評論
打印
Curbing climate change
控制氣候變化
The deepest cuts
一切為了減排
Our guide to the actions that have done the most to slow global warming
我們的行為指南已經最大限度減緩了全球變暖
ON SEPTEMBER 23rd 120-odd presidents and prime ministers will gather in New York for a UN meeting on climate change. It is the first time the subject has brought so many leaders together since the ill-fated Copenhagen summit of 2009. Now, as then, they will assert that reining in global warming is a political priority. Some may commit their governments to policies aimed at reducing greenhouse-gas emissions. What few will say is how many tonnes of carbon dioxide these will save—because they almost never do.
9月23日，120多位國家總統和首相將會匯聚紐約聯合國總部，就氣候變化議題舉行會議。這是自2009年一無所獲的哥本哈根氣候大會之后，國家元首們第一次為了此項議題聚會。就像當時一樣，他們如今也一致認為控制全球變暖是政治的頭等大事。一些元首們也許會承諾實行以削減溫室氣體排放為目標的相關政策。但很少人能明確說出這些政策最終將減少多少噸二氧化碳排放量—因為根本沒效果。
According to scientists, cutting carbon-dioxide emissions is an essential part of reducing catastrophic risks from climate change. Yet governments are persistently averse to providing estimates of how much carbon a policy saves. That may be because, in countries where climate change is controversial, it makes more sense to talk about the other benefits a scheme offers rather than its effect on carbon. Or it may be that, in countries which are enthusiastic about renewable energy, pointing out that it may not save that much carbon is seen as unhelpful. Or perhaps governments think climate change is so serious that all measures must be taken, regardless of cost (though their overall lacklustre record suggests this is not the case).
科學家表示，減少二氧化碳排放量是緩解由氣候變化導致的災難性后果的重要一步。但政府自始至終都不愿意預估他們的政策到底能少排多少碳。這也許是因為，在那些對氣候變化仍存爭議的國家，政府更愿意顯示他們實行的其他福利政策是多么有效，而非低碳減排?；蛘咴谀切嶂杂谠偕茉吹膰?，指出政府政策并沒有減少那么多碳排放也于事無補?；蛘哒J為氣候變化太重要了，可以不惜一切代價來完成（不過總的來看，根據他們拖拖拉拉的表現，這是不可能的）。
Whatever the reason, the end result is that while the world's governments have hundreds of policies for tackling climate change, some of them very expensive—China, America and the European Union spend $140 billion a year on subsidising renewable energy—it is hard to say which policies are having the greatest effect.
不管什么原因，結果就是盡管世界各個政府出臺了幾百條治理氣候變化的政策，有的還代價高昂—中國、美國和歐盟每年花費1400億補貼再生能源——很難說哪些政策是最有效的。
So The Economist has made a stab at a global comparison of carbon-mitigation efforts. Chart 1 is the result. It ranks 20 policies and courses of action according to how much they have done to reduce the atmosphere's stock of greenhouse gases. We have used figures from governments, the EU and UN agencies. As far as we know, this exercise has not been carried out before.
因此，《經濟學家》嘗試制作了一張全球各國碳減排成果的比較圖。圖表1是結果，列出了前20個政策和行動方案以及每個政策方案的大氣層溫室氣體的減少量。我們使用了政府、歐盟和聯合國各機構公布的數據。據我們所知，以前還沒有人做過這樣的比較。
Apples, meet oranges
當蘋果遇見橘子
First, a health warning: the policies and actions on our list are not strictly comparable. Some are global, some regional and some national. Some are long-standing; some new. A couple are not policies at all, such as the collapse of the Soviet Union, which led to the closure of polluting factories and to inefficient state farms reverting to grassland, locking up carbon.
首先有個溫馨提示：本次列出的政策和行動方案嚴格來說是不可比較的。一些是全球范圍的，一些是區域性或國家層面的。一些是長期執行的，另一些是新政。有幾條并不能算是政策，比如由蘇聯解體導致的污染工廠關門、效率底下的國有農場復歸草原，鎖住了碳。
And the numbers almost all come with caveats. It is fairly easy to estimate how much carbon a new field full of solar cells or a nuclear-power plant saves by looking at the amount of electricity it produces in a year and how much carbon would have been emitted if fossil fuels had been used instead, based on the local mix of coal, gas and oil. But as Paul Joskow of the Massachusetts Institute of Technology has pointed out, the standard “levelised” calculations, which divide the total amount of power a plant will produce over its lifetime by its total lifetime cost, are a poor way to compare fossil fuels and renewable energy.
這些數據都顯示出了警告信號。很容易估算出一片新鋪滿太陽能板或蓋滿核能工廠的曠野減少了多少碳排放，只要看看它每年發了多少電就可以了；另外，根據當地煤、氣、油的混合狀況也能很簡單地估計出如果以化石燃料替代之，將多排放多少碳。然而，正如麻省理工學院的Paul Joskow指出的那樣，標準的“水平化計算”——即用一座工廠整個使用年限所耗費的成本除以其產生的全部功率值，并不是一種比較化石燃料和再生能源的好方法。
Other measures have problems, too. Take the effects of fuel-efficiency standards. Would companies have curtailed their cars' emissions anyway to sell more of them to cost- and mileage-conscious drivers? And how much has better fuel efficiency encouraged drivers to drive farther?
其他的測量方法也有問題。以燃料效率標準為例。司機對成本和公里數很敏感，公司會為了向他們銷售更多汽車而減少汽車排量么？更高的燃料利用率又在多大程度上鼓勵了司機多開車？
A further complication is that many policies have benefits beyond—or indeed closer to hand than—those they offer in terms of climate. Burning less coal saves lives in the near future as well as reducing climate risks in decades to come. Saving forests preserves wildlife, not just carbon.
更加復雜的是，很多政策所帶來的好處不僅僅是治理氣候。燃燒更少的煤炭可以在不遠的將來挽救很多生命，也能減少未來幾十年內氣候變化帶來的各種危機。拯救森林不止是控制碳排放，也能保護野生動物。
So our table should be treated with caution. It is only safe to say that one policy is better than another in climate terms if it beats it by a wide margin.
所以這次談判應該謹慎對待。只有當某個政策提供了更多的回旋余地，才能說它是更好的。
As it happens, though, there are some very wide margins to be found. One policy stands head and shoulders above all others. And it is one that few people other than climate-policy specialists will have thought of in this context: the Montreal protocol, a 1987 agreement to phase out substances such as chlorofluorocarbons (CFCs) used in air conditioners, refrigerators and so on. It was enacted to limit the damage such substances were doing to the ozone layer, a goal which it has achieved.
正好，我們還有很多潛力有待發掘。有一個政策尤其值得注意，盡管除了環境政策研究專家以外其他人很少考慮到這一點：在蒙特利爾議定書中，一份1987年簽訂的協議要求逐步淘汰空調、電冰箱等家電中的氯氟化碳成分。這項協議意在防止此類物質繼續損害臭氧層，目前這個目標已經達成。
Like carbon dioxide and many other gases emitted by industry and agriculture—methane and nitrous oxide, for example—CFCs are greenhouse gases. And they are extremely potent ones, causing thousands of times more warming per molecule than carbon dioxide does. That means stopping CFC production, which was in the range of millions of tonnes a year, delivered a climate benefit equivalent to cutting carbon-dioxide emissions by billions of tonnes.
氟氯化碳就像二氧化碳和其他被工業農業排放出來的氣體（例如甲烷和一氧化二氮）一樣，都屬于溫室氣體。它們破壞力巨大，每分子所產生的熱量比二氧化碳要高幾千倍。這也就是意味著每年停止產生數百萬噸的氟氯化碳給緩解氣候變化帶來的好處，相當于減排數十億噸二氧化碳。
Collateral benefits
好處多多
Guus Velders of the Dutch National Institute for Public Health and the Environment has compared the warming effect that would have come about if the emissions of such chemicals had continued to grow at the rate they were growing before the protocol with what has come about thanks to their banning. The net effect is equivalent to that of a whopping 135 billion tonnes of carbon dioxide. That is more than twice today's total annual greenhouse-gas emissions, which are equivalent to about 50 billion tonnes of carbon dioxide (carbon dioxide itself makes up about three-quarters of that, with methane, nitrous oxide and some gases used in industry making up the rest). Durwood Zaelke of the Institute for Governance and Sustainable Development, a think-tank, says that if CFCs were uncontrolled the annual figure would be 8 billion tonnes higher. The Montreal protocol has had nearly as big an effect as all the rest of our list put together.
荷蘭國家公共健康和環境研究所的Guus Velders估算了如果這些化學氣體按照協議書禁令出臺之前的速度排放所帶來的溫室效應：其凈排量相當于1350億噸二氧化碳，比現在每年排放的溫室氣體總量（500億噸）的兩倍還要多（二氧化碳占溫室氣體排放量的四分之三，其余的是甲烷、一氧化二氮和其他工業氣體）?！爸卫砗涂沙掷m發展智庫”的Durwood Zaelke表示，如果氟氯化碳的排放未受控制，則每年會多排放80億噸。蒙特利爾協議書的效果比其他所有協議的總和還要顯著。
Trailing some way behind the Montreal protocol is a small group of measures—not really climate policies—that have been responsible for avoiding between 4% and 7% of greenhouse-gas emissions. According to the International Atomic Energy Agency, nuclear power avoided the production of 2.2 billion tonnes of carbon dioxide in 2010—that is, emissions would have been 2.2 billion tonnes higher if the same amount of electricity had been produced by non-nuclear plants. Energy from dams and other hydroelectric sources avoided 2.8 billion tonnes (though emissions of methane from the reservoirs behind some of those dams mean the net effects were less than that). Between them they generated 6,000 terawatt-hours of electricity in 2011, compared with 450TWhrs for wind and less than 60TWhrs for solar. The high rate at which new wind and solar capacity is being built will eat into this lead, but it will take some time to overturn it.
蒙特利爾協議書之后的其余各項措施——不完全是氣候政策——也減少了4%~7%的溫室氣體排放。根據國際原子能機構的研究，核能在2010年減排了22億噸二氧化碳——即如果由非核能工廠發電，二氧化碳將增加22億噸。大壩和其他水利發電減排了29億噸二氧化碳（如果計入大壩后面蓄水庫里產生的甲烷，則凈減排量要少一些）。這些在2011年共發電6000太瓦時，相比之下，風力發電貢獻了450太瓦時，太陽能發電則為60太瓦時。風能和太陽能發電會占有越來越高的比重，但這還需要時間徹底扭轉目前的趨勢。
The other item in this group is something of a cheat. In 2007 Su Wei of China's foreign ministry said that his country's one-child policy, by reducing the number of births between the late 1970s and the mid-2000s by 300m, had reduced carbon emissions by 1.3 billion tonnes in 2005 (because there were fewer people to consume goods which generated greenhouse gases in their production). Taking this argument further, one could say that the fall in global fertility since 1960 cut emissions even more. That is not exactly a climate policy. But it is a reminder that greenhouse gases are powerfully influenced by factors far beyond the scope of climate-change policies.
另一項政策則不太切題。在2007年，中國外交部的蘇偉表示，從 20世紀70年代到本世紀頭十年的中期，中國的出生人口因獨生子女政策減少了3億，到2005年，碳排放量因此減少了13億噸（因為生產商品的過程往往產生溫室氣體，人越少，消耗商品越少）。按照這個說法進一步思考，可以說，1960年后全球生育率的下降為減排做出的貢獻更大。那壓根不是氣候政策。但是，這表明溫室氣體排放量會受到非氣候變化政策因素的強烈影響。
Three other lessons emerge. First, policies to slow or reverse deforestation are more important than one might expect. Trees absorb carbon as they grow and release it when they are cut down. According to a recent study in Science, declining deforestation in Brazil meant that the country produced 3.2 billion tonnes less atmospheric carbon dioxide between 2005 and 2013 than it would have if the tree-felling had continued unabated. That is 400m tonnes a year. The slowdown in deforestation in tropical countries is one of the reasons that the conversion of forests to farmland now accounts for only 11% of greenhouse-gas emissions globally, much less than 20 years ago.
三個教訓值得學習。第一，減緩或逆轉森林伐木的政策比預想更重要。樹木生長時能吸收二氧化碳，被砍伐時則會釋放二氧化碳。據《科學》一項新研究表明，巴西實行減少森林砍伐的政策后，2005年到2013年間，其排放到大氣中的二氧化碳比不實行政策前少了32億噸。年排放量為4億噸。林地轉耕地的溫室氣體排放量現在僅占全球總排放量的11%，比20年前少了很多，而熱帶國家森林開伐的節奏放緩是緣由之一。
The other reason for deforestation's dramatically reduced share of total emissions, though, is that industrial emissions of carbon dioxide have continued to grow rapidly. The rise is not as fast as it might have been. Rules that make vehicles more efficient and improve the energy efficiency of buildings and appliances have done more than might be expected. America has been setting standards for vehicle greenhouse-gas emissions and fuel efficiency since the mid 1970s; the current rules are forecast to reduce carbon-dioxide emissions by 6 billion tonnes in 2012-25, meaning by about 460m tonnes a year. America's Department of Transportation reckons that overall such rules have reduced carbon-dioxide emissions by a cumulative 14 billion tonnes. Europe's equivalent regulations for passenger cars and light trucks do less (European vehicles were more efficient to start with) but are still respectable; being adopted by overseas manufacturers who want to sell cars in Europe gives them an unquantified extra clout.
導致森林砍伐二氧化碳排放量占比大幅下降的另一個原因在于，二氧化碳的工業排放量持續快速上漲。增長速度與預期有差異。提高交通工具使用效率以及提高房屋與電器的能源效率的政策比預期更有效。20世紀70年代起，美國為交通工具的溫室氣體排放以及燃料效率制定了標準。當前的政策可以預測，2012-2025年間，二氧化碳排放量將減少60億噸，相當于一年排放4.6億噸。美國交通部估計，總體來說，這些政策已累計減少二氧化碳排放量140億噸。歐洲針對轎車和輕型貨車出臺的類似政策，減排量不如美國（歐洲的交通工具之前更有效率），但依然顯著。這些政策也適用于想在歐洲賣車的海外制造商，這部分影響力無法量化。
Their time will come
他們的時機將會來臨
New EU rules on the design of boilers and water heaters are expected to save 136m tonnes of carbon dioxide a year within six years. China's Development Research Centre and the World Bank say that on the basis of 2010 figures energy-efficiency targets for Chinese state-owned enterprises save about the same amount; that scheme has recently been much expanded.
歐盟針對鍋爐以及熱水器設計的新規定，有望在六年內將年碳排放量減少1.36億噸。中國發展研究中心及世界銀行表示，根據2010年的數據，中國國有企業的能源效率目標也減少了相當量的碳排放，并近日計劃擴大這一目標。
Subsidies for solar and wind power do less than you might expect, considering the attention they receive. The European Environment Agency calculates that between mid-2008 and 2012, what it calls changes in the carbon intensity of energy (mainly, the rise in renewables) accounted for a third of the decline in carbon-dioxide emissions in the EU. Emissions fell 350m tonnes in that period, so renewable policies seem to be responsible for about 30m fewer tonnes of carbon dioxide a year, making them less effective than energy-efficiency measures.
以太陽能及風能補貼政策受到的關注度來看，其表現低于預期。歐洲環境署估計，在2008年中期到2012年，被其稱為能源碳強度（主要指可再生能源的增加）引起的變化占歐盟減排量的三分之一。在此期間，排放量下降3.5億噸。因此，可再生能源政策可以解釋約3300萬以下的減排量，這使得此項政策不如能源效率政策有效。
This estimate may be low. A separate calculation by Germany's environment ministry puts the figure for Germany alone at 100m tonnes in 2012. But even if the EU estimate is only half what it should be, renewables would still fall short of other carbon-mitigation policies. They are also extremely pricey. The cost of Germany's Energiewende (its transformation to a renewables-based electricity system) is 16 billion ($21 billion) a year. The cost of helping developing countries phase out CFCs under the Montreal protocol was just $2.4 billion all-told from 1990-2010. The Amazon Fund, which has done much to fight deforestation in Brazil, has mostly been funded by the Norwegian government at a cost of just $760m over 11 years.
數據可能被低估了。另一個由德國環境部估計的數據顯示，在2012年，僅德國的可再生能源政策產生的減排量就達1億噸。但是，即使歐盟的估計僅為實際的一半，可再生能源政策的減排效果也遠不如其他減排政策。這些政策的成本也很高。德國的能源轉型成本（以新能源為基礎的電力系統改革）是每年160萬歐元（210萬美元）。1990-2010年間，德國根據蒙特利爾議定書，幫助發展中國家逐步淘汰氟氯碳化物的總成本僅24億美元。在巴西，奮力對抗森林砍伐的亞馬遜基金會主要得到挪威政府的資助，11余年的成本僅為7.6億美元。
Over the next few years, the relative weights of all these policies will change. Nuclear energy is being phased out in Germany and may not recover to its pre-Fukushima heights in Japan. Although it is growing in China, its share of worldwide electricity generation—currently about a seventh—is likely to decline. The same may be true of hydropower. The share of solar and wind power, on the other hand, will rise as costs fall and capacity increases (installed capacity for these renewables doubled in 2012-14).
在接下來的幾年，所有政策的相對權重會發生變化。德國會逐步廢除核能，日本對核能的重視程度也可能無法恢復到福島核泄漏之前的水平。雖然在中國，核能政策的權重在不斷增強，但其在世界范圍內的發電份額—約七分之——可能下降。水力發電可能也面臨一樣的遭遇。另一方面，由于成本下降、容量增大（這幾類可再生能源的裝機容量在2012-2014翻倍）太陽能和風能的份額可能會增加。
The Economist asked Climate Action Tracker, a group of scientists who study emissions policies and actions, to calculate the policies likely to have the biggest impact in 2020. Their findings, in chart 2, suggest that the influence of the EU's renewables regime will grow considerably, though Europe will still be far from the zero-carbon energy system greens long for. Chinese efforts to boost renewables and energy efficiency are also likely to start bearing a lot more fruit. So, they think, could the UN's Clean Development Mechanism (CDM), which finances greenhouse-gas reduction measures in developing countries to offset emissions in rich ones.
本刊邀請來自氣候行動追蹤組織一群研究排放政策和行動的科學家，估計2020年最可能產生最大影響的政策。他們的結果（如圖2）表示，雖然歐洲依然達不到零碳排放能源系統的要求，歐盟可再生能源制度的影響力會大幅增強。中國推進可再生能源以及能源效率的政策也很可能產生更多的成效。因此，他們在想，資助發展中國家溫室氣體減排措施的聯合國清潔發展機制是否可以補償發達國家的排放量。
Much more to do
任重道遠
These estimates work on the basis of current policies. But one possible new measure would make a big difference. Hydrofluorocarbons (HFCs) are ozone-friendly replacements for CFCs, and are one of the fastest-growing greenhouse gases, having risen 40% since 1990. Emissions of HFCs are unrestricted, though CDM investments are used to reduce them in some cases. If the Montreal protocol were quickly amended to include them, says Mr Zaelke, it might do almost as much for greenhouse-gas emissions in the next 35 years as it did in 1990-2010.
這些估計都是基于當前的政策。但是，一項合理的新政策將會有重大意義。氫氟碳化物不破壞臭氧層，是對氟氯碳化物的替代品，也是增長最快的溫室氣體之一。1990年后，其排放量增長了40%。清潔發展機制曾投資減少一定程度的氫氟碳化物量，但其排放量仍不受限制。Zaelke表示，如果蒙特利爾議定書經修正后包含了這些內容，今后35年的溫室氣體排放量將達到1990-2010的水平。
Saving the equivalent of some 130 billion tonnes of carbon dioxide so cheaply would be a big win. But it is still only a tenth of what would need to be done to ensure that the temperature in 2100 is no more than 2C higher than it was at the time of the Industrial Revolution—the limit that the countries of the world have committed themselves to. Without the measures listed in chart 1 emissions might be equivalent to almost 70 billion tonnes of carbon dioxide a year, rather than 50 billion. But even the lower number is too high to meet the stated goal, and the overall trend is up, not down. World leaders gathering in New York are not only being vague about their climate policies. They are being dilatory, too.
以如此低的成本減少約1300億噸二氧化碳排放量意義重大。但是，若要保證2100年地球溫度與工業革命時期相比不超過2C——各國承諾的指標，其工作只完成了十分之一。如果沒有表1列出的各項政策，年碳排放量大約為700億噸，而不是500億噸。但即使碳排放量減少，對于完成既定目標來說，排放量依然很高，而且，碳排放量的總趨勢還在增加而不是減少。聚集在紐約的各國領導，不僅對其氣候政策界定不清，行動上也不夠積極。翻譯：楊詩露；校對：黃梅
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