
4
), ozone (O
3
) 
and water vapour, as well as nitrogen(I) oxide (N
2
O) and the gases 
that  are  released  into  the  atmo sphere  due  to  human  activity  – 
chlorofluorocarbons (freons). 
Carbon dioxide, methane and also water vapour in the atmo-
sphere  work  like  greenhouse  glass  (Figure 4.17).  They  let  solar 
radiation through, but hold up the infrared radiation reradiated 
from the Earth’s surface. Due to this effect, these gases are called 
greenhouse gases. The higher their concentration in the atmo sphere, 
the more infrared radiation is retained in the Earth’s atmo sphere 
and, as a consequence, the higher the temperature of the Earth’s 
surface. If the Earth’s atmo sphere were composed of nitrogen and 
oxygen only, i.e. the gases that do not contribute to the greenhouse 
effect, the Earth’s average yearly temperature would be only +6 °C 
(now it is approx. +15 °C). 
Infrared
radiation
Solar radiation
The Swedish chemist Svante Arrhenius proposed the hypothesis 
regarding the role of greenhouse gases – CO
2
 in particular – in the 
Earth’s climate formation as early as 1896. His calculation that 
doubling the CO
2
 concentration in the atmo sphere would cause 
a rise of the Earth’s average temperature by 5-6 °C has been fully 
confirmed today.
Even the slightest changes in the concentrations of greenhouse 
gases in the atmo sphere cause temperature changes on the Earth, 
causing further changes in the size of glaciers and ice shelves and 
caps, in the ocean level, patterns of currents, spatial structures of 
habitats and climate.
Figure 4.17. 
Principle of 
solar electromagnetic 
radiation absorption in 
the Earth’s atmosphere 
and in a greenhouse

---

4. HUMANS AND THE ENVIRONMENT