Select Committee on Science and Technology Minutes of Evidence

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 work.


  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 science.

  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 MoD.

  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 sources?

  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 UNFCCC negotiations;

    —  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 IPCC.

  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 variability".

  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 change—so 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 circulation—and 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 impact models.

  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 factors—greenhouse 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 scale.

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 (IACGEC).

  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 University Press.

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