Team Questions Session 3

1) Understanding Earth’s energy balance is essential to understanding the issue of global warming. For example, the solar energy striking Earth’s surface averages 168 watts per square meter (W/m2), but the energy leaving Earth’s surface averages 390 W/m2. Why isn’t Earth cooling rapidly?

Although the solar energy that strikes the Earth’s surface averages at 168 W/m2, it is not the only energy absorbed by the Earth’s surface. In fact, the earth’s surface also absorbs 324 W/m2 of longwave infrared radiation (LWIR) emitted downwards by the atmospheric greenhouse gases and clouds. Hence, the total amount of energy absorbed by the Earth’s surface would be 168 + 324 = 492 W/m2. The Earth’s surface does emit 390 W/m2 by emission of LWIR. However, that is also not the only energy emission by the Earth’s surface. In addition, the surface emits 78 W/m2 of heat due to evaporation of water into the atmosphere and 24 W/m2 of heat through conduction into the atmosphere. Hence, the total amount of heat emitted by the Earth’s surface would be 78 + 24 + 390 = 492 W/m2. The total amount of energy absorbed by the Earth’s surface equals to the total amount of energy leaving the Earth’s surface showing that the earth’s surface gains as much energy as it loses. Thus, the Earth would not be cooling rapidly.

2) Do you think the statement “This winter has lowered my concerns about global warming…” made by the cartoon is justified? Explain.

We don’t think the statement is justified because there is a difference between weather and climate. Weather is the state of the atmosphere with respect to wind, temperature etc. that is measured over a short period of time whereas climate is the pattern of weather measured over a long period of time. So, the fact that scientists have been using the climate to conclude if the Earth is getting warmer or cooler shows that it is more reliable that the weather, which can be unpredictable. Therefore, it doesn’t mean that just because it’s winter, that the Earth is getting cooler. Global warming is still occurring!

3) One of the first radar devices developed during World War II used microwave radiation of a specific wave range that triggers the rotation of water molecules. Why was the design not successful?

How radar works

Radar works by emitting a pulse of waves like radio or microwaves and ‘listen’ for it’s return. The transmitter sends regular pulses of microwaves and if there are objects nearby, the waves would reflect back to the receiver. (like how you hear your own echo from a cliff).

Why Microwave is not useful?

Microwave is able to rotate or vigorously vibrate water molecules. The atmosphere is filled with water molecules, in form of water vapour. Imagine you can see these waves… let’s take for example, shining a laser at the mirror and watching it reflect back to you. The medium in which the laser passes through, which is the air between you and the mirror, is unaffected, allowing the laser to travel in a relatively straight line. But what if every water molecule it encountered, vibrates and shifting its trajectory elsewhere, the ‘straightness’ of the line is now affected. And if your purpose is to find the mirror, you may be terribly mislead.

4) Now that you have studied air quality (Unit 1), stratospheric ozone depletion (Unit 2), and global warming (Unit 3), which do you believe poses the most serious problem for you in the short run? In the long run?

In the short run, we believe that air pollution poses the most serious problem for us because air is a necessity for life. It can cause serious health problem for us.

In the long run, climate change that causes global warming poses the most serious problem for us as it causes irreversible damage due to runaway greenhouse effect. We wouldn’t want our planet to end up like Venus!

 

About SAJU AASHIKA TREESA

CSC Batch 2014 LIVE created on 26/06/2014
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2 Responses to Team Questions Session 3

  1. Felipe Garcia (Asst Prof) says:

    i think question 3 is more related to the heating properties of the microwaves.

    Good work keep it up

  2. Felipe Garcia (Asst Prof) says:

    Hi guys, what about the other questions? in the first one think about the the way the earth emits, and what happens to that radiation,

    with respect to question 4 just think about short term and long term effects\

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