IPCC Issues: A Swag of Documents
Ian Castles and David Henderson
Over the past six months we have
voiced criticisms of work done under the auspices of the Intergovernmental
Panel on Climate Change (IPCC). In particular, we have queried
some of the methods and conclusions of the Special Report on Emissions
Scenarios (SRES). We have now brought together the various pieces
that we have written on this subject. They fall into three distinct
and successive groups.
First, there are three letters to the IPCC Chairman,
Dr Rajendra Pachauri---two from Castles (sent in August 2002)
and one (sent in October) from Henderson. These focus on the main
single ground of our criticism---namely, the use in the SRES of
nominal exchange rates, rather than purchasing power parity rates,
for expressing the GDP of different countries in a common unit
of measurement. They appear below as Document 1.
Second, there are three contributions that we were able
to make at an IPCC meeting. Although the IPCC has made no formal
substantive response to the criticisms we have made, we were invited
in mid-December to attend an Experts' Meeting of its Technical
Group on Climate Impact Assessment, held in Amsterdam on 7-10
January 2003. Arrangements were made in Amsterdam for an extended
technical discussion of the points we had raised in our letters
to Dr Pachauri, and both of us were given the opportunity to make
short presentations to the full meeting of the Group. The texts
that formed the basis for these presentations also appear below.
Castles presents a critique of the IPCC scenarios, while Henderson
makes the case, with some concrete suggestions, for wider professional
involvement in the economic aspects of the IPCC's work. Included
with these two presentation texts is a note by Henderson, first
drafted in Amsterdam, on a specific proposal made in the course
of the technical discussions there. These three texts make up
Third, following the Amsterdam meeting, we decided to
develop our case further, incorporating points that we had not
covered in the pieces listed above. Document 3 contains
two papers, one by each of us. The paper by Castles presents the
case for a review of the IPCC emissions scenarios, while the piece
by Henderson raises some further queries and concerns about both
the scenarios themselves and the IPCC process of which they form
For some readers, it might be
preferable to read the papers numbered 2(1) and 3(1) in sequence,
since both are by Castles, and similarly, to take 2(2) and 3(2)
together, since both are by Henderson, rather than working through
Documents 2 and 3 in order.
The contents of these documents
are more diverse, and less systematically put together, than would
have been the case if we had set out with the intention to provide
a full critique. All the eight texts were prepared at short notice,
in response to immediate opportunities and concerns. Critics of
our critique have rightly made the point that what we are saying
has not been subject to peer review. But given that the IPCC has
now embarked on the preparation of its Fourth Assessment report
(AR4), and will be meeting in Paris later this month, we think
it may be useful to circulate what we have written in its original
state---as a contribution, timely albeit rough and ready, to an
important debate which is now under way.
National Centre for Development Studies
Australian National University, Canberra
Westminster Business School, London.
5 February, 2003
The following document
comprises all eight texts mentioned above, in the order of their
presentation. For the aid of those readers who wish to take up
the 'navigation' suggestion which was also mooted above, we provide
a small contents listing with hyperlinks to the individual pieces.
Links returning the reader to this index have been inserted at
the conclusion of various pieces within the major document.
Document 1: Letters to Dr Pachauri
1 (1): Letter of 6 August 2002 from Ian Castles to Dr Rajendra Pachauri
Dr Rajendra Pachauri,
Intergovernmental Panel on Climate Change
Dear Dr Pachauri,
1. Thank you for your interest in my criticisms
of the IPCC Special Report on Emissions Scenarios (SRES),
and for inviting me to put my concerns in writing. I am taking
the liberty of sending copies of this letter to others who joined
in discussions on climate change issues with you in Canberra on
23 and 24 July, and also to a 'mailing list' of my colleagues
in the international statistical community, government agencies
and universities who follow my ongoing correspondence about the
use and abuse of statistics in public debates about globalisation,
poverty and the distribution of incomes both within and between
countries. I will of course forward any comments that you or the
SRES authors may have on my criticisms to all of those to whom
I am copying this letter.
2. As mentioned in our discussions, I was formerly
the Australian Statistician (1986 to 1994) and head of the Australian
Department of Finance (1979-86). I am a former President of the
International Association of Official Statistics (IAOS), a section
of the International Statistical Institute (ISI), and have been
a consultant to several national statistical offices and international
organisations on a range of statistical issues.
Statistics of Global Poverty
3. Following the release of the UNDP's Human
Development Report 1999 (HDR 1999), I made extensive statistical
criticisms of the treatment in that report of trends in global
poverty and inequality. At the request of the 2000 meeting of
the UN Statistical Commission (UNSC), those criticisms were examined
by a group of expert statisticians constituted as the Friends
of the Chair of the Commission. The report of the group upheld my more serious criticisms. In
particular, the Friends of the Chair of the UNSC held that HDR
1999 had made a 'material error' (i.e., one which left
the reader with 'a fundamentally distorted view of the phenomenon
being described') in relying on national accounting aggregates
converted into $US at current exchange rates to compare living
standards between countries.
4. The HDR Office of the UNDP accepted the
report, and has made major improvements in statistical presentation
and reporting in subsequent issues of the HDR.
5. Both the SRES and the Contribution of IPCC
Working Group III (WG III) to the Third Assessment Report (Climate
Change 2001: Mitigation) cite incorrect statements from pre-2000
issues of the HDR in support of claims about the international
distribution of incomes. Some of these statements involve exactly
the same 'material error' as that referred to in paragraph 3 above.
Thus the WG III Contribution includes the following:
The distributional dimension of global poverty was illustrated vividly by the Human Development Report 1989 (sic---the first HDR was published in 1990), in the form that came to be known as the champagne glass [reproduced as Figure 1.4 in the IPCC Report]. This representation of global income distribution shows that in 1988 the richest fifth of the world's population received 82.7% of the global income, which is nearly 60 times the share of the income received by the poorest fifth (1.4%). More recent statistics indicate that inequality has widened further since then and that in 1999 the richest quintile received 80 times the income earned by the poorest quintile (UNDP 1999) (section 1.3.1).
6. Another paragraph in the same section of
the Contribution of WG III cites statements in the World Bank's
World Development Report 2000 in support of similar claims
about high and rising global inequality. The Australian Treasury
has published a detailed critique of this analysis by the Bank,
and has cited statements included in this analysis as examples
of 'material errors in the use of statistics' ("Global poverty
and inequality in the 20th century: turning the corner",
2001, pps. 24-26, 34-40, available in pdf on the Treasury website
7. The SRES cites the UNDP's HDR 1993 in support
of the proposition that 'The poorest 20% of Bangladesh's population
... earn per capita incomes that are a factor of 700 lower than
that of the 20% richest Swiss population' (section 18.104.22.168). This
comparison is invalid, because it is based on the assumption that
the poor Bangladeshi family has converted the whole of its income
into foreign currency, and spent it on goods and services at average
world prices rather than Bangladeshi prices.
8. The same false assumption underlies the
claim that 'When measured across the four SRES regions in 1990,
income per capita differences are nearly 40 to 1 (between ASIA
and OECD90)' (SRES, section 22.214.171.124). The difference in average
incomes between these two regions, properly measured, was less
than 10 to 1 in 1990, and has since contracted significantly.
Thus the projected growth of real average incomes in the ASIA
region (i.e., developing Asia) between 1990 and 2100 that is assumed
in the A1 scenarios (an increase by a factor of about 140 to 1)
and the B1 scenarios (an increase by a factor of more than 70
to 1) would take incomes in that region to far higher levels than
the present OECD90 average, and possibly to higher levels than
the OECD90 average in 2100. (This latter comparison is more problematic,
because of the difficulty of allowing for the 'Gerschenkron effect').
9. The rates of growth in global GDP presented
in the SRES significantly understate the true increases in GDP
that underlie the emissions projections. This is because the regions
that are expected, by assumption, to achieve the highest rates
of economic growth in the twenty-first century are significantly
underweighted in the calculations of global GDP. An indication
of the possible extent of understatement can be derived by comparing
the IMF's estimate of the average annual rate of growth in world
GDP between 1994 and 2003 at market exchange rates (2.8 per cent)
with the corresponding estimate of this growth measured on the
correct basis using purchasing power parities (3.6 per cent).
In per capita terms, calculation of the growth rate on the discredited
exchange rate-based method used in the SRES yields an average
annual increase over this decade of only 1.4 per cent, compared
with an increase of 2.2 per cent on the correct purchasing power-corrected
basis (IMF, World Economic Outlook, May 2002, p. 157).
10. On the basis of estimates by Angus Maddison
which are used in the SRES itself in other contexts, average real
incomes in the United States increased by a factor of perhaps
5 to 1 in the nineteenth century, and average real incomes in
Japan increased by a factor of almost 20 to 1 in the twentieth
century. Thus the historical record gives no support to projections
that in the course of the twenty-first century there could be
increases in average incomes in the entire continent of Asia by
a factor of 140 to 1---or even of 70 to 1, which is the assumption
underlying the scenario yielding the lowest projected level
of emissions. Yet it is upon such fantastic assumptions that the
IPCC's projections of emissions, and therefore of temperatures,
The B1 IMAGE Projections
11. The B1 IMAGE projection is of particular
interest, because this is the marker projection that yields the
lowest increase in temperature between 1990 and 2100---between
1.4 degrees C. and 2.5 degrees C. for the seven climate models,
with a projected increase averaged over those seven models of
1.98 degrees C. from 1990 and of 1.82 degrees C. from 2000 (Climate
Change 2001: The Scientific Basis, Appendix II, Table II.
12. According to the SRES Terms of Reference
(SRES, Appendix I), the process for developing the scenarios was
to be: 'First, key input assumptions would be provided to modelers',
and 'Second, modelers would be asked to construct emissions scenarios
based on the input assumptions provided'.
13. In this case, the opposite process was
followed. The B1 IMAGE modelers (1) assumed an extraordinarily
rapid growth in annual global emissions of carbon dioxide from
the burning of fossil fuels (an increase of 1.6 billion tonnes
between 2000 and 2010, and a further increase of 1.5 billion tonnes
between 2010 and 2020, compared with increases of only 0.8 billion
tonnes in the 1980s and of 0.7 billion tonnes in the 1990s); (2)
allocated the whole of the very large increases in these emissions
in both decades to developing countries; and (3) used the model
to estimate the levels of income, energy use and emissions of
other greenhouse gases and aerosols that might be associated with
the assumed levels of fossil carbon dioxide emissions.
14. In the current decade, for example, the
results of the B1 IMAGE model are predicated upon assumed
increases in emissions of exactly 0.8 billion tonnes both in the
ASIA and the ALM (Africa, Latin America and the Middle East) regions.
In other words, the modellers assumed that increases in emissions
in each of the SRES developing regions (ASIA and ALM) would
be greater in the current decade than the increase for the world
as a whole between 1990 and 2000.
15. These assumptions are patently unrealistic,
even for a 'high emissions scenario'. They translate into increases
in per capita emissions of fossil carbon dioxide of 24% in ASIA
and of 46% in ALM. On this basis, the output of the B1 IMAGE model
suggests that GDP per head could rise by around 50% in both regions.
16. In the case of the ALM region, it is already
certain that such a growth in incomes will not occur. In the IMF's
World Economic Outlook May 2002, it is estimated that real
GDP per head declined in this region in 2001 and that there will
be a further decline in 2002 (p. 163). Even if the IMF's rather
optimistic 'world medium-term baseline scenario' for the years
2003 to 2007 were to be realised (p. 224), it would require a
further increase of no less than 40 per cent in real GDP in 'ALM'
in the succeeding three years to achieve the increase in decadal
GDP projected in the B1 IMAGE scenario. If the modelers had followed
the procedure laid down in the SRES terms of reference, they would
have 'fed in' a much lower rate of growth in GDP as a 'key output
assumption'. They could then have concluded that fossil carbon
emissions in this region will not increase by anything like 0.9
17. The projected growth in Asian GDP in the
current decade may well be realised, but with a far slower growth
in carbon dioxide emissions than is assumed in the B1 IMAGE projection.
There is no obvious reason why the rapid decline in 'emissions
intensity' in ASIA in the 1990s should not be maintained during
the current decade. Again, if the procedure for scenario development
laid down in the SRES terms of reference (paragraph 11 above)
had been followed, a fast rate of decline in emissions intensity
in this region would have been a 'key input assumption'. The output
of the model would then have revealed that carbon emissions would
not need to increase by anything like 0.8 billion tonnes.
18. In short, the B1 IMAGE projection, which
belongs to the 'storyline and scenario family' that features 'rapid
change in economic structures toward a service and information
economy', 'reductions in material intensity', 'the introduction
of clean and resource-efficient technologies' and 'global solutions
to economic, social and environmental sustainability', is itself
a 'high emissions scenario'---at least in the early decades of
the century. It assumes that there will be a sharp reversal in
the downward trend in global fossil fuel emissions per head that
occurred in the last two decades of the twentieth century. This
seems unlikely: under the 'reference' scenario in the World Energy
Council Commission Report Energy for Tomorrow's World (1993),
global carbon dioxide emissions per head were projected to decrease
by 7% between 1990 and 2020. It is significant that the WEC
study, unlike the SRES, was based on purchasing power parity estimates
19. I believe that it is important that governments
be advised as soon as possible that the economic projections used
in the IPCC emissions scenarios are technically unsound, having
been derived by converting national GDPs in nominal values into
a common currency using exchange rates. This procedure is not
permissible under the internationally-recognised System of
National Accounts, and was recently rejected by an expert
group in a report to the UN Statistical Commission. The practice
of using exchange rate conversion is especially inappropriate
in relation to projections of physical phenomena such as emissions
of greenhouse gases and aerosols.
20. In the introduction to the first edition
of his book Global Warming: The Complete Briefing (1994),
Sir John Houghton, then Co-Chairman of the Scientific Assessment
Working Group of the IPCC, said that 'scientists have a responsibility
to communicate the best possible information about the likely
magnitude of climate change, along with clear statements of the
assumptions made and the level of uncertainty in the estimates.'
As there was no clear statement of the assumptions underlying
the projections of the likely magnitude of climate change in the
IPCC's Third Assessment Report, I consider it vital that governments
be advised that the lowest of the SRES projections assumed
that GDP per capita would increase to more than 70 times its 1990
level in Asia (excluding Japan) and to nearly 30 times its 1990
level in Africa, Latin America and the Middle East, by the end
of the century. Contrary to statements made in the SRES, these
projections imply that real incomes in the whole of the developing
world will be many times greater than those in the richest countries
in the world today.
21. As I mentioned in our discussions, it would
also be desirable to seek the involvement of national statistical
offices and of the International Statistical Institute in the
new emissions projections that I understand are to be prepared
for the IPCC's Fourth Assessment Report.
23. I hope that these comments are helpful
to you. I repeat my congratulations to you on your appointment
as Chairman of the IPCC, and wish you well in your difficult but
National Centre for Development Studies
Australian National University
(2): Letter of 29 August 2002 from Ian
Castles to Dr Rajendra Pachauri
Dr Rajendra Pachauri,
Intergovernmental Panel on Climate Change
Dear Dr Pachauri,
In my letter to you of 6 August, I said that
I believed that it was "important that governments be advised
as soon as possible that the economic projections used in the
IPCC emissions scenarios are technically unsound, having been
derived by converting national GDPs in nominal values into a common
currency using exchange rates".
The pernicious consequences of using this false
method of measuring output are apparent in the analysis of greenhouse
issues in the World Development Report 2003, released by
the World Bank last week.
For example, the Bank argues that "non-OECD
countries use ... 3.8 times as much energy per dollar of GDP [as
OECD countries], and claims that "This disparity suggests
looking for ways that developing and transition countries can
increase efficiency and reduce fuel costs---with reduced GHG emissions
as a welcome side-benefit ..." The Bank goes on to wonder
"why these apparent 'win-win' situations are so elusive",
and decides that the answer lies in two types of institutional
failure: "distortions in energy policy [which] benefit special
interests", and the neglect by firms and households of profitable
ways of saving energy "because it is simply too much trouble
to pursue them" (p. 177).
There is a simpler answer to the question that
the Bank poses. The assumption of a huge margin of difference
in energy intensity between OECD and non-OECD countries which
the Bank is seeking to explain is false. The ratio of use of energy
per unit of GDP in non-OECD countries to that in OECD countries,
calculated using PPPs rather than the spurious exchange-rate conversion
basis favoured by the Bank (and the IPCC), is not 3.8:1 but 1.2:1.
On the same page of WDR 2003, the Bank
wonders what will happen when people "aspire to the current
lifestyle of a prosperous country", and puts forward some
"simple arithmetic" to show why the Bank supposes this
to be impossible:
"Among the prosperous countries, Norway
has one of the lowest rates of CO2 emissions
per capita from energy, owing in part to ample use of hydro-power.
Yet if the global population of 2050 emitted CO2
on average at this rate, the total would be about 2.5 times current
global emissions, which would greatly exceed the planet's absorptive
The argument is grossly misleading for a number
of reasons. But the key point that it illustrates is the Bank's
failure to understand the basis of the IPCC emissions projections,
the lowest of which assumes that developing countries will not
only aspire to but will in fact achieve far higher living standards
than those of the most prosperous countries today.
Pasted below is the text of an article which
appears under my name in this morning's Canberra Times, under
the heading "Greenhouse emissions calculations quite wrong".
It puts the view that the IPCC should base its climate projections
on realistic assessments of future greenhouse emissions, based
in turn on realistic projections of the future of the world economy,
rather than on the quantification of fantastic "storylines".
With best wishes,
Text from Canberra Times:
In January last year the Intergovernmental
Panel on Climate Change (IPCC) released its latest projections
of prospective global warming. The key finding was that "globally
averaged mean surface temperature is projected to increase by
1.4 to 5.8°C over the period 1990 to 2100".
The statement led to widespread alarm. Most
commentators, including many scientists, interpreted the IPCC's
new projected range as a forecast of massive rises in global
temperatures, but the IPCC made projections, not predictions,
by feeding hypothetical levels of future greenhouse emissions
into climate models. The output of such models cannot be better
than the input assumptions upon which they are based.
The simulated temperature increases in the
IPCC's lowest emissions scenario ranged from 1.4 to 2.5°C.
Some assumptions incorporated in this scenario were conservative,
but it also assumed an extraordinarily high rate of economic growth
in the developing world.
Specifically, the IPCC assumed that the volume
of goods and services produced per head in 2100 would be more
than 70 times 1990 levels in developing countries in Asia, and
nearly 30 times 1990 levels in other developing countries. Far
from marking the lower bound of likely outcomes, such astronomic
increases are extremely improbable.
The reasoning that produced these assumptions
was as follows. Productivity in the rich countries is likely to
continue to increase.
In 1990, average incomes in these countries,
on the exchange rate-converted basis used in the IPCC projections,
were 40 times higher than in Asian developing countries and 12
times higher than the average of developing countries elsewhere.
If this gap is to be substantially closed by 2100 on these assumptions,
this century must be an era of unprecedented growth.
In fact, average incomes in developing countries
are three or four times higher than the IPCC assumed. By adopting
the long-discredited method of converting incomes into a common
currency using current exchange rates, the IPCC modellers greatly
overstated the size of the development gap, but there are two
more fundamental objections to the modellers' argument.
First, living standards in the developing countries
in 2100 will depend on their actual economic growth during
the coming century. No significant country has ever achieved a
20-fold increase in output per head in a century, let alone the
30-fold or 70-fold increases projected by the IPCC for most of
the world's population.
Secondly, and paradoxically, the IPCC's model-builders
are hostile to wealth per se. They are obsessed by the
belief that growth in productivity and affluence inevitably leads
to unacceptable growth in greenhouse emissions. For example, they
argue that "if governments support the development of rapid-growth
sectors, the tendency may be to promote long-term economic growth,
increase household income and consumption, and hence increase
They even claim that "protectionist policies
may ... reduce national economic efficiency, which dampens economic
growth and tends to restrict growth in GHG emissions".
These concerns are misplaced. Economic growth
maximises the output of goods and services for a minimum expenditure
of scarce resources. Conversely, reductions in economic efficiency
tend to increase the volume of resources required to produce a
given volume of final output, and therefore raise the level
of GHG emissions.
In Britain, the first developed economy, average
carbon dioxide emissions exceeded 2.5 tonnes of carbon per head
of the population in 1880, before the motor age began.
Now Britain produces at least five times the
volume of goods and services per head as in 1880, but per capita
emissions of carbon dioxide have not increased at all.
According to economic historian Angus Maddison,
average incomes in China are now higher than in Britain in 1880,
but China's carbon emissions are only 0.6 tonnes of carbon per
head---less than a quarter of the levels in late-Victorian Britain.
And China's emissions per unit of output are
less than half their levels of twenty years ago.
Global carbon dioxide emissions per head from
the burning of fossil fuels reached a peak of over 1.2 tonnes
per head of population in 1979. They have since declined by nearly
10 per cent.
It is not true that the per capita emissions
of rich countries will necessarily increase as they become still
richer. No country in western Europe today emits the 3.2 tonnes
of carbon per head that Britons emitted in 1913, and per capita
emissions in the United States, Canada, Germany, France, the
Netherlands, Belgium and Sweden are now lower than the peak levels
reached in the 1970s or earlier.
None of the high-income countries of the Organisation
for Economic Co-operation and Development now emits the volume
of carbon per head that the failing Communist regime in East Germany
was emitting in the late 1980s, and poverty-stricken Communist
North Korea emits more carbon dioxide per head than South Korea
(and most other OECD countries).
It is true that per capita emissions
in most developing countries will increase as the world's poor
get richer, but this will be happening in a world in which
emissions in many rich countries will continue to decline.
Sadly, there is a serious risk that poverty
will escalate in many of the poorest countries, especially in
sub-Saharan Africa. The real problem is that the people of these
countries may remain very poor, not the impact on the world's
climate if they and the rest of the developing world become very
The IPCC should base its climate projections
on realistic assessments of future greenhouse emissions, not on
the quantification of improbable 'storylines' that assume that
all of the world's problems except climate change will be magically
National Centre for Development Studies
Australian National University
Letter of 28 October 2002 from David Henderson to Dr Pachauri
Dear Dr Pachauri,
The former head of the Australian Bureau of
Statistics, Ian Castles, who is an old friend of mine, wrote to
you on 6 August, and later on 29 August, to raise a number of
issues concerning the projections that are set out in the 2001
Special Report on Emissions Scenarios. In replying, you have
said that you will be making in due course a full response
I would like to take further two of the
arguments that Castles has made.
FIRST, there is the issue of whether comparative
cross-country GDP data should be given at market exchange rates
or in purchasing power parity (PPP) terms: in the scenario
projections, the former procedure was followed.
Ian Castles has made the case, here as in other
contexts, for choosing the PPP basis instead. In this he speaks
for the general body of economists and economic statisticians
who are working with these data; and as you know, the OECD, the
IMF and other agencies moved some years ago to the use of PPP-based
weighting systems for their projections. But reading Ian's letters
to you, I was puzzled to know how and why the choice of market
exchange rates would affect the SRES scenario projections
of total GDP and GDP per head for the 'Annex 2' countries over
the period 1990-2100, projections which he views as unrealistically
high. Why (I asked myself) should GDP projections for one group
of countries alone be affected by their relative position, in
relation to the rest of the world, in the base year from which the
projections start out?
Having now looked at the scenarios, I
think I have found an answer to that question.
The answer lies in the fact that the scenario
projections start from an assumption that the 'Annex 2' countries---broadly,
the developing countries---will progressively and substantially
gain ground over time, in terms of GDP per head, with respect
to the 'Annex 1' group (which comprises the core OECD countries
and the economies in transition). Each of the scenarios takes
as a point of departure an estimate of the extent of this catching
up, or convergence, over the whole period from 1990 to 2100.
With this procedure, the choice between market
exchange rates and PPP rates in the base year can make a substantial
difference. This is because with the former, as opposed to the
latter, there is significantly more ground to be made up: the
initial divergence, the 'gap', is greater. Hence projected GDP
in the poorer countries has to grow faster in order to achieve
the postulated degree of convergence in later periods---with corresponding
implications, other things being equal, for energy use and for
To illustrate this, one can compare the 1990-2100
projections in the B1 IMAGE scenario, which is one of the 'markers',
with how these projections would have looked if the same working
assumptions had been made but with Angus Maddison's PPP-based
1990 data as the point of departure. (Here I use Maddison's fine
book, The World Economy: A Millennial Perspective,
though with appropriate regrouping of countries).
The B1 IMAGE scenario projects for the Annex
1 countries an increase in GDP per head, between 1990 and 2100,
by a factor of just over 5. It further assumes that by 2100 the
ratio of per capita GDP in those countries to that of the Annex
2 countries will have fallen to just over 1.8. In the 1990 base
year this ratio (using market exchange rates) is put at 16.7.
In order to move from this initial ratio of 16.7 to the postulated
1.8 in 2100, given the projected growth in the Annex 1 group,
the total GDP of the Annex 2 countries is projected to rise, between
1990 and 2100, by a factor of just under 65.
Suppose now that we make the same assumptions
about the gap in 2100 (the 1.8 ratio) and the growth in per capita
GDP in the Annex 1 countries (the factor of 5), but start in 1990
from Maddison's PPP-based estimates for that year. With these,
the 1990 ratio of GDP per head in the Annex 1 countries to that
of the Annex 2 countries is 6.3 only, as compared with 16.7. To
bring this figure down to 1.8 by 2100 would require (if my arithmetic
is correct) an increase in the total GDP of the Annex 2 countries,
over the period 1990 to 2100, by a factor of only 24.5, as compared
with just under 65.
The use of PPP data as the 1990 starting point
of the scenarios would therefore have brought with it significantly
lower projections for GDP growth in the Annex 2 countries, and
hence lower figures for their CO2 emissions.
This in turn might have affected the leading and much-quoted conclusion
of the whole IPCC Third Assessment, namely, that the prospective
extent of global warming, as between 1990 and 2100, could be put
in a range of from 1.4 to 5.8 degrees C.
It seems to me that for this reason alone---though
there are a number of other substantial questions that could be
raised in relation to it---there is a good case for reviewing
the whole scenario exercise. This brings me to my other point.
SECOND, Ian Castles has suggested that in the
next IPCC Assessment national and international statistical agencies
should be brought in and represented. I agree with him: it is
high time that these agencies involved themselves in the process.
But I would take the argument further. I think that the central
economic departments of state---treasuries, ministries of finance,
ministries of economics, and organisations such as the US Council
of Economic Advisers---should likewise be taking an active part.
Their expertise is pertinent, and the economic stakes are high
enough to require their attention. They should not remain on the
I am sending copies of this letter, on a personal
basis, to a number of friends and acquaintances across the
world with whom I have been discussing these and related issues,
a few of whom are connected either with national statistical
offices or with central economic departments of state. I
am also sending it to two persons whom I have not met, because
of their current roles and responsibilities. One of these is Henry
Derwent, who led the British delegation to the recent COP8 meeting
in Delhi, and the other is Professor Glenn Hubbard, who is Chairman
of the US Council of Economic Advisers and of the OECD's Economic
Last, I attach a summary CV by way of orientation.
With best wishes for your exacting role and
(Westminster Business School, London)
Document 2: TGCIA Presentations and Memo
2 (1): Text used by Ian Castles
in making a presentation to the IPCC TGCIA Expert Meeting in Amsterdam
on 10 January 2003.
My thanks go first of all to the IPCC for inviting
me to this meeting to elaborate on concerns about the SRES which
I expressed in messages I sent to Dr. Pachauri, at his invitation,
some months ago. I am most grateful to the IPCC for meeting the
costs of my travel from Australia, and for giving serious consideration
to the issues that David Henderson and I have raised.
Although I have spent most of my life working
for the Australian Governments, I need to make clear that I am
not now affiliated with any government agency, nor indeed with
any other organisation involved in climate change matters.
Secondly, I want to thank Dr. Richard Moss
for the great efforts he has made to accommodate this presentation
within what was already a very full program for the meeting, and
also for finding many hours during his extremely busy program
to serve as convenor for the productive discussions which David
Henderson and I have had with SRES authors and other experts during
the course of this week.
My final thanks go to Professor Nakicenovic
and other participants for their courteous and frank approach
to these discussions. We did succeed in removing some of the differences
between us. And, for the rest, we now have a better understanding
of what our differences are.
In recent months I have been told, many times,
that I have not understood the purpose of the SRES scenarios---that
I do not know why and how they were prepared, nor how they are
being used in research. I have certainly learned more about these
matters in recent months, and especially in recent days. And I
have to say that the more I learn about the processes and the
outcome, the more uneasy I have become about the way that the
scenarios have been used by the IPCC and are being used by the
Let me agree at once that the SRES process
has been an open one. At the outset, an open and widely advertised
invitation was issued to modellers to take part in the exercise;
later, initial scenario results were posted on the internet and
revised in the light of comments received; and in the final stages,
following standard IPCC procedures, the draft SRES as well as
the scenarios were subject to a series of expert and government
But whatever the merits of the process, serious
ambiguities and contradictions remain. On the one hand, the SRES
authors state repeatedly that the scenarios 'are neither predictions
nor forecasts'; yet, on the other, the blurb on the back cover
states explicitly that the report 'describes new scenarios of
the future, and PREDICTS greenhouse gas emissions associated with
such developments' (emphasis added). Perhaps the statements can
be reconciled, along the lines that the scenarios themselves are
not predictions but that their quantification in terms of model
results are statements about the future which are conditional
upon the realisation of the stated assumptions about driving forces.
This seems to me to be splitting hairs, but in any case the key
question about the future turns upon the reasonableness and consistency
of those assumptions.
Where did the assumptions come from? The Terms
of Reference for the SRES required that modelling teams would
'be provided with information on the input assumptions and other
necessary information', and that the writing team, for its part,
'would ensure that the range of results reflects the underlying
uncertainty' (p. 324). And the report itself states that 'Quantitative
storyline targets recommended for use in all scenarios within
a given family included, in particular, population and GDP growth
assumptions' (p. 174).
It would seem to follow that the various storyline
targets relating to GDP should have reflected the full range of
underlying uncertainty relating to the future growth in world
output. But they did not do so. The SRES writing team analysed
hundreds of scenarios from 'different literature sources and other
scenario evaluation activities', which spanned 'a wide range of
assumptions about ... levels of economic development ... and other
factors' (p. 79) and found that, for 2050, the gross world product
(GWP) in most of the scenarios clustered around a rather narrow
range equivalent to 5 times the 1990 level (p. 94). In fact, less
than 5% of 166 scenarios analysed assumed that GWP would reach
6.5 times the 1990 level by 2050 (Figure 2-6a on p. 94).
Yet the storylines for the A1 and B1 scenario
families---the groups that include the scenarios with the highest
and the lowest projections of emissions---assume higher levels
of GWP in 2050 than more than 95% of the scenarios in the open
literature. In fact the storyline for the A1 scenario family,
which includes 17 of the 40 SRES scenarios, assumes a higher level
of GWP in 2050 than any of the 166 scenarios in the database.
For technical reasons that are explained in my letters to Dr.
Pachauri, the levels of future GWP which are in fact assumed in
the A1 and B1 scenarios are even higher than the projected levels
reported in the SRES.
The SRES identifies GDP as one of the main
'primary driving forces' of future greenhouse gas trajectories,
but uses an erroneous method of aggregating the GDPs of individual
countries and regions. It is surprising that this unacceptable
method was used in the report, because the UN System of National
Accounts that was formally adopted by governments and leading
international agencies in 1993 is explicit that 'When the objective
is to compare the volumes of goods and services produced or consumed
per head, data in national currencies must be converted into a
common currency by means of purchasing power parities and not
exchange rates'. This recommendation was soon reflected, insofar
as practice had not already changed, in the work of the IMF, the
OECD and other international agencies.
An exception, until recently, was the United
Nations Development Programme (UNDP), in its annual and widely-quoted
Human Development Report (HDR). But the UNDP has now changed its
ways, following a report by an expert group appointed by the UN
Statistical Commission, which said that the HDR's practice of
presenting international comparisons of GDP per head using market
exchange rates was a 'material error'---that is, an error 'which
left the reader with a fundamentally distorted view of the phenomenon
It is regrettable that 'material errors' of
this kind, taken from still-unreconstructed volumes of the HDR,
are presented both in the SRES and in Chapter 3 of the Report
of Working Group III of the IPCC. One might ask how many of the
multitude of authors and reviewers of both documents, and the
anonymous officials involved in the review process for these two
reports, were aware of the existence of the SNA and the fact that
its recommendations on the use of purchasing power parities had
been endorsed by UN member governments and the leading international
As someone who is strongly committed to the
application of sound scientific method in the social sciences
no less than in the natural sciences, I was concerned to learn
from Dr. Parry's presentation on Wednesday that the IPCC Data
Dissemination Centre now provides projections (or are they predictions?)
of GDP converted at exchange rates for all countries at 5-year
intervals to the year 2100, for the IPCC marker scenarios. I would
question whether such an exercise can be of any value. If it is
to be undertaken, the resulting projections should certainly be
accompanied by a strong 'health warning', which should make clear
that the numbers do not reflect relative volumes of output, and
therefore cannot properly be used in international comparisons
of living standards or GHG emissions.
There is a serious risk that the dissemination
of this material will be worse than useless: it will encourage
researchers to base their work on faulty data and to reach unsound
conclusions---as indeed the SRES authors themselves do in the
charts purportedly reporting historical data on 'energy intensity'
in various countries and the related discussion in the report
(p. 97, 125). The unprofessional use of statistics to make exaggerated
statements about differences in income levels between regions
and countries of the world (p. 197) places at risk the status
of the IPCC as an objective and policy-neutral body.
The SRES Summary for Policymakers claims that
'the ... 40 SRES scenarios together encompass ... the current
knowledge of and uncertainties that arise from scenario driving
forces such as demographic, social and economic ... that drive
the models, as described in the storylines' (p. 3). In my view,
this statement is not consistent with the fact that most of the
scenarios, including those that yield the lowest levels of future
emissions, assume higher levels of global output in the decades
ahead than does the bulk of the open literature.
In his very interesting paper in the session
'The SRES scenarios and application in climate research' on Wednesday
afternoon, Dr. Tom Wigley identified the A2G IMAGE and the B1T
MESSAGE scenarios as 'the extreme scenarios in terms of the 2100
forcing pattern'. He noted that the A2 IMAGE scenario projected
a burden of 780 parts per million (ppm) of CO2
in 2100, whereas the B1T MESSAGE scenario projected a burden of
480 ppm. And he described these extremes as capturing 'the total
range of possible variation'.
But do they? The B1 family of scenarios, including
the B1T MESSAGE scenario, is described in the SRES itself as assuming
a future world with 'high levels of economic activity' (p. 182)
and a 'high' rate of economic growth to a 'high' level of per
capita income in 2100 (Table 6-2a, p. 317). In the decade immediately
ahead, the projected rate of growth in world output in the B1T
MESSAGE scenario is far higher than that predicted by the leading
international institutions. For the developing regions, the B1T
MESSAGE projections of output growth are higher than the highest
of three scenarios considered by the World Bank in assessing progress
towards the achievement of the Millennium Development Goals. The
projection of fossil CO2 emissions in B1T
MESSAGE for 2010 is not particularly low---it is, in fact, around
the median for the 40 SRES scenarios (8.3 GtC) and represents
an average rate of increase in per capita emissions of 1.2% annually
between 1999 and 2010 (compared with an average annual rate of
DECREASE in per capita emissions between 1990 and 1999 of 0.8%).
Far from marking the lower bound of prospective emissions at the
end of this decade, the B1T MESSAGE projection of emissions of
the main greenhouse gas seems unlikely to be realised.
It is true that the projections in this scenario
rest upon optimistic assumptions about the rate of technological
advance and its application in the second half of the century---and
it is mainly for this reason that B1T MESSAGE marks the lower
extreme of the SRES scenarios in terms of the 2100 forcing pattern.
But it is not obvious that the technological advances assumed
in this scenario could only be achieved if developing countries
achieve unprecedented rates of growth in income and output in
the decades immediately ahead. This argues for the early development
of some variants to the SRES models, which combine the long-term
characteristics of these models with a more realistic appraisal
of short- and medium-term prospects for the developing countries.
Some of these variants would probably yield a model with a lower
forcing pattern in 2100 than that of B1T MESSAGE, although it
is impossible to be more specific until the detailed modelling
work is done.
I now pass to David Henderson. He will make
some further points relating to the scenario work, and offer some
ideas for strengthening it through a broader professional involvement
used by David Henderson in making a presentation to the IPCC TGCIA
Expert Meeting in Amsterdam on 10 January 2003.
Like Ian Castles, I am pleased to have had
the opportunity to take an active part in these proceedings. I
too would like to thank Dr Pachauri for the invitation to come
to Amsterdam as a full participant in the Experts' Meeting of
the TGCIA, Dr Moss for the time and effort that he has devoted
to chairing the technical discussions that Ian and I have taken
part in here, and Professor Nakicenovic and the other participants
in those discussions for their courteous and frank approach
I think that these discussions that Ian and
I have been involved in, with SRES authors and others under Richard
Moss's able chairmanship, can be aptly described in the traditional
diplomatic communique formula: we had a full and frank exchange
of views in a cordial atmosphere. Substantial differences remain,
as Ian has noted, but the meetings were helpful and constructive.
They also gave rise to a promising suggestion for taking things
further at the next stage, which I will mention at the end of
Before doing so, let me acknowledge, what you
will in any case have noticed, that both Ian and I are well beyond
the stage of being salarymen: neither of us has any official status,
and some of you may have drawn unflattering parallels with Jack
Lemmon and Walter Matthau. But the issues that we have raised
concerning the IPCC scenario work, as also some further issues
that we might have raised or taken further had this been possible,
do not just reflect the eccentric intuitions of two elderly retirees:
we are making central points which many if not most of our interested
professional colleagues would broadly endorse. Yet it needed outsiders
to raise these points that bear on the IPCC process, and bring
them to the attention of participants in that process.
Why this need for outsiders? The SRES lists
53 authors and 89 reviewers, and to these 142 persons one might
add those involved in the sections of the WGIII Report where similar
topics are treated in a similar way. Yet the issues that we have
raised were not picked up by, or at least did not clearly emerge
from, these serried ranks of IPCC participants. In the IPCC process,
as elsewhere, a lot of weight is given to peer reviewing. But
what has happened shows that multiplying peer reviewers is no
safeguard against dubious procedures and conclusions if the peers
are all drawn from the same restricted professional milieu.
The moral of this episode, as I see it, is
that the scenario exercise, and the IPCC's economic work more
generally, should be broadened. You need to establish a more extended,
and more fully representative, economic milieu. In particular,
you need to ensure wider participation, or at any rate greater
awareness of what you are doing, with respect both to institutions
and to professional ways of thinking.
As to institutions, what this chiefly involves
is (1) national and international statistical offices, and (2)
the central economic departments in member governments---i.e.,
treasuries, ministries of finance, ministries of economics, and
agencies such as the US Council of Economic Advisers. You need
a wider involvement of official responsibilities and expertise.
As to people as distinct from institutions,
the main need is for closer involvement of economic historians
and historically-minded economists. The historical element in
the IPCC's economic work is greatly in need of strengthening,
the sooner the better.
Alas---be warned!---broadening and reinforcing
the economic programme, and professional participation within
it, will not necessarily give the carbon cycle and global climate
change modellers a much firmer basis for their work: have no illusions
about what economists can say hope to say with confidence about
the future. But what I propose would bring with it two improvements.
- It would make the IPCC less vulnerable, less
exposed to charges of bias, superficiality, or omission.
- It could help to bring new ideas and insights
Under both headings, it would serve to make
this element in the IPCC process more professionally watertight,
which right now it is not.
I do not make these suggestions in a spirit
of reproach. The IPCC could no doubt have tried harder to involve
these missing groups of professionals; but equally---perhaps more
equally, so to speak---people within these groups could themselves
have shown greater interest in, and awareness of, IPCC-related
issues, and greater readiness to participate. In any case, what
chiefly matters is the future. What to do now?
On this, I would like to make two points. The
first is longer-term, and the second more immediate.
Should the scenario exercise be rethought?
Yes, chiefly for the reasons that we have given but also for some
others that we could have developed had time permitted. But does
a radical revision need to be put in place, or attempted, specifically
for AR4? I think the answer to that second question is No. The
work that has already been done on emissions scenarios, with suitable
amendments to take account of considerations of the kind to which
Ian has just referred, can provide an adequate basis for sensitivity
analysis in the next assessment. Rethinking can have a longer
time-horizon, which it will probably need.
However, the process of rethinking should begin
now; and in our technical discussion group we emerged with a proposal
for immediate action. In particular, the suggestion was made to
hold a specially convened experts' meeting to review the kinds
of issues that we had been debating within the group; and one
or two of us have taken this idea further through memoranda containing
specific proposals for giving effect to it. In my own memo I make
the suggestion that such a meeting could be jointly sponsored
by the IPCC and my former organisation, the OECD. So I will conclude
by expressing the hope that some of us will meet again in Paris
in the spring!
(3): Ideas for a Special Meeting
[The memorandum that appears below
sets out a suggestion by David Henderson as to the agenda, venue
and attendance for a meeting that could be held with the aim of
reviewing the kinds of projections of economic change that enter
into the scenario work of the IPCC. The memo builds on a proposal
for such a meeting that was made in the course of technical discussions
held in connection with an Experts Meeting of the IPCC's TGCIA,
which took place in Amsterdam on 7-10 January 2003. This text
makes some corrections to an earlier draft that was put together
in Amsterdam, and incorporates some improvements in wording suggested
there by Professor Nakicenovic.]
A proposal has been made, which
I support, for convening a special meeting to consider ways of
viewing and assessing long-term economic changes and development,
in the context of the work and mandate of the IPCC. I believe
that one object in holding such a meeting would be to secure the
interest, participation and advice of professionals who have not
so far been much involved in IPPC work. This would contribute
to a wider understanding of what has been done within the programme,
and could help to generate new ideas for its future conduct.
I have two groups of persons especially in
mind for closer involvement in the IPCC process, starting with
this proposed meeting. On the official side, there are representatives
of national statistical offices and finance ministries. In the
groves of academe, the main target groups are economic historians
and historically-minded economists. With this in mind, here are
some first suggestions as to venue, subject-matter and attendance.
Given the objective of drawing in treasuries
and official statistical agencies, in addition to the government
departments and agencies that are already involved with the IPCC,
a good place to hold the meeting would be the OECD where all these
ministries are accustomed to meet and where they each have their
own Secretariat back-up. Hence the meeting could be a joint IPCC-OECD
venture, held in Paris. (If the OECD's restricted membership raises
a problem, we could think in terms of tripartite sponsorship,
through involving the World Bank).
Subject matter. The title could be, "Long
Term Economic Scenarios in the Context of the Work of the IPCC".
Given (say) a day and a half for the meeting, the final morning,
or session, should look ahead to what could be done for the future.
The meeting should try to come up with clear proposals for action.
There should be a background paper, distributed
well in advance and primarily for information, on the past economic
projections and the SRES. The list of subject headings (and possible
speakers) for the meeting could be, or include:
- reviewing and building on the past: a historical
perspective: Nicholas Crafts
- projecting growth in poor countries and rich:
- the interactions of economic and technical
change: Paul David
- the basis for international comparisons:
- the uses and limits of model-based scenarios:
- Ways ahead: methods and ways of thinking:
- Ways ahead: participants and procedures:
an IPCC speaker.
(The fifth heading reflects a personal view
of mine, that the use of scenarios should not be viewed as the
only possible route to take).
Besides individuals, the OECD (Environment and Statistics Directorates,
Economics Department, and possibly other units), and the IPCC
(including leading SRES authors), we should I think try to involve
the IEA, the World Bank, the UNDP, the UN Statistical Commission,
and the IMF if they proved to be keen and ready to contribute.
One way of securing wide representation of OECD member governments
while keeping numbers manageable would be to get nominations of
individuals from the relevant OECD committees.
15 January 2003
3 (1): IPCC
Emissions Scenarios: The Case for a Review
In letters sent to the IPCC Chairman,
Dr Pachauri, in August 2002, I criticised the use in the IPCC
Special Report on Emissions Scenarios (SRES) of nominal exchange
rates, rather than purchasing power parity rates, for expressing
the GDP of different countries in a common unit of measurement.
My letters acknowledged that there are large differences in income
per capita between countries and regions of the world but argued
that, as a result of the use of an invalid method of comparison,
the authors of the report had greatly overstated the scale of
these differences at the beginning of the projection period. They
had thereby been led to overstate the growth in average incomes
in developing countries that would be required to achieve the
much more even distribution in global income that is envisaged
in most of the scenarios. Prospective levels of emissions in these
countries had probably been overstated as a result.
The IPCC has made no formal response to these
arguments. However, the IPCC's Data Dissemination Centre (DDC)
at the Centre for International Earth Science Information Network
(CIESIN) at Columbia University, which manages the dissemination
of socioeconomic data and applications relating to the SRES under
the guidance of the IPCC's Technical Group on Climate Impact Assessment
(TGCIA), now provides the following explanation on its website
The SRES report, in the majority of cases,
expressed economic growth using GDP estimates converted into
a common currency of US dollars using market exchange rates...
This was done in full recognition of the fact that the preferred
measure of wealth and poverty is to adjust GDP using purchasing
power parity (PPP) estimates---a practice initiated by the World
Bank in 1996... PPP estimates more accurately capture the command
over resources in poorer nations. As such, they would be the
preferred income measure for environmental impact and vulnerability
studies as well... The reason the SRES report adopted market-based
GDP is because most greenhouse gas emissions models in the peer-reviewed
literature, including the models used in SRES, are run based
on market GDP. Since the terms of reference of the SRES required
that it review and reflect the emissions scenario literature,
SRES GDP projections are also mostly market-based. In any event,
the disaggregated GDP data supplied to CIESIN from the SRES marker
models was in market exchange rates, so we have restricted our
country level numbers to market exchange rates as well' ('Country
level GDP Downscaled Projections. (p. 1).
The statement that the use of market exchange
rates to measure relative output and incomes in the SRES was 'done
in full recognition of the fact... that PPP estimates more accurately
capture the command over resources in poorer nations' is puzzling.
It appears to imply that claims in the report about the dimensions
of current disparities, which are based entirely on comparisons
made at market exchange rates, were known to be misleading at
the time that they were made.
The statement that the practice of adjusting
GDP using purchasing power parities was initiated by the World
Bank in 1996 is inconsistent with the reference in SRES to the
fact that the UNDP's Human Development Index, produced since 1990,
includes as one of its components 'income as measured by real
GDP per capita at PPP to represent command over resources to enjoy
a decent standard of living' (SRES, p. 115). This statement correctly
reflects the UNDP's approach, as outlined in the Human Development
The GNP figures typically used for international
comparisons do not adequately account for the distorting effects
of official exchange rates. To overcome these inadequacies, we
use here the purchasing-power-adjusted GDP estimates developed
in the International Comparison Project, a collaborative effort
of the UN Statistical Office, the World Bank, EUROSTAT, OECD,
ECE and ESCAP, now being expanded by USAID (p. 13).
The explanation that 'the terms of reference
of the SRES required that it review and reflect the emissions
scenario literature' is also puzzling, because the rate of growth
in global output projected in most of the SRES scenarios (including
those that yield the lowest projections of emissions) is substantially
higher than that assumed in almost all of the scenarios in the
literature. (This point was documented in the text of my presentation
to the TGCIA Experts Meeting on 10 January and is further elaborated
The DDC now provides projections of GDP converted
at exchange rates for all countries at 5-year intervals to the
year 2100, for each of the four IPCC marker scenarios. In my presentation
to the TGCIA Experts Meeting on 10 January, I questioned whether
these estimates were of any value, since they would encourage
researchers to base their work on faulty data.
The explanation accompanying the new disaggregated
estimates states that 'One initial finding of the downscaling
exercise is that the regional growth rate methodology is unacceptable
for some countries with high initial incomes that also happen
to lie within very high SRES GDP growth rate regions'. It acknowledges
that the resulting projections for the Republic of Korea and for
eight smaller countries imply 'unacceptably high incomes in 2100',
but says that the data for these countries cannot be excluded
from the spreadsheets because this would introduce large regional
discrepancies within SRES.
In fact the disaggregated estimates now available
on the IPCC's DDC reveal that the SRES projections of GDP in 2100
are 'unacceptably high' not only for the nine countries in respect
of which this is acknowledged in the explanatory notes, but for
many other developing countries and countries in transition. The
problem is attributable in part to the regional growth rate methodology,
but the more important cause is the extremely high growth in the
income of poor countries that is projected in the A1 and B1 scenarios
(which is attributable in turn to the overstatement of income
disparities at the beginning of the projection period).
The dimensions of the problem can be illustrated
by the case of South Africa. In 2000, this country's GDP per head,
converted from nominal values using exchange rates, was only 12%
of the US level. By 2050, the A1 marker scenario projects that
the per capita income of South Africans on this basis will have
reached more than four times the US level in 2000, and about twice
the level that the US will have reached in 2050. And by 2100,
this scenario projects that the per capita income of South Africans
will be approaching twenty times the US level in 2000, and more
than four times the US level at the end of the 21st century.
In the case of the B1 marker scenario (and
other scenarios in the B1 family, one of which yields the lowest
levels of emissions in the course of the century), the projected
levels of average income in both countries in 2100 are somewhat
lower than in the A1 marker scenario, but the level of affluence
of South Africans exceeds that of Americans by an even wider margin
than in the A1 projections. The total output of goods and services
in South Africa in 2100, according to these downscaled A1 scenario
projections, will be comparable to that of the entire world in
Other countries whose average income levels
in 2100 are projected to be higher than those of the US in that
year under the DDC downscaling exercise for the B1 scenario include
Germany, Italy, France and Japan among the OECD90 countries; the
Russian Federation and the Baltic States (Estonia, Latvia and
Lithuania) among the countries in transition; the Republic of
[South] Korea, the Democratic People's republic of [North] Korea,
Malaysia, Singapore and Hong Kong among Asian countries; and South
Africa, Libya, Algeria, Tunisia, Saudi Arabia, Israel, Turkey
and Argentina among the 'Africa, Latin America and the Middle
East' group of countries.
Under the A1 scenario, the US is projected
to have slipped even further down the ladder of relative affluence
by 2100. The disaggregated projections on the CIESIN website imply
that the countries that will by then have reached higher levels
of average real incomes than the US under this scenario include
most of those listed in the preceding paragraph together with
(among others) Thailand and the United Kingdom.
However, the disaggregated A1 scenario projections
imply that average incomes in the US will be nearly twice as high
as in Australia, which shows the lowest rate of incomes growth
of all major OECD countries under both the A1 and the B1 scenarios.
Among the developing and transition countries which are assumed
to enjoy higher average incomes than Australia in 2100, according
to the A1 projections published on the CIESIN website, are China,
Indonesia, Thailand, the Republic of Korea and Malaysia in Asia;
South Africa, Zimbabwe, Algeria, Tunisia, Libya, Gabon, Namibia,
Swaziland, Botswana and Mauritius in Africa; Brazil, Mexico, Venezuela,
Argentina, Chile, Uruguay and Panama in Latin America; Iran, Saudi
Arabia, Israel and many smaller countries in the Middle East;
the Russian Federation, Ukraine, Belarus, Poland, Hungary, Romania,
Bulgaria and the Czech and Slovak Republics among transition countries;
and Papua-New Guinea, Fiji, New Caledonia, Vanuatu and Samoa in
Many of these countries are assumed to have
higher average incomes than Australia in 2100 under the B1 scenarios
also: this is true, for example, of Zimbabwe. Although no one
can say with certainty that per capita incomes in Zimbabwe will
not exceed those in Australia in 2100, it is difficult
to believe that the SRES authors would consciously have made such
an assumption---and it is unlikely that the SRES would have been
accepted by reviewers and governments if the full implications
of the GDP assumptions had been exposed.
What are the implications for the SRES projections
of emissions of these very high projected rates of growth in economic
activity? It is not possible to be precise without undertaking
a major reworking of the scenarios. But there is no obvious reason
for supposing that the overstatement of prospective growth rates
and output levels in developing countries would NOT have led to
a significant overstatement of projected emissions.
The SRES Summary for Policymakers (SPM) claims
that the 40 SRES scenarios 'together encompass the current range
of uncertainties of future GHG emissions arising from different
characteristics of these models, in addition to the current knowledge
of and uncertainties that arise from scenario driving forces such
as demographic, social and economic, and broad technological developments
that drive the models, as described in the storylines ...' (p.
The implication of this statement, and of similar
statements in the body of the SRES, is that the preparation of
new scenarios is unnecessary, because the resulting projections
of emissions would differ only marginally from the existing set
and (in particular) would not result in a significant reduction
in the projected levels of emissions in the scenarios with the
lowest emissions profiles.
The scenario that yields the lowest cumulative
total of CO2 emissions through to the end
of this century is the B1T MESSAGE scenario, and this is also
the scenario which was identified by Dr. Tom Wigley, in his presentation
to the TGCIA meeting on 8 January, as representing the low extreme
of possible variation 'in terms of the 2100 forcing pattern.'
But there are a number of reasons for believing
that the B1T MESSAGE scenario does not by any means establish
a reasonable lower bound: lower emissions levels can be projected
on the basis of assumptions that are fully defensible. The following
list provides some indication of the range and extent of modifications
to B1T MESSAGE that would be necessary if this scenario is to
be used as a measure of the lower bound of 'the total range of
1) The B1T MESSAGE scenario assumes a far
higher rate of growth in output per head in developing countries
than does the bulk of the literature in the scenario database
(see SRES, p. 79 ff): The literature
review showed that the median average annual rate of GDP per capita
growth in developing countries was about 2.5% in each of the periods
1990-2020, 2020-2050 and 2050-2100 (Figure 3-10 on p. 119). The
rates of growth in these periods that were assumed in B1T MESSAGE
were, respectively, 4.2%, 4.6% and 2.6% (derived from tables on
pps. 529-30). A rough calculation suggests that, as a result of
the far higher growth rates assumed in the first half of the century,
the cumulative level of output in the developing countries for
the century as a whole exceeds the median level in the literature
by a factor of about 3.
2) So far as the first half of the century
is concerned, the B1T MESSAGE scenario also assumes a substantially
higher rate of growth in output than is envisaged in the B1 storyline
itself: The storyline postulates that,
by 2050, global per capita output will be about US$13,000 (p.
182), which is similar to the level of $12,755 assumed in the
preliminary B1 marker scenario (Table VI-4 on p. 368, line 3).
However, the final B1 IMAGE and the B1T MESSAGE scenarios assume
that average global GDP in 2050 will be $15,600, over 20% higher
than in the preliminary marker scenario (pps. 506, 526).
3) The higher growth in output that B1T
MESSAGE assumes in the first half of the century, over and above
that postulated in the B1 storyline, is entirely attributable
to faster growth in developing countries:
For 2050, projected per capita GDP in the ASIA region was 27%
higher, and in the ALM region 57% higher, in B1T MESSAGE than
in the preliminary B1 Marker (SRES, pps. 371-72, 529-30). An indication
of the impact of this difference on projected emissions is that
cumulative CO2 emissions in these two developing
regions from 1990 to 2050 in B1T MESSAGE are 78 GtC, or almost
30%, greater than in the original quantification of the B1 storyline
in the preliminary marker for this scenario (pps. 371-72, 529-30).
4) The B1T MESSAGE scenario assumes a higher
rate of global population growth in the first half of the century
than many demographers now believe to be likely: James Hansen's 'An Open Letter on Global Warming' quotes
demographer Joel Cohen's guess that 'Assuming business as usual
..., I would not be surprised by any population in the range 7-9
billion [in 2050]' (Natural Science, 26 October 2000, pps. 9-10).
On this basis the B1 scenario population projections may be well
above the lower end of the range of possible outcomes. It is possible
that further evidence in support of this proposition will emerge
from population projections that are soon to be released by the
UN Population Division.
5) The global level of CO2 emissions in 2000 was
well below the standardized base for that year reported for all
 SRES scenarios, including B1T MESSAGE: For
fossil CO2 emissions, the standardized
increase for the decade 1990 to 2000, calculated in the way explained
in Box 5-1 (p. 243), was 0.91 GtC, or 15%. The most widely quoted
estimate of the actual increase for the nine-year period 1990-99
(that published by the US Department of Energy-sponsored Carbon
Dioxide Information Analysis Centre) is 0.35 GtC, or 6%. On average,
therefore, the four unadjusted marker scenarios appear to have
overstated actual growth in fossil CO2
emissions in the 1990s by a factor of about 2: a surprisingly
wide margin having regard to the fact that trends in emissions
for the greater part of the decade were already known at the time
that the projections were produced. Whatever the reasons for this,
the effective base for all of the SRES projections of CO2 emissions (i.e., the standardized figure for the year
2000) is too high, by a margin of at least 5%.
6) The decrease in methane emissions in
industrialised countries between 1990 and 2000 was much greater
than projected in the standardized scenarios, including B1T MESSAGE:
For the OECD90 region, the standardized
scenarios show a fractional increase in CH4 emissions between
1990 and 2000. Data submitted to the UNFCCC by OECD countries
show an aggregate decrease of about 8% during this period. For
the REF region, the standardized scenarios show a decrease of
17% between 1990 and 2000. Partial information on the UNFCCC database
suggests that there was a decrease of more than 30% in this period.
7) Contrary to some assessments, the B1T
MESSAGE scenario projects a significant growth in global emissions
of methane during the next half century: The
scenario reports a projected increase of 44% in global CH4 emissions
between 2000 and 2050, compared with an increase of only 11% in
the B1 IMAGE marker scenario which uses the same (high) projections
of economic growth. In 'Proceedings of a Workshop On Air Pollution
as a Climate Forcing, Edited by James E. Hansen' (provided to
the TGCIA Expert Meeting), it is stated that there has been significant
progress in reducing methane emissions in the US and the European
Union, and that 'Such efforts, if international, will clearly
stabilise methane abundances, avoiding the large increases projected
in some of the SRES scenarios' (p. 2).
8) Again contrary to some assessments, the
B1T MESSAGE scenarios projects significant growth in global emissions
of CO: The scenario reports a projected
increase of 66% in these emissions between 2000 and 2050, compared
with a DECREASE of 46% for the B1 IMAGE marker scenario. According
to the Workshop Proceedings cited in 7) above, 'Control of CO
emissions ... is a clear indirect reduction in CH4 ' (p. 2).
It is stated in the SPM (p. 9) that 'The SRES
scenarios cover most of the range of carbon dioxide..., other
GHGs and sulfur emissions found in the recent literature and SRES
scenario database'; and that 'The SRES scenarios extend the IS92
range [of cumulative emissions between 1990 and 2100] towards
higher [carbon] emissions..., but not towards lower emissions.
The lower bound for both scenario sets is approximately 770 GtC.'
The obvious question that arises is why the
SRES scenarios did NOT extend the IS92 range towards lower emissions.
The B1T MESSAGE scenario that yields the lowest cumulative level
of emissions in the SRES set assumes a higher level of global
average income, both in 2050 and 2100, than do ANY of the six
IS92 scenarios (SRES Technical Summary, Table TS1, p. 33). Presumably
a scenario that incorporated more realistic assumptions about
the prospective growth in incomes in developing and transition
countries, but which was otherwise similar to the B1T MESSAGE
scenario, would have yielded significantly lower levels of cumulative
emissions than B1T MESSAGE. Why was such a scenario not developed
as part of the SRES set?
In my view, the 8 reasons given above, taken
together, establish a strong case for reworking the B1T MESSAGE
scenario, as part of a more general reexamination of the methods
and results of the SRES.
SRES and IPCC: Further Concerns
In this note I raise some additional queries
and concerns about the SRES emissions scenarios, as also the IPCC
process of which they form part. The note follows on from, and
complements, what is said in the text that formed the basis for
my presentation to the TGCIA in Amsterdam, and which forms Document
2 (2) above.
My further concerns fall under four headings:
- The neglect of the past.
- The treatment of the period from 1990 to
- Questionable presumptions.
- Overstating consensus.
SRES: the neglect of history
It is a surprising feature of the SRES that
in a document surveying the long-term future, which contains over
300 pages of main text and presents 40 different scenarios prepared
by six different modelling groups, there is no chapter which systematically
reviews the evidence of the past. The starting point for any such
quantitative future-oriented inquiry should be a clear and careful
survey of earlier developments and trends, going right up to the
present day. Such a survey should be both factual and analytical.
It should contain facts and figures, tables and diagrams, and
a commentary designed to bring out the main features of past changes,
to review the causal influences that may have been at work, and
to consider how far the evidence thus presented can be used to
throw light on future possibilities. It should serve not only
as a basis for reflecting on the future, but also as an authoritative
source of public information about the past.
SRES: treatment of the period
The starting point or base year for the SRES
was 1990, and all the scenarios generated model-based results
for the decade 1990-2000 as well as for the 21st century. But
by the time the SRES was published, in 2000, the decade of the
1990s was itself becoming past history. Even allowing for the
lag between events and the published data that relate to them,
and between the completion of a MS and its final publication,
it would have been possible for the scenario work to take account
of what had actually happened over most of the decade of the 90s.
Indeed, these recent developments could and should have found
a place in an opening chapter reviewing the past.
As it is, the SRES treatment of developments
over the 1990s seems curiously detached from what actually happened.
Consider for example the growth of world GDP. For publication
in 2000, the SRES could probably have drawn on the IMF data that
were available by April 1999. These would have yielded firm estimates
for the change in world GDP over the period 1990-97, a still provisional
figure for growth between 1997 and 1998, and the Fund projections
for changes over the two following years. Combining these would
have yielded a preliminary but soundly based estimate for growth
over the whole decade of the 1990s: it would in fact have shown
prospective world GDP in 2000 as 36.5 per cent above the 1990
figure. (The final outcome now appears as 39.4 per cent, since
the IMF's April 1999 projections for the final two years of the
decade proved to be too low).
Actual developments in the 1990s, as distinct
from model-generated data, appear not to figure in the SRES. Instead,
a wide variety of derived figures for world GDP in 2000 is offered,
without reference to the recorded course of change since 1990.
For example, across the various MESSAGE scenarios, produced by
the International Institute for Advanced Systems Analysis, the
figure shown for the increase in world GDP, as between 1990 and
2000, varies between 20.6 per cent and 35.4 per cent, as compared
with the 36.5 per cent referred to above which was available in
early 1999. Neither the spread of these scenario figures nor their
relationship to actual events over the decade is the subject of
comment, and the same applies to other scenario families in the
SRES. Consideration of the reasons why some model results diverged
substantially from actual developments over the decade---in respect
of energy consumption and CO2 emissions,
as well as GDP---could well have been given in the Report, both
as part of the assessment of past trends and in commenting on
the properties and performance of different models.
IPCC and SRES: questionable
In some IPCC work, as in other writings on
environmental issues, there is a tendency to portray the growth
of GDP and advances in technology as separable and countervailing
influences on 'sustainability'. Such a tendency is to be seen
most clearly in the continued use of the dubious 'IPAT' identity:
Impact = Population x Affluence x Technology
In this formulation, which is given a respectful
airing in the SRES (p. 105), a picture is presented in which increases
in GDP bring with them, inexorably, the menace of greater Impact:
in this respect, they are to be viewed as sources of concern.
On the positive side, by contrast, there is the influence of new
and improved Technology, which appears as an independent mitigating
This is a confused way of viewing ends, means
and interrelations. It casts economic progress as a problem, rather
than as a goal and an achievement; it leaves out of account the
fact that gains in material welfare have gone together with, and
indeed have partly comprised, a range of substantial environmental
improvements; and it mistakenly presents 'Technology' as a separate
influence, generated outside the economic process. It is as though
talented men (and occasionally, women) in white coats, acting
in their professional capacity from motives unconnected with the
pursuit of material gain and profit, can fortunately be made available,
given sound government policies, to rescue humanity and the planet
from the consequences of economic growth. But 'Technology' and
'Affluence' are doubly inseparable. Not only is technological
change a prime source of economic growth, but it is itself largely
driven by the perception of profit-directed opportunity; and indeed,
technological advances which people show themselves unwilling
to pay the costs of are prima facie not worth introducing.
Under this and (as I think) some other headings,
the IPCC milieu tends to take for granted, and lend support to,
ways of viewing economic events, relationships and goals which
are by no means established and agreed. These questionable presumptions,
though they enter into the IPCC process, have their origins outside
it: some have been endorsed by member governments and international
agencies. There is here a general problem, which involves not
just the IPCC but governments and the academic world as well---a
problem of determining whether and how far there is broad agreement
that can serve as a basis for policy, and if so, what form that
agreement can be said to take.
IPCC: overstating consensus
Since its establishment in 1988, the IPCC has
come a long way. It has brought to completion and publication
a series of extremely detailed and broadly agreed reports, covering
a wide range of extraordinarily complex issues and spanning several
forms of expertise; it has secured for these reports and their
conclusions, as also for its procedures, the broad approval of
its many and diverse member governments; it has informed the thinking
of those governments and prompted decisions by them; and it has
now established both a provisional set of conclusions and a well
defined process for continuing its work on the issues of climate
change. Its participants and supporters might understandably claim
that it has created a world-wide consensus on the nature of the
problems, the kinds of actions to be taken on them, and the conduct
of future inquiries into them.
I think there is a risk of overstating the
extent to which consensus exists, or should necessarily be aimed
at given the present state of knowledge and range of informed
opinion. Despite the IPCC's achievements, it would be wrong to
draw the conclusion that its status, ways of thinking and procedures
should now go unchallenged. It may be that the natural wish of
member governments for the IPCC to establish and present to them
a consensus view has been pushed too far.
In its economic aspects, partly for reasons
that Ian Castles and I have sketched out in these three documents,
the work and preconceptions of the IPCC are open to question,
in ways that have gone largely unnoticed by the many participants
in the process, official and unofficial. As I have noted in Document
2(2), peer review provides no real safeguard against such failures
of perception if the peers are drawn from the same milieu. To
be made more professionally watertight, the IPCC has to extend
its economic and statistical milieu, by involving a wider range
of interests, viewpoints and expertise. Mere numbers are not enough.
Whether and how far the same argument may apply
to other aspects of the IPCC's work, where other disciplines are
involved, is not for me to judge; but the Panel and its member
governments should perhaps consider the possibility that here
too the now existing milieu, if it is fair to use the term, could
usefully be broadened.
As to the member governments themselves, my
impression (it is no more) is that the extent of the consensus
that has been arrived at, and the readiness to endorse presumptions
that others would question, has been made possible by the fact
that, not surprisingly, the officials concerned have been largely
drawn from the ministries, departments and agencies that are concerned
with environmental issues. They too form a milieu. Its members
bring to bear their own specialised knowledge and expertise, but
within it economic aspects are not always well perceived or professionally
handled. Hence my argument, as put in Document 2 (2), that other
departments of state, with economic and statistical knowledge
and expertise, should be ready and able to play a part in the
It may be that the IPCC and the professional
groups associated with it, official and unofficial, are in danger
of becoming victims of their own success. In some important respects,
the networks and procedures that have been created appear as more
limited, and less free from bias and presuppositions, than is
generally realised. Broader professional involvement could admittedly
bring with it new disagreements and new elements of complexity
and uncertainty, thus putting consensus in question. But it would
strengthen the basis of knowledge and understanding which the
IPCC has rightly viewed as essential to its work and reputation.
Westminster Business School
4 February 2003
|Lavoisier the Man|
Bio and Image
|Click above for latest SOHO sunspot images.|
Click here for David Archibald on solar cycles.
|Where is that pesky greenhouse signature?|
Click here for David Evans's article.