Full and complete answers appreciated :) Thanks!! Exercise -4 On Earth we observ
ID: 287150 • Letter: F
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Full and complete answers appreciated :) Thanks!!
Exercise -4 On Earth we observe "Radiative Forcing" caused by increased concentrations of different greenhouse gases. At the moment the approximate value for this effect is 1-3 W/m2 a) Explain the expression "radiative forcing" Caused by this, at first the average temperature is increasing, with a slope of G 0.3 K/ (W/m2). However, through many so-called feedback mechanisms this temperature increase is influenced, in an amplifying as well as in a weakening manner. b) Give 4 examples of this kind of mechanisms and their (probable) effect (amplifying/weakening). Mathematically the effect of feedback can be described as follows: Al where G is the above-mentioned coefficient and H is the feedback-coefficient. c) Deduce the general expression for AT as a function of Al according to the diagram. d) Compute using the above-mentioned G and , and with H-+ 1.5.Explanation / Answer
a) Solar radiation received by the Earth is redistributed while it passes through the atmosphere and reaches the Earth's surface. Two of the most important redistributed components are Incoming Shortwave Radiation (ISR) and Outgoing Longwave Radiation (OLR). It is the difference between the two components which gives us a value known as Radiative Forcing (RF). The relation can be written as: RF = ISR - OLR
b) The most commonly understood feedbacks in the climate system are that of:
CO2: this trace gas in the atmosphere plays a major role in regulating the surface temperature of the earth. Carbon dioxide being emitted by anthropogenic activities acts as a greenhouse gas absorbs the OLR and amplifies the global temperature increase, thus having a positive feedback.
Clouds: they are mainly composed of water and ice, the surface of which acts as a major reflector of the ISR. The process of formation of clouds and reflection from them weakens the effect of temperature increase, so they give a negative feedback by reducing the intensity of warming.
Ice-albedo: snow and ice are good reflectors of ISR and the albedo (reflectivity) is quite high relative to other land surface features, but warming of climate decreases the volume of the strong reflectors, thus having a major role in positive feedback.
Oceans: these huge water bodies are sinks of heat and capable of absorbing large amounts of radiation. Their capability of absorbing heat and cooling the Earth system is reduced with increased warming, so they have a positive feedback on climate.
c) Change in average temperature is estimated using climate sensitivity parameter (in this case, G or the rate of increase in temperature defines the sensitivity) and radiative forcing (I) using the relation T=G(I). Since the term H gives a positive feedback on the loop, the relation between T and I can be given as:
T=G(I+H)
d) The temperature increase in the system can be computed using the following relation:
T=G(I+H)
= 0.3(3+1.5)
= 1.35 K
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