FENNER CONFERENCE ON THE ENVIRONMENT

Prospects for living in a drying climate
Dr Graeme Pearman

Graeme Pearman was Chief of CSIRO Atmospheric Research, 19922002. He contributed over 150 scientific papers, primarily on aspects of the global carbon budget. He now operates a consultancy company contracting to Monash University and to private and public sector organisations.

Graeme is a Fellow of the Australian Academy of Science (1988), the Royal Society of Victoria (1997) and the Australian Academy of Technological Sciences and Engineering (2005). He was awarded the CSIRO Medal (1988), a United Nation's Environment Program Global 500 Award (1989), Australian Medal of the Order of Australia (1999) and a Federation Medal (2003). He was recently science adviser to Al Gore during his visit to Australia.

His current activities include energy futures; sustainability science; scientific capacity building; public communication of science; and the role of science in modern societies.

My talk will really be about climate change, by and large, but I wanted to say right at the beginning that the issue of water is not just about climate change. There are many facets, and I think that is illustrated by the range of contributions that we will have from various people.

What I will try to do in the time available is to talk about some of the recent science assessments. Many of you would know that the Intergovernmental Panel on Climate Change has recently released the first of three parts of its Fourth Assessment Report, and I will be trying to convey to you what the content of that really is. I will talk a bit about that from the perspective of Australia, and then turn to some more general information about managing risk and uncertainty that I hope will lead into some of the papers that will follow, and about the management of complexity.

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Just to remind people: the Intergovernmental Panel on Climate Change is a process that was established with the expressed purpose of bridging the gap between a relatively fast developing area of science and a relatively fast developing area of policy internationally. It's an experiment. It is a human experiment that we have not undertaken before, and it is done simply because there is complexity on both sides the policy is complex, so is the science and we needed a mechanism that was different from what we had in the past.

So this group is not a formal group of researchers. It is an informal, if you like international, gathering of the scientists around the world, who together every six years provide an assessment of what the published research says. It doesn't do research; it simply assesses what is in the peer-reviewed literature.

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The Working Group I part of this Fourth Assessment Report, which is the one that is out now, is on the physical science basis of climate. On the ABC website, the address of which is shown on this slide, I have tried to summarise, in a few pages, what is in the report. So check that out if you want a summary of what I am saying here.

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This is a summary document produced in that process. I don't want to dwell on it too much except to say that the IPCC document is about 1200 pages long, it has 750 authors, it has taken five to six years to be put together, it is entirely based on the published literature, not on perceptions of individuals involved, and its content covers the various aspects of climate science across a wide range of disciplines. There is a summary for policy makers that you can download from the IPCC website. Just a little warning: it is politically influenced, whereas the bulk of the rest of the document, the 1200 pages, is not it is a reflection of what the scientists have actually put together over this period of time. I don't think the political influence makes too much difference, frankly, but there are some areas where individual nations have actually had their say as to how the wording should appear.

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So what does the report say? It says that when we look at the concentration of greenhouse gases these are the gases that have this impact on our climate, and in fact predetermine that we have the kind of temperature we have right at the moment we find that these have changed, and they have changed considerably. The frames here I have simply scanned directly off the summary report, so you can have a look at these if you go into the IPCC website. They show that over the last 10,000 years we know pretty well what has happened to carbon dioxide, and that it has gone up very suddenly with industrialisation. The same thing applies to nitrous oxide and to methane, two of the other major greenhouse gases. In fact, these records now go back over about 650,000 years. We have got a clear picture of what has happened to the composition of the atmosphere with regard to these gases.

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In this document there is a very significant effort to determine how each of the changes that could be occurring would drive the climate to a different state. This is not an easy area of science it is very complicated but this diagram summarises what it says. That is, the long-lived greenhouse gases, represented by the red bars at the top, have actually been the major driver or forcer of climate change since 1750 up to about the current time, and that there are other things that have forced the climate during this period of time. For example, the blue bars represent aerosol effects, or dustiness in the atmosphere, where we are actually less certain of the science than we are with the gases as to how they will have impacted.

Perhaps one of the more important findings of this document, particularly in view of some of the statements we continue to get in the media including, I believe, in the Sydney Morning Herald yesterday is that an assessment of the impact of solar variations suggests that the uncertainties in magnitude of that effect over this same period are as represented by the bar at the bottom of the diagram. So the conclusion here is quite clearly that the best science we have in the literature is suggesting that the major drivers of the climate change we have seen so far have been these gases and not natural variability, particularly related to changes in solar output.

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These graphs are a summary of what changes have occurred already to the climate of the Earth. Two of these are globally averaged, the third is averaged for the northern hemisphere. The temperature has gone up by about 0.7°C throughout the lower layers of the atmosphere, but that warming is also seen right through the atmosphere to the upper troposphere, where in the stratosphere it turns into a cooling. The sea level has gone up, primarily due to the fact that the water has expanded as it has got warmer. So we have had about 20 cm rise in sea level, averaged over the Earth's surface. I will come back to each of those in a moment.

There is also, in the last two decades, evidence that the warming has now started to impact on the glaciation of the planet. So the last box shows the northern hemisphere snow cover, which suggests that we are now seeing some significant changes in the areal extent of that cover.

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This slide is just to remind you that the warming is happening here. You can get these kinds of pictures off the Bureau of Meteorology website. This one shows the warming of the sea- surface temperatures around northern Australia over the last century. The magnitude of that warming is about the same as the global mean magnitude. This applies to air temperatures over the land as well.

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The two things that are clear in this document but pretty obvious from fairly simple physics are that if you actually warm the planet, first you will tend to have less ice and snow. The reality is that the data now show rather significant de-glaciation taking place. This is a picture that was used in Al Gore's film and shows the sea-ice extent over the Arctic. In the IPCC document the projection is that by 2050 there will be no summer sea-ice. This is a rather significant change to the energy budget of that part of the planet. If you consider sunlight falling on the ice cap you can imagine that most of it gets reflected back to space, and that is the way the energy budget for that region of the Earth has been. But if it falls on the oceans next to that ice, then about 90 per cent of it gets absorbed. So this is a very significant change to the energy budget at these latitudes of the northern hemisphere.

Next to that sea-ice extent, which of course does not impact on the sea level as it melts, there are the glaciers of Greenland. And these are very thick. They are at high altitude; they contain enough water to raise the sea levels of the world by about 7 metres. We do not know, and this report does not know, how to treat the potential for the melting of that ice sheet. The reality is that it is not modelled, simply because the physics and dynamics of the processes that will occur as we warm that ice sheet from above are not known. I think that this knowledge will develop over the next five or six years, perhaps by the time we get the next report, but that is the status at the moment.

People are monitoring what is happening in that ice sheet, by looking at the height of the sheet from altimeters on satellites, by looking at seismic activity within the ice sheet which is increasing significantly and in other ways, trying to understand the processes whereby that sheet will change as warming occurs.

But it is important to note that the projections that I will give you in a moment about the future do not include the possibility of some inconsistency in the way this ice sheet extends. And that applies also to parts of Antarctica.

It is not meant to be a doom-and-gloom story. What I am trying to do is to point out that there are things we know really well, but there are still things we don't know, some of which have the potential for large-magnitude impacts if they occur. But we don't know the probability of these occurring .

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These are key findings.

The planet has warmed by about 0.7°C.

Eleven of the last 12 years rank in the 12 warmest years we have just had a very warm decade in historical terms. ('Historical' means at least the record of the last 150 years when good records have been taken.)

Snow cover has decreased in most regions, especially in spring and summer. Much of the concern in China about climate change, for example, is about what is happening to the Tibetan plateau. There was a wonderful story in the newspaper in Perth when I was there just recently, with an interview of a shepherd from Tibet. He was asked, 'What do you think about this global warming issue?' and his response was, 'It's fantastic. Last year I only lost three lambs, and I didn't have to go so far down the mountain.' And then they interviewed other people, including members of the Chinese Academy, who are very concerned about the fact that there is a rapid demise of the Tibetan glaciers. These glaciers feed the main rivers of South-East Asia and East Asia, upon which about 200 to 300 million people depend. So the Chinese are very aware of this problem, and very concerned at the potential impacts of de-glaciation changes.

The summer period in the northern hemisphere has extended, on average over the last 100 years, by 12 days. This means that in areas of northern Siberia and Canada it is actually nearly a month and a half longer than it used to be. So it is not surprising from anyone's point of view that there are quite massive changes to biology taking place in these regions as a result of the fact that the growing season is now that much longer and things are that much warmer.

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This is a picture from an Australian scientist, John Church a colleague of mine in CSIRO summarising in the grey area all of the sea- level data now around the world, and showing the approximately 20- cm rise over that last period of history. The red areas are simply illustrating that we now have satellites with altimeters so that we can look at this on an almost daily basis, and just demonstrating that in fact we get the same answer if we use both approaches. And the lines going into the future are various ideas about what will happen. I'm not going to go into that in too much detail.

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We have found that Arctic sea-ice areal extent has declined by 2.7 per cent per decade over the last century, and that decline has been 10 per cent in the last decade. There is quite significant de-glaciation occurring now.

Sea levels have risen by just under 2 mm a year, with some indication that it is speeding up. We had predicted slightly less change to sea level than we are observing, suggesting that we don't have all of the physics and dynamics of the system in place.

And we are acidifying the oceans, because as this carbon dioxide in the atmosphere dissolves in the surface layers, it has already shifted the pH down by 0.1 units. We are anticipating this to continue as we increase carbon dioxide concentrations.

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The key messages are, firstly, that the greenhouse gases in the atmosphere far exceed those that we have had for 650,000 years. The conclusion is that the increases of these gases are primarily due to human activity. For carbon dioxide that is mainly a result of the combustion of fuels; for methane and nitrous oxide it is mainly related to agricultural and land -use changes.

The warming is unequivocal, in the view of the IPCC R eport. It is evident in the air, it is evident in the oceans, at least down to about 1000 metres, it is evident in the melting of snow and ice, and it is evident in the thermal expansion and therefore rise of sea levels. The warming is an effect of human activities at least five times greater than that due to solar output changes. So it is surprising to me that some of the sceptics continue to push the solar output idea, when actually mainstream science's main objective has been to try to understand why the temperature is changing as it is. What is the driver? Is it natural variability or not? The conclusion of this report is that it isn't.

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To go forward in time, what we actually have to do is to try to put together all of our knowledge of how a very complicated system the climate system works, write equations for each of the processes, and simultaneously solve those equations in very large models of the climate system. These are models that take about one million lines of Fortran code to describe to the computer what to do, and you can only do it in a very big computer.

The interesting thing is that at the time of the last r eport from IPCC, in 2001, most of the results in that report were based on two models there were other models reported, but most of the results really were based on two. In this latest report their results mostly are based on 23 models from around the world, and all of those models have been run in various modes and experimental states many times now, because (a) there is more interest scientifically in doing this, but (b) the computing power to do it is actually far greater than it was.

So these are results of 17 of those models for different emission futures. (I am not going to go into the details as to why I have used the 17. It would be fairly similar if I gave you the results from the 23.) The emphasis here is not on how different the models' projections are; the emphasis is on how different it will be, depending on what we do (what greenhouse-gas emissions occur and how we, as a global community, work to curb those emissions), to respond to this particular issue.

Among these coloured lines consider first the yellow one at the bottom of the slide. This is a hypothetical case where we, at the year 2000, stop any further increase in concentration. So it is an experimental statement of how much commitment we would have to further warming if we didn't do anything more in terms of increasing these gases.

The other colours represent various ideas about the way the future might look, but they are primarily ideas which, in the red case, suggest more or less a business-as-usual approach, using fossil fuel but having technological improvements take place, whereas the green and blue lines result from an attempt, nationally and internationally, to stabilise the climate. There is an acceptance that in fact it is not a good idea to have the planet continue to warm indefinitely, because we don't know where that will lead us.

So these are the kinds of scenarios that are discussed in this document. There isn't a lot of further discussion in P art I of the Fourth Assessment Report of the IPCC of these scenarios. There will be more on this in the third part, which comes out in May, considering a wide range of possible scenarios or views of the future.

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What does it tell you if you just take 17 of these models and look at what it means for the global world temperature? It means that over the century we see warming of the order of a couple of degrees or so, but it is not equal all over the planet. One of the reasons for that is the reason I have already given, that you have this very strong positive feedback between the ice, and the reflectivity of the Arctic ice, and the energy budget at those latitudes, causing greater warming at those latitudes. It is not the only reason, but it is partly the reason.

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The main findings, based on the 23 models, are that in less than 20 years, by 2025, we will have the same amount of warming that we have had in the last 100 years, and that over this century we will have somewhere between about 2°C and 4°C additional warming, unless there is a very significant effort to reduce the emissions and then work towards a stabilisation of the concentration of these gases.

When you change the mean temperature, you change extremes as well, and so there is a litany of potential impacts associated with changes in the frequency of extreme events, be they heat waves and the flow-on effects on the growing of grapes or the health of humans, the minimum temperatures and the frequency of frosts, and the positive nature of those sorts of things, or the changes to the actual growing season.

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There are then many issues around precipitation, which is not as easy to project into the future because it is a further complication in the physics and dynamics of the system. But it is expected that monsoons will actually increase in intensity, and that there will be a decrease in precipitation in the subtropics and mid latitudes. I will come back to that, because I think that is the really relevant point for this meeting.

There will be changes in extreme precipitation, in that the intensity of individual precipitation events is expected to become higher, but with longer periods between those events, particularly in the area where overall we lose rainfall.

Tropical cyclones and low-pressure systems in general are expected to be more intense. But there are issues around the projection of this for specific areas. Can we say with any degree of certainty what will happen on the Queensland coast with tropical cyclones? No, we can't, because while the anticipation is for these storms to be more intense, the actual latitude and longitude down which they penetrate may actually change because of the general circulation changes and the steering of these events by the mainstream dynamics of the atmosphere. So there are geographic shifts that we are not as confident about.

On mid-latitude storms, which I think are very important for much of Australia and for the water issue, the anticipation from these models is that there will be several degrees shift southwards of these storm belts. Several degrees may not sound like much, but it is something of the order of 400 kilometres southward movement of these storm belts. So the potential of that for the southern part of the continent is quite severe.

There will be lower pressures associated with these storms, as with the other lower-pressure systems. If you are in the region of these, they mean increased wind speed and wave heights.

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This is a picture from the summary, trying to summarise, at least for our winter, what is being said about precipitation.

In a warmer world we expect there to be, on average, more precipitation but that is only before you take into consideration the fact that there are dynamics within the circulation of the atmosphere, and the oceans, that lead to the sorts of things we already know. That is, if you happen to be in the mid latitudes of either hemisphere, there is a high-pressure belt, and that high-pressure belt is not conducive to making rain. The anticipation in both hemispheres is for this belt to intensify and to move slightly pole-ward, and that is what will culminate in this few degrees movement southwards, south of Australia, of the low-pressure systems.

The red stars show areas in which there is high degree of agreement amongst all of the modelling groups that this is the best prognosis that we can give. So for Australia, certainly south of 30°, there is a high degree of likelihood that we are going to have less rainfall. North of that latitude it is less certain, because of the uncertainties about exactly how tropical storms and the monsoon systems will behave.

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There are other components that you might be interested in, such as El Niño, a major driver of the year-to-year variability that I am sure you will see in diagrams from the following speakers. It is still confused. The models are not giving consistent ideas of exactly how these climatic features will behave . If anything, they are suggesting that the frequency and magnitude of El Niños will remain about the same, so that we would be seeing this variability superimposed, for the southern part of Australia, on what is already becoming a drier environment.

The monsoon issues are complicated by the fact that we do have higher rainfall already occurring in the north-west and central part of Australia, with a stronger monsoon. But it is possible that the best explanation for that is that there is now a bigger temperature gradient between Asia and north Australia during our monsoon season, as a result of aerosols over the Asian region. It is something that actually looked as if it happened after World War II in Europe, and we are having this process now as Asian development proceeds. So there is uncertainty about that wetting that is occurring in the north-west being a continued characteristic of the future climate for Australia.

Snow and ice changes are listed on the slide; I won't go into any more detail.

The significant new finding in this document is that there is unanimous agreement that there will be a loss of the CO₂ absorption capacity of the planet. This is for two reasons. One is that as you warm the oceans, the solubility of carbon dioxide goes down, but also so does the turning over of the deep oceans the pH changes, geochemistry changes.

But the other reason is the biology of the planet. The plants have actually been consuming, increasingly over the last two decades, more and more carbon, so that currently they are taking up about 2000 million tonnes of carbon that we are releasing into the atmosphere from fossil fuel combustion. This is a significant dampening of the effect that we would otherwise have had.

The biologists are uncertain about whether this will continue, but they mostly feel it won't and the debate is over whether it will stop doing this in the next 10 years or the next 50 years. There is agreement that it will stop, that it is a perturbation that won't continue. And when that happens, all of the projections that I have given you will be underestimates of the projections of change. So there remain significant differences between the ecosystem models and the biologists' views of exactly when this change will occur.

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We are talking about a sea-level rise by the end of the century of between 20 and 60 cm, and in the current science I think we have got a much better idea of the regionality of that. The concept in the general community is that sea level is level, but it isn't. It has hills and troughs in it that relate to the atmospheric pressure that overlays it. If you shift patterns of atmospheric pressure in the climate system, then you will have regional changes of sea level related to that and not only to the general rise of sea level. I think we are starting to get to the position of being able to provide better advice on a regional level about how that might manifest itself.

Acidity is expected to rise (and pH to fall) at least by as much again as has occurred already, and in the modelling the first part of the global ocean system that reaches super-saturation with regard to carbonate formation is in the Southern Ocean, some time in the second half of this century.

A good piece of news in this report is that there has been a much more serious examination of the whole issue as to whether deep ocean turnover (circulation), which is caused by the sinking of saline cold water at high latitudes in the North Atlantic and around Antarctica, could stop. There were some modelling efforts in the previous report that suggested this might happen. The state of the literature now is that it is unlikely to be discontinuous that is good news, because no-one would really want this to happen but that it will actually slow down. The circulation will slow down by up to 25 per cent over the century.

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What are the major findings, the major messages, from this? It is very likely, greater than 90 per cent, that most of the warming during the 21st century is due to greenhouse gases and extremely unlikely, less than 5 per cent, that the warming was caused by natural variability. The warming over the next few decades is likely to be at the rate of about 0.2°C per decade. And business-as-usual emissions that is, without real intervention globally are likely (greater than 90 per cent) to cause 21st century warming larger than during the 20th century.

So what about changes for Australia?

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This is what has happened to rainfall over the last century. You can see why we have problems. (As I said before, it is not just climate variability or change; it is also population and other dynamics.) We have had this loss in the total precipitation around the regions of the major cities of Australia, with a wetting in the north-west.

Is this due to climate change? Well, I can't say that, and I don't know any scientist who will give you a categorical answer on that. And it is an important message. The message is that scientifically we have rules. We have a culture that says that to accept a hypothesis like that, we have to be 99 per cent sure. And we are not 99 per cent sure that there are not other reasons why this pattern of change has occurred.

But managing the risk of its actually being climate change, and manifesting itself in the sorts of things we see in rural Australia and in water supplies in urban Australia, is a different matter. If you do as I have done in the last six months or so and spend a lot of time in rural New South Wales and Victoria, you find that the farmers have made their risk management assessment: 'The magnitude of this impact is sufficiently large that we are not going to wait until we are 99 per cent sure that this is climate change.' I will come back to that issue again, because I think it relates to a problem that exists between the concept of probabilities within science and the concept of probabilities used within the risk- management process.

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There are lots of changes that will be addressed in the second part of this IPCC R eport (which comes out in April) about the impacts. We are starting to see, since the last report in 2001, biologists, ecologists and social scientists around the world identifying responses to the changes we have had. And these are responses that are in the dynamics of the genetics of particular populations, through to the behavioural processes the nesting times, the migration times and so on. In Australia we now have growing sets of evidence that the 'small' half a degree or so warming that we have had is already impacting downstream on the ecology of our continent.

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This is what 15 of the models suggest will happen to temperature. Again I am not going to explain why I have only taken 15, but they are a subset of the 23, simply showing the warming that is anticipated by 2070, in this particular diagram, across the whole of the country with slightly higher warming at low latitudes and inland.

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This is what is anticipated from those same sets of models by 2030 so not for such a long period as for temperature. What it is demonstrating is that either annually averaged or for particular seasons, most of the country is anticipated to have less rain, but with some parts of central Australia possibly having more rain in certain seasons.

Of course, the water response to that depends on what happens to evaporation rates and the timing of events that allows land to dry between successive falls. All of these things are then reflected in a much more complicated way as to what finishes up available in the soil for use, or in the streams for human use.

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Key findings, therefore, are as follows. We get, through this century, a warming of 2.5°C to 3°C, depending slightly on the latitude and whether you are inland. For mean precipitation there is strong support for the idea of a loss of between 10 and 25 per cent, over the century, south of 30°C with east coast increases in summer and decreases in winter, but there is less robust certainty about those changes. We get changes in snow cover that are relevant for New South Wales and Victoria, and a potential evaporation increase. Almost all indications are for a moisture balance deficit and a drier Australian environment.

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As you might imagine, as you change the means by relatively small amounts, then you have flow-on effects on the frequency of extreme events. The slide shows just some of them. I am not going to go into details, but in some cases they are actually the important issue with regard to the survival of particular species or, in the case of extreme temperatures, sometimes the survival of people in heatwaves.

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This slide summarises some of the information that will be in the second part of the IPCC R eport. All I really want to do here is to indicate that the impacts of these things are not felt by any one sector. They really impact on all sectors, some of whom are already seeing it. You would know that the insurance industry is well down the track in trying to assess its position with regard to climate change.

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We all manage risk every day. We do it subconsciously, in the sense that we make decisions to do things based on weighing the magnitude of the outcome against the probability of its occurring. That is a different process from making a decision about whether you are scientifically sure that something has happened or that a hypothesis is proven or disproven.

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As I see it and it comes back, I think, to a couple of points that Kurt Lambeck made in his opening address we are really struggling to manage this issue of climate change, in the same way that we have struggled to manage the existing rainfall variability and shortage of water that Australia has experienced for the period that Kurt talked about. We have been talking about it for a long time; the problem is that it is complicated. The science is complicated. It impacts on many sectors. The disciplinary base that underpins this kind of work comes out of all kinds of areas within universities, within CSIRO, within other research agencies.

But, in addition to that, our applications are for a whole range of different sectors. We are worried about this from the point of view of biodiversity, human health and so on there is a list of them. It is complicated. And it is further complicated by the fact that we don't always agree on why we want to manage it. We want to manage it for a range of different human aspirations. We focus primarily on economic growth, and that is important. But actually we are also worried about social wellbeing, we are worried about environmental protection, and we are worried about intergenerational equity. When you get to my age and you have got grandchildren, that becomes a big focus.

I think we are overwhelmed by the complexity, and the government structures that we have in place within our national government, our state governments and even within corporate governance really struggle to deal with this kind of complexity. I think the science community has a bit of a problem here, because partly we have delivered information about this complex system in a highly disciplinary way, and that doesn't actually help. If you are a member of a Cabinet of a nation, you don't really want 100 different views of the world coming from different disciplines. You need some level of integration around these things to give you policy options. And that is why we talk about the concept of sustainability science and integrated assessment, which is starting to grow in importance around the world.

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The complexity is important, the self-interest governments have always had to balance that and the spectrum of uncertainty. We don't know everything and we won't know everything about the climate system. We have got, for example, some biology systems, some individual species, about which we know that the genetics are changing as a result of the change in climate already. But will we know that about the millions of species that are out there? We will never know that. The consequences are that we have to wait and see what happens, and we will have to live with the consequences. So some people would argue that that is the best reason for making sure we don't allow this to go too far.

The second dot point on this slide, that there is no guarantee that we can/will respond in time to avoid serious repercussions, is an important one that I don't want to debate here but that I would like you to take away. When I look at the governance structures for the UN and look at the governance structures that are occurring around Kyoto, and around the nation right at the moment on this issue of climate change and the water issue will be very similar then in my view there is no a priori reason for believing we are going to solve it. It is complicated, it is different, it challenges us in so many ways, and at the end of the day I think the only reason you can have some optimism about this is that there are going to be leaders who will come forward and provide us with some guidance as to how to go forward with this.

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I have here just a couple that have come forward. This is a statement by Gerry Hueston, from BP. Companies that I deal with now as a private consultant are showing enormous ability not only to handle the complexity of this issue but also to manage the risk. Some of them will be still highly sceptical of the science, but they understand there is a risk that the science might be right and they are trying to manage that in a sensible way.

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I could give you dozens of names. Business is way ahead of government in this regard, and I think it is because they are used to the risk management process much more so than governments .

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We had the Stern Report that came out recently, which is an interesting document in itself. I have been involved recently, with some economists, in a review of that document for the Victorian government, to try and see whether it is actually the kind of thing we should be doing here. I would strongly suggest it is exactly what we need to do throughout Australia. I can't, for the life of me, see the reason why we would hedge our investment in mitigating against climate change when we have no indication of what the economic costs of its happening are. The Stern Report is a very good, I think, first attempt to do that, although it is open to some criticism. We need to take that science and that approach further down the track.

Stern's conclusion was that it would be five to 20 times more expensive to let it happen than to actually do something about it, particularly if you act early.

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I will mention but not now go into the sustainability science, the integrated assessment approach. This must pose all sorts of issues for the scientists among the audience, and probably Roger Jones (and perhaps others also) will talk later about the important developments that are taking place.

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This Academy, a couple of years ago, actually attempted in one of its conferences to write a blueprint for how science may have to be modified in the way it operates, in order to provide better underpinning information for these very complex, multidisciplinary areas such as water resources and climate.

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This statement came from Margaret Beckett, UK Foreign Secretary, late last year, emphasising that this is not an environment problem; this is a problem for all sectors. In Australia, I think, it is a problem particularly for the water sector.

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In summary, the recent science strongly reinforces the views that global warming is occurring and is primarily a result of human activity. Australia is particularly vulnerable in that it may lose 10 to 30 per cent of its precipitation through this century , and experience a drier climate.

I think the tertiary effects of climate change on natural ecosystems have been grossly understated. Most of us may say that another 1°C or 2°C warming is not going to be all that important. It is simply because we have no perception of what a 1°C or 2°C warming actually did geologically to the biology of the Earth. It was massive. And I think in the next five years we will see a lot more evidence of those changes starting to take place.

There is an emerging urgency, I think reflected in the discussions that have occurred at the UN and in the UK this week, that we don't have 10 or 15 years to develop Kyoto II or whatever will follow Kyoto from now on.

The challenges exist in how we manage this complexity and respond to options, and this is really an issue of coping with sustainability.