第1个回答 2014-03-06
THE EARTH IS BECOMIG WARMER-BUT DOES ITMATTER?
During the 20th century the temperature of the earth rose about onedegree Fahrenheit. That probably does not seem much to you or me, but it is arapid increase when compared to other natural changes. So how has this comeabout and does it matter? Earth care's Sophie Armstrong explores thesequestions.
There is no doubt that the earth isbecoming warmer(see Graph 1) and that it is human activity that has caused thisglobal warmig rather than a random but natural phenomenon.
All scientists subscribe to the view that the increase in theearth's temperature is due to the burning of fossil fuels like coal, naturalgas and oil to produce energy. Some byproducts of this process are called"greenhouse" gases, the most important one of which is carbondioxide. Dr Janice Foster explains: "There is a natural phenomenon thatscientists call the "greenhouse effect".This is when small amounts ofgases in the atmosphere, like carbon dioxide, methane and water vapour, trapheat from the sun and therefore warm the earth. Without the'greenhouse effect
the earth would be about thirty-threedegrees Celsciu cooler than it is. So, we need those gases. The problem beginswhen we add huge quantities of extra carbon dioxide into the atmosphere. Itmeans that more heat energy tends to be trapped in the atmosphere causing theglobal temperature to go up.
We know that the levels of carbon dioxide have increased greatlyover the last 100 to 150 years. It was a scientist called Charles Keeling, whomade accurate measurements of the amount of carbon dioxide in the atmospherefrom 1957 to 1997. He found that between these years the carbon dioxide in theatmosphere went up from around 315 parts to around 370 parts per million(seeGraph 2)
All scientists accept this data. They also agree that it is theburning of more and more fossil fuels that has resulted in this increase incarbon dioxide. So how high will the temperature increase go? Dr Janice Fostersays that over the next 100 years the amount of warming could be as low as 1 to1.5 degrees Celsius, but it could be as high as 5 degrees.
However, the attitude of scientists towards this rise in completelydifferent. On the one hand, Dr Foster thinks that the trend which increases thetemperature by 5 degrees would be a catastrophe. She says, " We can'tpredict the climate well enough to know what to expect, but it could be veryserious." Others who agree with her think there may be a rise of severalmetres in the sea level, or predict severe storms, floods, droughts, famines,the spread of diseases and the disappearance of species. On the other hand,there are those, like George Hambley, who are opposed to this view, believethat we should not worry about high levels of carbon dioxide in the air. Theypredict that any warming will be mild with few bad environmental consequences.In fact, Hambley states, "More carbon dioxide is actually a positivething. It will make plants grow quicker; crops will produce more; it willencourage a greater range of animals-all of which will make life for humanbeings better."
Greenhouse gases continue to build up in the atmosphere. Even if westart reducing the amount of carbon dioxide and other greenhouse gases, theclimate is going to keep on warming for decades or centuries. No one knows theeffects of global warming. Does that mean we should do nothing? Or, are therisks too great?本回答被提问者采纳