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Global warming

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The increase of concentration of carbon dioxide and other greenhouse gases posed a threat to the earth’s ability to regulate the amount of heat retained in the atmosphere. The increase of heat seriously threatens the global climate equilibrium that determines the patterns of winds, rainfalls, surface temperatures, ocean currents and sea level.

Over the past century the planet has warmed 0,3 to 0,6 degree C. Most of the scientists think that this warming was caused by human activities but there are some skeptics who believe to reflect the natural variability of the global climate.

With every passing year the scientific case for greenhouse warming from human causes continues to strengthen. Still some uncertainty remains as to global warming, as well as to how exactly it will affect earth’s ecosystems and people.

Global warming is expected to rise much more rapidly in the polar regions than in the rest of the world. As the polar air warms, the ice here will thin, and since the polar cap plays a crucial role in the world’s weather system, the consequences could be disastrous. And this process has already begun. The thick ice that has for ages covered the Arctic Ocean at the Pole has turned to water. In August 2000 an ice free patch of ocean about a mile wide was opened at the very top of the world. The Russian icebreaker “Yamal” with tourists aboard reached the North Pole for the first time in human history.

Scientists compared data collected by submarines in the 1950s and 1960s with observations from the 1990s and came to the conclusion that the ice cover over the entire Arctic basin has thinned by 45 per cent. Besides this the extent of ice coverage has significantly shrunk in recent years.

In many land areas north of the Arctic Circle the spring snowmelt now comes earlier every year and deeper in the tundra below, the temperature is steadily rising. If the frozen tundra thaws, enormous quantities of methane are expected to be produced and released into the atmosphere. Since each methane molecule is twenty times more effective in trapping heat than each molecule of carbon dioxide, there will be a great increase in the overall concentrations of greenhouse gases and global warming will be accelerated.

Since the 1960s warmer average temperatures have brought an earlier spring and a later winter over the higher latitude areas of the Northern Hemisphere, advancing the growing season by about 7 days in spring and extending it about 2 to 4 days in the fall. This has spurred greater plant growth over a wide swath of territory, including Alaska, Canada, Scandinavia, Northern Europe and northern sections of Russia and China. Scientific studies also show a 10 per cent reduction of snow cover in higher latitudes.

Not only the plants reacted to surface warming. Field studies of a small American butterfly, known as Edith’s checkerspot butterfly, have shown the first convincing evidence that the geographic range of an animal species has shifted in response to climate change. Scientists have long ago predicted, that as global temperatures get warmer, the geographic ranges of plants and animals will shift toward the poles or to higher elevations to maintain their preferred temperature conditions. This is precisely what happens to the checkerspot. Over a number of decades, butterfly colonies on the southern limit of the range died, while new colonies formed on the northern limit of the range and also at higher elevations. But many other species of plants and animals will not be as lucky as checkerspot – global development and habitat loss will stand in their way, increasing the possibility of extinction for them.

Global warming will dramatically change the face of the Earth. If the polar ice caps melt, the sea level will rise and low-lying territories with very dense populations will disappear. This will cause massive migrations of people. For example, about ten million residents of Bangladesh will lose their homes. Where will they go?

Global warming is expected to change winds and ocean current patterns. As a result vast territories of rich, fertile lands will turn into deserts.

Such disasters as tornados, floods, droughts and hurricanes may become more frequent, and occur, in such places where they never (or seldom) happened before.

Computer models predict that global warming will expand the incidence and distribution of many illnesses, such as malaria, yellow fever, cholera and several kinds of encephalitis.

Mosquitoes, which transmit malaria parasites, can live only where temperatures routinely exceed 15 degrees C. Winter freezing kills their eggs and adults. But as the air becomes warmer, mosquitoes proliferate faster and bite more people. As the whole areas heat up, mosquitoes will expand into formerly forbidden territories, brining illnesses with them. Some models predict that by the end of the 21st century malaria will spread to the north and south of the tropics, including the eastern states of the USA, nearly all European countries, the European part of Russia, and vast territories of the Siberia.




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