於1996年的「IPCC」預測在2100年全球地表的平均溫度將會上升華氏2到6度，且除非限制溫室氣體的排放量，否則這種增溫趨勢將持續進行。「IPCC」同時也預測這種升溫現象可能造成的結果，包括：在2100年海平面將升高6至37英吋；極端的氣候型態（如熱浪和乾旱）出現的頻率及長短將增加；由於高溫使得水蒸發的速率加快，許多地區豪雨及水災的機率也會增加。這種極端的降雨現象已經開始在美國(有完整的資料可比對)出現。
氣候變遷對人類健康有負面的影響，且影響範圍廣泛。如熱浪頻率愈高，死亡率愈高，並且增加許多傳染病發生的區域，如將瘧疾和登革熱帶到溫帶地區（包括部分的美國）。
由於50％至70％的人口居住在海岸邊，海平面的上升及愈來愈多的狂風巨浪對人類將有毀滅性的影響，上百萬人的家園可能遭受到定期的洪水侵襲甚至於永遠沈沒於海中；諸如非洲等熱帶地區由於氣候變遷降低農作物產量，這些地區的居民已經愈來愈營養不良及必須忍受長期的飢荒；至於溫帶或北方的區域，其農作物的產量增加與否，則視氣候變遷對害蟲、雜草繁殖速率所造成的影響而定。
全球溫暖化在下一世紀將改變許多自然的生態系，尤其是較高緯度的生態系（如靠近北極的森林和凍原）可能將使三分之一的森林組成改變，及沿海生態系嚴重影響到漁場及海洋生物的多樣性。
我們的挑戰
有效且及時地處理氣候變遷的問題可能是目前世界各國有史以來所面對到最棘手、複雜的挑戰。由於過去排放的溫室效應氣體會停留在大氣層中一個甚至更多世紀，所以全球溫暖化的趨勢目前已無法避免。此外政府體系對於未來環境變化造成的威脅，應變能力通常不足。以全球溫暖化的例子來說，許多經濟上具有決定性的重大國家或組織，包括：石油公司、石油輸出國家、以及許多如汽車、石化、金屬製造等相當依賴石油的工業，還有如英國石油及殼牌等總部位於歐洲的跨國性石油公司最近才終於接受全球溫暖化的事實，而開始投入資金在尋求替代的能源，並且保證降低溫室氣體的排放量。
發展中國家帶來進一步的不確定性。雖然工業國家尤其美國試圖降低溫室氣體排放量，但是發展中國家的排放量正處於快速增加的時期，而其排放量在下一世紀將可能遠超過工業國家。這些國家是否願意簽署條約限制排放量，將取決於他們是否相信很快的便有乾淨又有效率的能源系統出現，以及他們是否能充分獲得工業國家的資助。在「布宜諾斯艾利斯」有一個較正面的進展：阿根廷和哈薩克這兩個發展中國家共同簽訂一份聲明，聲明中指出他們願意逐步地降低溫室氣體的排放量。
Leonie Haimson是 Liberty Tree Alliance網站的前特約專欄作家，也是「The Way Things Really Are: Debunking Rush Limbaugh on the Environment」的作者之一
In 1996, the IPCC projected that the average surface temperature of the Earth would rise another two to six degrees Fahrenheit by the year 2100, with continued increases thereafter, unless concerted measures are adopted to limit the emissions of greenhouse gases. The IPCC has predicted several probable consequences of future warming, including sea level rises of an additional six to 37 inches by the year 2100, and increased frequency and duration of many extreme weather events, such as heat waves and droughts. Heavy rains and flooding are also predicted to occur more frequently in many parts of the world, since higher temperatures lead to more rapid rates of evaporation and precipitation. In the United States, where the best data are available, an increased number of extreme rainfall events has already been observed.
Climate change is likely to have wide-ranging and mostly adverse effects on human health. The greater frequency of heat waves is expected to raise mortality rates from heat stress, and to enlarge the potential ranges of many infectious diseases, for example, bringing malaria and dengue fever into the temperate zone, including parts of the United States.
For the 50 percent to 70 percent of the human population living in coastal areas, rising sea levels and more frequent storm surges could have devastating effects, subjecting millions of people's homes to periodic flooding or permanent submergence. In many parts of the tropics such as Africa, where inhabitants are already prone to malnutrition and famine, harvests are projected to decline as a result of climate change. In some temperate and northern regions, agricultural production could increase, depending on how the expected proliferation of pests and weeds due to climate change balances out the fertilizing effects of increased carbon dioxide.
Global warming also has the potential to transform many of the world's natural ecosystems over the next century, causing, for example, about one-third of the Earth's forested area to undergo major shifts in composition. Among ecosystems most likely to experience serious disruption are those at higher latitudes, such as far northern forests and tundra, as well as coastal ecosystems, with dramatic consequences for fisheries and marine biodiversity.
Our Challenge
Addressing the problem of climate change in an effective and timely manner is probably the most complex and difficult challenge the nations of the world have ever faced. Additional warming is already inevitable, given past emissions, since most greenhouse gases once released remain in the atmosphere for a century or more. Moreover, political systems usually respond inadequately in anticipation of future threats. In this case, there are powerful economic interests fighting decisive action, including the fossil fuel corporations and their allied unions, OPEC countries, and the many industries that rely heavily on the use of fossil fuels, such as auto, chemical, and metal-producing companies. Nevertheless, several multinational oil corporations headquartered in Europe, including British Petroleum and Shell, have recently accepted the reality of global warming, begun to invest more intensively in alternative energy, and pledged to reduce their emissions of greenhouse gases.
Developing nations bring further uncertainties to the mix. Though the industrialized countries, especially the United States, lead the world in per capita greenhouse gas emissions, the total emissions of developing nations are growing at a faster rate and are expected to surpass those of the industrialized world early in the next century. Whether these countries can be persuaded to enter into binding agreements to cap their emissions will most likely depend upon whether they believe they will be able to develop fast enough by adopting clean, efficient energy systems, and whether they will be sufficiently assisted in doing so by the richer, industrialized nations. One positive step forward in Buenos Aires was an announcement from two members of the developing world bloc, Argentina and Kazakhstan, that they will voluntarily take steps to limit their emissions.
Leonie Haimson was the climate columnist for the former Liberty Tree Alliance website. She co-authored The Way Things Really Are: Debunking Rush Limbaugh on the Environment for the Environmental Defense Fund, and edited Common Questions on Climate Change for the U.N. Environment Program.
版權歸屬 Earth Day Network，環境信託協會
