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World issues

Global warming

The retreating Pasterze Glacier, Austrian AlpsThe retreating Pasterze Glacier, Austrian Alps The Earth is becoming warmer. The average temperature has risen by more than 0.5°C in the past century and is predicted to rise by 2°C by 2050—although this figure is far from certain. The effects may be felt by more frequent droughts or floods, violent storms and changing climates. Glaciers are retreating (shrinking). The ice caps at both poles may start to melt, resulting in rising sea levels and the flooding of coastal regions where most cities are located. The acidification of the oceans, the extinction of many animal species, and the steep decline in crop yields are among the other disastrous possible effects of global warming. Most scientists are convinced that human activities—industries, power stations, cars and planes—has contributed to a huge increase in what are known as greenhouse gases (including carbon dioxide and methane) in the atmosphere, causing global warming.

Emissions that increase greenhouse gasesEmissions that increase greenhouse gases

The greenhouse effectThe greenhouse effect

Greenhouse effect

The Sun’s rays warm the surface of the Earth. The surface then reflects this radiation back into space. Some gases in the atmosphere, such as carbon dioxide (CO2) and methane, trap part of this outgoing radiation, keeping the surface warm—just like a greenhouse. But an excessive amount of these greenhouse gases warms up the Earth too much. Human activities have resulted in a large increase of greenhouse gases, especially carbon dioxide, in the atmosphere. Vehicles and power stations give off exhaust gases from burning oil or coal (“fossil fuels”). These add billions of tonnes of carbon dioxide to the atmosphere.
The carbon cycleThe carbon cycle

The ice shelves of West Antarctica are so vast that, if they melted completely—global warming may one day achieve this outcome—the water released into the ocean from these alone would cause sea levels to rise globally between one and three metres (3–10 ft).

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