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The Kyoto Protocol
By Fred Pearce,
Environment Correspondent,
New
Scientist
Two things are inconvertible. Over the past century the world has been getting warmer; the past decade has been much the warmest since records began. and scientists predict that it will continue to heat up.
Two things are uncertain. First, it is not
yet clear what has caused global warming so far. Has it occurred because human
activities have added to the "greenhouse gases" in the atmosphere?
Or has it
resulted from natural temperature fluctuations?
Second, nobody knows precisely how much the world will warm for a given
amount of added greenhouse gases.
Much hinges on socalled "feedbacks" how the
planet itself responds to being warmed up.
The greenhouse effect is no myth.It is a natural feature of the atmosphere. Certain gases, such as water vapour, carbon dioxide (CO2) , and methane, are called "greenhouse gases" because they trap solar heat in the lower atmosphere. Without them, Earth would be frozen.
But humans are adding to these gases, producing pollutants that cause a gas buildup in the atmosphere. Most important of these human contributions is CO2, which is given off whenever we burn carboncontaining materials, such as coal, oil, or wood. CO2 remains in the atmosphere on average for more than a century.
Over the past 200 years, its concentration in the air has risen by a third, largely because growing population have burned more trees and failed to replace them and brecause they have begun to burn massive quantities of fossil fuels.
If we carry on as we are, there will be twice as much CO2 in the atmosphere by late next century. And the heating power of the sun at the earth´s surface will rise by about 4 watts per square metre to 240 watts. Not a lot, you might think. But it will raise temperatures directly by an average 1º C.
What in uncertain is how much the changes in the planet caused by warming will themselves amplify that warming. Most solar heat reaching polar regions is reflected from the white ice right back into space. If we melt some of the ice caps, less heat will be reflected. Likely results a warmer Earth. Global warming will also evaporate moere water from the oceans into the air. Water vapour is the most important greenhouse gas of all. So again,extra warming is likely.
Copyright 1996, The World Wild Fund For nature
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VOCABULÁRIO
features:
these:
average:
than
that:
more:
build up
RESPONDA EM PORTUGUÊS
1) Quais são os gases denominados "gases efeito estufa"?
2) Qual é a importância dos gases que causam o efeito
estufa?
3) O que aconteceria se não tivessemos o
vapor da àgua, o dióxido de carbono e o gás metano na atmosfera?
4) Qual é o gás que mais contribui para com a poluição da
atmosfera?
5) Por até quantos anos o CO2 permanece
na atmosfera?
6) Qual é a razão que levou a
triplicar a concentração de CO2 na atmosfera nos últimos 200 anos?
7) Qual será a temperatura média do sol até o final do século
21?
8) Qual é o mais importante dos gases que
produzem o efeito estufa?