According to a weather expert's prediction. theatmosphere will be 3C warmer m the year 2050 than it is today, if man continues to bum fuelsat the present rate. If this warming up took place, the ice caps in the poles would begin to melt.thus raising sea level several meters and severely flooding coastal cities. Also, the increase inatmospheric temperature would lead to great changes in the climate of the northernhemisphere, possibly re9ulting in an alteration of the earth's chief food-growing zones.

　　In the past, concern about a man-made warming of the earth has concentrated on the Arcticbecause the Antarctic is much colder and has a much thicker ice sheet. But the weather expertsare now paying more attention to West Antarctic, which may be affected by only a few degreesof warming: in other words, by a warming on the scale that will possibly take place in the nextfifty years from the burning of fuels.

　　Satellite pictures show that large areas of Antarctic ice are already disappearing. The evidenceavailable suggests that a warming has taken place. This fits the theory that carbon dioxidewarms the earth.

　　However. most of the fuel is burnt in the northern Hemisphere, where temperatures seem to befalling. Scientists conclude. therefore. that up to now natural influences on the weather haveexceeded those caused by man. The question is: Which natural cause has most effect on theweather?

　　One possibility is the variable behavior of the sun. Astronomers at one research station havestudied the hot spots and "cold” spots (that is, the relatively less hot spots) on the sun. As thesun rotates, every 27.5 days. it presents hotter or "colder" faces to the earth, and differentaspects to different parts of the earth. This seems to have a considerable effect on chedistribution of the earth's atmospheric pressure, and consequently on wind circulation.The sun is also variable over a long term: its heat output goes up and down in cycles. chelatest trend being, downward.

　　Scientists are now finding mutual relations between models of solar-weather interactions andthe actual climate over many thousands of years, including the last Ice Age. The problem is thatche models are predicting that the world should be entering a new Ice Age and it is not. Oneway of solving this theoretical difficulty is to assume a delay of thousands of years while thesolar effects overcome the inertia (慣性) of the earth's climate. If this is right. the warmingeffect of carbon dioxide might thus be serving as a useful counterbalance to the sun’sdiminishing heat.

　　[1]大氣中二氧化碳的作用很像單向的鏡子——即鑲在溫室屋頂?shù)牟ＡВ试S陽(yáng)光進(jìn)入，卻阻止熱量散失。

　　據(jù)氣象專(zhuān)家預(yù)測(cè)，如果人類(lèi)繼續(xù)以目前的速度消耗燃料，到2050年時(shí)大氣溫度將比現(xiàn)在高3C。如果真的發(fā)生升溫，兩極的冰冠會(huì)開(kāi)始融化，從而使海平面上升幾米，違成海濱城市洪水泛濫。而且，大氣溫度升高也將引起北半球氣候劇變，可能會(huì)導(dǎo)致地球上主要的糧食生產(chǎn)帶發(fā)生變化。

　　過(guò)去，人們關(guān)注人為造成的地球升溫時(shí)，注意力集中在北極地區(qū)，因?yàn)槟蠘O寒冷得多，冰層也厚得多。但現(xiàn)在氣象專(zhuān)家更關(guān)注南極西部。因?yàn)榧词箿囟戎簧仙龓锥龋@個(gè)地區(qū)也會(huì)受到影響，也就是說(shuō)，在未來(lái)50年內(nèi)因?yàn)橄娜剂隙赡芤鸬哪欠N幅度的升溫，南極西部也會(huì)受到影響。

　　衛(wèi)星圖片顯示，南極大面積的冰塊正在消融。已有的證據(jù)表明，溫度已經(jīng)升高了。這種情況符合二氧化碳使地球變暖的理論。

　　然而，大部分燃料是在北半球消耗的，這里的溫度卻似乎在下降。科學(xué)家因此得出結(jié)論：到目前為止，自然因素對(duì)大氣的影響超過(guò)人類(lèi)因素的影響。問(wèn)題是：哪一種自然因素對(duì)天氣影響最大?

　　[3]一種可能性是變化無(wú)常的太陽(yáng)活動(dòng)。一個(gè)研究站的天文學(xué)家們研究進(jìn)太陽(yáng)表面的熱點(diǎn)和“冷”點(diǎn)(即相對(duì)而言不太熱的區(qū)域)。太陽(yáng)旋轉(zhuǎn)時(shí)，每隔27.5天，其較熱或較“冷”的一面就朝向地球，給地球上的不同地區(qū)帶來(lái)不同的特點(diǎn)。這似乎對(duì)地球上的氣壓分布影響很大，并因此影響大氣循環(huán)。從長(zhǎng)期來(lái)看，太陽(yáng)也是多變的：它的熱量輸出周期性地上升或下降，最近的趨勢(shì)是下降。

　　科學(xué)家現(xiàn)在發(fā)現(xiàn)了太陽(yáng)-天氣互動(dòng)模式與包括上一個(gè)冰川期在內(nèi)的幾千年間的實(shí)際氣候之間的相互關(guān)系。[4]問(wèn)題是，互動(dòng)模式預(yù)示世界應(yīng)該正進(jìn)入新的冰川期，但事實(shí)上并沒(méi)有出現(xiàn)這樣的情況。解決這個(gè)理論難題的一個(gè)方法是做這樣的假設(shè)：太陽(yáng)雖然對(duì)地球有影響，但要克服地球氣候的慣性，因此冰川期要推遲幾千年到來(lái)。[5]如果這個(gè)假設(shè)成立，二氧化碳的溫室效應(yīng)可以對(duì)太陽(yáng)正在下降的熱量起到有益的抵消平衡作用。