Global warming

5. GLOBAL WARMING NATURAL CLIMATE VARIATIONS - The Earth’s climate has evolved in a cyclical way.

- During the ice ages, temperatures wer so low that an ice sheet (indlandsis o casquete de hielo)extended over the Earth’s surface.

- During interglacial periods, like the one we are in, temperatures increase and the ice sheet is limited to the polar regions and glaciers.

5. GLOBAL WARMING THE GREENHOUSE EFFECT - Carbon dioxide (CO2) and other greenhouse gases occur naturally in the atmosphere.

- They fulfil the function of maintaining a suitable temperature on the planet.

- They allow solar radiation to enter the atmosphere and retain part of the heat from the Sun.

5. GLOBAL WARMING GLOBAL WARMING -

Current climate studies have identified a steady rise in temperature over the past century, caused by both natural variability and human activity.

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Large- scale burning of coal and oil derivatives since the Industrial Revolution has produced an increase in CO2 emissions.

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This intensifies the greenhouse effect and contributes to global warming.

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This is producing changes in the global climate which affect all ecosystems.

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Over the last century, the Earth’s average temperature has increased by 0.74 ºC. This has caused a number of glaciers to retreat and sea levels to rise.

It does not appear that this increase can be explained only by natyral climate variations.

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