\myquote{%
We stand now at the transition point from
hydrocarbon dependence to the start of the `New Energy Era',
in which no fossil fuels will be used.
}{Sir Peter Masefield, speaking in 1975.}
% \end{quote}
Similar \ind{magic playing field}s are created by exploiting people's
confusion of ``electricity'' and ``energy''.
Electricity is only one way in which we get energy;
we get most of our energy in forms other
than electricity -- natural gas and petrol, for example (for
heating and transport, respectively).
So even if renewables could supply ``all of our electricity'',
that would not mean that all our energy consumption was covered.
In fact electricity
accounts for only one fifth or a third of our energy consumption,
depending how you do the accounting.
% so even if renewables could supply 80\% of our electricity,
% that would represent less than one fifth of our current
% energy demand.
%% To have real impact, renewables must
\item[\npageref{isaGHG}]
{\nqs{Carbon dioxide is a greenhouse gas}.}
For an accessible explanation of this fact, see
`The \COO\ problem in 6 easy steps'
\tinyurl{34pj5e}{http://www.realclimate.org/index.php/archives/2007/08/the-co2-problem-in-6-easy-steps/}.
Some key steps from the explanation:
a doubling in \COO\ is estimated
to increase the `\ind{forcing}' by about
4\,\Wmm. `Forcing' is the strange name used
to describe the warming effect of greenhouse
gases. The total forcing of all
% greenhouse effect
the natural greenhouse substances is about 150\,\Wmm.
An increase of 4\,\Wmm\
is roughly equivalent to a 2\% increase in
the intensity of the incoming sunlight.
% The natural 11-yearly variations
% in the solar constant are about 0.1\%.
% An increase in forcing of 4\,\Wmm\ is expected
% to increase global mean temperature by about 3\degreesC.
% For another online explanation with more equations, see
% \tinyurl{2hn5jk}{http://my.net-link.net/~malexan/Climate-Model.htm}.
A second yardstick was recommended
by one hundred global business leaders
in a statement issued by the
World Economic Forum on 20th June 2008.
% CEOs
% http://www.weforum.org/en/initiatives/ghg/index.htm
% -- moving to a global average of about 2-2.5 tonnes CO2-equiv
% per person (by 2050?)
If you also learn that a safe, sustainable level of
\COO\ emissions for the next century
is 20\% of current emissions, we deduce
\begin{oldcenter}
{\sc Yardstick number 2}\\
`we need average
% {\bf safe\/}
emissions to be $0.8$ \tonnes\ of \COO\ per year per person'.
\end{oldcenter}
\noindent%
So, if you want
everyone to have equal pollution rights, you now know that that round-trip
flight in the 747 uses up more than one year's allowance!
The same page of {{\em The Times}\/} that contains a helpful
article suggesting
``Seven simple ways you can make an immediate
and positive impact on our environment''
also promotes ``The Art of Travel'':
`Discover a variety of enjoyable road journeys
across the UK and win a luxurious family
long weekend in Edinburgh -- with Renault Espace'.
We need
% two things: {\em{arithmetic}\/} and
{\em simple facts\/} in the form of {\em{comprehensible}\/}
numbers.
% recently removed section heading
%\section*{Inaccuracy as an aid to understanding}
I'd like to emphasize that
the calculations we will do are
%% consciously and
deliberately inaccurate.
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
% U.K.\ is
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 fossil fuel emissions are currently
7\,billion \tonnes\ of carbon per year, then we can instantly
note, without a calculator, that
the average emissions per person are just a little more than
1 \tonne\ of carbon per person per year. (Because 7 divided by 6
is 1.) This is a useful yardstick to remember:\medskip
\begin{center}
{\sc Yardstick number 1}\\
``average
{\bf current\/} emissions are 1 \tonne\ of carbon per year per person.''\medskip
\end{center}
By the way, one \ton\ of carbon is equivalent to roughly 4 tons of \COO\ ($44/12$ tons, to
be precise);
\input{COOratioFig.tex}
% (One \tonne\ of \COO\ is equivalent to
% $12/44$\,\tonnes\ of carbon, a bit more than a quarter
% of a \tonne.)
this yardstick's figure of 4 tons of \COO\ per year is a bit smaller than
the 5.5 tons of \COOe\ per year mentioned a few pages back because
the 5.5 tons included all greenhouse-gas emissions.
If you also learn that a round-trip intercontinental flight
% in a 747
emits nearly two \tonnes\ of \COO\ per passenger (which is about half a \tonne\ of carbon),
%% 1.83 tonnes for LHR to ZAMBIA, ``cost 11.91''
then the yardstick helps you realise that just one
such plane-trip per year corresponds to half of the average person's
carbon emissions.
% New yardstick suggested by the world economic forum
% CEOs
% http://www.weforum.org/en/initiatives/ghg/index.htm
% -- moving to a global average of about 2-2.5 tonnes CO2-equiv
% per person (by 2050?)
Did it bother you that I said that 7 divided by 6 is 1?
% then I said that 12/44 is $1/3$.
This mistake really is
%% ese mistakes really are
deliberate. If the yardstick said `average personal emissions are 1.167 \tonnes\
of carbon per year', it would no longer be a yardstick. A yardstick
is easy to handle. It's hard to remember `1.167' \tonnes. One \tonne\ is much
easier to remember, and it's easier to work with:
everyone can divide or multiply
by 1 without the help of a calculator.
Continuing the example,
if you also learn that a safe, sustainable level of
fossil fuel emissions for the next century
is not 7\,billion \tonnes\ of carbon per year
but 2\,billion \tonnes\ of carbon per year, we deduce
\begin{oldcenter}
{\sc Yardstick number 2}\\
`we need average
% {\bf safe\/}
emissions to be $\dfrac{1}{3}$ \tonne\ of carbon per year per person'.
\end{oldcenter}
\noindent%
(Two billion divided by six billion.) So, if you want
everyone to have equal pollution rights, you now know that that round-trip
flight in the 747 uses up more than one year's allowance!
% Similarly knowing that the population of the United Kingdom is one
% hundredth of the world, we can deduce what level of emissions
% would be fair for the U.K., either dividing :
% We're getting ahead of ourselves. We'll come back to carbon pollution
% in chapter \ref{ch.coo}.
% Wherever possible
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 (5.6\,m/s, or
12\,miles per hour).
% 12.4\,miles per hour).
I back up these everyday estimates with other peoples'
calculations and with statistics from official sources.
Let me close this preface
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
fundamental limits to sustainable energy, not current
economic feasibility.
% Business decisions care about undercutting rivals by 5\%.
While economics is always changing, the fundamental limits won't
ever go away. We need to understand these limits.
In the calculations, I'll mainly use the United Kingdom
%% or England, or
and occasionally the whole world, but
you should find it easy to redo the calculations for
whatever country you are interested in.
\medskip% BREATH