Unit 10. The greenhouse effect

The near-ultraviolet radiation from the Sun produces the ozone (0₃) layer, which in turn shields the Earth from such radiation. Almost all ul­traviolet radiation is absorbed by the ozone layer and oxygen. This is vi­tally important for living things because ultra-violet is extremely harm­ful and potentially lethal to most forms of life.

The atmosphere is almost perfectly transparent to incoming radiation of the visible band. The Earth reradiates this energy as infrared (heat) waves. Water vapor, carbon dioxide (C0₂), nitrous oxide (N₂0), ozone (0₃), and some other gases absorb infrared wavelengths, much of which gets reradiated back toward the Earth (see fig. 2). The atmosphere there­fore behaves like glass in a greenhouse, allowing passage of light rather than heat. This phenomenon is termed the «greenhouse effect». If the Earth had no atmosphere (but the same reflectivity to solar radiation, or albedo, as it has now), its average surface temperature would be -18 °C instead of comfortable +15 °C found today. Thus, the result of green­house effect is a net wanning of the earth-atmosphere system and the Earth surface temperature.

Fig. 2. The greenhouse effect. Atmosphere, like glass in a greenhouse, prevents in­frared radiation escape

The first law of thermodynamics states that when energy of one from disappears, an equivalent amount of energy appears in some other from. It means that, in any case, light energy can be neither created nor de­stroyed as it passes through the atmosphere. It may, however, be trans­formed into equivalent amount of another type of energy, such as bio­chemical energy , energy of motion (kinetic energy), or heat.

According to the second law of thermodynamics the efficiency of any energy transformation is never «perfect»: when energy changer from one from to another, some of the energy is lost to the system as «useless» heat. The laws of thermodynamics hold for all energy trans­formations, including those involving the biochemical energy of life. In accordance with these laws, the earth-atmosphere system balances ab­sorption of short-wave solar radiation bv emission of long-wave infrared (heat) radiation to space.

Exercise 1. Review the questions.

1. What is the source of energy supporting all life and meteorological processes?

2. What is the energy flux: a) entering the outer atmosphere; b) teach­ing the Earth’s surface?

3. Why doesn't all energy radiated by the Sun reach the Earth’s sur­face?

4. What part of the Sun’s radiation falls in the visible band of the so­lar spectrum?

5. What happens to the ultraviolet portion of solar radiation when it passes through the atmosphere?

6. To what radiation is the atmosphere more transparent: to the visi­ble sunlight or to heat (infrared) radiation?

7. What would the average Earth’s surface temperature be if there were no greenhouse effect?

8. Why do we call the first law of thermodynamics the law of energy conservation?

9. What is the second law of thermodynamics?

Exercise 2. Look at and answer the questions.

1. What colors give the white color when mixed?

2. Is it correct: the shorter the radiation wavelength the higher its quanta energy?

3. What is the wavelength band of the visible light (in meters and na­nometers)?

4. What is the wavelength range in which the Earth releases the energy?

5. Which light has a longer wavelength, green, red or violet?

Exercise 3. Translate the words:

1) ozone; 2) solar; 3) mineral; 4) toxic; 5) spectrum; 6) thermonu­clear; 7) process; 8) lethal; 9) hydrogen; 10) ultraviolet; 11) oxygen.

Exercise 4. Say it in English using the following phrases: would be provided, for drive, such as, the outer layer, reach, the remaining part, vitally important, reradiate, behave like glass, let light pass prevent... escape, conservation, neither ... nor, total amount, according to ..., is lost to the system, useless, the laws hold forincluding.

1. Жизнь на земле была бы невозможной без солнечной энергии. Солнечное излучение обеспечивает жизнедеятельность всех экоси­стем в биосфере, управляет системой климата и всеми метеороло­гическими процессами на земле, такими как ветер, дожди, волны в океанах и другими.

2. Солнечная постоянная — это поток энергии, достигающий внешнего слоя атмосферы. Солнечная постоянная равна 1367 Вт/м², но только около 150 Вт/м достигает поверхности земли.

3. Около половины энергии излучения солнца падает на землю в видимом диапазоне длин волн, около 2 % — в ультрафиолетовом диапазоне, а остальная часть — в ближнем инфракрасном. Почти вся ультрафиолетовая радиация поглощается озоновым слоем и ки­слородом атмосферы, что жизненно важно для биосферы.

4. Земля переизлучает солнечную энергию в космическое про­странство в виде тЪплового излучения (тепла). Атмосфера ведет се­бя подобно стеклу в теплице: она позволяет проходить свету, но препятствует уходу тепла.

5. Первый закон термодинамики — это закон сохранения энергии. Энергия в замкнутой системе не может ни создаваться, ни уничто­жаться; она преобразуется из одной формы в другую, и ее общее количество является постоянной величиной.

6. Согласно второму закону термодинамики, когда энергия пре­образуется из одной формы в другую, некоторое количество энер­гии теряется системой как «бесполезное» тепле.

7. Законы термодинамики справедливы для всех процессов пре­вращения энергии, включая биологические процессы.

Exercise 5. Read the numbers and units of measure.

1. 2 — zero point two, point two

25. — one point twenty five 4'¹ — four and five seventh

3² — three squared, three square three to the power of two 10 ⁷ — ten to the minus seventh power

1 m — one meter

I cm — centimeter

1 mm — millimeter

1 nm — 1 nanometer

1 W/m² — one watt per square meter

1 billion = 10⁹ (here «billion» is used as it is accepted in the USA)