WORLD METEOROLOGICAL DAY ADDRESS, 2003

Our future climate

I find myself in an unaccustomed situation. Having, over many years, stood where Bill Downey has been standing to welcome everyone to the celebration of World Meteorological Day and to introduce the Bureau’s Long Service and Excellence award winners and our guest speaker, I am accustomed, by this stage in the proceedings, to being back into my comfort zone and ready to relax and enjoy the Address.

As it happens, the shoe is now on the other foot and I have the challenge, over the coming forty minutes, of providing you with some new and, I hope, useful perspectives on the issues and dilemmas posed by the World Meteorological Day theme of “Our Future Climate”.

I should begin by explaining why I am giving this year’s World Meteorological Day Address.

The first, and most nearly factual, reason is that in all the flurry of activity through the second half of last year, I suddenly realised that it was already Christmas and thus indecently late to ask anyone else to do it.

My second reason, and the one towards which I will progressively rationalise, is that, after forty-five years of professional engagement with climate from almost every quarter, in circumstances where I have felt bound to remain strictly within my personal and institutional areas of competence, I feel some obligation, at this stage, to attempt to provide both a broader and a more personal perspective on a few of the important issues that now confront everyone who has reason to contemplate the implications of our future climate.

I am doing so at a very volatile stage in the evolution of the science and policy of climate change. By way of some historical context, it is interesting to note that it is:

I am also conscious that the scientific and policy literature on past, present and future climate has grown at a frightening rate over the past decade (my own very limited subset of the literature is ceiling high!) and that subsequent World Meteorological Day Addresses by Sir Ninian Stephen, the Hon Dr Barry Jones, Sir John Houghton, Dr Brian Tucker, Professor Stuart Harris and others have addressed many of the challenges that Les Hollings set down in his 1990 Address.

The climate issue is now so complex and so multifaceted that it is difficult to provide even a simple overview of the greenhouse effect without immediately opening up a host of controversial issues that all demand detailed discussion in their own right. The booklet on ‘The Greenhouse Effect and Climate Change’, which you have received on the way in, represents the Bureau’s attempt to provide a simple, but hopefully rigorous and balanced, summary of the current state of understanding of the science of climate change. I will, therefore, pass very lightly over the science and focus on a few of what seem to me to be the important issues that stand in the way of better community understanding and response to the challenges posed by our future climate.

I will, in particular, offer a few observations on the operation of the much-maligned Intergovernmental Panel on Climate Change (IPCC) which is variously represented in the media as super-oracle or sinister and subversive perpetrator of a cruel hoax on the global community. I will, however, stop short of substantive comment on the Kyoto Protocol, because that really is well beyond my area of competence. But, having been at the centre of the processes that led to the formulation of several of the key articles of the Framework Convention on Climate Change (FCCC), I will offer a comment or two on the role of science in the Convention, thirteen years on.

The challenge of climate science

There is no doubt, however, that enormous progress has been made over the past few decades, through the coordinated efforts of the international climate research community and in response to society’s expectation that science should be able to help prepare for the future by forewarning of years of drought and flood and by providing pointers to the nature and scale of any possible longer-term human-induced changes to global and regional climate.

This is not the occasion for a lecture on the physical basis of climate, but I would like to provide just a little context for what I will say later when I venture towards the periphery of my field of competence. I will mention just four points.

First, the general character of the climate on earth is determined primarily by our distance from the sun (Figure 1) and the fact that the earth is round and rotating. Our planetary temperature (255K or -18°C) is set by the self-adjusting balance between the incoming short-wave radiation from the sun and the outgoing long-wave radiation from the earth. The spherical shape of the earth means that there is a temperature gradient from equator to poles and the rotation of the earth causes the air and ocean currents which strive to reduce these temperature differences to develop their own rotation which generates the familiar circulation systems of the daily weather map (Figure 2).

Second, the presence in the atmosphere of some trace gases (water vapour, carbon dioxide, methane…) which let virtually all the short-wave solar energy in but absorb and re-emit the outgoing long-wave radiation produces what is known, colloquially but inaccurately, as the greenhouse effect (Figure 3) by keeping the earth’s surface much warmer than the atmosphere above and much warmer than the planetary temperature that it would otherwise settle down to, on average, if there were no atmosphere and no greenhouse gases.

Third, the greenhouse effect is just one of a complex web of physical, dynamical, chemical and biological processes taking place in the atmosphere-ocean-land surface system which help determine the actual nature and patterns of climate on earth (Figure 4).

Fourth, while we can conduct only very limited experiments on the real ocean-atmosphere-earth climate system, we can build enough of the basic science of climate into computer models (Figure 5) of the global climate system to conduct a wide range of simulation experiments which enable us to explore how the real climate might respond to such external influences as changes in the earth’s orbit, insertion of a veil of volcanic dust into the stratosphere or changes in the chemical composition of the atmosphere.

The matter of time-scale

Let me begin with climate. It is sometimes said that climate is what you expect and weather is what you get. This is almost true in that it captures the important concept of climate as the average or statistical synthesis of the rapidly varying day-to-day weather. But it misses the important point that the average weather for one January can be quite different from that of the previous January and the averages for a complete year can be quite different from those for the year before. This realisation led to the development in climatology of the concept of climate ‘normals’ – essentially the averages over a recent internationally agreed thirty-year period – as a general guide to what to expect in any immediate future year.

But, this is a trap because, even from the limited historical records that we have, we find that, at any location on the earth, the climate has always been changing over a wide range of timescales – from year to year, decade to decade and century to century as well as over much longer timescales of thousands and millions of years. And, as we have begun to better understand the workings of the global climate system, we have realised that these changes can result either from internal interactions within the atmosphere-ocean system or from external influences of natural or human origin.

If we accept that climate is some sort of statistical average of atmospheric conditions and that even the average is always changing, we need to ask what we mean by future climate and to what extent it is actually or potentially predictable. Let me explain through some examples.

In my 1993 Ian McLennan Oration, I used a simple schematic chart (Figure 8) which attempted to capture the concept of uncertainty of future climate on century timescales. It shows the smoothed global mean temperature trend through the twentieth century in the context of present understanding of the climatic history of the earth over the last 100 million years (shown on a highly condensed timescale). And it presents a number of possibilities for the twenty-first century ranging from substantial greenhouse warming on top of a naturally occurring warming trend to a future with only limited greenhouse warming offset by strong natural cooling which dominates the temperature trend throughout the second half of the century.

The problem of terminology

One of the most serious problems that has dogged the climate debate at the science-policy interface and confused the public and political discussion of future climate, since greenhouse warming became an issue in the 1980s, has been the issue of terminology.

The unfortunate reality is that, whenever scientists, who speak in the language of the IPCC, and policy people, who speak in the language of the FCCC, refer to ‘climate change’, they are usually talking about different things. I firmly believe that a great deal of the public and political confusion about climate change in the world today is the direct result of each community having attached its own interpretation and connotations to statements about climate change made by the other.

In the IPCC community ‘climate change’ means change on all timescales, irrespective of the cause, and it thus includes both natural variability and any change that may result from human interference with the working of the climate system. Regrettably, in my view, those who negotiated the FCCC chose to define ‘climate change’ as only that part that is due to human activity. Thus, when an IPCC scientist says there is unambiguous evidence of climate change, the Convention people (and, of course, the media) hear, and usually promulgate, an unambiguous conclusion that humans have changed the climate.

The IPCC process

Because its reports have become so central to the public and political and political debate about climate change, I must say a little about the IPCC as a process, as a community of climate experts and as an institutional player on the international climate stage.

The first observation I must make is that, in all three senses in which the term is used, the IPCC appears to be seriously misunderstood, and is usually misrepresented, by many of those from outside the expert climate community who quote its reports and who set out to praise or bury it.

I have read literally hundreds of critiques of various aspects of the operation of the IPCC, including complete books which purport to provide informed analysis of the IPCC process, but which describe a process that I scarcely recognise and attribute motives and views that I am virtually certain were never held by those to whom they are ascribed.

The IPCC is clearly flawed insofar as it is a human construct. It suffers from most of the failings of human nature, the influence of interest groups and those impediments to trust and cooperation among nation states that have prevented them collectively from producing a perfect world. It is also the most remarkably successful example that I have encountered in my professional career of individual scientists, scientific institutions, environmental and business groups and governments working together with a shared commitment to ensuring that profoundly important national and international policy decisions are based on transparent and objective assessment of the findings of rigorous science.

While I have conceded that the IPCC is flawed, its shortcomings are not, for the most part, those for which it is usually criticised in the media or by the substantial community of greenhouse sceptics. So, I would like to take the few moments that I can spend on it here to explain what the IPCC is, how it works and why I consider most of the conventional wisdom on its failings to be misinformed and ultimately a disservice to us all.

The IPCC was set up because the interplay of sound science, scientific and environmental alarmism, scientific and business scepticism and government and public confusion over the widely different messages coming from the ‘experts’ in the late 1980s had produced a situation where everyone felt in need of someone, or something, that could provide an informed, objective and balanced assessment of what was known, and what was not known, about greenhouse warming, what it would mean for humanity and what, if anything, could or should be done about it.

In designing the concept of the IPCC, its sponsoring agencies, WMO and UNEP, felt it necessary to provide a mechanism that would ensure that:

The IPCC process itself is actually remarkably transparent and straightforward, even if both exhaustive and exhausting. It involves the assembly of balanced groups of experts representative of the full range of scientific opinion and given the task of producing an objective assessment of everything of relevance to the climate change issue that has been published in the peer-reviewed literature; followed by submission of their draft assessment to several layers and several stages of peer and other review; and then by a process in which a hundred or more national delegations, mostly made up of climate experts from the governments to whom the report will be directed, work through, line by line, the Lead Author scientists’ own 5-10 page summary of their 500-1000 page complete assessment in circumstances in which:

The product of this process, the 5-10 page ‘Summaries for Policymakers’, which are supplemented by 40-50 page Technical Summaries and the complete thousand-odd page underlying reports, are sometimes maligned as the product of science by consensus. They are, in fact, the antithesis of that. They are the product of the most vigorous and rigorous process of scientific disagreement and debate that I have ever observed. They put every bit as much emphasis on identifying what is not agreed as they do on what is agreed. And the Lead Authors are acutely conscious that there own personal scientific reputations are dependent on their being able to demonstrate to their scientific peer community that they have produced a fair, objective and balanced assessment.

I have spent more than 1500 hours over the past fifteen years in intergovernmental sessions of the IPCC and its Working Groups as well as a great deal of additional time working with Lead Authors in the writing and review process. I have seen Lead Authors and delegates subject to the most intimidating pressure from both environmental and business lobbyists and I have seen delegations shamelessly pursuing their national interests by dressing up their political objectives as scientific argument. But I have not yet seen an IPCC report where I believe the finally approved words could be fairly accused of being the product of political negotiation rather than honest scientific debate and agreement. I would not have been prepared to continue with the IPCC process if they had.

That said, I freely acknowledge that many IPCC reports contain awkward and ambiguous wording and that the IPCC has, on several occasions, gone perilously close to politicisation and failure. I single out its Sixteenth Session in Montreal in May 2000 when its approval of its Special Report on Land Use, Land Use Change and Forestry followed many days and nights of political posturing and manoeuvring but in which ultimately all the Lead Authors and national delegations were prepared to agree that the approved words were the product of science rather than politics.

Scenarios, projections and predictions

The IPCC community have employed the concept of ‘scenarios’ to describe a set of alternative inputs to the climate models that are used to demonstrate, for example, how the global climate system might respond to a range of different concentrations of greenhouse gases in the atmosphere. The input scenarios are not forecasts and the IPCC has been meticulous in refusing to attach relative probabilities to their occurrence. They are ‘what if?’ devices aimed at demonstrating the modelled sensitivity of the global climate system to different levels of greenhouse forcing. By the same token, the outputs from the models are not, in any sense, to be regarded as predictions of actual future climate. To underline this point, the IPCC has, since 1992, referred to model outputs as projections and, when numbers are quoted (be they global warming rates or anything else), they are always directly tied to the input scenarios from which they derive.

One of the most frequently used, but, of course, highly artificial, input scenarios has been that of instantaneous doubling of the atmospheric concentrations of carbon dioxide. The IPCC assessment of the impact that this would have on global mean temperature is a warming of between 1.5 and 4.5°C with a best estimate of around 2.5°C. It is worth stressing that neither the estimated global mean warming for doubled carbon dioxide, which is often referred to as the climate sensitivity (Figure 10), nor the 1.5 to 4.5°C range, which is a measure of the uncertainty in the modelling process, have changed since the IPCC’s First Assessment Report in 1990. In other words, despite the enormous scientific advances and the vast literature that has built up on greenhouse warming, the IPCC’s summary assessment of the impact of greenhouse gases on global mean temperature has remained unchanged over the fifteen years of its operation.

Other scenarios have also been used to demonstrate – still on a ‘what if?’ basis – how the climate system might be expected to respond under different levels of greenhouse forcing as well as the introduction of other possible influences such as offsetting aerosol cooling. Some have used a range of per-annum percentage increases in greenhouse gas concentrations while still others have started one or two stages further back with emission scenarios, or scenarios of the global economic, social and technological conditions that produce the emissions. In 2000, the IPCC finalised its so-called Special Report on Emission Scenarios (SRES) which attempted to provide a coherent set of about 40 scenarios to span the range of the many hundreds of emission scenarios (and emissions forecasts) published in the peer-reviewed literature, as a mechanism for facilitating intercomparison of the outputs (in terms, for example, of global mean warming or sea level rise) of the climate models (Figure 11).

Even though – and we are going back to the late 1980s – the IPCC scientists stressed that the ‘predictions’ from the climate models were nothing more than ‘what if?’ assessments to indicate how the real climate system might be expected to respond to enhanced greenhouse forcing, and that the estimates of warming must always be linked to the input scenarios, the media and those who sought to make the case for greenhouse gas emission reduction, almost invariably quoted the highest values of warming, avoided any reference to the input scenarios and presented them as IPCC forecasts of actual future global climate. The IPCC – and I place on record that it was Brian Tucker of CSIRO who was instrumental in achieving the change – soon realised that we had to find a different word from ‘prediction’ to describe the output of the climate models. And so the word ‘projection’ entered the IPCC lexicon in 1992.

Regrettably, however, it made little difference to the media. Over the following decade, no matter how meticulously the IPCC reports have linked the climate model projections to their input scenarios and no matter how forcefully the IPCC has asserted that it has no basis for attaching any probabilities of occurrence to the emission or concentration scenarios, the media and greenhouse gas reduction advocates have continued to strip away the caveats and quote the highest global warming numbers to convey the impression of impending climate catastrophe; and the IPCC critics and greenhouse sceptics either quote the lowest numbers to suggest that there is no problem or strip away the caveats and quote the highest numbers to discredit the IPCC as irresponsible and driven by a green agenda.

It may be that the posturing and debate that this has produced have ultimately helped in enhancing communication and understanding of the issues at stake but no aspect of the work of the IPCC has brought me closer to despair about our ability to use science wisely to inform policy-making. The distinction between scenarios, projections and predictions is fundamental to the whole process, yet the more forcefully one makes the point as a scientist, the more resolutely many in the policy community seem to turn off. The most frustrating response after a much more detailed and, I would like to believe, more lucid explanation that I have had the time to present here is “what you’re really saying is …”, followed by a statement that makes absolutely clear that the respondent has completely missed the point.

There are many other issues associated with the use of the IPCC SRES scenarios that are the subject of ongoing work and Ian Castles, who is here today, has been involved in lengthy debate on the rigour of their economic and statistical underpinning. My concern, however, is to reinforce what I regard as the much more fundamental point that the emission scenarios used in the IPCC reports are no more than a set of ‘what if?’ devices, put together to enable policymakers to see what might happen to climate if future emissions or concentrations were to increase in line with any of the range of futures described in the published peer-reviewed literature.

Criticism of the IPCC

Sadly, the IPCC’s explicit commitment to objectivity and transparency has, to some extent, worked against it. When IPCC Lead Authors identify what is generally accepted in the expert community and then spell out their areas of uncertainty and disagreement (eg on the representativeness of the conventional temperature record, the lack of a clear warming trend in satellite data, uncertainties in climate feedbacks, the reliability of the treatment of a range of physical processes in the models …) the critics then seize on the uncertainties in isolation, present them to the world as if they hadn’t already been identified and acknowledged by the IPCC Lead Authors and seek to use them to discredit both the IPCC process and its findings. By the same token, those wishing to use the IPCC findings in support of campaigns for greenhouse gas reduction, make no mention of the caveats or the uncertainties. Each side then criticises the IPCC (whoever, or whatever, they consider the IPCC to be) for not speaking up in support of their stance. And, the more forcefully the IPCC Chairman, Lead Authors or other participants in the assessment process attempt to restate or clarify the agreed position, the more certainly the media eyes will glaze over.

What is dangerous interference?

Like Professor Yuri Izrael of Russia, I see this issue differently. As I see it, the international climate science community spent most of the 1980s telling world leaders and their governments that we were convinced that greenhouse gas emissions resulting from human activities were interfering with the working of the global climate system and that we were concerned that that interference could be dangerous for humanity. The international political and policy community responded by negotiating the Framework Convention on Climate Change with an ultimate objective of “… stabilisation of greenhouse gas concentrations in the atmosphere at a level that would prevent (sic) dangerous anthropogenic interference with the climate system”. While the Convention itself does point, in very general terms, towards some of the criteria that might be used to determine what would constitute ‘dangerous interference’, I believe the international climate science community (broadly defined to include not just those dealing with the working of the climate system but also those concerned with the interaction of climate with society, economy and environment) are now under heavy obligation to provide the sound scientific advice that is needed to help inform the policy/political decision on what is ‘dangerous’.

This will not be an easy task because it will require that the potential impacts of different levels of climate change be assessed in many sectors on many time-scales and according to many different criteria. It will lead on to even more difficult assessments of the balance of benefits and costs of the impacts of alternative climate futures and alternative greenhouse mitigation strategies and ultimately to identification of the likely relative winners and losers from different levels of climate change. But I believe it is essential if the global community are ultimately to reach properly informed judgement on an integrated strategy for living with climate and dealing with anthropogenic climate change. I am optimistic that, at last, the issues will be addressed directly, if tentatively, as a crosscutting issue in the IPCC’s forthcoming Fourth Assessment Report due for completion in 2007.

Is the world warming and will it continue?

My simple answers to these questions, which I believe to be consistent with the accumulated body of scientific knowledge in the tens of thousands of pages of IPCC reports, are as follows:

Will our climate change?

I believe this question is, at present, completely unanswerable. There are many global climate models that have been run on increasingly finer spatial scales to provide patterns of change at the regional level or, even if not run on those scales, have been downscaled by various techniques to suggest patterns of regional change of temperature, rainfall and so on.

The IPCC reports have stressed that the level of confidence in these regional ‘projections’ is very low but this has not deterred some scientists with great faith in their models from suggesting a higher level of confidence than some of their colleagues, including me, are prepared to concede. And, in some ways more seriously, agreement amongst models on regional patterns has been used to bolster confidence in the proposition that the likely patterns of future climates will be the same as the patterns that emerge from the models.

I have to say that this is the area where I err most significantly on the conservative side of the IPCC consensus. I do not believe that we can yet, and may not for at least another couple of decades be able to, say anything reliable on future greenhouse-induced climate change at the regional and local scale beyond suggesting that the odds favour stronger warming over large land areas than over the oceans or for the global average. In my personal assessment, we simply do not yet understand the interaction of the various scales of motion in the atmosphere-ocean system well enough to know how global greenhouse warming will manifest itself in changes in the behaviour of the individual weather systems that make up climate and hence in climatic rainfall patterns at the regional and local scale.

So, let me return to the question of what can be said about future greenhouse-induced climate change over Australia. I offer just two observations:

Should we be planning to adapt?

The role of the Bureau

Firstly, I would like to stress that meteorology is the science of both weather and climate and the Bureau of Meteorology nationally and the WMO (and, before it, the International Meteorological Organization) internationally have always attached comparable importance to both weather and climate. In 1913, Hunt, Taylor and Quayle wrote on the Climate and Weather of Australia. In 1979, the WMO established the World Climate Programme (WCP) as the counterpart to the WMO World Weather Watch (WWW) and, in its early 1980s reorganisation, the Bureau of Meteorology brought most of its climate functions together to establish the National Climate Centre (NCC).

But National Meteorological Services have always prided themselves in being apolitical, scientific, operational service agencies and we, in the Bureau, soon recognised that, with the emergence of greenhouse, it would be essential that climate issues in Australia be addressed on a much broader basis than appropriate for the scientific and service-orientated Bureau. Through most of the 1980s, therefore, we put a great deal of effort into fostering the establishment of an integrated cross-portfolio National Climate Programme, as a national counterpart to the World Climate Programme, that would ensure a coordinated national approach to the full dimensions of the then emerging climate change issue.

For various reasons, including some unfortunate accidents of timing, we failed and greenhouse soon got taken up as an issue separate from the realities of climate. When the Bureau of Meteorology was transferred from the Administrative Services to the Environment Portfolio in 1990, the then Departmental Secretary, Mr Tony Blunn, proposed that the Bureau assume responsibility for the entire climate change issue at the Commonwealth level, including that of managing the national policy response. Perhaps unwisely, in hindsight, I declined his offer and argued that it would be better that the Bureau stick to its scientific service and advisory role and keep out of the policy arena. In some ways, I believe that has helped us to maintain the scientific integrity of the Bureau role but, if I were to have that time over again, I would, at least, think longer and harder about its potential implications for the overall national handling of the climate issue than I did a decade ago.

But that is history and the Bureau’s role remains very much that of the national authority for climate monitoring, research, modelling and service provision, working with partner agencies such as CSIRO and the Australian Greenhouse Office, in all elements of its role. The Bureau of Meteorology Research Centre (BMRC) and the National Climate Centre (NCC) have contributed effectively, within their limited resources, to the Australian scientific effort on greenhouse-induced climate change; and I am confident that the NCC, in particular, is moving gradually forward on the vitally important challenge of incorporating the findings of recent international research into its operational systems for climate prediction on the seasonal to interannual timescale.

Have we served the world well?

I believe, however, that there is a very real question as to whether the world has been well served by the way it has been done. Views usually polarise sharply in answering that question but my own honest answer is that I do not know.

On the one hand, I believe we have incurred enormous cost, including opportunity cost, through the elaborate international and national processes and programs that we have set up in order to try to slow and eventually halt, at some non-dangerous level, the build up of greenhouse gas concentrations in the atmosphere. Even in the fairly narrow field of climate system research, where the political agenda on greenhouse gas reduction had already, by the early 90s, run well ahead of the science, the cost of the scientific effect devoted to supporting the policy process at the expense of real progress in the science has been huge.

On the other hand, if, sound science and objective assessment do, indeed, eventually provide compelling evidence that the impacts of climate change will be as dangerous to the planet and its inhabitants as some experts fervently believe, then those in the scientific community whose belief in the seriousness of the threat of greenhouse warming has turned them into warriors for the environment will, indeed, have served our grandchildren’s generation well.

I have worried, along with many others in this room, about the Kyoto Protocol; in particular whether, given the very small impact that even full implementation of Kyoto could be expected to have on global warming, the substantial economic cost of the emission reductions it requires is justified. In my view, such justification as exists for proceeding with Kyoto must be based on the symbolic significance of making a start on a much bigger challenge and the stimulus that it is providing for the accelerated development of new low carbon technologies that will enable the world to slow, and eventually halt, the build up of greenhouse gas concentrations before they reach a dangerous level. But, I fully recognise that people of goodwill and genuine concern for the future of humanity can hold diametrically opposite views on this question.

Looking to the future

I would like, however, to finish by identifying what I see as the five key national imperatives if we are to do a better job with climate in the decades ahead than we have in the recent past:

Australia enjoys a wide range of climates within our subset of the global climatic regime (Figure 15) and we have a generally high level of national awareness of our vulnerability to the recurring cycles of drought and flood. We do not know what our future climate will be like, but we are beginning to learn enough about what it could be like to enable us to prepare for the future with a lot more wisdom and confidence than we could a decade ago (Figure 16).

Ends