When the Industrial Revolution started,

工業革命開始時，

the amount of carbon sitting underneath Britain in the form of coal

埋藏在英國地下的

was as big as the amount of carbon sitting under Saudi Arabia

煤礦蘊藏量相等於

in the form of oil.

沙烏地阿拉伯的石油蘊藏量，

This carbon powered the Industrial Revolution,

這些煤炭推動了工業革命，

it put the "Great" in Great Britain,

讓大不列顛夠格稱為「大」國

and led to Britain's temporary world domination.

也讓英國短暫地稱霸世界。

And then, in 1918, coal production in Britain peaked,

時間來到1918年，英國的煤產量升至頂點，

and has declined ever since.

此後便一蹶不振。

In due course, Britain started using oil and gas from the North Sea,

其間，英國開始使用北海的

and in the year 2000,

石油和石油氣，而2000年時，

oil and gas production from the North Sea also peaked,

北海石油與石油氣的產量

and they're now on the decline.

也達到了顛峰，現在正在衰退。

These observations about the finiteness

觀察這些有限的、容易開採的、

of easily accessible, local, secure fossil fuels,

本土的、安全的化石燃料，

is a motivation for saying, "Well, what's next?

讓我們有股衝動要問：「接下來會怎樣？

What is life after fossil fuels going to be like?

化石燃料用盡後，生活會變成怎樣呢？

Shouldn't we be thinking hard about how to get off fossil fuels?"

我們不是應該殫思竭慮

Another motivation, of course, is climate change.

擺脫化石燃料的方法嗎？」

And when people talk about life after fossil fuels

另一個動機，當然是氣候的轉變。

and climate change action,

而人們論及化石燃料耗盡後的生活，

I think there's a lot of fluff,

與氣候變化的補救措施時，我認為其中有很多誤解，

a lot of greenwash, a lot of misleading advertising,

很多表裡不一的廠商，很多誤導的廣告，

and I feel a duty as a physicist to try to guide people around the claptrap

身為物理學家，我有責任

and help people understand the actions that really make a difference,

指引群眾避開譁眾取寵的話術陷阱，

and to focus on ideas that do add up.

協助群眾瞭解那些能實質改變現狀的行動，

Let me illustrate this

並集中焦點於合情理的想法。

with what physicists call a back-of-envelope calculation.

讓我以物理學家所謂的

We love back-of-envelope calculations.

「信封背面的算式」來闡述此事。

You ask a question, write down some numbers,

我們喜歡「信封背面的算式」。

and get an answer.

你提出一條問題，你寫下一些數字，

It may not be very accurate, but it may make you say, "Hmm."

然後你自己找答案。

So here's a question:

這樣未必能作到精準，但可能會讓你發出沉吟之聲：

Imagine if we said, "Oh yes, we can get off fossil fuels.

「嗯。」

We'll use biofuels. Problem solved.

那麼問題來了：想像一下，如果

Transport ... We don't need oil anymore."

我們說：「是啊，我們能擺脫化石燃料。

Well, what if we grew the biofuels for a road

我們會使用生化燃料。問題解決。

on the grass verge at the edge of the road?

運輸方面，我們不再需要石油了。」

How wide would the verge have to be for that to work out?

好，我們用在路邊種草叢

OK, so let's put in some numbers.

來培植生化原油如何？

Let's have our cars go at 60 miles per hour.

需要多少面積的草叢才能成事呢？

Let's say they do 30 miles per gallon.

好，我們來代入一些數字。

That's the European average for new cars.

假設我們的汽車以每小時60英哩行駛，

Let's say the productivity of biofuel plantations

假設這些車子每加侖可以行駛30英哩。

is 1,200 liters of biofuel per hectare per year.

那是歐洲新車款的平均數。

That's true of European biofuels.

就是說生化燃料製造廠的產量

And let's imagine the cars are spaced 80 meters apart from each other,

是每年每平方頃1,200升的生化燃料。

and they're perpetually going along this road.

這是歐洲生化燃料界的現況。

The length of the road doesn't matter,

再假設每輛汽車的間距是80米，

because the longer the road, the more biofuel plantation.

而且每輛車都是恆動地

What do we do with these numbers?

行駛於道路。

Take the first number, divide by the other three, and get eight kilometers.

道路的長度無所謂，因為道路愈長，

And that's the answer.

我們的生化燃料廠就越多。

That's how wide the plantation would have to be,

我們怎樣用這些數字運算呢？

given these assumptions.

好，你們用第一個數字，

And maybe that makes you say, "Hmm.

然後用餘下的三個數字除之，結果是八公里。

Maybe this isn't going to be quite so easy."

那就是答案。

And it might make you think,

那就是各廠房間該有的距離，

perhaps there's an issue to do with areas.

基於以上的假設。

And in this talk, I'd like to talk about land areas, and ask:

對此，你可能會說：「嗯，

Is there an issue about areas?

這件事好像沒那麼容易。」

The answer is going to be yes, but it depends which country you are in.

你也許還會想，關於土地面積

So let's start in the United Kingdom,

可能有某些爭議，而今天這次演說，

since that's where we are today.

我想談談土地面積，還要問問各位，

The energy consumption of the United Kingdom,

土地面積是否有爭議？答案是有，

the total energy consumption -- not just transport, but everything --

但需取決於你居住的國家。

I like to quantify it in lightbulbs.

所以我們就英國開始，

It's as if we've all got 125 lightbulbs on all the time,

因為那是我們現在住的地方。

125 kilowatt-hours per day per person

英國的能源消耗，

is the energy consumption of the UK.

能源消耗總值，不只是運輸，而是囊括全部，

So there's 40 lightbulbs' worth for transport,

我喜歡以燈泡來量化這數字。

40 lightbulbs' worth for heating,

那就像我們每個人全天開着125顆電燈泡，

and 40 lightbulbs' worth for making electricity,

每人每天125千瓦，

and other things are relatively small,

這就是英國的能源消耗量。

compared to those three big fish.

所以共有40個電燈泡可用於交通，

It's actually a bigger footprint if we take into account

40個電燈泡可用於暖氣。

the embodied energy in the stuff we import into our country as well.

40個電燈泡可用於發電，

And 90 percent of this energy, today, still comes from fossil fuels,

比起那三條「大魚」，

and 10 percent, only, from other, greener -- possibly greener -- sources,

其他的相對來說小得多。

like nuclear power and renewables.

其實，如果我們將進口產品的實際耗能也計算進去，

So.

廠房所需的面積會更大

That's the UK.

而今天這些能源有百分之九十

The population density of the UK is 250 people per square kilometer.

仍來自化石燃料，只有百分之十

I'm now going to show you other countries by these same two measures.

來自其他較環保的──可能較環保的──資源，

On the vertical axis, I'm going to show you how many lightbulbs --

如核能和再生能源。

what our energy consumption per person is.

因此，

We're at 125 lightbulbs per person,

這就是英國的情況，而英國人口密度

and that little blue dot there is showing you the land area

是每平方公里250人，

of the United Kingdom.

現在我要讓你們看看其他國家

The population density is on the horizontal axis,

以相同兩種計算方式的結果。

and we're 250 people per square kilometer.

在垂直軸，我會指出

Let's add European countries in blue,

有多少電燈泡──也就是我們的個人能源消耗量，

and you can see there's quite a variety.

我們的個人消耗量是125個電燈泡，

I should emphasize, both of these axes are logarithmic;

而那個小藍點表示的是

as you go from one gray bar to the next gray bar,

英國的土地面積，

you're going up a factor of 10.

而人口密度就在橫線軸，

Next, let's add Asia in red,

我們每平方公里有250人。

the Middle East and North Africa in green,

然後我們以藍色標示加入的歐洲國家，

sub-Saharan Africa in blue,

你們會發現差異相當明顯。

black is South America,

我必須強調，這兩條軸線

purple is Central America,

都是對數。你們從這條灰線

and then in pukey-yellow, we have North America,

移到另一條灰線時，差異是10的平方。

Australia and New Zealand.

再來，我們用紅色標示加入的亞洲，

You can see the great diversity of population densities

以綠色標示中東和北非，

and of per capita consumptions.

以藍色標示次撒哈拉非洲，

Countries are different from each other.

黑色是南美洲，

Top left, we have Canada and Australia, with enormous land areas,

紫色是中美洲，

very high per capita consumption -- 200 or 300 lightbulbs per person --

然後是噁心的黃色，北美洲、

and very low population densities.

澳洲和新西蘭在此。

Top right: Bahrain has the same energy consumption

你們可看到，這些地區的人口密度

per person, roughly, as Canada --

以及人均消耗量的差異極大。

over 300 lightbulbs per person,

每國家各有不同之處。

but their population density is a factor of 300 times greater,

左上方是加拿大和澳洲，土地面積龐大，

1,000 people per square kilometer.

人均消耗量也極高，

Bottom right: Bangladesh has the same population density as Bahrain,

每人200 至300個電燈泡，

but consumes 100 times less per person.

而人口密度非常低。

Bottom left: well, there's no one.

右上方的巴林的人平均能量消耗

But there used to be a whole load of people.

幾乎和加拿大ㄧ樣。

Here's another message from this diagram.

每人超過300個電燈泡，

I've added on little blue tails behind Sudan, Libya,

但是這國家的人口密度高了300倍，

China, India, Bangladesh.

每平方公里1,000人。

That's 15 years of progress.

右下方，孟加拉和巴林人口密度相若，

Where were they 15 years ago, and where are they now?

但人平均消耗量只有百分之ㄧ。

And the message is,

左下方，嗯，罕無人煙。

most countries are going to the right, and they're going up.

但這裏從前有一大群人。

Up and to the right: bigger population density

這張圖表還蘊藏了另一則訊息。

and higher per capita consumption.

我在蘇丹、利比亞、中國、印度、孟加拉

So, we may be off in the top right-hand corner, slightly unusual,

後頭加上了藍色細線。

the United Kingdom accompanied by Germany,

那是15年來的進展。

Japan, South Korea, the Netherlands,

15年前他們在何方？而今天他們又在哪兒呢？

and a bunch of other slightly odd countries,

另一個訊息是，大部分國家都在向右移，

but many other countries are coming up and to the right to join us.

還會向上移。

So we're a picture, if you like,

上右方，人口密度更高

of what the future energy consumption

人均消耗量也更高。

might be looking like in other countries, too.

所以，也許我們還沒到最右邊的上面，

I've also added in this diagram now some pink lines

有點奇怪的是，英國之後接著

that go down and to the right.

德國、日本、南韓、荷蘭，

Those are lines of equal power consumption per unit area,

和一連串有點古怪的國家，

which I measure in watts per square meter.

不過很多其他國家正向右上方移動，

So, for example, the middle line there, 0.1 watts per square meter,

準備加入我們。

is the energy consumption per unit area of Saudi Arabia,

所以如果要用比喻，我們像是一種未來的寫照，

Norway, Mexico in purple, and Bangladesh 15 years ago.

那些國家也可能會步上我們的後塵。

Half of the world's population lives in countries

現在我在圖表上又加了幾條粉紅線，

that are already above that line.

由左上向右下。

The United Kingdom is consuming 1.25 watts per square meter.

用這幾條線劃分單位土地耗電量相同的區域，

So is Germany, and Japan is consuming a bit more.

計算單位是每平方米消耗的瓦數。

So, let's now say why this is relevant.

所以，舉例來說，中間線那條線，

Why is it relevant?

每平方米0.1瓦，是沙地阿拉伯、挪威、

Well, we can measure renewables in the same units

墨西哥的單位土地能源消耗，以紫色顯示，

and other forms of power production in the same units.

和15年前的孟加拉，

Renewables is one of the leading ideas

而世界人口有一半都住在

for how we could get off our 90 percent fossil-fuel habit.

這條線右上方的國家。

So here come some renewables.

英國目前的消耗量是

Energy crops deliver half a watt per square meter

每平方米1.25瓦。

in European climates.

德國亦然，而日本的消耗量稍高。

What does that mean?

好，我們現在來

You might have anticipated that result,

說說為何這件事意義重大，為何意義重大？

given what I told you about the biofuel plantation a moment ago.

我們用相同面積使用再生能源來計算，

Well, we consume 1.25 watts per square meter.

或是相同面積使用其他形式製造的能源。

What this means is,

我們使用的能源有90%要依賴石化燃料，

even if you covered the whole of the United Kingdom with energy crops,

使用再生能源是劃時代的解決方案之ㄧ。

you couldn't match today's energy consumption.

我們現在有幾種再生能源。

Wind power produces a bit more -- 2.5 watts per square meter.

歐洲地區的農產能源

But that's only twice as big as 1.25 watts per square meter.

每平方米可提供0.5瓦。

So that means if you wanted, literally, to produce total energy consumption

這代表什麼？你們可能猜到答案了，

in all forms, on average, from wind farms,

基於我剛剛對你們說過的，

you need wind farms half the area of the UK.

生化燃料製造廠。

I've got data to back up all these assertions, by the way.

好，我們每平方米消耗1.25瓦。

Next, let's look at solar power.

這代表即使我們將能源農作物

Solar panels, when you put them on a roof,

種滿整個大英帝國，

deliver about 20 watts per square meter in England.

也無法滿足現今的能源消耗量。

If you really want to get a lot from solar panels,

風力能源的產值稍高，

you need to adopt the traditional Bavarian farming method,

每平方米2.5瓦，但那也不過比每平方米1.25瓦

where you leap off the roof,

多ㄧ倍而已。

and coat the countryside with solar panels, too.

那表示，如果我們要用風力發電來

Solar parks, because of the gaps between the panels, deliver less.

供應全國所有的能源消耗，

They deliver about 5 watts per square meter of land area.

我們需要的風力發電廠將占據半個英國。

And here's a solar park in Vermont, with real data,

附帶一提，所有的假設我都有數據支持，

delivering 4.2 watts per square meter.

其次，讓我們看看太陽能。

Remember where we are, 1.25 watts per square meter,

太陽能板，在英國，我們在屋頂設置太陽能板時，

wind farms 2.5, solar parks about five.

每平方米大約能產生20瓦。

So whichever of those renewables you pick,

如果我們真的想大量使用太陽能板發電，

the message is, whatever mix of those renewables you're using,

我們得採用傳統的巴伐利亞耕作法，

if you want to power the UK on them,

鋪完屋頂後我們要跳下來，把郊野農地也鋪上

you're going to need to cover something like

太陽能板。

20 percent or 25 percent of the country

太陽能電廠，因為板子之間有空隙，

with those renewables.

產能較少。太陽能產生的能量

I'm not saying that's a bad idea; we just need to understand the numbers.

大約是每平方米的土地 5 瓦。

I'm absolutely not anti-renewables. I love renewables.

這是佛蒙特洲ㄧ間太陽能發電廠的實際數據，

But I'm also pro-arithmetic.

每平方米4.2瓦的產能。

(Laughter)

記着我們住哪兒，每平方米1.25瓦，

Concentrating solar power in deserts delivers larger powers per unit area,

風力發電廠2.5瓦，太陽能發電廠大約5瓦。

because you don't have the problem of clouds.

所以，無論如何，無論我們選擇了哪種再生能源，

So, this facility delivers 14 watts per square meter;

我們的啟發是，無論我們如何搭配使用這些再生能源，

this one 10 watts per square meter;

如果英國想依賴這些再生能源，

and this one in Spain, 5 watts per square meter.

這些再生能源的裝置

Being generous to concentrating solar power,

大約會覆蓋英國國土的

I think it's perfectly credible it could deliver 20 watts per square meter.

百分之 20 或 25。

So that's nice.

我不是在批評這個點子。

Of course, Britain doesn't have any deserts.

我們必須了解這些數據。

Yet.

我絕對不是反對再生能源。我愛再生能源。

(Laughter)

但我也喜歡算術。(眾笑)

So here's a summary so far:

將太陽能發電裝置集中於沙漠，

All renewables, much as I love them, are diffuse.

產生的能量較高，因為這樣不會有

They all have a small power per unit area,

雲層遮蔽的問題，

and we have to live with that fact.

所以這種設施的產能是每平方米14瓦，

And that means, if you do want renewables to make a substantial difference

這個是每平方米10瓦，

for a country like the United Kingdom

西班牙的這個是每平方米5瓦。

on the scale of today's consumption,

以太陽能做為發電主力，

you need to be imagining renewable facilities that are country-sized.

我認為每平方米20瓦的電力

Not the entire country,

絕對沒問題，所以這是可行的。

but a fraction of the country, a substantial fraction.

當然，英國沒有任何沙漠。

There are other options for generating power as well,

至少目前還沒有。(眾笑)

which don't involve fossil fuels.

這是至此為止的總結

So there's nuclear power, and on this ordinance survey map,

所有這些再生能源，和我對它們的愛一樣，到處都是。

you can see there's a Sizewell B inside a blue square kilometer.

所有再生能源每單位面積的產能都不高，

That's one gigawatt in a square kilometer,

我們要接受這項事實。

which works out to 1,000 watts per square meter.

那表示，今天如果我們真的想用再生能源

So by this particular metric,

來大幅改變像英國這種國家的

nuclear power isn't as intrusive as renewables.

能源消耗量，

Of course, other metrics matter, too,

我們設想的再生能源設備的規模

and nuclear power has all sorts of popularity problems.

是國家級的，不是蓋滿整個國家，

But the same goes for renewables as well.

而是國土的某個區域，可觀的區域。

Here's a photograph of a consultation exercise in full swing

還有其他方式能產生能源，

in the little town of Penicuik just outside Edinburgh,

其中不包括化石燃料。

and you can see the children of Penicuik celebrating

那就是核能，而這張地形測量圖上，

the burning of the effigy of the windmill.

我們可以看到賽滋威爾 B 核電廠

So --

位於ㄧ片方形的藍色中。

(Laughter)

意思是一平方公里 10 億瓦，

People are anti-everything,

產量達到每平方米1,000瓦。

and we've got to keep all the options on the table.

由於這個度量的產值那麼高，核能

What can a country like the UK do on the supply side?

不像再生能源那麼佔空間。