Memorandum submitted by the Department
of the Environment, Transport and the Regions
1. The Department welcomes this inquiry
by the Select Committee. Man-made climate change is one of the
greatest challenges facing mankind. The international scientific
community have evolved one of the most thorough and ambitious
systems for assessing the science of climate, and the UK science
base and the Meteorological Office have played a key role in its
2. Within Government, the Department of
the Environment, Transport and the Regions takes the lead on policy
on combating man-made climate change. Working with other Departments
and Agencies it represents the UK at international fora including
the Intergovernmental Panel on Climate Change (IPCC). The Chief
Executive of the Met Office, supported by the Director of the
Hadley Centre, provides specific advice on climate matters including
climate change modelling. The Department is able to draw on the
UK science base for advice on climate change impacts. Overall
a high level co-ordination of UK research on climate change and
other global environmental issues is undertaken by the Inter-Agency
Committee on Global Environmental Change. This committee is currently
being reviewed by the Office of Science and Technology, DTI.
3. However the Department has recognised
from the beginning that global warming is a global problem and
that it would require an international scientific consensus before
international action could be taken. For that reason the UK was
one of the founder nations of the IPCC. DETR has given substantial
financial support to the work of the Panel and has supported the
chair of the scientific assessment working group, Sir John Houghton.
The IPCC is now the pre-eminent source of advice on climate change
4. DETR also supports, through its research
programme, the assessment and prediction of climate change, largely
through global climate modelling at the Hadley Centre. While the
Hadley Centre is widely recognised as having built the world's
leading climate change model, the Department assures the quality
of the programme through an independent Science Review Group of
the country's leading experts. The Department also commissions,
from the University of East Anglia's (UEA) Climatic Research Unit
(CRU), independent assessments of the output of the model against
current meteorological data sets. A 10-year independent review
of the Hadley Centre has just been commissioned by the DETR and
5. The Department receives frequent advice
from its contractors, particularly the Hadley Centre, on its research
results and current developments in the science. It also seeks
advice from time to time through the wider science base.
6. The IPCC was formed in 1988 under the
auspices of WMO and UNEP to assess the current state of knowledge
on climate change. It is independent of the UN Framework Convention
on Climate Change (UNFCCC) though its work plan relates to the
programme of the Convention. The IPCC currently works through
three working groups, each with shared chairs. The scientific
assessment working group (Working Group I) (WGI)) is the one of
most direct relevance to the Committee's inquiry and is chaired
by Sir John Houghton and Professor Ding Yihui of China. It is
supported by a Secretariat located at the Hadley Centre.
7. The IPCC commissions lead authors to
provide assessment of research published in the peer reviewed
scientific literature. Those assessments must cover the full range
of evidence and interpretations. The assessments are then open
to peer review. The IPCC WGI peer review process currently involves
about a thousand experts world-wide. The IPCC WGI then meets in
full (usually about 100 nations are involved) to agree the policy
makers summary to the set of authored chapters. Published IPCC
reports are subsequently considered by the UNFCCC. The IPCC's
approach fully accords with best practice in scientific assessments,
in particular with guidance on The Use of Scientific Advice
in Policy Making, "The May Guidelines".
8. The remainder of this memorandum addresses
the Committee's specific questions. The committee will already
have received a memorandum from the Meteorological Office on man-made
climate change science, and our response takes this into account.
How and from whom does the Government receive
scientific advice on climate change? Which of these are the principal
9. The principal source of advice is the
reports of the IPCC. These remain the definitive analysis of the
global scientific literature. Advice on the significance of scientific
evidence emerging between IPCC assessments is provided primarily
by the Met Office, through the Hadley Centre, and by other research
institutes and universities. For assessing regional impacts of
climate change the Government is advised by a number of world
leading centres (eg the UEA, the Environmental Change Institute
(ECI) at Oxford University, the Institute of Terrestrial Ecology
and the Institute of Hydrology). The Department's independent
review group, the Climate Change Impacts Review Group, published
and assessment of the impacts on the UK in 1996. The UK Climate
Impacts Programme, with a secretariat at the ECI, seeks to involve
a wide range of stakeholders in the process of assessing and responding
to the potential impacts of climate change in the UK.
How is conflicting advice evaluated and verified?
10. The IPCC draws on evidence that has
been peer reviewed. It provides assessments of competing hypotheses.
Where it is possible to conclude between hypothesis on the basis
of current evidence IPCC will do so. Otherwise it will attempt
to judge the weight that can be attached to alternative explanations.
To facilitate this process DETR supported workshops where scientists
can meet to review the strength of their respective points of
view and identify experiments or analysis that could decide between
them. The Department has also commissioned reports to be published
in the peer reviewed literature reviewing specific problems. This
has included reviews of solar effects and the stability of the
Western Antarctic Ice Sheet.
What is your understanding of potential alternative
explanations for the upward trend in earth temperatures other
than increasing concentrations of CO2?
11. These have been reviewed extensively
by the IPCC, and are covered in the Met Office Memorandum. The
explanations are not necessarily mutually exclusive. The important
issue for policy is to assess the likely contribution of man-made
emissions to the observed and likely future rise in global temperatures
How does the Government assess alternative explanations
and what conclusions have been drawn regarding their validity?
12. This is principally a matter for the
IPCC. The role of Governments is to ensure that the assessment
is undertaken to the highest standards. The IPCC procedures have
been developed drawing on best practice in Europe and elsewhere,
including the May Guidelines. Alternative explanations
for the rise in global temperatures were explored extensively
in the second report and will be covered more fully in the third
report. It should be noted that the Hadley Centre programme has
a significant component which addresses this question.
How does the Government assess the validity of
various climate change models such as that developed by the Hadley
Centre of the Meteorological Office? What methodology has been
developed for critical appraisal of climate change models and
who conducts such appraisals on behalf of the Government?
13. The Hadley Centre was established in
1990 specifically to:
be a world-leading institution in
order to provide the government with the most up-to-date advice
on all aspects of natural and man-made climate change;
provide the scientific basis for
act as a national focus for climate
change research in the UK; and
provide timely, authoritative contributions
to international scientific assessments, including those of the
14. The Hadley Centre's work programme is
agreed in advance between the Centre's experts and DETR officials;
it is carefully defined with deliverables due on agreed dates.
The Hadley Centre's programme is kept under review by an independent
panel of scientists.
15. It is important to understand the origins
and pedigree of the Hadley Centre's model. Because of its origins
as a weather forecasting model, its dynamics have been rigorously
tested against the need to produce accurate weather forecasts.
However, the model has a much more comprehensive treatment of
physical processes than weather forecasting models and some climate
model developments have led to improvements in weather forecasts.
The Hadley Centre continues to benefit from improvements in the
dynamics undertaken by the Met Office for forecasting purposes.
The Hadley Centre's model is the choice of many workers outside
the Hadley Centre; for instance the NERC's UGAMP (Universities
Global Atmospheric Modelling Programme) uses the Hadley Centre
model extensively, and many researchers into the impacts of climate
change choose to use the Hadley Centre's output. Indeed, a current
assessment of climate impacts in the USA is using output from
the Hadley Centre.
16. An independent Science Review Group
(SRG), composed of leading UK experts regularly reviews the work
of the Hadley Centre. SRG meetings are held twice a year and explore
one or two topical aspects of the climate prediction programme
on each occasion. Separately, a major review, covering all aspects
of the management, performance and scientific excellence of the
Hadley Centre, was conducted 5 years after the Centre was established,
and a 10-year review has just been commissioned. This will involve
a wide-ranging review of the science of the Hadley Centre by a
small panel of international experts. It will also include an
assessment of its overall management and cost effectiveness, how
well it delivers its products to the user community (policy makers,
other scientists and the general public) and how it is placed
to maintain its leading position in climate research.
17. The Hadley Centre models have been included
in a number of independent international model intercomparison
projects each of which focus on a different aspect of climate
simulation. The two that have the most general coverage of present
and future climate are AMIP (Atmospheric Model Intercomparison
Project) and CMIP (Coupled Model Intercomparison Project). A similar
project, PMIP (Palaeoclimate Model Intercomparison Project), is
concerned with simulation of past climates, in particular the
Mid-Holocene (6,000 years Before Present) and the last glacial
maximum (21,000 year BP). Because climate conditions were very
different at those times, and because relatively large amounts
of palaeoclimate data exist for these periods, they provide a
good test of climate models. All of these projects are hosted
by the PCMDI (Program for Climate Model Diagnosis and Intercomparison),
which is based at the Lawrence Livermore National Laboratory and
funded by the US Department of Energy. The PCMDI assists in the
projects with the provision of common validation datasets, model
documentation and statistical analysis tools but the validation
and comparison is conducted by individual sub-projects. There
were 26 validation sub-projects in the first phase of AMIP, each
of which addressed different areas and published their results
in the peer-reviewed scientific literature. There are currently
more than 100 articles in the literature from AMIP and CMIP. Some
of the sub-projects have continued into the current phase of AMIP
when more advanced models are being tested.
18. Despite the reluctance to define models
as good or bad, the CMIP has recently concluded a comparison of
12 GCMs in which the Hadley Centre model was ranked in the top
six for all indicators and ranked best overall in simulations
of the current climate.
19. The Department also commissions its
own independent validation of the Hadley Centre models. For nearly
10 years this has been undertaken by the Climatic Research Unit
at the University of East Anglia. They have been awarded the contracts
to undertake this work since they have unique expertise within
the UK to undertake this task. Their work includes compiling approved
datasets of climate observations, comparing different datasets
including those from other sources, studying changes in observed
climate, and comparing the Hadley Centre's and other climate models
with the observations to assess the models' abilities to reproduce
observed climate satisfactorily.
20. Key conclusions from the most recent
contract with CRU included: "We have shown in earlier analyses
the relative performance of Hadley Centre models in simulating
the observed pattern of mean monthly precipitation for global
land areas. These earlier analyses showed the generally superior
performance of the Hadley Centre models over other modelling centres
and also the improved performance between successive versions
of the Hadley Centre model . . . Compared to other models, HadCM2
and HadCM3 are performing creditably." (Reference 3).
21. The ability of the models to simulate
El Niño phenomena has also been examined by CRU. They concluded
that "The observed levels of interannual temperature variability
associated with ENSO events are best simulated by the HadCM2 model
in comparison to other IPCC DDC (Data Distribution Centre) models"
(although they went on to note that all of the models were deficient
in some respect of their El Niño temperature response).
22. As well as comparing the most obvious
outputs of the model (temperature, precipitation, El Niño)
there is a move towards increasingly sophisticated validation.
HadCM2 has been shown to reproduce the observed relationship between
airflow and surface weather over the UK, ie not only are precipitation
amounts correctly predicted, they are correct for the right reasons,
increasing confidence in the model's use for national scenarios.
What is the nature of the UK's involvement with
the Intergovernmental Panel on Climate Change? How important is
the IPCC as a source of advice and guidance? How is IPCC advice
delivered, assessed and used by Government?
23. This has been addressed in the opening
to this Memorandum.
To what extent has Working Group 1 of the IPCC
examined potential alternative explanations? To what extent have
the results of such work been taken into account in the development
of UK Government policy on climate change?
24. Working Group 1 of the IPCC has drawn
on a wide range of scientific sources and has examined all natural
factors potentially affecting climate, especially solar variability
and natural, volcanic aerosol, which are the most important natural
climate forcing mechanisms on the time scale of the current global
warming. The IPCC concluded in the SAR (reference 4) that "The
balance of evidence suggests a discernible human influence on
global climate". However, they were not able at that stage
to "quantify the human influence on climate . . . because
the expected signal is still emerging from the noise of natural
25. In the SAR the IPCC compared the observed
pattern of climate change (using geographical, seasonal and vertical
trends rather than a single global trend) with model simulations
and concluded that "the probability is very low that these
correspondences could occur by chance as a result of natural internal
variability only. The vertical patterns of change are also inconsistent
with those expected for solar and volcanic forcing." The
TAR will assess the many new analyses of climate change attribution.
For instance, the chapter headings of the TAR agreed in IPCC WGI
plenary include "How well can natural factors explain observed
climate change?" and "How well can anthropogenic forcing
explain observed climate change?"
26. Another factor that has been suggested
as giving the appearance of global warming is the biasing of temperature
measurements due to changes in measurements methods and urbanisation.
The IPCC devote considerable effort to correcting this effect
but concluded in the SAR that the "estimate of warming since
the late 19th century has not significantly changed" from
the First Assessment Report, although the subject is still under
review for the TAR. The SAR also notes that "Remote sensing
techniques hold promise for the eventual world-wide estimate of
urban temperature bias."
27. There are a number of other factors
that affect climate, both man-made and natural, but are not directly
considered in most climate models at present. Generally this is
due to a lack of sufficient understanding of these factors and
their effect on climate, as well as to the limitation of computational
power. These factors are kept under review through the activities
of contributing authors and through other international research
programmes, which have close ties to the IPCC. In the SAR, the
IPCC identified the most important of these as "the indirect
effects of sulphate aerosol, the radiative effect of trace gases
other than CO2, and the forcings associated with large
scale land use changes or the carbonaceous aerosols generated
by biomass burning". (In fact the indirect effects of sulphate
aerosol, and the radiative effect of gases other than CO2,
have since been included in the Hadley Centre model.) Each of
these will be addressed in further detail in the TAR. Additional
factors included for assessment in the TAR include forcings due
to tropospheric ozone changes and the interactions between atmospheric
chemistry and climate. Further attention will also be paid to
the subject of solar forcing.
28. The SAR of the IPCC provided the Government
with a clear indication that there was an increasingly urgent
need to tackle climate change and it underpinned efforts to reach
an agreement at Kyoto. It also provides the rationale for the
UK to develop its domestic goal to reduce its emissions of CO2
by 20 per cent, beyond its Kyoto commitments. The IPCC has also
shaped the Government's appraisal of the long-term need to reduce
emissions further and in due course to widen the scope to other
nations of the need for emissions limitation and reduction targets.
It is likely the TAR will provide an even clearer rationale to
move beyond the Kyoto targets and will provide the scientific
underpinning for negotiations for the second commitment period
(2013-17) which has to begin before 2005.
Does the Government consider that, despite acknowledged
limitations and uncertainities, climate change models are the
most robust method for providing information on climate change?
What, if any, other alternatives have been considered?
29. Yes, the Government does consider that
global climate models, especially general circulation models (GCMs),
are the most robust method for providing information on climate
change. It is important that the method used to make future projections
is capable of:
(a) simulating all the feedback mechanisms
involved with climate, because these are where the main uncertainties
lie and also because their interactions with each other need to
be taken into account, and
(b) producing projections on a spatial resolution
useful for understanding impacts and planning adaptation policies.
30. GCMs are the only tools capable of fulfilling
these criteria. Other methods which have been considered and,
indeed, are valuable in certain circumstances include simpler,
less computationally-intensive models. For instance, these can
be used to investigate the global average temperature changes
which would result from particular emissions scenarios, and thus
permit a wider range of policy options to be investigated, on
a quicker time-scale, than would be the case using only GCMs.
It should be noted, however, that the simpler models assume an
understanding of the climate system, which can only really be
provided through observations and GCMs. Simple models cannot of
course provide regional predictions.
31. The DETR is currently funding the refinement
of a well-known simple model, MAGICC, and its use to investigate
the IPCC's new emission scenarios in time for their climate consequences
to be reported in the IPCC TAR.
32. Other simple models are needed for some
applications, such as investigating climate variablity on very
long-time scales such as the study of ice age cycles.
33. Some have proposed that past climates,
induced by varying solar forcing, can give an indication of the
effects of climate changeso called "proxy climates".
Indeed much can be learned about the behaviour of the climate
system from studies of palaeo-data. However, such studies can
only give imperfect insights into the response to greenhouse gas
increases as they are related often to solar changes which, although
of a comparable magnitude at the global scale, can affect the
climate system in quite different ways at the regional level.
34. More generally it is important to assess
observations of the climate. Recent studies on climate change
detection and attribution rely upon estimates of natural climate
variability (against which recent changes are measured). The short
duration and very limited spatial coverage of the instrumental
record has been supplemented with palaeodata from diverse sources,
but the uncertainties associated with much of the palaeodata mean
that in practice the best indication of natural variability is
derived from the control run of a well-validated model. Whilst
the Government does believe that this is a valid practice, it
is keen to see the compilation of improved datasets. Examples
of its activies in this area include:
DETR is to be represented on the
Steering Committee of the new NERC Thematic Programme PRESCIENT
(Palaeoclimate Research and Earth System Modelling for Enhanced
Climatic and Environmental Prediction);
DETR and MoD are to co-fund (with
an in-kind contribution from NERC) the UK contribution to the
USA-initiated ARGO project, for improved global ocean monitoring
of temperature, salinity and currents.
The UK supports the GCOS initiative
which aims to provide a global climate observing system which
meets the needs of the UNFCCC process and underlying research
on the climate system.
How adequate are existing global climate change
models as a basis for policy development and implementation?
35. To answer this we need to consider the
key policy issues. Firstly policy makers wanted to know (a) whether
climate change was already happening and (b) how serious a problem
it is for the world as a whole and for the UK. Secondly, if it
is decided it is a problem then we need to assess the response
of the climate system to different mitigation policies and also
to consider adaption requirements.
36. Full climate models (GCMs) enable us
to explore all these issues by assessing historic changes and
the projected changes in climate given future greenhouse gas emission
scenarios. They are based on physical principles so they do not
depend on some calibration period. This is important when we are
going into uncharted territory. Climate models are spatially resolved
so can, in broad terms, identify specific regions that could be
particularly sensitive to climate change. By being physically
based it is possible also to explore the sensitivity of projections
to uncertainties in our understanding and quantification of physical
processes. It is also possible to explore non-linear changes,
such as rapid changes to the ocean circulationand the Hadley
Centre and other modelling centres have done this. They can also
be used to investigate potential feedbacks such as the effect
of warming on cloudiness or effects on the carbon cycle.
37. With regard to the first issues, question
(a) was a key issue in the first half of the last decade. The
Hadley Centre was the first to use a full ocean-atmosphere GCM
to assess the match between the historic temperature record and
the historic increase in greenhouse gases and aerosols. Their
initial results showed clearly that the temperature rise and the
key forcing mechanisms were consistent. This work contributed
significantly to a key conclusion of the SAR that "the balance
of evidence suggests that there is a discernible human influence
on global climate." This work has been refined to show even
more clearly that the recent rise in temperature cannot be explained
without taking into account the rise in greenhoue gas concentrations.
38. On question (b) above, a variety of
types of climate models can be used to assess future climate changes
but the most comprehensive tool is the GCM as noted above. In
fact only GCMs can provide the spatial variation in climate predictions
which are needed to assess the potential impacts on human society
and the environment. Since these are local, GCMs can provide enough
spatial detail to investigate impacts and adaptation issues. GCMs
are thus also suitable for addressing the impact of different
mitigation policies and the need to adapt. Recent work at the
Hadley Centre with impact modellers has enabled us to assess more
quantitatively the impacts of climate change and these show that
impacts become increasingly serious under a middle of the road
business as usual scenario towards the middle of the next century
with the potential for significant loss of tropical forest and
the numbers of people at risk from hunger and dislocation due
to sea level rise.
39. On the second main issue, increasingly
GCMs will be used to assess adaptation needs. These require models
with increased spatial resolution, and the Hadley Centre has developed
regional models, which provide this, and increasingly sophisticated
40. State of the art models, such as those
used at the Hadley Centre, are now very sophisticated and powerful
tools. Even so they cannot be used without interpretation. Projections
of future climate change depend on our assumptions about emissions
scenarios, as well as the sophistication of the models. However,
even the best models need to be tested and their response understood
in detail. This is particularly true at the local and regional
level when assessing impacts and adaptation. Indeed, it is essential
to consider ensembles of model runs (using the same forcing factorsgreenhouse
gas emissions for example but slightly different initial conditions)
and where possible to compare results from different models. This
is a very active area of research and requires careful consideration
of uncertainties. Nevertheless, we have no other tool that could
adequately predict the effects of climate change at the regional
What mechanisms exist to ensure co-ordination
of research effort and policy development across Government departments
in relation to climate change?
41. Climate change policy is co-ordinated
through an inter-departmental committee (the Inter-Departmental
Liaison Group) and, in the widest sense, research is co-ordinated
through the Inter-Agency Committee on Global Environmental Change
42. In addition the Department's research
programme plans are reviewed by research managers and co-ordinators
from other government departments and the research councils. Departmental
plans are usually circulated for comment and Research Council
proposals are usually sent to DETR for comment. Departmental science
advisors have been invited from time to time onto the steering
committees of NERC thematic programmes and have served on the
various NERC Boards. The DETR also funds the UK Climate Impacts
Programme, with the aim of drawing stakeholders of all kinds,
including other Government Departments, into the debate.
43. The DETR also provides the focal point
for IPCC and seeks comments widely across Government on IPCC reports
and keeps them informed of developments in the IPCC.
1. Bolin, Bert et al, 1986: "The
Greenhouse Effect, Climatic Change and Ecosystems", International
Council of Scientific Unions.
2. Tett, Simon F B et al, 1999 Nature
399, 569-572, "Causes of twentieth-century temperature
change near the Earth's surface".
3. M Hulme, Final Report to DETR for contract
EPG 1/1/48, June 1997 to March 1999.
4. Houghton, J T et al, "Climate
Change 1995: The Science of Climate Change", Cambridge