08.b Boek sewtha.pdf
Tekst van het document
Copyright David JC MacKay 2009. This electronic copy is provided, free, for personal use only. See www.withouthotair.com.
Sustainable Energy — without the hot air
Version 3.5.2. November 3, 2008. This Cover-sheet must not appear in the printed book. high-resolution edition.
Copyright David JC MacKay 2009. This electronic copy is provided, free, for personal use only. See www.withouthotair.com.
The quest for safe, secure and sustainable energy poses one of the most critical challenges of our age. But how much energy do we need, and can we get it all from renewable sources? David MacKay sets out to find the answer through a forensic numerical analysis of what we use and what we can produce. His conclusions starkly reveal the difficult choices that must urgently be taken and readers interested in how we will power our society in the future will find this an illuminating read. For anyone with influence on energy policy, whether in government, business or a campaign group, this book should be compulsory reading. This is a technically precise and readable account of the challenges ahead. It will be a core reference on my shelf for many years to come. Tony Juniper Former Executive Director, Friends of the Earth Engagingly written, packed with useful information, and refreshingly factual. Peter Ainsworth MP Shadow Secretary of State for Environment, Food, and Rural Affairs
This is a really valuable contribution to the continuing discussion of energy policy. The author uses a potent mixture of arithmetic and common sense to dispel some myths and slay some sacred cows. The book is an essential reference work for anyone with an interest in energy who really wants to understand the numbers. Lord Oxburgh KBE FRS Former Chairman, Royal Dutch Shell This is a brilliant book that is both a racy read and hugely informative. Prof David Newbery FBA So much uninformed rhetoric is thrown about on climate change and energy systems that there is an urgent need for an authoritative study setting out just what can and cannot realistically be done to achieve sustainable energy. This hugely important book fills that gap both technically and highly readably. It should be a ‘must read’ not only at home and in industry, but on each Government Minister’s desk, and not just in the UK. Michael Meacher MP Former Environment Minister
David MacKay sets out to dispel the half truths, distortions and nonsense which make up so much of what we’re told about climate change and our energy needs. This book is readable, accessible and thorough. He cuts through unfounded opinion and takes us to facts and figures which speak for themselves. It’s a useful guide for both layman and expert. I heartily recommend it.
David MacKay’s book sets the standard for all future debate on energy policy and climate change. His dedication to the facts and to rational argument is admirable in a field beset by propaganda and wishful thinking on all sides, and even if his conclusions eventually date, as all scientific work must, his approach will live on for a very long time.
Graham Stuart MP
David Howarth MP
This remarkable book from an expert in the energy field sets out, with enormous clarity and objectivity, the various alternative low-carbon pathways that are open to us. Policy makers, researchers, private sector decision makers, and NGOs, all will benefit from these words of wisdom.
The choices that we make (or fail to make) in the coming years about sustainable energy will determine what world future generations will inherit. How do we arrive at rational decisions? In his book, David MacKay does not tell us what to choose but how to. Basic arithmetic is all it takes to distinguish between viable strategies and pipedreams. Anybody who feels responsible for the future of our society should read this book.
Sir David King FRS Chief Scientific Adviser to the UK Government, 2000–08 Started reading your book yesterday. Took the day off work today so that I could continue reading it. It is a fabulous, witty, no-nonsense, valuable piece of work, and I am busy sending it to everyone I know. Matthew Sullivan Carbon Advice Group Plc
Prof Daan Frenkel FRS A total delight to read. Extraordinarily clear and engaging. Chris Goodall Author of Ten Technologies to Save the Planet continued on next page
Copyright David JC MacKay 2009. This electronic copy is provided, free, for personal use only. See www.withouthotair.com.
David MacKay’s book is an intellectually satisfying, refreshing contribution to really understanding the complex issues of energy supply and use. It debunks the emotional claptrap which passes for energy policy and puts real numbers into the equations. It should be read by everyone, especially politicians. Prof Ian Fells CBE Founder chairman of NaREC, the New and Renewable Energy Centre Preventing climate chaos will require sophisticated and well informed social, economic and technological choices. Economic and social ‘laws’ are not immutable – politicians can and should reshape economics to deliver renewable energy and lead cultural change to save energy – but MacKay reminds us that even they “canna change the laws of physics”! MacKay’s book alone doesn’t have all the answers, but it provides a solid foundation to help us make well-informed choices, as individuals and more importantly as societies. Duncan McLaren Chief Executive, Friends of the Earth Scotland MacKay brings a welcome dose of common sense into the discussion of energy sources and use. Fresh air replacing hot air. Prof Mike Ashby FRS Author of Materials and the environment By focusing on the metrics of energy consumption and production, in addition to the aspiration we all share for viable renewable energy, David MacKay’s book provides a welcome addition to the energy literature.
“Sustainable Energy – without the hot air” is a vast undertaking that provides both a practical guide and a reference manual. Perhaps ironically for a book on sustainable energy, MacKay’s account of the numbers illustrates just how challenging replacing fossil fuel will be, and why both energy conservation and new energy technology are necessary. Darran Messem Vice President Fuel Development Royal Dutch Shell This is a must read for anyone who wants to help heal our world. Carol Atkinson Chief Executive of BRE Global
At last a book that comprehensively reveals the true facts about sustainable energy in a form that is both highly readable and entertaining. A “must read” for all those who have a part to play in addressing our climate crisis. Robert Sansom Director of Strategy and Sustainable Development EDF Energy So much has been written about meeting future energy needs that it hardly seems possible to add anything useful, but David MacKay has managed it. His new book is a delight to read and will appeal especially to practical people who want to understand what is important in energy and what is not. Like Lord Kelvin before him, Professor MacKay realises that in many fields, and certainly in energy, unless you can quantify something you can never properly understand it. As a result, his fascinating book is also a mine of quantitative information for those of us who sometimes talk to our friends about how we supply and use energy, now and in the future. Dr Derek Pooley CBE Former Chief Scientist at the Department of Energy, Chief Executive of the UK Atomic Energy Authority and Member of the European Union Advisory Group on Energy The need to reduce our dependence on fossil fuels and to find sustainable sources of energy is desperate. But much of the discussion has not been based on data on how energy is consumed and how it is produced.
This book fills that need in an accessible form, and a copy should be in every household. Prof Robert Hinde CBE FRS FBA Executive Committee, Pugwash UK What a lovely book . . . I feel better in a way that a cancer patient might feel after reading something in-depth about his disease. Richard Procter Beautifully clear and amazingly readable. Prof Willy Brown CBE I took it to the loo and almost didn’t come out again. Matthew Moss
Copyright David JC MacKay 2009. This electronic copy is provided, free, for personal use only. See www.withouthotair.com.
Sustainable Energy — without the hot air
Copyright David JC MacKay 2009. This electronic copy is provided, free, for personal use only. See www.withouthotair.com.
Copyright David JC MacKay 2009. This electronic copy is provided, free, for personal use only. See www.withouthotair.com.
Sustainable Energy — without the hot air David JC MacKay
UIT CAMBRIDGE, ENGLAND
Copyright David JC MacKay 2009. This electronic copy is provided, free, for personal use only. See www.withouthotair.com.
First published in England in 2009. UIT Cambridge Ltd. PO Box 145 Cambridge CB4 1GQ England Tel: +44 1223 302 041 Web: www.uit.co.uk Copyright © 2009 David JC MacKay All rights reserved. ISBN 978-0-9544529-3-3 (paperback) ISBN 978-1-906860-01-1 (hardback) The right of David JC MacKay to be identified as the author of this work has been asserted by him in accordance with the Copyright, Designs and Patents Act 1988. While this publication intends to provide accurate and authoritative information in regard to the subject matter covered, neither the publisher nor the author makes any representation, express or implied, with regard to the accuracy of information contained in this book, nor do they accept any legal responsibility or liability for any errors or omissions that may be made. This work is supplied with the understanding that UIT Cambridge Ltd and its authors are supplying information, but are not attempting to render engineering or other professional services. If such services are required, the assistance of an appropriate professional should be sought. Many of the designations used by manufacturers and sellers to distinguish their products are claimed as trade-marks. UIT Cambridge Ltd acknowledges trademarks as the property of their respective owners. 10 9 8 7 6 5 4 3 2 1 3.5.2
Copyright David JC MacKay 2009. This electronic copy is provided, free, for personal use only. See www.withouthotair.com.
to those who will not have the benefit of two billion years’ accumulated energy reserves
Copyright David JC MacKay 2009. This electronic copy is provided, free, for personal use only. See www.withouthotair.com.
Preface What’s this book about? I’m concerned about cutting UK emissions of twaddle – twaddle about sustainable energy. Everyone says getting off fossil fuels is important, and we’re all encouraged to “make a difference,” but many of the things that allegedly make a difference don’t add up. Twaddle emissions are high at the moment because people get emotional (for example about wind farms or nuclear power) and no-one talks about numbers. Or if they do mention numbers, they select them to sound big, to make an impression, and to score points in arguments, rather than to aid thoughtful discussion. This is a straight-talking book about the numbers. The aim is to guide the reader around the claptrap to actions that really make a difference and to policies that add up.
This is a free book I didn’t write this book to make money. I wrote it because sustainable energy is important. If you would like to have the book for free for your own use, please help yourself: it’s on the internet at www.withouthotair.com. This is a free book in a second sense: you are free to use all the material in this book, except for the cartoons and the photos with a named photographer, under the Creative Commons Attribution-Non-Commercial-ShareAlike 2.0 UK: England & Wales Licence. (The cartoons and photos are excepted because the authors have generally given me permission only to include their work, not to share it under a Creative Commons license.) You are especially welcome to use my materials for educational purposes. My website includes separate high-quality files for each of the figures in the book.
viii
Copyright David JC MacKay 2009. This electronic copy is provided, free, for personal use only. See www.withouthotair.com.
How to operate this book Some chapters begin with a quotation. Please don’t assume that my quoting someone means that I agree with them; think of these quotes as provocations, as hypotheses to be critically assessed. Many of the early chapters (numbered 1, 2, 3, . . . ) have longer technical chapters (A, B, C, . . . ) associated with them. These technical chapters start on page 254. At the end of each chapter are further notes and pointers to sources and references. I find footnote marks distracting if they litter the main text of the book, so the book has no footnote marks. If you love footnote marks, you can usefully add them – almost every substantive assertion in the text will have an associated note at the end of its chapter giving sources or further information. The text also contains pointers to web resources. When a web-pointer is monstrously long, I’ve used the TinyURL service, and put the tiny code in the text like this – [yh8xse] – and the full pointer at the end of the book on page 344. yh8xse is a shorthand for a tiny URL, in this case: http://tinyurl.com/yh8xse. A complete list of all the URLs in this book is provided at http://tinyurl.com/yh8xse. I welcome feedback and corrections. I am aware that I sometimes make booboos, and in earlier drafts of this book some of my numbers were off by a factor of two.
While I hope that the errors that remain are smaller than that, I expect to further update some of the numbers in this book as I continue to learn about sustainable energy. How to cite this book: David J.C. MacKay. Sustainable Energy – without the hot air. UIT Cambridge, 2008. ISBN 978-0-9544529-3-3. Available free online from www.withouthotair.com.
ix
Copyright David JC MacKay 2009. This electronic copy is provided, free, for personal use only. See www.withouthotair.com.
Contents I
Numbers, not adjectives . . . . . . . . . . . . . . . . . 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
II
1
Motivations . . . . . . . . . . . . . . . . . . . . . . . . . . The balance sheet . . . . . . . . . . . . . . . . . . . . . . Cars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wind . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Planes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Solar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Heating and cooling . . . . . . . . . . . . . . . . . . . . . Hydroelectricity . . . . . . . . . . . . . . . . . . . . . . . Light . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Offshore wind . . . . . . . . . . . . . . . . . . . . . . . . Gadgets . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wave . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Food and farming . . . . . . . . . . . . . . . . . . . . . . Tide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stuff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Geothermal . . . . . . . . . . . . . . . . . . . . . . . . . . Public services . . . . . . . . . . . . . . . . . . . . . . . . Can we live on renewables? . . . . . . . . . . . . . . . .
2 22 29 32 35 38 50 55 57 60 68 73 76 81 88 96 100 103
Making a difference . . . . . . . . . . . . . . . . . . . .
113
19 20 21 22 23 24 25 26 27 28 29 30 31 32
114 118 140 155 157 161 177 186 203 214 222 231 240 250
Every BIG helps . . . . . . . . . . . . . . . . . . . . . . . Better transport . . . . . . . . . . . . . . . . . . . . . . . Smarter heating . . . . . . . . . . . . . . . . . . . . . . . Efficient electricity use . . . . . . . . . . . . . . . . . . . Sustainable fossil fuels? . . . . . . . . . . . . . . . . . . . Nuclear? . . . . . . . . . . . . . . . . . . . . . . . . . . . Living on other countries’ renewables? . . . . . . . . . . Fluctuations and storage . . . . . . . . . . . . . . . . . . Five energy plans for Britain . . . . . . . . . . . . . . . . Putting costs in perspective . . . . . . . . . . . . . . . . What to do now . . . . . . . . . . . . . . . . . . . . . . . Energy plans for Europe, America, and the World . . . The last thing we should talk about . . . . . . . . . . . . Saying yes . . . . . . . . . . . . . . . . . . . . . . . . . .
Copyright David JC MacKay 2009. This electronic copy is provided, free, for personal use only. See www.withouthotair.com.
III
IV
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .
251
Technical chapters . . . . . . . . . . . . . . . . . . . .
253
A B C D E F G H
Cars II . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wind II . . . . . . . . . . . . . . . . . . . . . . . . . . . . Planes II . . . . . . . . . . . . . . . . . . . . . . . . . . . . Solar II . . . . . . . . . . . . . . . . . . . . . . . . . . . . Heating II . . . . . . . . . . . . . . . . . . . . . . . . . . . Waves II . . . . . . . . . . . . . . . . . . . . . . . . . . . . Tide II . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stuff II . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
254 263 269 283 289 307 311 322
Useful data . . . . . . . . . . . . . . . . . . . . . . . .
327
I J K
Quick reference . . . . . . . . . . . . . . . . . . . . . . . Populations and areas . . . . . . . . . . . . . . . . . . . . UK energy history . . . . . . . . . . . . . . . . . . . . . .
328 338 342
List of web links . . . . . . . . . . . . . . . . . . . . . . . . . .
344
Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . .
348
Index
355
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
About the author
. . . . . . . . . . . . . . . . . . . . . . . . .
367
Copyright David JC MacKay 2009. This electronic copy is provided, free, for personal use only. See www.withouthotair.com.
Copyright David JC MacKay 2009. This electronic copy is provided, free, for personal use only. See www.withouthotair.com.
Part I
Numbers, not adjectives
Copyright David JC MacKay 2009. This electronic copy is provided, free, for personal use only. See www.withouthotair.com.
1
Motivations We live at a time when emotions and feelings count more than truth, and there is a vast ignorance of science. James Lovelock
I recently read two books, one by a physicist, and one by an economist. In Out of Gas, Caltech physicist David Goodstein describes an impending energy crisis brought on by The End of the Age of Oil. This crisis is coming soon, he predicts: the crisis will bite, not when the last drop of oil is extracted, but when oil extraction can’t meet demand – perhaps as soon as 2015 or 2025. Moreover, even if we magically switched all our energyguzzling to nuclear power right away, Goodstein says, the oil crisis would simply be replaced by a nuclear crisis in just twenty years or so, as uranium reserves also became depleted. In The Skeptical Environmentalist, Bjørn Lomborg paints a completely different picture. “Everything is fine.” Indeed, “everything is getting better.” Furthermore, “we are not headed for a major energy crisis,” and “there is plenty of energy.” How could two smart people come to such different conclusions? I had to get to the bottom of this. Energy made it into the British news in 2006. Kindled by tidings of great climate change and a tripling in the price of natural gas in just six years, the flames of debate are raging. How should Britain handle its energy needs? And how should the world? “Wind or nuclear?”, for example. Greater polarization of views among smart people is hard to imagine.
During a discussion of the proposed expansion of nuclear power, Michael Meacher, former environment minister, said “if we’re going to cut greenhouse gases by 60% . . . by 2050 there is no other possible way of doing that except through renewables;” Sir Bernard Ingham, former civil servant, speaking in favour of nuclear expansion, said “anybody who is relying upon renewables to fill the [energy] gap is living in an utter dream world and is, in my view, an enemy of the people.” Similar disagreement can be heard within the ecological movement. All agree that something must be done urgently, but what? Jonathan Porritt, chair of the Sustainable Development Commission, writes: “there is no justification for bringing forward plans for a new nuclear power programme at this time, and . . . any such proposal would be incompatible with [the Government’s] sustainable development strategy;” and “a nonnuclear strategy could and should be sufficient to deliver all the carbon savings we shall need up to 2050 and beyond, and to ensure secure access to reliable sources of energy.” In contrast, environmentalist James Lovelock writes in his book, The Revenge of Gaia: “Now is much too late to establish sustainable development.” In his view, power from nuclear fission, while 2
David Goodstein’s Out of Gas (2004).
Bjørn Lomborg’s The Skeptical Environmentalist (2001).
The Revenge of Gaia: Why the earth is fighting back – and how we can still save humanity. James Lovelock (2006). © Allen Lane.
Copyright David JC MacKay 2009. This electronic copy is provided, free, for personal use only. See www.withouthotair.com.
1 — Motivations
3
not recommended as the long-term panacea for our ailing planet, is “the only effective medicine we have now.” Onshore wind turbines are “merely . . . a gesture to prove [our leaders’] environmental credentials.” This heated debate is fundamentally about numbers. How much energy could each source deliver, at what economic and social cost, and with what risks? But actual numbers are rarely mentioned. In public debates, people just say “Nuclear is a money pit” or “We have a huge amount of wave and wind.” The trouble with this sort of language is that it’s not sufficient to know that something is huge: we need to know how the one “huge” compares with another “huge,” namely our huge energy consumption. To make this comparison, we need numbers, not adjectives. Where numbers are used, their meaning is often obfuscated by enormousness. Numbers are chosen to impress, to score points in arguments, rather than to inform.
“Los Angeles residents drive 142 million miles – the distance from Earth to Mars – every single day.” “Each year, 27 million acres of tropical rainforest are destroyed.” “14 billion pounds of trash are dumped into the sea every year.” “British people throw away 2.6 billion slices of bread per year.” “The waste paper buried each year in the UK could fill 103 448 double-decker buses.” If all the ineffective ideas for solving the energy crisis were laid end to end, they would reach to the moon and back. . . . I digress. The result of this lack of meaningful numbers and facts? We are inundated with a flood of crazy innumerate codswallop. The BBC doles out advice on how we can do our bit to save the planet – for example “switch off your mobile phone charger when it’s not in use;” if anyone objects that mobile phone chargers are not actually our number one form of energy consumption, the mantra “every little helps” is wheeled out. Every little helps? A more realistic mantra is: if everyone does a little, we’ll achieve only a little. Companies also contribute to the daily codswallop as they tell us how wonderful they are, or how they can help us “do our bit.” BP’s website, for example, celebrates the reductions in carbon dioxide (CO2 ) pollution they hope to achieve by changing the paint used for painting BP’s ships.
Does anyone fall for this? Surely everyone will guess that it’s not the exterior paint job, it’s the stuff inside the tanker that deserves attention, if society’s CO2 emissions are to be significantly cut? BP also created a web-based carbon absolution service, “targetneutral.com,” which claims that they can “neutralize” all your carbon emissions, and that it “doesn’t cost the earth” – indeed, that your CO2 pollution can be cleaned up for just £40 per year. How can this add up? – if the true cost of fixing climate change were £40 per person then the government could fix it with the loose change in the Chancellor’s pocket! Even more reprehensible are companies that exploit the current concern for the environment by offering “water-powered batteries,” “biodegrad-
For the benefit of readers who speak American, rather than English, the translation of “every little helps” into American is “every little bit helps.”
Copyright David JC MacKay 2009. This electronic copy is provided, free, for personal use only. See www.withouthotair.com.
4
Sustainable Energy – without the hot air
able mobile phones,” “portable arm-mounted wind-turbines,” and other pointless tat. Campaigners also mislead. People who want to promote renewables over nuclear, for example, say “offshore wind power could power all UK homes;” then they say “new nuclear power stations will do little to tackle climate change” because 10 new nuclear stations would “reduce emissions only by about 4%.” This argument is misleading because the playing field is switched half-way through, from the “number of homes powered” to “reduction of emissions.” The truth is that the amount of electrical power generated by the wonderful windmills that “could power all UK homes” is exactly the same as the amount that would be generated by the 10 nuclear power stations! “Powering all UK homes” accounts for just 4% of UK emissions. Perhaps the worst offenders in the kingdom of codswallop are the people who really should know better – the media publishers who promote the codswallop – for example, New Scientist with their article about the “water-powered car.”∗ In a climate where people don’t understand the numbers, newspapers, campaigners, companies, and politicians can get away with murder. We need simple numbers, and we need the numbers to be comprehensible, comparable, and memorable. With numbers in place, we will be better placed to answer questions such as these:
∗ See this chapter’s notes (p19) for the awful details. (Every chapter has endnotes giving references, sources, and details of arguments. To avoid distracting the reader, I won’t include any more footnote marks in the text.)
1. Can a country like Britain conceivably live on its own renewable energy sources? 2. If everyone turns their thermostats one degree closer to the outside temperature, drives a smaller car, and switches off phone chargers when not in use, will an energy crisis be averted? 3. Should the tax on transportation fuels be significantly increased? Should speed-limits on roads be halved? 4. Is someone who advocates windmills over nuclear power stations “an enemy of the people”? 5. If climate change is “a greater threat than terrorism,” should governments criminalize “the glorification of travel” and pass laws against “advocating acts of consumption”? 6. Will a switch to “advanced technologies” allow us to eliminate carbon dioxide pollution without changing our lifestyle? 7. Should people be encouraged to eat more vegetarian food? 8. Is the population of the earth six times too big?
Figure 1.1. This Greenpeace leaflet arrived with my junk mail in May 2006. Do beloved windmills have the capacity to displace hated cooling towers?
Copyright David JC MacKay 2009. This electronic copy is provided, free, for personal use only. See www.withouthotair.com.
5
1 — Motivations
Why are we discussing energy policy?
The climate-change motivation The climate-change motivation is argued in three steps: one: human fossilfuel burning causes carbon dioxide concentrations to rise; two: carbon dioxide is a greenhouse gas; three: increasing the greenhouse effect increases average global temperatures (and has many other effects).
total oil production (million barrels per day)
6 5
Netherlands Denmark
4
Norway
3 2 1
United Kingdom
price ($)
0 1970 1980 1990 2000 150 100 50 0
Figure 1.2. Are “our” fossil fuels running out? Total crude oil production from the North Sea, and oil price in 2006 dollars per barrel. 18 electricity capacity (kWh/d/p)
Three different motivations drive today’s energy discussions. First, fossil fuels are a finite resource. It seems possible that cheap oil (on which our cars and lorries run) and cheap gas (with which we heat many of our buildings) will run out in our lifetime. So we seek alternative energy sources. Indeed given that fossil fuels are a valuable resource, useful for manufacture of plastics and all sorts of other creative stuff, perhaps we should save them for better uses than simply setting fire to them. Second, we’re interested in security of energy supply. Even if fossil fuels are still available somewhere in the world, perhaps we don’t want to depend on them if that would make our economy vulnerable to the whims of untrustworthy foreigners. (I hope you can hear my tongue in my cheek.) Going by figure 1.2, it certainly looks as if “our” fossil fuels have peaked. The UK has a particular security-of-supply problem looming, known as the “energy gap.” A substantial number of old coal power stations and nuclear power stations will be closing down during the next decade (figure 1.3), so there is a risk that electricity demand will sometimes exceed electricity supply, if adequate plans are not implemented. Third, it’s very probable that using fossil fuels changes the climate.
Climate change is blamed on several human activities, but the biggest contributor to climate change is the increase in greenhouse effect produced by carbon dioxide (CO2 ). Most of the carbon dioxide emissions come from fossil-fuel burning. And the main reason we burn fossil fuels is for energy. So to fix climate change, we need to sort out a new way of getting energy. The climate problem is mostly an energy problem. Whichever of these three concerns motivates you, we need energy numbers, and policies that add up. The first two concerns are straightforward selfish motivations for drastically reducing fossil fuel use. The third concern, climate change, is a more altruistic motivation – the brunt of climate change will be borne not by us but by future generations over many hundreds of years. Some people feel that climate change is not their responsibility. They say things like “What’s the point in my doing anything? China’s out of control!” So I’m going to discuss climate change a bit more now, because while writing this book I learned some interesting facts that shed light on these ethical questions. If you have no interest in climate change, feel free to fast-forward to the next section on page 16.
7
Oil
16 14
Coal
12 10 8 6 4
2 Nuclear 0 2010
2015
2020
2025
Figure 1.3. The energy gap created by UK power station closures, as projected by energy company EdF. This graph shows the predicted capacity of nuclear, coal, and oil power stations, in kilowatt-hours per day per person. The capacity is the maximum deliverable power of a source.
Copyright David JC MacKay 2009. This electronic copy is provided, free, for personal use only. See www.withouthotair.com.
6
Sustainable Energy – without the hot air Figure 1.4. Carbon dioxide (CO2 ) concentrations (in parts per million) for the last 1100 years, measured from air trapped in ice cores (up to 1977) and directly in Hawaii (from 1958 onwards).
400 340 350 330
CO2 concentration (ppm)
300
320
250
310
200
300
150
290
I think something new may have happened between 1800 AD and 2000 AD. I’ve marked the year 1769, in which James Watt patented his steam engine. (The first practical steam engine was invented 70 years earlier in 1698, but Watt’s was much more efficient.)
280
100
270 50
1769 260 1600
0
1700
1800
1900
2000
2000
In the 30 years from 1769 to 1800, Britain’s annual coal production doubled. After another 30 years (1830), it had doubled again. The next doubling of production-rate happened within 20 years (1850), and another
World coal
1 0.8 0.6 0.4 0.2
al
Something did happen, and it was called the Industrial Revolution. I’ve marked on the graph the year 1769, in which James Watt patented his steam engine. While the first practical steam engine was invented in 1698, Watt’s more efficient steam engine really got the Industrial Revolution going. One of the steam engine’s main applications was the pumping of water out of coal mines. Figure 1.5 shows what happened to British coal production from 1769 onwards. The figure displays coal production in units of billions of tons of CO2 released when the coal was burned. In 1800, coal was used to make iron, to make ships, to heat buildings, to power locomotives and other machinery, and of course to power the pumps that enabled still more coal to be scraped up from inside the hills of England and Wales. Britain was terribly well endowed with coal: when the Revolution started, the amount of carbon sitting in coal under Britain was roughly the same as the amount sitting in oil under Saudi Arabia.
1.2
co
We start with the fact that carbon dioxide concentrations are rising. Figure 1.4 shows measurements of the CO2 concentration in the air from the year 1000 AD to the present. Some “sceptics” have asserted that the recent increase in CO2 concentration is a natural phenomenon. Does “sceptic” mean “a person who has not even glanced at the data”? Don’t you think, just possibly, something may have happened between 1800 AD and 2000 AD? Something that was not part of the natural processes present in the preceding thousand years?
K
1800
U
1600
James Watt (1769)
1400
Steam engine (1698)
1200
GtCO 2 per year
1000
0 1600
1700
1800
1900
Figure 1.5. The history of UK coal production and world coal production from 1600 to 1910. Production rates are shown in billions of tons of CO2 – an incomprehensible unit, yes, but don’t worry: we’ll personalize it shortly.
Copyright David JC MacKay 2009. This electronic copy is provided, free, for personal use only. See www.withouthotair.com.
7
1 — Motivations
4000
30
3500
25
3000
10
1500 1000 500 0
1800
1900
World oil
2.8
2000
0 1700
3
2500
5 1600
3.4
1700
1800
World
2.6
England+Wales
2.4
1900
2000
Eventually other countries got in on the act too as the Revolution spread. Figure 1.6 shows British coal production and world coal production on the same scale as figure 1.5, sliding the window of history 50 years later. British coal production peaked in 1910, but meanwhile world coal production continued to double every 20 years. It’s difficult to show the history of coal production on a single graph. To show what happened in the next 50 years on the same scale, the book would need to be one metre tall! To cope with this difficulty, we can either scale down the vertical axis:
2.2 GtCO2 per year
15
En gl an d+ W
20
3.6
3.2
1769
al es
35
1769
2 1.8 1.6 1.4 1.2
1.2 20
0.8
15
1
1600
1700
1800
0
1700
co
al
James Watt (1769)
Saudi oil
0.2
K
0 1900
0.4
Steam engine (1698)
oil
0.6
U
U
0
World
World co 1769
al
5 K
0.2
World coal
0.4
0.8
10
co
0.6
James Watt (1769)
Steam engine (1698)
GtCO 2 per year
al
1
World coal
Population (millions)
doubling within 20 years of that (1870). This coal allowed Britain to turn the globe pink. The prosperity that came to England and Wales was reflected in a century of unprecedented population growth:
1800
1900
2000
or we can squish the vertical axis in a non-uniform way, so that small quantities and large quantities can be seen at the same time on a single graph. A good way to squish the axis is called a logarithmic scale, and that’s what I’ve used in the bottom two graphs of figure 1.7 (p9). On a logarithmic scale, all ten-fold increases (from 1 to 10, from 10 to 100, from 100 to 1000) are represented by equal distances on the page. On a logarithmic scale, a quantity that grows at a constant percentage per year (which is called “exponential growth”) looks like a straight line. Logarithmic graphs are great
1700
1800
1900
Figure 1.6. What happened next. The history of UK coal production and world coal production from 1650 to 1960, on the same scale as figure 1.5.
Copyright David JC MacKay 2009. This electronic copy is provided, free, for personal use only. See www.withouthotair.com.
8
Sustainable Energy – without the hot air
for understanding growth. Whereas the ordinary graphs in the figures on pages 6 and 7 convey the messages that British and world coal production grew remarkably, and that British and world population grew remarkably, the relative growth rates are not evident in these ordinary graphs. The logarithmic graphs allow us to compare growth rates. Looking at the slopes of the population curves, for example, we can see that the world population’s growth rate in the last 50 years was a little bigger than the growth rate of England and Wales in 1800. From 1769 to 2006, world annual coal production increased 800-fold. Coal production is still increasing today. Other fossil fuels are being extracted too – the middle graph of figure 1.7 shows oil production for example – but in terms of CO2 emissions, coal is still king. The burning of fossil fuels is the principal reason why CO2 concentrations have gone up. This is a fact, but, hang on: I hear a persistent buzzing noise coming from a bunch of climate-change inactivists. What are they saying? Here’s Dominic Lawson, a columnist from the Independent: “The burning of fossil fuels sends about seven gigatons of CO2 per year into the atmosphere, which sounds like a lot. Yet the biosphere and the oceans send about 1900 gigatons and 36 000 gigatons of CO2 per year into the atmosphere – . . .
one reason why some of us are sceptical about the emphasis put on the role of human fuel-burning in the greenhouse gas effect. Reducing man-made CO2 emissions is megalomania, exaggerating man’s significance. Politicians can’t change the weather.” Now I have a lot of time for scepticism, and not everything that sceptics say is a crock of manure – but irresponsible journalism like Dominic Lawson’s deserves a good flushing. The first problem with Lawson’s offering is that all three numbers that he mentions (seven, 1900, and 36 000) are wrong! The correct numbers are 26, 440, and 330. Leaving these errors to one side, let’s address Lawson’s main point, the relative smallness of man-made emissions. Yes, natural flows of CO2 are larger than the additional flow we switched on 200 years ago when we started burning fossil fuels in earnest. But it is terribly misleading to quantify only the large natural flows into the atmosphere, failing to mention the almost exactly equal flows out of the atmosphere back into the biosphere and the oceans. The point is that these natural flows in and out of the atmosphere have been almost exactly in balance for millenia. So it’s not relevant at all that these natural flows are larger than human emissions. The natural flows cancelled themselves out.
So the natural flows, large though they were, left the concentration of CO2 in the atmosphere and ocean constant, over the last few thousand years. Burning fossil fuels, in contrast, creates a new flow of carbon that, though small, is not cancelled. Here’s a simple analogy, set in the passport-control arrivals area of an airport. One thousand passengers arrive per hour, and
Copyright David JC MacKay 2009. This electronic copy is provided, free, for personal use only. See www.withouthotair.com.
9
1 — Motivations
400
Figure 1.7. The upper graph shows carbon dioxide (CO2 ) concentrations (in parts per million) for the last 1100 years – the same data that was shown in figure 1.4.
380
Here’s a portrait of James Watt and his 1769 steam engine.
CO 2 concentration (ppm)
360
340
320
The middle graph shows (on a logarithmic scale) the history of UK coal production, Saudi oil production, world coal production, world oil production, and (by the top right point) the total of all greenhouse gas emissions in the year 2000. All production rates are expressed in units of the associated CO2 emissions.
300
280 1769 260 1000
1200
1400
1600
1800
2000 World total l coa
rld Wo
0.1
James Watt (1769) Steam engine (1698)
1000
Saudi oil
coa l
1
World oil
UK
GtCO 2 per year
10
In contrast to the ordinary graphs on the previous pages, the logarithmic scale allows us to show both the population of England and the population of the World on a single diagram, and to see interesting features in both.
World population (millions)
100
UK ships (kt) UK pig iron (kt/y)
10 England+Wales population (millions) 1000
1200
1400
1600
The bottom graph shows (on a logarithmic scale) some consequences of the Industrial Revolution: sharp increases in the population of England, and, in due course, the world; and remarkable growth in British pig-iron production (in thousand tons per year); and growth in the tonnage of British ships (in thousand tons).
1800
2000
Copyright David JC MacKay 2009. This electronic copy is provided, free, for personal use only. See www.withouthotair.com.
10 there are exactly enough clockwork officials to process one thousand passengers per hour. There’s a modest queue, but because of the match of arrival rate to service rate, the queue isn’t getting any longer. Now imagine that owing to fog an extra stream of flights is diverted here from a smaller airport. This stream adds an extra 50 passengers per hour to the arrivals lobby – a small addition compared to the original arrival rate of one thousand per hour. Initially at least, the authorities don’t increase the number of officials, and the officials carry on processing just one thousand passengers per hour. So what happens? Slowly but surely, the queue grows. Burning fossil fuels is undeniably increasing the CO2 concentration in the atmosphere and in the surface oceans. No climate scientist disputes this fact. When it comes to CO2 concentrations, man is significant. OK. Fossil fuel burning increases CO2 concentrations significantly. But does it matter? “Carbon is nature!”, the oilspinners remind us, “Carbon is life!” If CO2 had no harmful effects, then indeed carbon emissions would not matter. However, carbon dioxide is a greenhouse gas. Not the strongest greenhouse gas, but a significant one nonetheless.
Put more of it in the atmosphere, and it does what greenhouse gases do: it absorbs infrared radiation (heat) heading out from the earth and reemits it in a random direction; the effect of this random redirection of the atmospheric heat traffic is to impede the flow of heat from the planet, just like a quilt. So carbon dioxide has a warming effect. This fact is based not on complex historical records of global temperatures but on the simple physical properties of CO2 molecules. Greenhouse gases are a quilt, and CO2 is one layer of the quilt. So, if humanity succeeds in doubling or tripling CO2 concentrations (which is where we are certainly heading, under business as usual), what happens? Here, there is a lot of uncertainty. Climate science is difficult. The climate is a complex, twitchy beast, and exactly how much warming CO2 -doubling would produce is uncertain. The consensus of the best climate models seems to be that doubling the CO2 concentration would have roughly the same effect as increasing the intensity of the sun by 2%, and would bump up the global mean temperature by something like 3 ◦ C. This would be what historians call a Bad Thing. I won’t recite the whole litany of probable drastic effects, as I am sure you’ve heard it before.
The litany begins “the Greenland icecap would gradually melt, and, over a period of a few 100 years, sea-level would rise by about 7 metres.” The brunt of the litany falls on future generations. Such temperatures have not been seen on earth for at least 100 000 years, and it’s conceivable that the ecosystem would be so significantly altered that the earth would stop supplying some of the goods and services that we currently take for granted.
Sustainable Energy – without the hot air
Copyright David JC MacKay 2009. This electronic copy is provided, free, for personal use only. See www.withouthotair.com.
11
1 — Motivations
Greenhouse gas pollution (tons CO2 e/y per person)
Climate modelling is difficult and is dogged by uncertainties. But uncertainty about exactly how the climate will respond to extra greenhouse gases is no justification for inaction. If you were riding a fast-moving motorcycle in fog near a cliff-edge, and you didn’t have a good map of the cliff, would the lack of a map justify not slowing the bike down? So, who should slow the bike down? Who should clean up carbon emissions? Who is responsible for climate change? This is an ethical question, of course, not a scientific one, but ethical discussions must be founded on facts. Let’s now explore the facts about greenhouse gas emissions. First, a word about the units in which they are measured. Greenhouse gases include carbon dioxide, methane, and nitrous oxide; each gas has different physical properties; it’s conventional to express all gas emissions in “equivalent amounts of carbon dioxide,” where “equivalent” means “having the same warming effect over a period of 100 years.” One ton of carbon-dioxide-equivalent may be abbreviated as “1 t CO2 e,” and one billion tons (one thousand million tons) as “1 Gt CO2 e” (one gigaton). In this book 1 t means one metric ton (1000 kg). I’m not going to distinguish imperial tons, because they differ by less than 10% from the metric ton or tonne.
In the year 2000, the world’s greenhouse gas emissions were about 34 billion tons of CO2 -equivalent per year. An incomprehensible number. But we can render it more comprehensible and more personal by dividing by the number of people on the planet, 6 billion, so as to obtain the greenhouse-gas pollution per person, which is about 51/2 tons CO2 e per year per person. We can thus represent the world emissions by a rectangle whose width is the population (6 billion) and whose height is the percapita emissions.
5 World greenhouse gas emissions: 34 GtCO2 e/y 0
0
1
2
3 population (billions)
4
5
6
Copyright David JC MacKay 2009. This electronic copy is provided, free, for personal use only. See www.withouthotair.com.
12
Sustainable Energy – without the hot air
Now, all people are created equal, but we don’t all emit 51/2 tons of CO2 per year. We can break down the emissions of the year 2000, showing how the 34-billion-ton rectangle is shared between the regions of the world: North America
ce an ia
5 GtCO2 e/y
Eu ro p
e
15
a A si
M
id
10
Sub-Saharan Africa
20
dl e Ea So st ut & C N en h A or m tr th al er ic A A a m fr ic er a ic a & C ar ib be an
O
Greenhouse gas pollution (tons CO2 e/y per person)
25
5
0
0
1
2
3
4
population (billions)
This picture, which is on the same scale as the previous one, divides the world into eight regions. Each rectangle’s area represents the greenhouse gas emissions of one region. The width of the rectangle is the population of the region, and the height is the average per-capita emissions in that region. In the year 2000, Europe’s per-capita greenhouse gas emissions were twice the world average; and North America’s were four times the world average. We can continue subdividing, splitting each of the regions into countries. This is where it gets really interesting:
5
6
Copyright David JC MacKay 2009. This electronic copy is provided, free, for personal use only. See www.withouthotair.com.
13
1 — Motivations
Am
er
ica
Qatar, United Arab Emirates
A Ca Un ust na ited ra da Sta lia tes of
25
5 GtCO2 e/y
0
So ut hA fr i
ut h
Ko re
Jap a an n
0
1
2
3
4
population (billions)
The major countries with the biggest per-capita emissions are Australia, the USA, and Canada. European countries, Japan, and South Africa are notable runners up. Among European countries, the United Kingdom is resolutely average. What about China, that naughty “out of control” country? Yes, the area of China’s rectangle is about the same as the USA’s, but the fact is that their per-capita emissions are below the world average. India’s per-capita emissions are less than half the world average. Moreover, it’s worth bearing in mind that much of the industrial emissions of China and India are associated with the manufacture of stuff for rich countries. So, assuming that “something needs to be done” to reduce greenhouse gas emissions, who has a special responsibility to do something? As I said, that’s an ethical question. But I find it hard to imagine any system of ethics that denies that the responsibility falls especially on the countries
In d Ph ia Vi ilip etn p amine Ba s ng lad es h Ni ge DR r i a C
In d Pa one k is s ia tan
Ch ina
Th ail an d
ek ist a
Eg
5
an
So
Uz b
Br az M il ex ico
yp
t
10
ca
Turkmenistan Singapore
ue la
15
Ta iw
Ire
lan d
20
R G us Un erm sian ite a F d K ny ede Ita l ing Sau rati Fr y an do di Ar on c e m abia Ira n Tu rk ey Ven ez
Trinidad & Tobago
Ne th erl an ds
Greenhouse gas pollution (tons CO2 e/y per person)
Kuwait
5
6
Copyright David JC MacKay 2009. This electronic copy is provided, free, for personal use only. See www.withouthotair.com.
14
Sustainable Energy – without the hot air
to the left hand side of this diagram – the countries whose emissions are two, three, or four times the world average. Countries that are most able to pay. Countries like Britain and the USA, for example.
Historical responsibility for climate impact
1
2
4
5
3 population (billions)
Congratulations, Britain! The UK has made it onto the winners’ podium. We may be only an average European country today, but in the table of historical emitters, per capita, we are second only to the USA. OK, that’s enough ethics. What do scientists reckon needs to be done, to avoid a risk of giving the earth a 2 ◦ C temperature rise (2 ◦ C being the rise above which they predict lots of bad consequences)? The consensus is clear. We need to get off our fossil fuel habit, and we need to do so fast. Some countries, including Britain, have committed to at least a 60% reduction in greenhouse-gas emissions by 2050, but it must be emphasized that 60% cuts, radical though they are, are unlikely to cut the mustard. If the world’s emissions were gradually reduced by 60% by 2050, climate sci-
tan Sou th A Nig fr i c er ia a
a Ch ina
Ind ia
0
Ind one si
0
Pak is
an
Ira Tur n ke
5
Br a zil Me x ic o Jap
10
y
Un Un ited S Ge ited tate rm s any Kingd of A Ru s s ia om mer ica nF Fra ed e nce Ital rat ion y
Average pollution rate (tons CO2 /y per person)
If we assume that the climate has been damaged by human activity, and that someone needs to fix it, who should pay? Some people say “the polluter should pay.” The preceding pictures showed who’s doing the polluting today. But it isn’t the rate of CO2 pollution that matters, it’s the cumulative total emissions; much of the emitted carbon dioxide (about one third of it) will hang around in the atmosphere for at least 50 or 100 years. If we accept the ethical idea that “the polluter should pay” then we should ask how big is each country’s historical footprint. The next picture shows each country’s cumulative emissions of CO2 , expressed as an average emission rate over the period 1880–2004.
6
Copyright David JC MacKay 2009. This electronic copy is provided, free, for personal use only. See www.withouthotair.com.
15
1 — Motivations
carbon dioxide
5 4 3
16-43% chance of > 2C
2 1
9-26% chance of > 2C
0 2000
nitrous oxide
Land use, biomass burning: 10% Waste: 3.4%
2100
Figure 1.8. Global emissions for two scenarios considered by Baer and Mastrandrea, expressed in tons of CO2 per year per person, using a world population of six billion. Both scenarios are believed to offer a modest chance of avoiding a 2 ◦ C temperature rise above the pre-industrial level.
methane
Agricultural by-products: 12.5%
2050
Figure 1.9. Breakdown of world greenhouse-gas emissions (2000) by cause and by gas. “Energy” includes power stations, industrial processes, transport, fossil fuel processing, and energy-use in buildings. “Land use, biomass burning” means changes in land use, deforestation, and the burning of un-renewed biomass such as peat. “Waste” includes waste disposal and treatment. The sizes indicate the 100-year global warming potential of each source. Source: Emission Database for Global Atmospheric Research.
Energy: 74% World greenhouse-gas emissions
6 tCO 2 /y per person
entists reckon it’s more likely than not that global temperatures will rise by more than 2 ◦ C. The sort of cuts we need to aim for are shown in figure 1.8. This figure shows two possibly-safe emissions scenarios presented by Baer and Mastrandrea (2006) in a report from the Institute for Public Policy Research. The lower curve assumes that a decline in emissions started in 2007, with total global emissions falling at roughly 5% per year. The upper curve assumes a brief delay in the start of the decline, and a 4% drop per year in global emissions. Both scenarios are believed to offer a modest chance of avoiding a 2 ◦ C temperature rise above the pre-industrial level. In the lower scenario, the chance that the temperature rise will exceed 2 ◦ C is estimated to be 9–26%. In the upper scenario, the chance of exceeding 2 ◦ C is estimated to be 16–43%. These possibly-safe emissions trajectories, by the way, involve significantly sharper reductions in emissions than any of the scenarios presented by the Intergovernmental Panel on Climate Change (IPCC), or by the Stern Review (2007). These possibly-safe trajectories require global emissions to fall by 70% or 85% by 2050.
What would this mean for a country like Britain? If we subscribe to the idea of “contraction and convergence,” which means that all countries aim eventually to have equal per-capita emissions, then Britain needs to aim for cuts greater than 85%: it should get down from its current 11 tons of CO2 e per year per person to roughly 1 ton per year per
Copyright David JC MacKay 2009. This electronic copy is provided, free, for personal use only. See www.withouthotair.com.
16
Sustainable Energy – without the hot air
person by 2050. This is such a deep cut, I suggest the best way to think about it is no more fossil fuels. One last thing about the climate-change motivation: while a range of human activities cause greenhouse-gas emissions, the biggest cause by far is energy use. Some people justify not doing anything about their energy use by excuses such as “methane from burping cows causes more warming than jet travel.” Yes, agricultural by-products contributed one eighth of greenhouse-gas emissions in the year 2000. But energy-use contributed three quarters (figure 1.9). The climate change problem is principally an energy problem.
Warnings to the reader 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-ofenvelope 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 roundtrip 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-
“Look – it’s Low Carbon Emission Man” Figure 1.10. Reproduced by kind permission of PRIVATE EYE / Peter Dredge www.private-eye.co.uk.
Copyright David JC MacKay 2009. This electronic copy is provided, free, for personal use only. See www.withouthotair.com.
1 — Motivations 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 20 km/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-
17
Copyright David JC MacKay 2009. This electronic copy is provided, free, for personal use only. See www.withouthotair.com.
18
Sustainable Energy – without the hot air
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!