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

 
4.2.1.  Energy flow and the Earth’s climate
The main source of energy on the Earth is the Sun. The key 
factors that determine the extent to which the Sun’s energy reaches 
the Earth are the following:
 
Š
distance covered by radiation;
 
Š
angle at which solar radiation reaches the Earth’s surface;
 
Š
composition of the atmosphere and the interaction of solar and 
cosmic radiation with gases forming the Earth’s atmosphere.
Earth’s energy balance 
Different types of radiation reach the Earth: the Sun’s electro-
magnetic  radiation  and  the  flow  of  ionised  particles  (for  example, 
oxygen or helium atomic nuclei) and elementary particles, as well 
as  the  flow  of  particles  and  radiation  from  outer  space  (cosmic 
radiation).  The  Earth’s  climate  is  mostly  affected  by  the  flow  of 
electro magnetic radiation. The radiation from the Sun that reaches 
the Earth comprises the full spectrum of electro magnetic radiation: 
γ-rays,  X-rays,  ultraviolet  radiation  as  well  as  the  visible  light, 
infrared radiation and radio waves. The energy of electro magnetic 
radiation decreases with the increase in wavelength; therefore, 
most of the radiation that reaches the Earth has high energy and a 
relatively short wavelength.
A considerable part of solar radiation (γ-rays, X-rays and ultra-
violet radiation with short wavelength) does not even reach the 
Earth’s surface because it is absorbed already in the upper layers of 
the atmo sphere or is reflected back into outer space. High energy 
solar radiation transformations in the Earth’s atmo sphere are 
determined by the interaction of γ-rays, X-rays and short-wavelength 
ultraviolet radiation with atmo spheric gases.
The visible light (wavelength approx. 0.40-0.70 µm) is essential 
for sustaining the life of green plants and most animals, as it carries 
the energy necessary for photosynthesis and regulates the animal 
reproduction times,  migration  and  many  other  life  processes. 
Infrared radiation (thermal radiation) has a much lower energy; 

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4. HUMANS AND THE ENVIRONMENT
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nonetheless, it has a vital role in the Earth’s climate formation, 
because it warms the lower layers of the atmo sphere and the Earth’s 
surface. 
The intensity of incoming solar radiation is approximately in 
equilibrium with the intensity of energy reflected from the Earth’s 
surface  (Figure 4.16).  The  flow  of  energy  that  reaches  the  upper 
layers  of  the  Earth’s  atmo sphere  has  an  intensity  of  ~1370 W/m
2
. 
Most of this energy is reflected back into space or absorbed as a result 
of interaction with gases in the Earth’s atmo sphere. The intensity of 
the flow of energy that finally reaches the upper layer of the tropo-
sphere is just 342 W/m
2
.
Greenhouse
gases
Infrared
radiation
emitted  
Radiation 
emitted
by the Sun 
Absorbed into
the atmosphere
Reflected from
the Earth’s
surface
Reflected
solar radiation
Back
radiation 
Absorbed
Absorbed
107 W/m
2
30 W/m
2
168 W/m
2
390 W/m
2
67 W/m
2
350 W/m
2
324 W/m
2
324 W/m
2
235 W/m
2
165 W/m
2
342 W/m
2
107 W/m
2
236 W/m
2
Approximately 30% of solar radiation is reflected back into space.