APPENDIX 8
Memorandum submitted by The Met Office
EXECUTIVE SUMMARY
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.
SECTION A: UPWARD
TREND IN
THE EARTH'S
TEMPERATURE AND
ITS CAUSES
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.
SECTION B: EVALUATION
OF MODELS
OF CO2 AND
CLIMATE CHANGE
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).
ARTWORK C
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).
ARTWORK D
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).
ARTWORK E
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).
ARTWORK F
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.
SECTION C: ADVICE
TO GOVERNMENT
ON CLIMATE
CHANGE
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
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