Select Committee on Science and Technology Appendices to the Minutes of Evidence


Memorandum submitted by The Met Office


  1.  The Met Office's Hadley Centre for Climate Prediction and Research carries out a broad programme of work into understanding the processes which control climate; representing them in a climate model; using this to simulate changes over the past 100 years and forecast changes over the next 100 years; monitoring recent trends in climate and attributing these to specific causes.

  2.  The evidence is compelling that (a) there has been a rise in CO2 of about one-third since pre-industrial times due to human activities and that (b) there has been a rise of about 0.6ºC in global mean temperature over the period of instrumental measurements since 1860.

  3.  Considerable research has been carried out by The Met Office's Hadley Centre to identify the relative contributing factors causing this rise in temperature. This involves a full analysis of all the known physical mechanisms as well as the development and use of a state-of-the-art global climate model to simulate the climate record. The conclusions are:

    —  climate change since 1860 is greater than that due to natural climate variability alone and cannot be reproduced from purely natural factors such as volcanoes and solar activity;

    —  most climate change since 1945 has been due to human activities; and

    —  solar variability and lack of volcanic activity can partly explain the higher temperatures in the 1940s and 1950s.

  4.  Global climate models are the most scientifically comprehensive tools available for analysing climate and predicting change. The climate model developed and used by The Met Office's Hadley Centre is recognised as being world-leading, and has been comprehensively and successfully evaluated by examining its ability to:

    —  maintain a stable realistic climate over a 1,000 year timescale;

    —  reproduce the temperature trends over the last 150 years;

    —  give realistic representations of natural climate variability such as El Niño;

    —  be used with success in an essentially similar form as a weather forecasting model; and represent different palaeoclimate epochs.

  5.  Our findings and predictions are widely recognised, accepted, and used by Government and policymaking, especially those at Department of the Environment, Transport and the Regions (DETR) who have the policy lead in Government. Continued government funding of The Met Office's research, largely through DETR, is strong evidence of the value Government attributes to our work. Therefore we have good reason to believe that our advice has been influential on Government policy on climate change. Government also contributes to, and uses the findings of, the authoritative assessments of the Intergovernmental Panel on Climate Change (IPCC), which represent a consensus of international scientific opinion. The Met Office's Hadley Centre is a major contributor to IPCC assessments.

1.  Organisational details

  1.1  The Met Office is a government agency, operating as a trading fund, whose responsibilities include research into climate change, carried out by its Hadley Centre for Climate Prediction and Research. The Centre was established in 1990 and was built on a 20 year history of climate change research in The Met Office. The work is funded under contracts from the Department of the Environment, Transport and the Regions (DETR) (about £8 million per annum), the Ministry of Defence (MoD) (about £3 million per annum) and the European Commission (about £0.3 million per annum). This annual income of £11m supports some 100 people in the Hadley Centre, many of whom are recognised world experts in various aspects of meteorology and climatology, as well as the essential supercomputing facility which runs the climate models. The atmosphere and ocean modelling activities which comprise the climate models are developed in complementary research programmes which themselves support the other Met Office functions in weather forecasting and oceanography. These research programmes amount to a further £8 million per annum, and are funded by The Met Office's core customers. Thus The Met Office is able to maintain a larger research programme than either climate research or weather forecasting could maintain on its own, giving the UK a capability which is unique across the world. It is this synergy which helps ensure the Hadley Centre's world-class excellence.

  1.2  The Committee has asked specifically for an indication of the research which The Met Office conducts in relation to climate change. There is a broad programme of work at the Hadley Centre, which can be summarised under the following headings.

    —  To understand processes in the atmosphere, ocean, cryosphere and on land which control climate and its change.

    —  To develop a climate model which represents these processes with increasing realism.

    —  To use the climate model to simulate recent change and variability, and to predict change over the next 100 years.

    —  To monitor global and national climate trends, using observations from land, sea, air and space.

    —  To combine observations and model simulations in order to attribute recent climate change to specific causes.

    —  Based on the above activities, to provide Government with the research results, advice and analysis it needs to inform policy.

    —  To communicate results more generally to a range of stakeholders, including government, media, industry, pressure groups and IPCC.

    —  To take advantage of underpinning research carried out in the UK, especially that at NERC institutes, and elsewhere.

  1.3  Since its inception in 1990 the Hadley Centre has achieved a number of important advances, and some of these are listed in Annex A. The Hadley Centre predictions of climate change and other relevant assessments are regularly communicated to DETR officials and ministers, and to other government departments. Therefore, we believe we can be categorised as a "key organisation" as defined by the Guidance Note on Submitting Evidence, and therefore we are providing substantial evidence.

2  Objectives of this Memorandum

  2.1  This memorandum aims to address the three issues raised by the inquiry under the following sections:

    A.  The factors which can cause climate to change, how these have been systematically explored as possible contributory factors to the upward trend in global temperatures, and the current best assessment of the specific causes.

    B.  How the models used to predict future concentrations of carbon dioxide and of climate change have been validated.

    C.  How Government has been advised of the above, and the extent to which it has accepted this advice.

  2.2  The other specific questions posed to The Met Office by the Committee, on the validity of climate change models, the scrutiny of possible alternative explanations for apparent trends in climate other than increasing CO2, and the dissemination of our output to Government, are also dealt with comprehensively in this memorandum.

  2.3  Much of the background discussion on the greenhouse effect, greenhouses gases, climate modelling, observations, predictions and detection is only given in brief. A more detailed coverage can be found in the recent booklet "The greenhouse effect and climate change: a briefing from the Hadley Centre" available from The Met Office. Specific results are drawn from the work of the Hadley Centre and include research being carried out worldwide as appropriate.


3.  Observations of climate change

  3.1  Figure 1 shows the change in global-mean, annual-average, near-surface air temperature (generally simply referred to as surface temperature) from 1860, when the first reliable global data is available, to 1999. The long term trend (solid line) shows a relatively stable period in the last half of the last century, a rise from about 1920 to 1940, followed by another period of little change to the mid 1970s. From then to the present day temperature has risen more rapidly, such that 1998 was the warmest year, and the 1990s easily the warmest decade, on record. Overall there has been a rise of about of 0.6ºC in the period of instrumental measurements. Superimposed on this long term trend can be seen substantial natural year to year and decade-to-decade variability. We have considerable confidence in the temperature record; it has been carefully compiled and quality controlled by The Met Office in collaboration with the University of East Anglia, and three independent records (air temperature over land, air temperature over sea, and the temperature just below the sea-surface) show similar trends. Temperature rises have generally been greater at higher latitudes and over land areas.

  3.2  Over the last 40 years the troposphere (the lowest 10-15km of the atmosphere) has warmed, and above this stratosphere has cooled. Instruments on satellites can remotely sense the temperature of the atmosphere, and there has been some well publicised disagreement about the extent to which they also show a warming. Recent work at the Hadley Centre has shown good agreement between satellite and in-situ (weather balloon) measurements in the atmosphere at a height of three-five km for the period where they overlap (1979 to the present). Figure 2 confirms that the trend of temperatures in the atmosphere over the last 35 years is similar to that at the surface, but also shows differences on a shorter timescale which are still a subject of investigation.

4.  Potential explanations of the trend and how these have been assessed

  4.1  There are several factors which could contribute to recent climate change; these will be briefly described and examined as possible causes of observed climate change over the century.

  4.2  On a timescale of tens and hundreds of thousands of years, changes in the earth's orbit around the sun have led to a succession of ice ages and interglacials (the Milancovic theory). The earth emerged from the last ice age about 10,000 years before present (y BP), temperatures peaked about 6 000y BP and have very slowly declined since then. Except for some isolated events for which the reasons are understood, these changes are too slow to be significant in the context of the last 100 years and the next 100 years. Although the earth is likely to enter another ice age, this is unlikely to be for several thousand years.

  4.3  On timescales of years to decades, the climate changes due to natural interactions between various components of the climate system (eg oceans and atmosphere). This is usually known as internal variability, as it is not driven by a factor external to the climate system. To examine this as the cause of recent change, we ideally require many hundreds or thousands of years of climate data, to see if there are periods in the past where climate has changed at the same rate as it has over the last century. Because, of course, such data have not been collected, we have to resort to either (a) a simulation of natural climate variability by a climate model or, (b) proxy temperature data, deduced from tree rings, etc.

  4.4  The observed rise in temperature since 1860 is about twice as great as its variability simulated by a 1000-year experiment with the climate model, when all climate drivers are held constant. Thus, if the model simulation of natural internal variability is realistic, then the temperature rise over the last 100 years cannot be explained by internal climate variability.

  4.5  Figure 3 shows average Northern Hemisphere (NH) temperature since AD1000 constructed by the University of Massachusetts from analysis of tree rings, ice cores, lake sediments, corals, etc. Although there are large uncertainties, the figure shows the degree of natural variability (which in this case includes internal variability and also the effect of solar changes and volcanoes) and indicates a sharp increase over the last 100 years. Again, if the proxy data are accurate, the recent rise is outside the bounds of natural variability. Both this and the model simulation described in the paragraph above indicate the detection of climate change, but cannot attribute it to a specific cause.

  4.6  Two natural factors, volcanic "dust" and solar energy, can influence climate. Sulphur dioxide gas emitted by volcanoes will, if energetic enough, reach the stratosphere and form small sulphate particles, often known as volcanic dust, which can persist for a few years. This will reflect sunlight away from the earth and hence temperatures. The amount of volcanic dust in the stratosphere has varied considerably; from about 1880 to 1920 there were a number of energetic volcanoes which gave a high dust index; the period to about 1960 was cleaner, but since then a succession of volcanoes has kept dust index high for considerable periods. This volcanic dust variability can produce significant changes in global temperatures.

  4.7  The earth's surface is warm due to the amount of solar energy (sunlight) falling on it; this is balanced by outgoing invisible infra-red energy emitted by the earth and atmosphere. If the sun's energy increases, the additional heat received will raise the temperature of the earth. Reconstructions of solar energy output show that it has varied over the last few hundred years. Simple calculations based on change in the amount of energy falling on the earth show that this would have produced a temperature change of only some 0.1 to 0.2ºC over the last century.

  4.8  To see if these two natural factors, solar output and volcanic dust, can explain recent climate change, we have driven the Hadley Centre climate model (described in Section B, paragraph 5) with changes in both. We find that the temperature change simulated by the model does not agree with that observed (Figure 4), and in particular does not give the steep rise over the last two decades. The two factors together do, however, lead to a relatively warm period in the 1940s and 1950s, when volcanic activity was low but solar activity was high.

  4.9  There have also been suggestions that solar changes can affect climate via a secondary mechanism. The two main theories here concern the modulation of the ozone layer, and the modulation of cosmic rays and clouds. The latter theory points out that increases in the sun's activity will reduce the flux of cosmic rays striking the earth. It then postulates that cosmic rays have the ability to enhance cloud formation, and hence a reduction in cosmic rays will reduce the coverage of clouds. This will allow more solar radiation to reach the earth's surface and hence warm climate. Theories of the indirect effect on climate of solar activity have been investigated in a report prepared by the University of Reading under contract to The Met Office, at DETR's request, a copy of which is at Attachment A.[2] They conclude that solar induced changes in ozone could potentially amplify direct solar forcing, but published studies disagree on this. Regarding the cosmic ray/cloudiness theory, they find that:

    —  the variation in cloudiness is apparent, but is not systematic, does not exist in all data sets and may be influenced by El Niños or volcanic eruptions.

    —  there is a low confidence that a significant observational link exists between cosmic rays and clouds, but this possibility cannot be excluded.

    —  although there is a possible mechanism linking cosmic rays and clouds, there is no evidence that it occurs in the atmosphere, as definitive experiments are lacking.

    —  any link is more likely to be via high clouds, and to have caused a cooling over the past century, rather than contributing to a warming.

  4.10  The climate of the earth is strongly influenced by the greenhouse effect. Certain gases in the atmosphere absorb some of the infra-red energy emitted by the earth and reradiate it. The net result of this is to trap some of the heat which would otherwise escape to outer space, and hence to warm the earth's surface and lower atmosphere. The greenhouse effect due to natural greenhouse gases, mainly water vapour and carbon dioxide, keeps the earth about 33ºC warmer than it would otherwise be. Increases in the concentration of greenhouse gases due to human activities, such as the emission of carbon dioxide from fossil fuel combustion, and the release of new greenhouse gases, such as chlorofluorocarbons, will augment the natural greenhouse effect. The rise in concentrations of the major greenhouse gases (carbon dioxide, methane, nitrous oxide, CFCs, ozone in the lower atmosphere) due to human activities has been observed using instruments and the analysis of gases from ice core air bubbles and these were included in the climate model. Temperatures simulated by the model rise throughout the period, and match those observed up to about the 1960s, after which they grow much more quickly than observed, to become about 0.3ºC too high by the end of the 20th century.

  4.11  Ozone occurs naturally in the stratosphere and its concentration has been decreasing over the last few decades due to chemical reactions with chlorine compounds formed from CFCs. This will have had the effect of a slight cooling of climate.

  4.12  Human activities also lead to amounts of small particles (aerosol) in the lower atmosphere which (as with volcanic dust in the stratosphere) reflect back sunlight and directly cool climate. The most significant example is sulphur from the burning of fossil fuels, which oxidises to sulphate particles. This direct cooling effect is augmented by an indirect effect arising from the ability of aerosol to increase the reflectivity of clouds. The increase in sulphate aerosols has been added to those in greenhouse gases to explore the climate impact of all man-made emissions; whereas the observed rising temperature trend since 1970 is well simulated, the warmth of the 1940s to 1960s is not.

  4.13  Finally, the model was driven with observed or reconstructed changes in all natural and all man-made factors. Figure 5 shows that this simulates a global temperature trend which includes within its range of uncertainty (blue shading) the observational record (red line).

  4.14  The discussion above demonstrates how the global temperature rise can be explained only when both natural and human factors are taken into account. However, this agreement could be the fortuitous result of the cancellation of factors, for example if man-made climate change has been overestimated but is partly offset by internal climate variability. As a more rigorous test, we have also used comparisons between simulated and observed patterns of climate change, both the geographical distribution across the earth's surface and through the depth of the atmosphere. We have shown that observed changes from 1963-95 in atmospheric temperature patterns can be most closely simulated by the climate model only when human-made changes in greenhouse gases, sulphate aerosol and stratospheric ozone are taken into account. More recent work (Reference 9), based on the evolution of changes in the geographical distribution of surface temperature by season, indicates that human activities are largely responsible for changes since 1945. This technique discriminates against natural variability, volcanic and solar as possible causes.

  4.15  From the evidence above, it can be seen that Hadley Centre scientists have applied substantial scrutiny to the question of what has caused recent climate change, to the extent that we can reasonably claim to be leading research in this area. Other institutes also play important roles, and we have excellent links with many of them, particularly Rutherford Appleton Laboratory, Scripps Institute of Oceanography (California), Massachusetts Institute of Technology, Max Planck Institut (Hamburg) and the Programme for Climate Model Diagnosis and Intercomparison in California. A workshop of selected leading international experts in this topic was organised by the Hadley Centre in 1997, supported by DETR and the European Commission. Senior staff at the Hadley Centre have been chosen as lead authors of the two IPCC chapters on "Monitoring climate change" and "Detection of climate change and attribution of causes" reflecting the status of the Hadley Centre in these key areas.

5.  Conclusions drawn on the cause of recent climate change

  The work described above leads to the following conclusions, which represent our best estimate of the causes of recent climate change:

    —  Climate change observed since 1860 is greater than that due to natural variability.

    —  Natural factors (volcanoes and solar activity) cannot reproduce the observed trend over the last 100 years.

    —  Emissions from human activity alone cannot explain all of the observational record.

    —  The inclusion of both natural and man-made causes can give a satisfactory agreement with observations.

    —  The use of statistical techniques to compare observations of patterns of climate change with those simulated by the climate model, allows us to judge that most of the climate change since 1945 has been due to human activities.

    —  Solar variability and lack of volcanic activity may explain the relative warmth of the 1940s and 1950s.


6.  Critical appraisal of climate models

6.1  To predict climate change we need to estimate:

    —  what the emissions of greenhouse gases (and other pollutants) will be in the future;

    —  what proportion of these emissions will remain in the atmosphere as increased concentrations;

    —  how the additional heating due to this will change climate.

  6.2  For future emissions, we use scenarios derived by the Intergovernmental Panel on Climate Change (IPCC), each based on a range of future projections of socio-economic factors such as population, economic growth, energy generation and use, etc. We do not have the expertise to comment on the extent to which any or all of these scenarios is likely to correspond to real future emissions, but we note that the most recent IPCC "B2" scenario does at least give rise to CO2 concentration increases which are close to those observed over the recent past.

  6.3  Based on these emissions, future concentrations of CO2 are calculated by IPCC using a model from the University of Bern. The ocean component of the model has been tuned to the measured progressive uptake of nuclear bomb radiocarbon, and validated using ocean measurements of CFCs.

  6.4  Concentrations of other greenhouse gases (eg methane, ozone) are derived from Hadley Centre models of chemical reactions in the atmosphere, given projections of future emissions. The atmospheric chemistry models are assessed by comparison with observations from surface sites, ozonesondes and aircraft; model-simulated ozone profiles appear to be generally similar to those observed. Similarly, concentrations of sulphate aerosol from both human-made and natural sulphur emissions, are generated by the Hadley Centre sulphur cycle model. This is assessed by intercomparison with other climate models, and by comparison with measured values in the atmosphere. Both these show that the simulated concentrations of sulphur aerosols are substantially less than those observed or those from other models; development work is underway to improve this.

  6.5  To predict climate change resulting from increases in greenhouse gas concentrations and changes in aerosol, we construct a mathematical model, based largely on the established laws of classical physics, which represents processes within and between components of the earth's climate system: the atmosphere, the oceans, the land and the cryosphere (snow and ice). That developed at The Met Office's Hadley Centre, arguably the most advanced available today, divides the climate system into a grid, 2.5º latitude by 3.75º longitude in the atmosphere and 1.25º by 1.25º in the oceans, with 19 levels in the atmosphere, 20 levels in the ocean and 5 levels in the land. All told, there are some one million grid points, at which equations describing the climate system are solved every half hour for a model experiment lasting typically 250 years.

  6.6  The development of the Hadley Centre climate model benefits substantially from other research in The Met Office's programme. The climate model is a variant of the weather prediction model, and hence incorporates any improvements to the latter. This is particularly true of the atmospheric processes represented in the model: the global circulation of the atmosphere, convection, the boundary layer, clouds, etc. Many of these representations are generated from specific observations carried out by The Met Office's C-130 research aircraft. Similarly, the ocean and sea-ice components benefit from advances in The Met Office's operational ocean model developed for the Royal Navy.

  6.7  The Hadley Centre climate model also incorporates representation of many processes in the atmosphere, oceans and land derived from research carried out worldwide but in particular by other UK institutes, particularly those of the Natural Environment Research Council (NERC). The description of vegetation and the terrestrial carbon cycle, for example, has been developed in conjunction with the Institute of Hydrology, and that in the oceans with the Southampton Oceanography Centre. The Hadley Centre climate model is now used by the NERC Universities Global Atmospheric Modelling Project, and their research feeds into the development of the model. Hence the advice to Government on climate change, based as it is on results from the Hadley Centre climate model, benefits from the underpinning NERC research.

  6.8  The model has been improved, both in terms of the range of the processes incorporated and the accuracy with which they are represented. The basic mechanism by which increased greenhouse gases alter climate is well understood, and we can make a good estimate of the temperature rise which would follow a given increase in atmospheric CO2, for example. But the consequences of an initial warming can act to produce a substantial feedback, either to enhance or reduce it. For example, as the atmosphere warms it can contain more water vapour, which is itself a powerful greenhouse gas, and this multiplies the original warming. Because of these connections between different parts of the climate system, we need a model which incorporates them all interactively.

  6.9  Currently, the operational climate prediction model (known as HadCM3) includes atmosphere, land, oceans, cryosphere, and the generation and climate impact of sulphate aerosols from SO2 emissions. It does not yet include the natural carbon cycle, although a development model which does incorporate it has recently been used to produce the first climate prediction taking into account carbon feedbacks. It shows a substantially larger rate of climate change, due mainly to increased respiration of CO2 from soils as the climate warms.

  6.10  Following optimisation of the physical processes in the model, it is run for many centuries given only the amount of energy received from the sun. It settles down to a climate close to that of the real earth and (unlike earlier models) it maintains a stable climate without the need to impose artificial transfers of heat and water between the atmosphere and ocean. This ability to simulate current climate increases our confidence in the realism of its predictions for the future.

  6.11  The predictions of climate change which are made by the most recent Hadley Centre model are shown in Figure 6, based on the IPCC "B2" scenario of emissions. Global-average temperature rise is estimated to be about 2.3ºC higher than today's by 2100. The rate of rise will be twice as great over land as over sea, and larger at high latitudes than at the equator.

  6.12  Before using the model to simulate and predict climate, we test its realism in a number of ways. Firstly it has to give a reasonably realistic representation of some types of natural climate variability, such as the El Niño/La Niña, the monsoon and the North Atlantic Oscillation, and the overall internal variability of climate. Secondly, we examine the internal operation of the climate system, for example the way in which heat is transported around the oceans, by comparing model simulations with measurements. Thirdly we require it to give an adequate simulation of change over the last 50-100 years when driven by known changes in greenhouse gases, etc. Fourthly, it should be able to represent different climates in the past (palaeoclimates), particularly the warmth of 6,000 years ago and the Last Glacial Maximum 21,000 years ago. Fifth, a variant of the model is used for weather forecasting, providing a different, but nonetheless demanding, test.

  6.13  These comparisons have been carried out and the results have been published (or submitted for publication) in the peer-reviewed literature; a list of publications and reports is given in Annex C.[3] The model does not give perfect representations of climate and its variability, and we make an informed judgement based on the degree of agreement about its suitability for use in predicting change in the future.

  6.14  Climate models from a number of research centres are routinely intercompared under a World Meteorological Organisation programme. Results from the most recent intercomparison, which involved the previous generation model, showed that the Hadley Centre model gave the smallest overall errors of any model when compared to observed climatology.

  6.15  Much of the uncertainty in climate change predictions comes from the poor understanding of the processes which give rise to feedbacks referred to earlier. The strength of some of these, such as that associated with water vapour, have been validated using present-day climate variability as a surrogate for climate change. This is not consistent with the view of Lindzen that amplification from water vapour feedback in the real world is much less than that in climate models, and this disagreement is currently being explored using a version of the model with very high vertical resolution, to see if the processes which Lindzen suggests are important.

  6.16  The predictions of change which we do make are accompanied by estimates of uncertainty, based on the imperfect behaviour of the model (particularly the feedbacks between different parts of the climate system). Typically, the 2.3ºC rise in global temperature predicted from the present day to 2100 is given an uncertainty ranging from about 1.3ºC to 3.5ºC. These values are calculated from the span of predictions from a number of climate models, although it should be stressed that the range is not a statistically rigorous one; for example, it does not correspond to one or two standard deviations. Work is underway at the Hadley Centre to "calibrate" the climate model using observations over the last 100 years, and use this to derive a better, statistically-based, estimate of future change and its uncertainty. The first paper on this technique has recently been submitted to Nature.

  6.17  Recent discussions have focused on the likelihood of rapid climate change, due, for example, to changes in ocean circulation. The model predicts that, for man-made greenhouse gas emissions many times those projected, the ocean thermohaline circulation will decrease but will not collapse.

Figure 1: The global-mean, annual average, surface temperature from 1860-1999, relative to that at the end of the 19th century (blue bars), together with a smoothed curve (red) showing the long-term trend. (Source: The Met Office Hadley Centre and University of East Anglia).

Figure 2: The global temperature change from 1965-1998, (a) at the surface (grey line) and (b) 3-5 km up in the atmosphere (blue line). (Source: The Met Office Hadley Centre).


Figure 3: A reconstruction of Northern Hemisphere annual average temperature change from 1000 to 1998 (purple), with the range of uncertainty in yellow. The last 100 years, shown in red, are the same instrumental record as in Figure 1. (Source: Professor Michael Mann, University of Massachussets).


Figure 4: Model simulation of the range of global temperature change 1860-1998 due only to natural variability, solar activity and volcanoes (blue band), compared to observations (red line). The model simulation is inconsistent with observations, suggesting that recent climate change is not natural. (Source: The Met Office Hadley Centre).


Figure 5: Model simulation of the range of global temperature change 1860-1998 due to the combination of natural factors and human activities (blue band), compared to observations (red line). The simulation is consistent with recent climate change, suggesting that human factors have contributed to the recent change. (Source: The Met Office Hadley Centre).


Figure 6: Prediction of temperature rise resulting from the IPCC "B2" emissions scenario, global average (red), over land (green) and over sea (blue). (Source: The Met Office Hadley Centre).

  To investigate the robustness of this prediction, various idealised experiments are being carried out with the model, so that the reasons for the stability of ocean circulation can be understood.

  6.18  Finally, it is always possible that, because of climate processes of which we are unaware and which are therefore not represented in models, climate could change in a way very different from model predictions. This is analogous to the case of the ozone hole, which was not predicted by 1980s models of stratospheric ozone depletion as scientists were ignorant of the type of process which created it (chemical reaction on ice surfaces). That the climate model is able to simulate changes over the past 100 years shows that this is unlikely, but cannot be ruled out, and provides part of the rationale for ongoing research.

7.  Conclusion on models of climate change

  Global climate models are the most scientifically comprehensive tools available for analysing climate and predicting change. The Met Office's Hadley Centre climate model, used as the basis of advice to Government, is recognised as being world-leading. It has been comprehensively evaluated by examining its ability to:

    —  maintain a stable realistic climate over a 1000 year timescale

    —  reproduce the temperature trends over the last 150 years

    —  give realistic representations of natural climate variability such as El Niño

    —  be used successfully in an essentially similar form as a weather forecasting model

    —  represent different palaeoclimate epochs.


8.  Advice to Government from The Met Office Hadley Centre

8.1  Work carried out by The Met Office's Hadley Centre is defined each year with MoD and DETR, based on their requirements including those to inform policy development. Results from the programme enable Government to base its climate change policy on a sound scientific footing. Additionally, because of the internationally recognised quality of the research, it allows the UK to speak with authority and weight at the negotiations for reduction of greenhouse gas emissions under the UN Framework Convention on Climate Change. For example, the Deputy Prime Minister's statement to the November 1999 Bonn Conference of Parties to the Convention specifically referred to Hadley Centre results in calling for more rapid progress towards implementing the Kyoto Protocol.

  8.2  The DETR contract contains an annex specifically devoted to communication of research results and advice to Government, and contact with DETR staff is on a daily basis. Communication comes in several main forms:

    —  DETR receive specific deliverables which are part of the contract; typically about 60 reports per year. The most recent on the attribution of climate change was delivered in May 1999.

    —  Hadley Centre staff brief DETR science staff on ongoing progress with work and recent results at the earliest opportunity before these have been enshrined in reports.

    —  Hadley Centre staff give presentations to senior officials and ministers as and when the need and opportunity arise; these have recently included Mr Prescott and Mr Meacher and, under previous Governments, the Prime Minister and Secretaries of State. An example of a recent briefing on climate change attribution, to the Head of Global Atmosphere Division on 16 June 1999, which included a description of the cosmic ray-cloudiness-climate change theory, is at Attachment B.[4]

    —  Hadley Centre staff respond to ad-hoc requests from DETR, for example in preparing UK responses to draft assessments from IPCC (such as the recent one on the use of carbon sinks within the Kyoto Protocol), in drafting ministerial speeches, or in critiquing media stories.

  8.3  The Hadley Centre is able to provide briefing to DETR on the many scientific, pseudo-scientific and non-scientific theories which are put forward, often from sources other than the peer-reviewed scientific literature, which imply predictions of change either much greater or much lower than that from models. Where the arguments are substantial and scientific, and leave cause for doubt, the briefing is followed up with a more detailed assessment and, in some cases, a programme of research. Scientific controversies which we have addressed in detail over the past 5 years (the scientific aspects of which have, in some cases, been covered in Section 3) include:

    —  why is there no apparent satellite data does not show any indication of global warming?

    —  has recent warming been due to changes in solar activity?

    —  will the UK become colder, following a shut-down of the Gulf Stream due to climate change?

    —  is amplification of change from water vapour feedback much less than in climate models?

    —  will hurricanes and storms increase dramatically as global warming advances?

    —  will sea-level rise by several metres over the next 100 years?

    —  are many recent global weather disasters due to climate change?

    —  is the rise in CO2 concentration over the last 200 years natural?

  8.4  Hadley Centre staff also brief officials and ministers of other government departments. In the past 10 years this has included FCO, MoD, MAFF, Department of Health, DfID/ODA and DTI; Annex D[5] lists briefings to ministers and senior advisors. We have also made contributions to assessments by MoD, Department of Health and MAFF of the impacts of climate change on their departmental interests.

  8.5  At the request of DETR, easily-accessible reports for wider circulation are produced from time to time. To illustrate not only changes in climate, but also the impacts these might have for socio-economic sectors, the Hadley Centre has published booklets to coincide with the last three Conferences of Parties to the UNFCCC. Briefings are also regularly given to business (particularly oil companies and utilities), pressure groups, overseas governments and the media.

  8.6  The content and progress of the programme of work of the Hadley Centre is kept under review by a Science Review Group, consisting of leading experts in the UK in the topics covered by the Programme, which meets twice a year. In addition, a more general review, including the involvement of international experts, was carried out in 1995 and is underway in 2000.

  8.7  We have good reason to believe that the advice given on climate change is accepted by Government, and makes a substantial impact on the development of UK policy on climate change, for the following reasons:

    —  The Hadley Centre is requested by DETR to participate in the annual Conference of Parties to the UN Framework Convention on Climate Change, and has given presentations on scientific developments at all five of them so far.

    —  As mentioned above, Government frequently alludes to results from Hadley Centre research in furtherance of its policy.

    —  The content of Government responses and Ministerial speeches include input submitted by Hadley Centre staff.

    —  Our contributions to assessments made by a number of Government departments have appeared in official reports.

9.  Advice to Government from the Intergovernmental Panel on Climate Change

  9.1  In addition to direct advice based on research carried out at the Hadley Centre, Government is also able to draw on international assessments undertaken by the Intergovernmental Panel on Climate Change (IPCC). These assessments provide the common scientific, technical and socio-economic background to negotiations of Parties to the United Nations Framework Convention on Climate Change (UNFCCC). The IPCC is organised into three working groups and a task force on national greenhouse gas inventories. Working Group I assesses the scientific aspects of the climate system and of climate change. Group II addresses the vulnerability of human and natural systems to climate change, the negative and positive consequences of climate change, and options for adapting to them. Group III assesses options for limiting greenhouse gas emissions and otherwise mitigating climate change.

  9.2  The IPCC produces a range of reports and assessments to meet the information needs of policymakers. Comprehensive assessments reports are produced about every five years; the next one will be in 2001. About 400 of the world's leading experts, from 120 countries, are directly involved in drafting, revising and finalising these. In addition, about 2,500 experts participate in reviewing the reports as they are being prepared. Each working group report also contains a 30-50 page Technical Summary, and a 5-10 page Summary for Policymakers which summarises the key findings in a non-technical style. These Summaries for Policymakers are approved line-by-line by governments (with the concurrence of the lead authors) at an intergovernmental meeting. There is also a Synthesis Report which provides a policy relevant synthesis and integration of the three working group reports.

  9.3  In addition to the major reports the IPCC also publishes Special Reports and Technical Papers, which address topics on which governments request a scientific or technical perspective. Through its worldwide network of experts the IPCC seeks to reflect the full range of scientific-technical views and expertise. One of the fundamental principles of IPCC is that its reports should provide accurate, unbiased, policy relevant, but not policy prescriptive information. By following this principle, and through the rigorous drafting and approval process, IPCC products have become standard works of reference, widely used by policy makers, scientists and other experts. Hence, IPCC is one of the processes which Government uses to obtain scientific advice on climate change.

  9.4  The Hadley Centre is heavily involved in all aspects of the IPCC process. The 1995 assessment was greatly influenced by new results from the Hadley Centre, and this is likely to be the case in the current assessment. Sir John Houghton is currently co-chair of IPCC Working Group I, and has been since the IPCC was established in 1988. The UK government (DETR) provides funds to support the work of IPCC, through direct contributions and through the provision of the Technical Support Unit, located at the Hadley Centre, which manages the work of IPCC Working Group I.

  9.5  Advice to Government from IPCC carries a broader consensus, and covers a wide range of topics, than Government's own research programmes, such as that at the Hadley Centre. On the other hand, the Hadley Centre programme is more tuned to the specific needs of the UK Government, can respond quickly (in hours if necessary), and provide advice which may be clearer than that which is allowed under the IPCC requirement of consensus.

10.  Conclusion on advice to Government, and its acceptance

  We are confident that results from the programme of research work carried out by The Met Office's Hadley Centre, including the issue of the causes of recent climate change, are and have been recognised, accepted and used effectively by Government. We believe that the high scientific standard of this research, taken together with the broader consensus from IPCC assessments, has substantially influenced the development of UK policy on climate change, and has impacted on international negotiations on reduction of greenhouse gas emissions.

February 2000

2   Not printed. Back

3   Not printed. Back

4   Not printed. Back

5   Not printed. Back

previous page contents next page

House of Commons home page Parliament home page House of Lords home page search page enquiries index

© Parliamentary copyright 2001
Prepared 21 March 2001