Warnings to the reader

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OK, enough about climate change. I'm going to assume we are motivated to get off fossil fuels. Whatever your motivation, the aim of this book is to help you figure out the numbers and do the arithmetic so that you can evaluate policies; and to lay a factual foundation so that you can see which proposals add up. I'm not claiming that the arithmetic and numbers in this book are new; the books I've mentioned by Goodstein, Lomborg, and Lovelock, for example, are full of interesting numbers and back-of-envelope calculations, and there are many other helpful sources on the internet too (see the notes at the end of each chapter).

What I'm aiming to do in this book is to make these numbers simple and memorable; to show you how you can figure out the numbers for yourself; and to make the situation so clear that any thinking reader will be able to draw striking conclusions. I don't want to feed you my own conclusions. Convictions are stronger if they are self-generated, rather than taught. Understanding is a creative process. When you've read this book I hope you'll have reinforced the confidence that you can figure anything out.

I'd like to emphasize that the calculations we will do are deliberately imprecise. Simplification is a key to understanding. First, by rounding the numbers, we can make them easier to remember. Second, rounded numbers allow quick calculations. For example, in this book, the population of the United Kingdom is 60 million, and the population of the world is 6 billion. I'm perfectly capable of looking up more accurate figures, but accuracy would get in the way of fluent thought. For example, if we learn that the world's greenhouse gas emissions in 2000 were 34 billion tons of CO2-equivalent per year, then we can instantly note, without a calculator, that the average emissions per person are 5 or 6 tons of CO2-equivalent per person per year. This rough answer is not exact, but it's accurate enough to inform interesting conversations. For instance, if you learn that a round-trip intercontinental flight emits nearly two tons of CO2 per passenger, then knowing the average emissions yardstick (5-and-a-bit tons per year per person) helps you realize that just one such plane-trip per year corre

Figure 1.10. Reproduced by kind permission of PRIVATE EYE / Peter Dredge www.private-eye. co.uk.

"Look - it's Low Carbon Emission Man"

Figure 1.10. Reproduced by kind permission of PRIVATE EYE / Peter Dredge www.private-eye. co.uk.

sponds to over a third of the average person's carbon emissions.

I like to base my calculations on everyday knowledge rather than on trawling through impersonal national statistics. For example, if I want to estimate the typical wind speeds in Cambridge, I ask "is my cycling speed usually faster than the wind?" The answer is yes. So I can deduce that the wind speed in Cambridge is only rarely faster than my typical cycling speed of 20km/h. I back up these everyday estimates with other peoples' calculations and with official statistics. (Please look for these in each chapter's end-notes.) This book isn't intended to be a definitive store of super-accurate numbers. Rather, it's intended to illustrate how to use approximate numbers as a part of constructive consensual conversations.

In the calculations, I'll mainly use the United Kingdom and occasionally Europe, America, or the whole world, but you should find it easy to redo the calculations for whatever country or region you are interested in.

Let me close this chapter with a few more warnings to the reader. Not only will we make a habit of approximating the numbers we calculate; we'll also neglect all sorts of details that investors, managers, and economists have to attend to, poor folks. If you're trying to launch a renewable technology, just a 5% increase in costs may make all the difference between success and failure, so in business every detail must be tracked. But 5% is too small for this book's radar. This is a book about factors of 2 and factors of 10. It's about physical limits to sustainable energy, not current economic feasibility. While economics is always changing, the fundamental limits won't ever go away. We need to understand these limits.

Debates about energy policy are often confusing and emotional because people mix together factual assertions and ethical assertions.

Examples of factual assertions are "global fossil-fuel burning emits 34 billion tons of carbon dioxide equivalent per year;" and "if CO2 concentrations are doubled then average temperatures will increase by 1.5-5.8°C in the next 100 years;" and "a temperature rise of 2°C would cause the Greenland ice cap to melt within 500 years;" and "the complete melting of the Greenland ice cap would cause a 7-metre sea-level rise."

A factual assertion is either true or false; figuring out which may be difficult; it is a scientific question. For example, the assertions I just gave are either true or false. But we don't know whether they are all true. Some of them are currently judged "very likely." The difficulty of deciding which factual assertions are true leads to debates in the scientific community. But given sufficient scientific experiment and discussion, the truth or falsity of most factual assertions can eventually be resolved, at least "beyond reasonable doubt."

Examples of ethical assertions are "it's wrong to exploit global resources in a way that imposes significant costs on future generations;" and "polluting should not be free;" and "we should take steps to ensure that it's unlikely that CO2 concentrations will double;" and "politicians should agree a cap on CO2 emissions;" and "countries with the biggest CO2 emis-

sions over the last century have a duty to lead action on climate change;" and "it is fair to share CO2 emission rights equally across the world's population." Such assertions are not "either true or false." Whether we agree with them depends on our ethical judgment, on our values. Ethical assertions may be incompatible with each other; for example, Tony Blair's government declared a radical policy on CO2 emissions: "the United Kingdom should reduce its CO2 emissions by 60% by 2050;" at the same time Gordon Brown, while Chancellor in that government, repeatedly urged oil-producing countries to increase oil production.

This book is emphatically intended to be about facts, not ethics. I want the facts to be clear, so that people can have a meaningful debate about ethical decisions. I want everyone to understand how the facts constrain the options that are open to us. Like a good scientist, I'll try to keep my views on ethical questions out of the way, though occasionally I'll blurt something out - please forgive me.

Whether it's fair for Europe and North America to hog the energy cake is an ethical question; I'm here to remind you of the fact that we can't have our cake and eat it too; to help you weed out the pointless and ineffective policy proposals; and to help you identify energy policies that are compatible with your personal values.

We need a plan that adds up!

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