Английский язык

Greenhouse effect. A car or greenhouses are heated under the sun, because light energy sinking inside through the glass is absorbed and converted into the thermal energy that cannot pass through the glass. When the heat is trapped in this way, temperature rises. The Earth's atmosphere is heated likewise: light goes through the atmosphere while greenhouse gases, that act as "a blanket" holding heat, absorb infrared radiation. For instance, the temperature and climate we are used to are ensured by carbon dioxide concentration in the atmosphere at the level of 0.03 %. By raising this concentration, we increase the tendency for climate warming. Thus, the higher the greenhouse gas concentration, the stronger the greenhouse effect.

Greenhouse gases make up around 0.1 % of the atmosphere, which is mainly comprised of nitrogen –78 % and oxygen – 21 %. The main greenhouse gases enhancing anthropogenic changes in the atmosphere are carbon dioxide (CO₂) methane (CH₄), nitrous oxide (N₂O)and chlorofluorocarbons (CFCs).

Forests on the Earth occupying around 28 percent of the land and the world's oceans occupying 70 % of the total surface of the Earth can influence the global carbon cycle, the level of atmospheric CO₂ and the climate. While growing, forests absorb carbon dioxide from the atmosphere and accumulate it in phytomass and forest humus. According to assessments of the World Wildlife Fund, forests account for 80 % of carbon contained in vegetation and 40 percent of the total soil carbon. Scientists estimated that every year 1.6+1.0 billion tons of carbon are emitted into the atmosphere due to destruction of forests and land use change.

Carbon dioxide concentration in the world's oceans is several times higher in the deep than at the surface. This is because the level of inorganic carbon dissolved in water in the form of bicarbonate ions in equilibrium with CO₂ is almost two orders more than in the atmosphere. If life in the ocean ceases, concentration of inorganic carbon in the depth and at the surface will become equal, leading to manifold increase in the atmospheric CO₂ concentration. Therefore, the ocean biota regulates atmosphere CO₂ concentration and through this regulations maintains the surface temperature within the limits optimal to the life. A number of climatologists suggest that the world's oceans have a great potential to absorb CO₂, and when water temperature rises, the capability of the ocean to absorb carbon increases. Thus, we can infer that the world ocean will probably play a stabilizing role in the carbon dioxide balance in global warming.

5. Answer the following questions:

1. Which gases are greenhouse gases?

2. Why is it necessary to differentiate between the natural greenhouse effect and anthropogenic greenhouse effect?

3. What changes does the anthropogenic greenhouse effect entail?

4. In what way do forests and oceans influence the global carbon cycle?

5. Which role does the World Ocean play in the carbon dioxide balance?

6. Read and render the following text.

Treat of Global Climate Change.

Some scientists believe that the global climate warming can have positive effects. For instance, agricultural crops and livestock yield can increase. That means the local climate change. However, despite these assumptions, it is as yet unknown how microorganisms will behave that can impact the quality of water, soils and air. We all are witnesses of hurricane winds, dust storms, and soil salinization and flooding even in quite safe areas.

Modeling of climatic processes shows that this concentration of greenhouse gases will entail an average warming of the Earth's surface by 1.5-4.5 ^oC. Warming will probably be stronger in polar areas (up to10 ^oC) and less – near the equator (1-2 ^oC). Significant differences arise relating to how this warming will influence cloudiness and how it will affect the distribution of solar radiation. However no one repudiates the probability of warming.

At first sight warming seems moderate. However, air temperature increases by 4.5 – 5.5 ^oC above the peaks of 38^o C can be catastrophic. Moreover such warming will entail melting of mountain and polar ices sufficient to raise the world ocean level by 1.5 m. This will cause flooding and more exposure of vast littoral areas to storms, i.e. it will force people to leave settled coastal areas and migrate deep inland. In this connection many countries of the world face a number of vital questions. To what extent are we ready to rearrange and re – equip all seaports with regard to rising sea levels? Are the inland cities and towns ready to receive millions of resettled people? These and other acute questions require answers.