【文： Michael Shellenberger ；譯：Alan Chiu】
當我還是個小孩時，雙親不時也會帶我與妹妹到沙漠露營。很多人都以為沙漠空無一物，但父母教導我們觀察周圍如鷹、鷲和龜的野生動物。
完成高中後，我搬到加州並開始從事環保活動。我幫助拯救了該州最後一個古老紅木森林，亦阻止了一個沙漠放射性廢料儲存庫的建造計劃。
在三十而立不久的 2002 年，我決定致力投身於處理氣候變化的事業。當時，我憂慮全球暖化最終會破壞很多人類一直努力保護的自然環境。
我認為解決方案非常簡單：家家戶戶的屋頂都建太陽能板，每條道路上都是電動車等等。主要的障礙，我認為是來自政治方面。因此，我協助組織了美國最大工會和環保團體聯盟，計劃於再生能源行業投資 3,000 億美元；這不僅會阻止氣候變化，亦可為這個快速發展的高科技行業，創造數以百萬計新工作崗位。
我們的努力在 2007 年終於得到回報。當時的總統候選人奧巴馬與我們有一致的理念，他在任的 2009-2015 年間，美國於再生能源及其他形式的潔淨能源上，投資了 1,500 億美元。不過，很快我們就碰上麻煩。
首先是土地問題。來自屋頂的太陽能電力發電成本，大約是大型太陽能發電場的兩倍，但太陽能和風力發電場都需要大量土地。另外，太陽能和風力發電場都需要新的長輸電管道，地方社區和保育人仕因試圖保護野生動物，特別是鳥類而反對大興土木。
另一個挑戰是，太陽能和風能只能間歇發電的特性。當無太陽照射、無風吹動，必須要有另一種能迅速填補電力空缺的能源。
興幸的是，有很多人正在研究解決方案。其中一個方案是將加州水壩改造成大型電池。概念是這樣：當太陽照射、有風吹動時，你可以運用該些電力將水泵上山，將其儲存起來；到日後需要時，山上的水經渦輪排到山下製造電力。
經仔細研究後，對比再生能源造成的生態問題，其他問題來源似乎是小巫見大巫。例如，全球無數的家貓殺死了數以十億計雀鳥，風力發電機所殺的則有近一百萬隻。
當時對我而言，透過更多技術創新可以解決絕大部分太陽能和風能擴張帶來的問題。
不過，隨著歲月流逝，問題依然存在，並且在某些情況下變得更糟：加州在再生能源方面有世界領先地位，但我們還沒有將水壩轉化成電池，部分原因是出於地理問題。縱然有合適的堤壩和水庫，也需付上昂貴改造費用。
更大問題是，堤壩累積的水有許多其他用途例如灌溉農作物和供城市市民使用，再加上河流和水庫的水稀少且不可靠，因此用於上述其他目的之堤壩儲水將變得越來越珍貴。
如果沒有大型太陽能儲電裝置，加州不得不在陽光非常充裕的日子，阻止來自太陽能發電場的電力，或付錢給鄰近州份送贈這些電力，避免影響原有電網。
儘管你可能聽過「電池革命 (battery revolution) 」，但受限於已充分理解的技術和經濟原因，這回事只聽樓梯響。
至於家貓，牠們不會殺死大型、稀有、受威脅的鳥類；牠們殺的是如麻雀、知更鳥和橿鳥的小型常見鳥類。殺死如鷹、鷲、貓頭鷹和神鷲的大型、受威脅及瀕臨滅絕的鳥類，是風力發電機。
事實上，對重要鳥類來說，風力發電機是過去幾十年來最嚴重的新威脅。快速轉動的發電機就像頂級捕獵者，而大型鳥類從未演化至適應到其存在。
另一方面，太陽能發電場也造成類似巨型生態影響。建造太陽能發電場就像建造任何其他種類的農場一樣，必須移除整個區域的野生動物。
為了建造加州其中一個最大太陽能發電場，開發商聘請了生物學家將受威脅沙漠龜品種拉出其洞穴，然後將牠們放到農夫車後面的籠，再運到其他地方，但中途有大量死亡出現。
當了解到這些影響時，我逐漸意識到，沒有多少創新技術可以解決到再生能源的根本問題。
你可以使太陽能板更便宜、風力發電機更大，但你不可能令陽光更平均地照射地表或令風更可靠地吹動。我開始了解能源物理學與環境的關係。為了從弱能量流中產生大量電力，你需要將其分散到大面積區域發電。換句話說，再生能源的問題本質上不在於技術上，而是自然問題。
處理本質上不可靠且耗用大量土地的能源，需要很高經濟成本。
已經有很多報道指，太陽能板和風力發電機的成本近年如何降低，但是，這些在中國大型工廠生產的一次性成本，會被應付其不可靠性的高成本所抵消。
就以加州為例， 在 2011-17 年間，太陽能板成本下降了約 75％ ，但同期電費比美國其他地區高五倍。同樣的情況也出現於世界太陽能和風力發電領導國德國。 隨著再生能源使用規模增加，其電價在 2006-17 年間卻錄得 50％ 增長。
我曾經認為應對氣候變化的代價很高。 但看過德國和法國情況後，我再也不敢相信這種說法。
儘管到 2025 年前，德國會投資 5,800 億美元於偏重於再生能源的電網，其碳排放量自 2009 年以來一直平穩，但電力成本卻增加了 50％ 。
與此同時，法國每產生一單位電力的碳排放量僅為德國的十分之一，前者的電費僅為後者稍高於一半。這是怎樣做到？是通過核能。
然後，在德國施壓下，法國於過去十年在再生能源投資了 330 億美元。結果是什麼？法國供電造成的碳濃度 (carbon intensity) [1] 上升，電價也有所增加。
那所有有關核能昂貴、太陽能和風能便宜的新聞頭條是甚麼一回事？這由於 70-80％ 核能成本來自建造核電廠，而太陽能和風能的成本不包括輸電管道、新水壩或其他形式電池的高成本，因此很大程度上造成錯覺。
核電是否安全，以及所產生的廢料會如何處理，是合理的疑問。
事實上，自 1960 年代以來，科學家們一直在研究不同能源的健康和安全。每個大型研究，包括近期於英國醫學期刊《刺針》發表的報告，都發現了同樣事情：核能是製造可靠電力的最安全方法。
聽起來雖然很奇怪，但核電廠安全的原因與核武這樣危險的原因相同。核電廠所用的燃料和核彈所用的材料鈾，每質量可產生的熱量是同量化石燃料和火藥的 100 萬倍。
在過程中，破壞原子比破壞化學鍵釋放的能量更多，而鈾原子特別之處是容易分裂。
由於核電廠在不需使用火的情況下產生熱量，因此不會以煙塵的形式排放出空氣污染。 相比之下，世衛指燃燒化石燃料和生物質 (biosmass) 產生的煙塵導致每年 700 萬人早死。
即使在最嚴重事故中，核電廠也會釋放少量的鈾原子中的少量放射性粒子物質，這些鈾原子會分裂產生熱量。
在核電廠平均 80 年的壽命期內，不足 200 人將死於如切爾諾貝爾這種最嚴重的核事故，亦無人會死於如福島事件中洩漏的少量放射性物質。
因此，氣候科學家占士漢臣 (James Hansen) 和同事發現，核電廠迄今實際上已拯救了近 200 萬條、原被空氣污染殺死的生命。
由於其能源密度 (energy density) [2] ，核電廠所需的土地遠遠少於其他再生能源。 即使在陽光充沛的加州，太陽能發電場需要比核電廠多 450 倍的土地才能產生同等能量。
與能量密度低的太陽能和風能相比，能量密度高的核能在發電時需要的材料少得多，產生的廢物亦遠遠較少。
一個可樂罐的鈾，足以提供大部份美國或澳洲人，最饕餮生活方式所需的所有能量。在發電過程結束時，核電廠產生的高放射性廢料量與使用過的鈾原料，一樣也是那個可樂罐。從環保角度來看，核能是最好的能源，因為當中產生的廢物很少，且無一種污染物會進入環境。
瑞士核計劃 45 年來產生的所有核廢料都可以放在桶內，再封存於籃球場大的倉庫裡，就像所有用過的核燃料一樣，從來連一隻蒼蠅也沒傷害過。
與核電廠相比之下，太陽能板所用的水泥、玻璃、石屎和鋼材等材料多 17 倍，並且產生多 200 倍的廢物。
我們傾向以為太陽能板是潔淨的，但事實是，在 20-25 年壽命結束後，我們無任何棄置計劃可處理太陽能板。
專家擔心，太陽能板將與其他形式的電子垃圾，一起被運到非州和亞洲的貧窮社區拆解——常見的是用鎚砸碎——當地居民將因此接觸到有毒重金屬如鉛、鎘和鉻的灰塵。
無論到世界哪一方，我都會問尋當百姓他們對核能和再生能源的看法。他們指自己幾乎甚麼都不知道之後，往往承認核能很強而再生能源很弱。他們的直覺是正確的，但大多數人錯誤認為弱者較為安全——這也是可以理解的。
再生能源真的更安全嗎？ 答案：不是。令人驚訝的是，風力發電機比核電廠殺死更多人。
換言之，燃料的能量密度決定了它對環境和健康的影響。 在更廣泛的土地上鋪設更多「地雷」和更多設備將對環境和人類安全造成更大影響。
的確，你可以站在太陽能板旁邊而不會承受太大傷害；而站在全面發電的核反應堆旁邊將會致死。
可是，當涉及到為數以十億計人發電時，生產太陽能板和風力發電機，並將之散到大面積範圍使用，對人類和野生動物的影響同樣大大增加。認為陽光微弱的直覺有時也會出現於電影中。 這就是為什麼沒有人詫異，最近推出的反烏托邦科幻電影《銀翼殺手》續集開場中，出現反烏托邦場景，當中的加州沙漠充滿太陽能發電場，並與摧毀沙漠龜生態的一模一樣。
在過去數百年，人類已經從使用高物質密度 (matter-dense) 的燃料轉為高能量密度的：首先從木材、糞便和風車等再生燃料，轉為煤、石油和天然氣等化石燃料，最終再轉用鈾。
能源進步對人與自然都有整大的正面影響。 當停止使用木材作為燃料時，我們容許草原和森林重新生長，並讓野生動物重返棲息地。
當停止在家園燃燒木材和糞便時，我們不再於室內吸入有毒煙塵；當從化石燃料轉向鈾時，室外空氣污染被清除之外，也減少人類暖化地球的幅度。
因此，核電廠是一項由化石燃料過渡的革命性技術——這個重大歷史突破，與之前從木材到化石燃料的工業轉型一樣重要。
核能的問題在於不受歡迎，它是化石燃料、再生能源、反核武器運動者和反人類環境保護主義者，長達 50 年共同努力提倡禁止此技術下，所創造的受害者。
而作為回應，核能業就如患上「被虐婦女症候群 (Battered Woman Syndrome) 」，不斷為廢料與安全這些最好的優勢道歉。
最近，核能業界為應對氣候變化提出「我們需要結合不同清潔能源使用」當中包括太陽能、風能和核能。這是我曾經相信的概念，並四處宣揚，部分是因為這是人們想要聽到的。問題卻是這絕非實際上可做到。
以法國作例，該國電力自從由大部份來自核能，轉至核能混合較多再生能源的發電組合，已因增加使用天然氣造成更多碳排放，而太陽能和風能的不可靠性亦造成電費增加。
石油和天然氣投資者知道這一點，這亦是為何他們會與再生能源企業建立政治聯盟，以及為何石油和天然氣公司花費數以百萬計美元廣告費宣傳太陽能，並向環保組織提供數以百萬計美元作為公共關係開支。
究竟我們可以做些甚麼？ 最重要是科學家和環保主義者開始道出再生能源和核能的真相，以及能源密度和環境影響之間的關係。
專門研究蝙蝠的科學家最近警告，風力發電機即將使一個具遷徙習性物種灰毛尾蝠 (hoary bat) ，推向滅絕邊緣。
另一位曾協助加州沙漠建造巨型太陽能發電場的科學家向《高鄉新聞》表示：「所有人都知道另覓地方安置沙漠龜並不可行。 當你在推土機前行過時，你會哭起來；當你移除這些動物與仙人掌時，很難想像這計劃是個好主意。」
我認為，我們這些積極參與氣候事務的人傾向於再生能源是相當自然的事，因為這些科技似乎是一種協調人類社會與自然世界的方式。集體地來看，我們一直在自以為對自然好的誤區之中，情況與引導我們在超市購買標有「全天然」產品的宣傳沒有什麼不同。但現在是我們這些自稱為地球守護者的人，也應該再了解一下科學理論，並開始質疑我們的行動造成甚麼影響。
既然我們現在知道再生能源無法拯救地球，我們是否真的會袖手旁觀讓其摧毀地球？
註：
碳濃度是每噸能源所產生的碳排放量。
能量密度是指在一定空間或質量物質中儲存能量的大小。
* * *
When I was a boy, my parents would sometimes take my sister and me camping in the desert. A lot of people think deserts are empty, but my parents taught us to see the wildlife all around us, including hawks, eagles, and tortoises.
After college, I moved to California to work on environmental campaigns. I helped save the state’s last ancient redwood forest and blocked a proposed radioactive waste repository set for the desert.
In 2002, shortly after I turned 30, I decided I wanted to dedicate myself to addressing climate change. I was worried that global warming would end up destroying many of the natural environments that people had worked so hard to protect.
I thought the solutions were pretty straightforward: solar panels on every roof, electric cars in every driveway, etc. The main obstacles, I believed, were political. And so I helped organize a coalition of America’s largest labor unions and environmental groups. Our proposal was for a $300 billion dollar investment in renewables. We would not only prevent climate change but also create millions of new jobs in a fast-growing high-tech sector.
Our efforts paid off in 2007 when then-presidential candidate Barack Obama embraced our vision. Between 2009–15, the U.S. invested $150 billion dollars in renewables and other forms of clean tech. But right away we ran into trouble.
The first was around land use. Electricity from solar roofs costs about twice as much as electricity from solar farms, but solar and wind farms require huge amounts of land. That, along with the fact that solar and wind farms require long new transmissions lines, and are opposed by local communities and conservationists trying to preserve wildlife, particularly birds.
Another challenge was the intermittent nature of solar and wind energies. When the sun stops shining and the wind stops blowing, you have to quickly be able to ramp up another source of energy.
Happily, there were a lot of people working on solutions. One solution was to convert California’s dams into big batteries. The idea was that, when the sun was shining and the wind was blowing, you could pump water uphill, store it for later, and then run it over the turbines to make electricity when you needed it.
Other problems didn’t seem like such a big deal, on closer examination. For example, after I learned that house cats kill billions of birds every year it put into perspective the nearly one million birds killed by wind turbines.
It seemed to me that most, if not all, of the problems from scaling up solar and wind energies could be solved through more technological innovation.
But, as the years went by, the problems persisted and in some cases grew worse. For example, California is a world leader when it comes to renewables but we haven’t converted our dams into batteries, partly for geographic reasons. You need the right kind of dam and reservoirs, and even then it’s an expensive retrofit.
A bigger problem is that there are many other uses for the water that accumulates behind dams, namely irrigation and cities. And because the water in our rivers and reservoirs is scarce and unreliable, the water from dams for those other purposes is becoming ever-more precious.
Without large-scale ways to back-up solar energy California has had to block electricity coming from solar farms when it’s extremely sunny, or pay neighboring states to take it from us so we can avoid blowing-out our grid.
Despite what you’ve heard, there is no “battery revolution” on the way, for well-understood technical and economic reasons.
As for house cats, they don’t kill big, rare, threatened birds. What house cats kill are small, common birds, like sparrows, robins and jays. What kills big, threatened, and endangered birds—birds that could go extinct—like hawks, eagles, owls, and condors, are wind turbines.
In fact, wind turbines are the most serious new threat to important bird species to emerge in decades. The rapidly spinning turbines act like an apex predator which big birds never evolved to deal with.
Solar farms have similarly large ecological impacts. Building a solar farm is a lot like building any other kind of farm. You have to clear the whole area of wildlife.
In order to build one of the biggest solar farms in California the developers hired biologists to pull threatened desert tortoises from their burrows, put them on the back of pickup trucks, transport them, and cage them in pens where many ended up dying.
As we were learning of these impacts, it gradually dawned on me that there was no amount of technological innovation that could solve the fundamental problem with renewables.
You can make solar panels cheaper and wind turbines bigger, but you can’t make the sun shine more regularly or the wind blow more reliably. I came to understand the environmental implications of the physics of energy. In order to produce significant amounts of electricity from weak energy flows, you just have to spread them over enormous areas. In other words, the trouble with renewables isn’t fundamentally technical—it’s natural.
Dealing with energy sources that are inherently unreliable, and require large amounts of land, comes at a high economic cost.
There’s been a lot of publicity about how solar panels and wind turbines have come down in cost. But those one-time cost savings from making them in big Chinese factories have been outweighed by the high cost of dealing with their unreliability.
Consider California. Between 2011–17 the cost of solar panels declined about 75 percent, and yet our electricity prices rose five times more than they did in the rest of the U.S. It’s the same story in Germany, the world leader in solar and wind energy. Its electricity prices increased 50 percent between 2006–17, as it scaled up renewables.
I used to think that dealing with climate change was going to be expensive. But I could no longer believe this after looking at Germany and France.
Germany’s carbon emissions have been flat since 2009, despite an investment of $580 billion by 2025 in a renewables-heavy electrical grid, a 50 percent rise in electricity cost.
Meanwhile, France produces one-tenth the carbon emissions per unit of electricity as Germany and pays little more than half for its electricity. How? Through nuclear power.
Then, under pressure from Germany, France spent $33 billion on renewables, over the last decade. What was the result? A rise in the carbon intensity of its electricity supply, and higher electricity prices, too.
What about all the headlines about expensive nuclear and cheap solar and wind? They are largely an illusion resulting from the fact that 70 to 80 percent of the costs of building nuclear plants are up-front, whereas the costs given for solar and wind don’t include the high cost of transmission lines, new dams, or other forms of battery.
It’s reasonable to ask whether nuclear power is safe, and what happens with its waste.
It turns out that scientists have studied the health and safety of different energy sources since the 1960s. Every major study, including a recent one by the British medical journal Lancet, finds the same thing: nuclear is the safest way to make reliable electricity.
Strange as it sounds, nuclear power plants are so safe for the same reason nuclear weapons are so dangerous. The uranium used as fuel in power plants and as material for bombs can create one million times more heat per its mass than its fossil fuel and gunpowder equivalents.
It’s not so much about the fuel as the process. We release more energy breaking atoms than breaking chemical bonds. What’s special about uranium atoms is that they are easy to split.
Because nuclear plants produce heat without fire, they emit no air pollution in the form of smoke. By contrast, the smoke from burning fossil fuels and biomass results in the premature deaths of seven million people per year, according to the World Health Organization.
Even during the worst accidents, nuclear plants release small amounts of radioactive particulate matter from the tiny quantities of uranium atoms split apart to make heat.
Over an 80-year lifespan, fewer than 200 people will die from the radiation from the worst nuclear accident, Chernobyl, and zero will die from the small amounts of radiant particulate matter that escaped from Fukushima.
As a result, the climate scientist James Hanson and a colleague found that nuclear plants have actually saved nearly two million lives to date that would have been lost to air pollution.
Thanks to its energy density, nuclear plants require far less land than renewables. Even in sunny California, a solar farm requires 450 times more land to produce the same amount of energy as a nuclear plant.
Energy-dense nuclear requires far less in the way of materials, and produces far less in the way of waste compared to energy-dilute solar and wind.
A single Coke can’s worth of uranium provides all of the energy that the most gluttonous American or Australian lifestyle requires. At the end of the process, the high-level radioactive waste that nuclear plants produce is the very same Coke can of (used) uranium fuel. The reason nuclear is the best energy from an environmental perspective is because it produces so little waste and none enters the environment as pollution.
All of the waste fuel from 45 years of the Swiss nuclear program can fit, in canisters, on a basketball court-like warehouse, where like all spent nuclear fuel, it has never hurt a fly.
By contrast, solar panels require 17 times more materials in the form of cement, glass, concrete, and steel than do nuclear plants, and create over 200 times more waste.
We tend to think of solar panels as clean, but the truth is that there is no plan anywhere to deal with solar panels at the end of their 20 to 25 year lifespan.
Experts fear solar panels will be shipped, along with other forms of electronic waste, to be disassembled—or, more often, smashed with hammers—by poor communities in Africa and Asia, whose residents will be exposed to the dust from toxic heavy metals including lead, cadmium, and chromium.
Wherever I travel in the world I ask ordinary people what they think about nuclear and renewable energies. After saying they know next to nothing, they admit that nuclear is strong and renewables are weak. Their intuitions are correct. What most of us get wrong—understandably—is that weak energies are safer.
But aren’t renewables safer? The answer is no. Wind turbines, surprisingly, kill more people than nuclear plants.
In other words, the energy density of the fuel determines its environmental and health impacts. Spreading more mines and more equipment over larger areas of land is going to have larger environmental and human safety impacts.
It’s true that you can stand next to a solar panel without much harm while if you stand next to a nuclear reactor at full power you’ll die.
But when it comes to generating power for billions of people, it turns out that producing solar and wind collectors, and spreading them over large areas, has vastly worse impacts on humans and wildlife alike.
Our intuitive sense that sunlight is dilute sometimes shows up in films. That’s why nobody was shocked when the recent sequel of the dystopian sci-fi flick, “Blade Runner,” opened with a dystopian scene of California’s deserts paved with solar farms identical to the one that decimated desert tortoises.
Over the last several hundred years, human beings have been moving away from matter-dense fuels towards energy-dense ones. First we move from renewable fuels like wood, dung, and windmills, and towards the fossil fuels of coal, oil, and natural gas, and eventually to uranium.
Energy progress is overwhelmingly positive for people and nature. As we stop using wood for fuel we allow grasslands and forests to grow back, and the wildlife to return.
As we stop burning wood and dung in our homes, we no longer must breathe toxic indoor smoke. And as we move from fossil fuels to uranium we clear the outdoor air of pollution, and reduce how much we’ll heat up the planet.
Nuclear plants are thus a revolutionary technology—a grand historical break from fossil fuels as significant as the industrial transition from wood to fossil fuels before it.
The problem with nuclear is that it is unpopular, a victim of a 50 year-long concerted effort by fossil fuel, renewable energy, anti-nuclear weapons campaigners, and misanthropic environmentalists to ban the technology.
In response, the nuclear industry suffers battered wife syndrome, and constantly apologizes for its best attributes, from its waste to its safety.
Lately, the nuclear industry has promoted the idea that, in order to deal with climate change, “we need a mix of clean energy sources,” including solar, wind and nuclear. It was something I used to believe, and say, in part because it’s what people want to hear. The problem is that it’s not true.
France shows that moving from mostly nuclear electricity to a mix of nuclear and renewables results in more carbon emissions, due to using more natural gas, and higher prices, to the unreliability of solar and wind.
Oil and gas investors know this, which is why they made a political alliance with renewables companies, and why oil and gas companies have been spending millions of dollars on advertisements promoting solar, and funneling millions of dollars to said environmental groups to provide public relations cover.
What is to be done? The most important thing is for scientists and conservationists to start telling the truth about renewables and nuclear, and the relationship between energy density and environmental impact.
Bat scientists recently warned that wind turbines are on the verge of making one species, the Hoary bat, a migratory bat species, go extinct.
Another scientist who worked to build that gigantic solar farm in the California desert told High Country News, “Everybody knows that translocation of desert tortoises doesn’t work. When you’re walking in front of a bulldozer, crying, and moving animals, and cacti out of the way, it’s hard to think that the project is a good idea.”
I think it’s natural that those of us who became active on climate change gravitated toward renewables. They seemed like a way to harmonize human society with the natural world. Collectively, we have been suffering from an appeal-to-nature fallacy no different from the one that leads us to buy products at the supermarket labeled “all natural.” But it’s high time that those of us who appointed ourselves Earth’s guardians should take a second look at the science, and start questioning the impacts of our actions.
Now that we know that renewables can’t save the planet, are we really going to stand by and let them destroy it?
Michael Shellenberger is a Time Magazine “Hero of the Environment,” and president of Environmental Progress, an independent research and policy organization. Follow him on Twitter @ShellenbergerMD
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