生命電視 台中五方講堂

作者：諾姆．莫爾(Noam Mohr)

《摘要》

全球暖化讓全球環境面臨人類有史以來最嚴重的威脅。但因為焦點全部集中在二氧化碳的排放，主要的環保組織所發表的數據，無法顯示我們今天所得知的其他氣體，才是造成全球暖化的主要元兇。結果，他們自然就忽略可以在一生當中，有效降低全球暖化效應的最佳對策：倡導素食。

全球暖化與二氧化碳

    環保團體認為全球暖化對地球形成的威脅最大，這個面向是正確的，全球氣溫已經至少高於過去千年以來的記錄，而且增加的速度遠超過科學家的預測值，該預期後果包括沿海氾濫、極端異常氣候的增加、疾病的蔓延和大量的物種滅絕。

    很遺憾地，環保團體投注的焦點，只放在減少二氧化碳的排放方面，國家立法全神貫注在提高燃油經濟標準、降低發電廠的二氧化碳排放量、及投資替代能源等方面。對一般消費者的建議也集中在二氧化碳面向：買燃油效率佳的車和家電，並且減少使用頻率。

    這是很嚴重的誤判，根據傑姆斯漢森(James Hansen)博士等人所發表的數據顯示，由大氣中觀測導致暖化的主要因素，不是二氧化碳的排放，雖然聽起來像是在質疑全球暖化的研究工作，但實際並非如此：漢森是美國太空總署戈達德太空研究院(Goddard Institute for Space Studies)主任，擁有「全球暖化論始祖」的封號。他長期支援抗暖化行動，其理論曾被艾爾高爾及經常為環保組織所引用，他常和以推翻科學驗證過程為目的的質疑者辯論。他的結論受到全球暖化專家們的普遍採納，包括傑姆斯麥克卡西(James McCarthy )博士—聯合國政府間氣候變遷小組第二工作團聯合主席等大人物在內。

    把焦點單獨集中在二氧化碳，會加深誤解的程度。人類行為會產生大量的二氧化碳，比其他所有溫室氣體加起來還要多，這是正確的，然而，這並不代表二氧化碳就是地球暖化的最大禍首。很多其他的溫室氣體，吸熱能力比二氧化碳還強很多，有一些甚至具有成千上萬倍的威力。當我們談及不同溫室氣體導致暖化的潛力時--所定義的氣體為在未來一百年，其數量會導致暖化現象者--結果發現，其他氣體所造成的全球暖化問題，比二氧化碳還要嚴重。

    除了過度渲染二氧化碳的影響之外--因為廢氣排放的主要來源是汽車和發電廠—其同時也會產生氣膠(Aerosol)微粒。氣膠事實上具有可以冷卻全球氣溫的成分，而其大量的冷卻作用，差不多可以抵銷二氧化碳的暖化效應。出人異料之外的結果是，二氧化碳排放源對全球氣溫的影響，在近期內將會被調整為趨近於零。

    因為擔心製造污染的企業，會以該理由做為排放廢氣的擋箭牌，所以該結果尚未完整地透露給環保團體，例如，憂思科學家聯盟（Union of Concerned Scientists)，已將數據交由其他氣象專家審查，漢森的結論也獲得正面的認定。但是，該組織也同樣採用持反向意見氣候專家所誤用的數據，以反對二氧化碳的抑制，這種對立意見的糾葛是無法釐清的。

    雖然二氧化碳在近期所造成的影響很有限，但在長期而言，減量對氣候變遷仍有關鍵性的影響。氣膠的存續期間很短，只能在空氣中存續幾個月的時間，而二氧化碳對大氣的加溫作用，卻可以持續數十年到數世紀之久。此外，我們無法假設氣膠的排放速度，會與二氧化碳並駕齊驅。假如我們今天一開始就失去對抗二氧化碳的良機，在我們被廢氣排放淹沒時，即為時晚矣。

    儘管如此，我們仍然可以看到非二氧化碳溫室氣體源，確是實際導致全球暖化的主因，加上未來五十年我們即將面臨的全球暖化現象，這些事實將會如影隨形。如果我們希望抑制未來半世紀的全球暖化趨勢，必須正視非二氧化碳的廢氣排放，並採行因應對策，而最佳的策略就是素食。

甲烷與素食主義

    最重要的非二氧化碳溫室氣體，顯然就是甲烷，而全球最大的甲烷來源，就是畜牧業。

    甲烷所造成的全球暖化效應，幾乎是所有其他非二氧化碳溫室氣體的總和。甲烷是一種溫室效應威力，比二氧化碳強21倍的溫室氣體，當大氣中的二氧化碳濃度，高達工業革命前的31%，甲烷濃度卻已超過兩倍。人為因素的二氧化碳排量，只佔自然界來源的3%，而甲烷卻是自然界的1.5倍。事實上，人類所致甲烷的釋放作用，可能加重暖化情形，反過來刺激濕地有機微生物的腐敗--這是自然界甲烷的最主要來源。

    由於全球人為所致的暖化現象，幾乎有一半是甲烷排放所造成，因此，減少甲烷排量應是當務之急。甲烷的來源包括煤礦業和垃圾掩埋--但遍布全球的最大來源是畜牧業，一年可以製造一億噸的甲烷，而且該數字仍在持續上升中：全球肉品消耗量在過去五十年已翻升五倍，而且看不到什麼減少的跡象，約85%的甲烷源自牲畜的消化過程，雖然一頭牛所釋放的甲烷量相當少，但全世界數以億萬計的牲畜，對環境產生的集體效應卻相當鉅大。畜牧業另外15%的甲烷排放來自大量的「鹹水湖」，用來儲存未處理過的牲畜排泄物，而且在美國早已被環保人士以污染水源的禍首名義，成為眾矢之的。

    結論很簡單：減緩全球暖化最有效的方法，可以說是減少或避免肉品消費。只要加入素食(或嚴格一點：純素)行列，我們就可以遏止甲烷排放的最主要來源--這個要為當今造成全球暖化效應，負起幾乎一半責任的溫室氣體。

素食的優點多於二氧化碳減量

    除能立刻降低全球暖化效應的優點之外，改食用無甲烷排放的食品，要比找出降低二氧化碳排量的切入點更為容易。

    首先，不需限制溫室氣體減量，因為在採行素食的過程中，即可以達到該效果。原則上，甚至可以做到100%減量，只會略微產生一點負作用而已，相反地，要透過減少二氧化碳達到相同的減量效果，無法避免對經濟產生破壞作用，即便是信心十足的二氧化碳削減策略，也還達不到削減一半的程度。

    第二，改為較低溫室氣體排放的飲食，比改變石化燃料技術，以消除二氧化碳的排放要快，大部分的反芻動物農場，牲畜進出率為一至兩年，所以減少肉品消費，幾乎可以立即明顯降低甲烷的排放，汽車和發電廠的更新率，換言之要花數十年，即便很便宜，而且也有無廢氣排放的燃料可供使用，但當今我們經濟所仰賴的大量基礎建設，也要花多年的時間建造，並且緩慢地逐步替換。

    同樣地，甲烷不像二氧化碳可以在空氣中存續一個世紀以上，它只能在大氣中循環八年，所以降低甲烷的排放量，可以快速地讓地球清涼一點。

    第三，削減二氧化碳排放，要和汽車與石油企業等強權和富豪事業相抗衡，耗時費力。環保團體已就高效能燃油的休旅車，及淘汰無法符合現代環保標準的發電廠等議題，進行多年的遊說行動，仍然無疾而終。而在此同時，素食品卻隨手可得，而且每餐都能發揮減少農牧業甲烷排放的作用。

    另外，民意調查顯示，民眾關心全球暖化現象已經很普遍，而熱心環保人士卻時常感到心有餘而力不足，除非是剛好要買車或大型電器，多數人都想盡點心力、做些改變，但除了寫信給國會議員和關掉電燈之外，卻不知道要由何處切入。減少或避免肉品消費，是關心全球暖化的民眾，每天都能採取的幫助地球行動。

    最後，值得一提的是，降低源自飼養牲畜的溫室氣體，對環境有很多附帶利益，因為較少的甲烷含量，可以減少對流層所含的臭氧量，它會污染及危害到人類健康和農作物。此外，排放甲烷的工廠化農場，同樣也耗盡國家的供水系統，大部份的野生環境被剷平，供做牧場用地和種植飼料作物。增建牧場以滿足西式與日俱增的肉品食慾，已經是造成第三世界國家伐林及沙漠化的主要原因。在美國，工廠化農場囤積排泄物的鹹水湖，是造成水源污染的頭號元兇，確實，由於畜牧業對石化燃料的高度需求，一般美國人的飲食所產生的二氧化碳污染，遠超過一個蔬食者。

良心建議

‧各類型的組織團體，應考慮將推廣素食，列入抗全球暖化活動的主要項目之一，至少積極倡導環保的人士，應該在任何對抗全球暖化的活動中，建議個人可以採取的實質行動，提到素食。

‧政府應擬定政策鼓勵素食，可採取的機制包括對肉品課徵和汽油一樣的環保稅，提供農牧場轉型補助金，鼓勵種植農作物而非畜牧，或由政府經辦加強素食方案，例如學校營養午餐或發行素食糧食券等。

A New Global Warming Strategy:

How Environmentalists are Overlooking Vegetarianism as the Most Effective Tool Against Climate Change in Our Lifetimes
by Noam Mohr

Download the Full Report (.pdf)

Summary
Global warming poses one of the most serious threats to the global environment ever faced in human history. Yet by focusing entirely on carbon dioxide emissions, major environmental organizations have failed to account for published data showing that other gases are the main culprits behind the global warming we see today. As a result, they are neglecting what might be the most effective strategy for reducing global warming in our lifetimes: advocating a vegetarian diet.

Global Warming and Carbon Dioxide
The environmental community rightly recognizes global warming as one of the gravest threats to the planet. Global temperatures are already higher than they’ve ever been in at least the past millennium, and the increase is accelerating even faster than scientists had predicted. The expected consequences include coastal flooding, increases in extreme weather, spreading disease, and mass extinctions.

Unfortunately, the environmental community has focused its efforts almost exclusively on abating carbon dioxide (CO2) emissions. Domestic legislative efforts concentrate on raising fuel economy standards, capping CO2 emissions from power plants, and investing in alternative energy sources. Recommendations to consumers also focus on CO2: buy fuel-efficient cars and appliances, and minimize their use. ,

This is a serious miscalculation. Data published by Dr. James Hansen and others show that CO2 emissions are not the main cause of observed atmospheric warming. Though this may sound like the work of global warming skeptics, it isn’t: Hansen is Director of NASA’s Goddard Institute for Space Studies who has been called “a grandfather of the global warming theory.” He is a longtime supporter of action against global warming, cited by Al Gore and often quoted by environmental organizations, who has argued against skeptics for subverting the scientific process. His results are generally accepted by global warming experts, including bigwigs like Dr. James McCarthy, co-chair of the International Panel on Climate Change’s Working Group II.

The focus solely on CO2 is fueled in part by misconceptions. It’s true that human activity produces vastly more CO2 than all other greenhouse gases put together. However, this does not mean it is responsible for most of the earth’s warming. Many other greenhouse gases trap heat far more powerfully than CO2, some of them tens of thousands of times more powerfully. When taking into account various gases’ global warming potential—defined as the amount of actual warming a gas will produce over the next one hundred years—it turns out that gases other than CO2 make up most of the global warming problem.

Even this overstates the effect of CO2, because the primary sources of these emissions—cars and power plants—also produce aerosols. Aerosols actually have a cooling effect on global temperatures, and the magnitude of this cooling approximately cancels out the warming effect of CO2. The surprising result is that sources of CO2 emissions are having roughly zero effect on global temperatures in the near-term!

This result is not widely known in the environmental community, due to a fear that polluting industries will use it to excuse their greenhouse gas emissions. For example, the Union of Concerned Scientists had the data reviewed by other climate experts, who affirmed Hansen’s conclusions. However, the organization also cited climate contrarians’ misuse of the data to argue against curbs in CO2. This contrarian spin cannot be justified.

While CO2 may have little influence in the near-term, reductions remains critical for containing climate change in the long run. Aerosols are short-lived, settling out of the air after a few months, while CO2 continues to heat the atmosphere for decades to centuries. Moreover, we cannot assume that aerosol emissions will keep pace with increases in CO2 emissions. If we fail start dealing with CO2 today, it will be too late down the road when the emissions catch up with us.

Nevertheless, the fact remains that sources of non-CO2 greenhouse gases are responsible for virtually all the global warming we’re seeing, and all the global warming we are going to see for the next fifty years. If we wish to curb global warming over the coming half century, we must look at strategies to address non-CO2 emissions. The strategy with the most impact is vegetarianism.

Methane and Vegetarianism
By far the most important non-CO2 greenhouse gas is methane, and the number one source of methane worldwide is animal agriculture.

Methane is responsible for nearly as much global warming as all other non-CO2 greenhouse gases put together. Methane is 21 times more powerful a greenhouse gas than CO2. While atmospheric concentrations of CO2 have risen by about 31% since pre-industrial times, methane concentrations have more than doubled. Whereas human sources of CO2 amount to just 3% of natural emissions, human sources produce one and a half times as much methane as all natural sources. In fact, the effect of our methane emissions may be compounded as methane-induced warming in turn stimulates microbial decay of organic matter in wetlands—the primary natural source of methane.

With methane emissions causing nearly half of the planet’s human-induced warming, methane reduction must be a priority. Methane is produced by a number of sources, including coal mining and landfills—but the number one source worldwide is animal agriculture. Animal agriculture produces more than 100 million tons of methane a year. And this source is on the rise: global meat consumption has increased fivefold in the past fifty years, and shows little sign of abating. About 85% of this methane is produced in the digestive processes of livestock, and while a single cow releases a relatively small amount of methane, the collective effect on the environment of the hundreds of millions of livestock animals worldwide is enormous. An additional 15% of animal agricultural methane emissions are released from the massive “lagoons” used to store untreated farm animal waste, and already a target of environmentalists’ for their role as the number one source of water pollution in the U.S.

The conclusion is simple: arguably the best way to reduce global warming in our lifetimes is to reduce or eliminate our consumption of animal products. Simply by going vegetarian (or, strictly speaking, vegan), , , we can eliminate one of the major sources of emissions of methane, the greenhouse gas responsible for almost half of the global warming impacting the planet today.

Advantages of Vegetarianism over CO2 Reduction
In addition to having the advantage of immediately reducing global warming, a shift away from methane-emitting food sources is much easier than cutting carbon dioxide.

First, there is no limit to reductions in this source of greenhouse gas that can be achieved through vegetarian diet. In principle, even 100% reduction could be achieved with little negative impact. In contrast, similar cuts in carbon dioxide are impossible without devastating effects on the economy. Even the most ambitious carbon dioxide reduction strategies fall short of cutting emissions by half.

Second, shifts in diet lower greenhouse gas emissions much more quickly than shifts away from the fossil fuel burning technologies that emit carbon dioxide. The turnover rate for most ruminant farm animals is one or two years, so that decreases in meat consumption would result in almost immediate drops in methane emissions. The turnover rate for cars and power plants, on the other hand, can be decades. Even if cheap, zero-emission fuel sources were available today, they would take many years to build and slowly replace the massive infrastructure our economy depends upon today.

Similarly, unlike carbon dioxide which can remain in the air for more than a century, methane cycles out of the atmosphere in just eight years, so that lower methane emissions quickly translate to cooling of the earth.

Third, efforts to cut carbon dioxide involve fighting powerful and wealthy business interests like the auto and oil industries. Environmental groups have been lobbying for years to make fuel-efficient SUVs available or phase out power plants that don’t meet modern environmental standards without success. At the same time, vegetarian foods are readily available, and cuts in agricultural methane emissions are achievable at every meal.

Also, polls show that concern about global warming is widespread, and environmental activists often feel helpless to do anything about it. Unless they happen to be buying a car or major appliance, most people wanting to make a difference are given little to do aside from writing their legislators and turning off their lights. Reducing or eliminating meat consumption is something concerned citizens can do every day to help the planet.

Finally, it is worth noting that reductions in this source of greenhouse gas have many beneficial side effects for the environment. Less methane results in less tropospheric ozone, a pollutant damaging to human health and agriculture. Moreover, the same factory farms responsible for these methane emissions also use up most of the country’s water supply, and denude most of its wilderness for rangeland and growing feed. Creating rangeland to feed western nations’ growing appetite for meat has been a major source of deforestation and desertification in third world countries. Factory farm waste lagoons are a leading source of water pollution in the U.S. Indeed, because of animal agriculture’s high demand for fossil fuels, the average American diet is far more CO2-polluting than a plant-based one.

Recommendations
Organizations should consider making advocating vegetarianism a major part of their global warming campaigns. At a minimum, environmental advocates should mention vegetarianism in any information about actions individuals can take to address global warming. Government policy should encourage vegetarian diets. Possible mechanisms include an environmental tax on meat similar to one already recommended on gasoline, a shift in farm subsidies to encourage plant agriculture over animal agriculture, or an increased emphasis on vegetarian foods in government-run programs like the school lunch program or food stamps.