Are Climate Change Measurements Wrong?
By Sanjay Suri*
There is a stir in the scientific
community as two experts challenge the widely accepted climate change
reports issued by an intergovernmental panel. One of the critics,
David Henderson, explained their doubts in a conversation with Tierramérica.
LONDON - The Intergovernmental Panel on Climate
Change (IPCC) should not base its next climate report on its flawed
greenhouse gas emissions projections, says David Henderson, former
chief economist of the Organization for Economic Cooperation and
Development (OECD) and now a visiting professor at the Westminster
Business School in London.
Henderson and Ian Castles, of the National
Center for Development Studies at Australian National University
and formerly head of Australia's national office of statistics,
have co-authored a critique of the IPCC's Special Report on Emissions
Scenarios, which is to be used as a basis for future assessments
of climate change.
Henderson and Castles's analysis, to be published
in the next edition of Energy and Environment journal, argues that
the methodology used to estimate the accumulation of greenhouse
gases (produced from combustion of petroleum, natural gas and coal)
in the atmosphere by 2100 is erroneous and assumes an exaggerated
level of economic growth for developing countries.
The two experts' challenge was published recently
in the British magazine the Economist, and comes as a sharp blow
to the credibility of the IPCC, whose opinions on the human causes
of climate change have otherwise been considered the consensus of
the international scientific community on the matter.
According to the Third Assessment Review on
climate change, published in 2001 by the IPCC, it is likely that
within a century the average earth surface temperatures will have
risen by 1.4 to 5.8 degrees centigrade with respect to 1990 averages,
and that sea level would rise 0.09 to 0.88 meters as a result of
melting polar icecaps.
In an exclusive dialogue with Tierramérica,
Henderson calls on the IPCC to give economic and statistical issues
greater weight in the climate change calculations and expresses
hope for a "full and open debate" on the issue.
On what basis do you challenge the
IPCC's Special Report on Emissions Scenarios?
Contrary to accepted international practice, the 40 scenarios presented
in the Report convert GDP (gross domestic product) data for the
countries of the world to a common measure using market exchange
rates, rather than purchasing power parity rates. Because of this
flawed procedure, and also because of built-in assumptions about
the extent to which the gap between rich and poor countries will
be closed over this century, the scenarios yield projections of
GDP for developing regions which are improbably high.
Does this mean that the figures for
prospective emissions are too high?
What it means is that the even the scenarios which show the lowest
cumulative emissions over the century do not in fact represent reasonable
lower limits. These projections do not, as is claimed for them,
encompass the full range of uncertainties about the future. They
should not be taken as the accepted basis for the IPCC's coming
Fourth Assessment Review of climate change issues.
The IPCC met last week in Paris. What
do you think should have emerged from that meeting in relation to
the future work of the Panel?
For a start, I hope that the Panel will recognize that our critique
of the Special Report on Emissions Scenarios is well founded. What
we are saying does not merely represent the views of two isolated
persons -- neither I nor my co-author (Castles) have any official
status. What we are saying would receive wide professional backing.
But what action would you want the
IPCC to take? Should the whole emissions scenarios exercise be redone?
I understand that it would be difficult to repeat an exercise on
this scale in time for the IPCC's Fourth Assessment Review. But
a more limited exercise should begin now to review the basis for
the work on emissions, and to arrive at a new set of projections
which, though less elaborately derived, would give a sounder basis
than the present figures.
There are very great uncertainties
in these and the other projections that the IPCC makes because in
keeping with its mandate from governments, it has to look a century
ahead. Would what you propose do much to reduce these uncertainties?
No, because economists can't claim to be able to see the future
at all clearly. But what we suggest would provide a basis, a starting
point, which was more professionally watertight than the present
Do you have any other suggestions for
Yes, what we are saying goes beyond the work on emissions scenarios.
More generally, we think that the IPCC should try to ensure a more
balanced, informed and professional treatment of the economic and
statistical aspects of its work. On the official side, there should
be a greater involvement of economic ministries and statistical
agencies. Among the academics who take part, there should be better
representation of economic historians and historically minded economists.
Has the IPCC responded in any way to
what you have been saying?
Yes it has. We started by writing to the Chairman of the Panel,
Dr R.K. Pachauri, and as a result we were invited to a special IPCC
experts' meeting last month. Although the meeting already had a
full agenda, we were given the chance to make presentations to it,
and technical discussions were held outside the main meetings to
consider the points we were making.
Will the IPCC be making a more formal
response to your critique?
Yes, I believe that will happen soon, and we hope it will. We would
like t o see a full and open debate. The various communications
that we have sent to the IPCC are to be published soon in Energy
and Environment journal. When the editor there offered to publish
what we had written, we made it a condition that she should invite
the IPCC to publish an article by way of response. She accepted
our proposal, and I understand that the IPCC has accepted her invitation.
* Sanjay Suri is an IPS editor.
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