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Report of the Senate Environment, Communications, Information Technology and the Arts References Committee
The Heat Is On: Australia's Greenhouse Future
Table of Contents

Chapter 2

The potential impacts of global warming         (Part a)

The balance of evidence, from changes in global mean surface air temperature and from changes in geographical, seasonal and vertical patterns of atmospheric temperature, suggests a discernible human influence on global climate. [1]

2.1 This chapter sets out the current state of knowledge about climate change and predictions of future climate change, including at a regional level. The chapter includes a discussion of scientific opinion on the potential for stabilising the global climate system, current areas of uncertainty in relation to the operations of the global climate system, and the predictive ability of climate change models. The chapter concludes with a discussion of the need for further research, particularly in relation to climate change in Australasia and its potential impact on Australia's environment, biodiversity and economy.

Introduction

2.2 The reality of human-induced (`anthropogenic') global warming is now widely accepted in the international community. The Australian Government's National Greenhouse Strategy (NGS) states that:

The world's climate scientists have provided us with a clear message - that the balance of evidence suggests a discernible human influence on global climate. Scientists have further reported that climate is expected to change in the future as concentrations of greenhouse gases in the atmosphere increase, and that for many regions the effects are likely to be adverse. These findings… have been accepted and endorsed by Australia. [2]

2.3 Greenhouse gases (carbon dioxide CO2, water vapour H2O, methane CH4, nitrous oxide N2O, and ozone) are naturally present in the atmosphere and have the effect of trapping solar radiation, bringing the average temperature of the Earth to about 15ºC. Since the 1950s, scientists have sought to establish whether human activities are changing the volume and composition of these gases in the atmosphere. By comparing contemporary measurements of atmospheric CO2 with the analysis of air recovered from polar ice cores, it has been possible to establish that concentrations of the major greenhouse gases are increasing. [3]

2.4 A number of synthetic gases also impact on climate change, including hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulphur hexafluoride (SF6). Some of these gases have been used as substitutes for ozone depleting substances like CFCs and HCFCs in airconditioners and refrigeration, while SF6 is used in aluminium, magnesium and semiconductor manufacture. While the quantities of emissions of these gases are currently comparatively low their global warming potency is thousands of times more than carbon dioxide [4] and their use is projected to grow. [5]

2.5 The IPCC cautions that `stabilisation of the concentrations of very long-lived gases, such as SF6 or perfluorocarbons, can only be achieved effectively by stopping emissions'. [6] The NGS (Measure 7.2) calls for the development of environmental management strategies for synthetic gases through coordinated action by all jurisdictions in consultation with industry. It states that, `Governments will work with industry to develop environmental management strategies for each of the synthetic gases included in the Kyoto Protocol - HFCs, PFCs and SF6. The Strategy for HFCs will address the use of HFCs in non-refillable containers'. [7]

2.6 A 1960s study by the Massachusetts Institute of Technology first documented concerns about climate change and, in the 1970s, the United Nations Secretary General made reference to the possibility of a `catastrophic warming event' in his report on the environment. Scientific research and international action then began to gather pace with the 1979 World Climate Conference and the establishment of the Intergovernmental Panel on Climate Change (IPCC). [8]

2.7 The IPCC is an international group of over 300 independent scientists and experts that was established to provide the most authoritative assessments of the state of knowledge of global climate change. It was given a mandate to assess the state of existing knowledge about the world's climate system and climate change; the environmental, economic, and social impacts of climate change; and the possible response strategies.

2.8 The First Assessment Report of the IPCC, published in 1990, laid the scientific and technical base for the negotiation of the United Nations Framework Convention on Climate Change (UNFCCC). Later work of the IPCC seeks to provide `scientific, technical and socio-economic information' that will help policymakers interpret and respond to the basic objective of the UNFCCC, as described in Article 2:

... stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system. Such a level should be achieved within a time­frame sufficient to allow ecosystems to adapt naturally to climate change, to ensure that food production is not threatened and to enable economic development to proceed in a sustainable manner. [9]

2.9 The IPCC's reports are drafted by leading scientists, and subject to rigorous and exhaustive peer review. The reports provide `state of the art reviews of the scientific literature in each of the specialised fields of climate science relevant to the determination future climate change'. [10] The draft reports are also reviewed by UNFCCC member governments, and approved at meetings of the IPCC where member governments, intergovernmental and non-governmental organisations are also present. For example, the process of drafting the Second Assessment Report, approved in December 1995, was as follows:

Following a resolution of the Executive Council of the World Meteorological Organization (July 1992), the IPCC decided to include an examination of approaches to Article 2, the Objective of the UN Framework Convention on Climate Change (UNFCCC), in its work programme. It organized a workshop on the subject in October 1994 in Fortaleza, Brazil, at the invitation of the Government of Brazil. Thereafter, the IPCC Chairman assembled a team of lead authors… under his chairmanship to draft the Synthesis. The team produced the draft which was submitted for expert and government review and comment. The final draft Synthesis was approved line by line by the IPCC at its eleventh session (Rome, 11­15 December 1995), where representatives of 116 governments were present as well as 13 intergovernmental and 25 non­governmental organizations. It may be noted for information that all Member States of the World Meteorological Organization and of the United Nations are Members of the IPCC and can attend its sessions and those of its Working Groups. [11]

2.10 The IPCC assessment reports remain the most authoritative account of the state of greenhouse science and of the possible impacts of global climate change. The 1996 Second Assessment Report states that the IPCC's task `is to provide a sound scientific basis that would enable policymakers to better interpret dangerous anthropogenic interference with the climate system'. The IPCC's reports seek to:

Highlight what we know about the vulnerabilities of ecosystems and human communities to likely climate changes, especially in regard to agriculture and food production and to other factors such as water availability, health and the impact of sea-level rise which are important considerations for sustainable development. [12]

2.11 During its inquiry, the Committee heard evidence from a number of climate change scientists and organisations, both international and local. International witnesses included the Chairman of the IPCC, Dr Robert Watson; the Hadley Centre for Climate Change Prediction and Research (UK); and the Potsdam Institute for Climate Impacts Research (Germany).

2.12 Within Australia, the Committee heard scientists from the CSIRO Division of Atmospheric Research, the Commonwealth Bureau of Meteorology, Monash University, and the Antarctic Co-operative Research Centre at the University of Tasmania. The Committee also visited the CSIRO's Atmospheric Research Division in Melbourne.

The First and Second IPCC Assessment Reports

2.13 The IPCC has released two major assessments of the state of climate change research, in 1990 and 1995. A third is currently being drafted and reviewed, and is due to be released in 2001. The Committee was also able to hear evidence about some of the possible conclusions of the third assessment. [13]

2.14 The key finding of the First Assessment Report was that atmospheric levels of greenhouse gases were rising due to human activities and that, if they were to continue rising unchecked, global average temperature would rise at around 0.3ºC per decade (3ºC by 2100). This would represent the fastest sustained global rate of temperature change seen for the last ten thousand years. Within a century such warming could take the Earth to temperatures not experienced since the warm period before the last ice age, over one hundred thousand years ago. [14]

2.15 The Second Assessment Report updated and refined the first assessment based on the growth of scientific research and evidence since 1990, along with improvements to climate change models. In particular, the Report described:

• anthropogenic interference with the climate system, both in terms of interference to the present day and possible consequences of future interference;
• sensitivity and adaptation of systems to climate change, including terrestrial and aquatic ecosystems, hydrology and water resources management, agriculture and forestry, human infrastructure, human health, and technology and policy options for adaptation;
• an analytical approach to the stabilization of atmospheric concentration of greenhouse gases;
• technology and policy options for mitigation;
• equity and social considerations; and
• sustainable paths of economic development, including the social, adaptation and mitigation costs of climate change. [15]

Human-induced climate change to the present day

2.16 The Second Assessment Report stated that atmospheric concentrations of greenhouse gases have grown significantly since pre­industrial times: carbon dioxide (CO2) from about 280 to almost 360 parts per million by volume (ppmv3); methane (CH4) from 700 to 1720 parts per billion by volume (ppbv); and nitrous oxide (N2O) from about 275 to about 310 ppbv. [16]

2.17 The Report also stated that global mean surface temperature has risen by between 0.3ºC and 0.6ºC since the late 19th century, and that global sea levels have risen by between 10 and 25 cm over the past 100 years. Much of this rise, it said, `may be related to the global mean temperature'. These temperature and sea level changes, the Report concluded:

… [are ]unlikely to be entirely natural in origin. The balance of evidence, from changes in global mean surface air temperature and from changes in geographical, seasonal and vertical patterns of atmospheric temperature, suggests a discernible human influence on global climate. There are uncertainties in key factors, including the magnitude and patterns of long term natural variability. [17]

2.18 The rise in atmospheric concentrations of greenhouse gases, said the Report, `can be attributed largely to human activities, mostly fossil fuel use, land use change and agriculture. Concentrations of other anthropogenic greenhouse gases have also increased. An increase of greenhouse gas concentrations leads on average to an additional warming of the atmosphere and the Earth's surface. Many greenhouse gases remain in the atmosphere - and affect climate - for a long time'. [18]

2.19 The Report also acknowledged that while there were high levels of certainty about global trends, it was more difficult to assess patterns of variability or changes at regional scales:

There are inadequate data to determine whether consistent global changes in climate variability or weather extremes have occurred over the 20th century. On regional scales there is clear evidence of changes in some extremes and climate variability indicators. Some of these changes have been toward greater variability, some have been toward lower variability. However, to date it has not been possible to firmly establish a clear connection between these regional changes and human activities. [19]

2.20 The CSIRO also outlined a range of significant observed changes in climate over the past century. These included:

• the Atlantic, the Pacific and the Indian ocean basins now show warming over the past 20 years;
• the upper atmosphere (lower stratosphere) is showing a cooling trend, consistent with a `greenhouse' signal;
• a widespread retreat of glaciers in the tropics and mid-latitude regions;
• a record published in 1998 of the recent temperature record in the context of the past 1000 years, shows that 20th century warming counters a millennial-scale cooling trend due to gradual changes in the Earth's orbit;
• precipitation (measured over land) has increased about 1 per cent since the beginning of the 20th century, which is considered statistically significant;
• consistent with the increase in precipitation is an increase in cloud cover and a decrease in the difference between day and night temperatures;
• heavy extreme precipitation has generally increased in areas where average precipitation has risen;
• the pressure at high altitude observations is increasing consistent with surface warming; and
• the temperature profiles down bore-holes in the earth's crust indicate recent global warming. [20]

Possible consequences of future interference

2.21 The IPCC's Second Assessment Report refined previous models and developed six global warming scenarios (IS92a-f), with projections based on an assumption of little or no abatement action. The models differ according to a graded range of assumptions about population and economic growth, land-use, technological change, energy availability and fuel use. They predict emissions increases between 1990 and 2100. The scenarios predict that by 2100 CO2 emissions would range from approximately six billion tonnes (similar to present levels) assuming low population and economic growth, to as much as 36 billion tonnes. [21]

2.22 A summary of the assumptions used by the IPCC in developing these models is listed below:

Table 2.1

The 1992 IPCC Scenarios - Summary of Assumptions [22]

2.23 Low range emissions scenarios (IS92c) combined with low values for climate sensitivity predict a temperature increase of 1ºC by 2100, the mid-range scenario (IS92a) predicts 2ºC and the highest range (IS92e) scenarios 3.5ºC. The IPCC stated that in all cases the rate of warming would be greater than the last ten thousand years, and that only 50 to 90 per cent of the total temperature change would have been realised by 2100 owing to the thermal inertia of the oceans. Temperatures would continue to increase beyond that time, even if the level of greenhouse gases had been stabilised. [23]

2.24 The same models also predict possible sea-level rises due to thermal expansion of the oceans and the melting of glaciers and ice-sheets. The mid-range IS92a scenario predicts a rise of 50 cm by 2100, whilst the highest emissions scenario projects a rise of 95 cm. Again, these rises would continue beyond 2100 even if emissions were stabilised. The IPCC states that models built on the scale of hemispheres or continents produce more certainty, while regional level changes are less easy to model, and that there is greater confidence in temperature projections than hydrological changes. [24]

2.25 In summary, the IPCC explained that:

All model simulations… show the following features: greater surface warming of the land than the sea in winter; a maximum surface warming in high northern latitudes in winter; little surface warming over the Arctic in summer; an enhanced global mean hydrological cycle; and increased precipitation and soil moisture in high latitudes in winter… .

Warmer temperatures will lead to a more vigorous hydrological cycle; this translates into prospects for more severe droughts and/or floods in some places and less severe droughts and or floods in other places. Several models indicate an increase in precipitation intensity, suggesting a possibility for more extreme rainfall events. Knowledge is currently insufficient to say whether there will be any changes in the occurrence or geographical distribution of severe storms such as tropical cyclones. [25]

2.26 The Second Assessment Report also sought to predict the impacts of these trends on ecosystems and human communities. Reviewing the available scientific studies, the IPCC suggested that global warming could have the following natural effects:

• a reduction in biodiversity;
• altered growing seasons and boundary changes between grasslands, shrublands and forests;
• major changes in the vegetation types of one third of the world's forests, with the greatest changes at high latitudes and the least in the tropics. Entire forest types could disappear while new ecosystems are established. During such periods of high forest mortality large amounts of CO2 could be released into the atmosphere;
• higher temperatures in deserts, threatening sensitive organisms, and increased desertification in arid and semi-arid areas;
• the extinction of some high altitude species due to loss of habitat;
• a geographical redistribution of wetlands, and increased risks to sensitive coastal ecosystems such as saltwater marshes, mangroves, beaches, coral reefs and river deltas; and
• the extinction of aquatic species at the low-latitude boundaries of cold and cool water species ranges. [26]

2.27 Possible effects on human communities and productivity include radical and hard-to-predict changes to crop yields and productivity, which could vary markedly across localities. While the IPCC thought that mean global production levels could be maintained in the face of climate change, the potential effect of increased pests or possible climate variabilities has not been factored into existing studies. There were serious concerns about the regional level impacts of climate change on food production and nutrition. [27]

2.28 The IPCC clearly stated that there was increased risk of hunger and famine in some locations. The world's poorest people, especially those living in tropical and sub-tropical areas or dependent on isolated agricultural systems in arid and semi-arid regions, were most at risk. The IPCC also said that warming would exacerbate other trends in reducing the availability of global wood supplies. [28]

2.29 Other projections indicate very serious potential impacts in the form of flooding, storms and land losses. Coastal populations are most at risk. With a 50 cm rise in sea-level, the numbers of people currently at risk from flooding as a result of storm surges would increase from 46 million per year to 92 million. A 100 cm rise would increase the vulnerable to 118 million, and while this is at the extreme end of IPCC estimates, they point out that sea-level rise will continue beyond 2100. They state that studies using the one metre projection indicate serious risks for small islands and deltas, which is of particular concern to some Pacific island nations. [29]

2.30 The IPCC estimates that land losses from sea-level rise would range from 0.05 per cent in Uruguay, one per cent for Egypt, six per cent for the Netherlands, 17.5 per cent in Bangladesh to 80 per cent in Majura Atoll in the Marshall islands. The IPCC stated that countries with higher population densities would be more vulnerable and that, in some cases, flooding `could threaten entire cultures'. In such cases, `sea-level rise could force internal or international migration of populations'. [30]

2.31 The assessment also stated that `climate change is likely to have wide-ranging and mostly adverse effects on human health, with significant loss of life'. These include:

• increases in mortality and illness from the higher intensity and duration of heatwaves, with cardio-respiratory illness the most likely danger;
• fewer cold-related deaths due to temperature rises in cold regions;
• indirect effects such as potential for increased incidence of vector-borne disease (malaria, dengue, yellow fever and viral encephalitis), because of the extended geographical and temperature range for vector organisms such as mosquitos;
• some increases in non-vector borne diseases like cholera, giardia and salmonella through higher temperatures and flooding; and
• a potential reduction in fresh water supplies and nutritious food, and increased air pollution. [31]

More Recent Scientific Findings

2.32 In the course of its inquiry, the Committee heard from a number of leading international and Australian scientists and scientific organisations on the latest global warming trends and impacts. A number of these witnesses are lead authors for the IPCC Third Assessment Report to be completed in 2001. The Committee was told that most research since the IPCC Second Assessment Report strengthens the conclusion that the balance of evidence suggests a discernible human influence on climate. Climate scientists believe that attempts to quantify the anthropogenic influence indicate that it may account for a substantial fraction of the observed global temperature change over the 20th century.

2.33 In recent years, estimation of anthropogenic signals has been improved through the use of newer climate models, ensemble simulations and the inclusion of additional anthropogenic and natural factors. Statistical techniques have been extended, in particular applying optimal detection methods and estimating both natural and anthropogenic signals based on spatial and temporal information. The robustness of results to the use of different assumptions and different model data has been improved. [32]

2.34 Most studies indicate that some human influence is needed to explain 20th century temperature changes. Regression techniques in a number of studies suggest that model estimates of anthropogenic temperature changes are broadly consistent with observed changes. [33]

2.35 The Director of the Australian Bureau of Meteorology, Professor John Zillman, told the Committee that the forthcoming Third Assessment Report of the IPCC `strengthens the conclusion that `the balance of evidence suggests a discernible human influence on global climate'. He listed a number of key messages coming out of the drafting process for the Report:

The first is that the evidence for sustained global warming over the past century, but particularly since 1945, is stronger than at the time of the finalisation of the Second Assessment Report of the IPCC in 1995. Most of the earlier discrepancies that have been debated between satellite measurements and surface measurements of temperature in the atmosphere appear to have been resolved. Also… new reconstructions of the temperature trends over the Northern Hemisphere for the past 1,000 years suggests that the recent warmth - that is in the last two decades - is unprecedented over this time frame.

The second key message is that both the present atmospheric concentration of carbon dioxide and its rate of increase during the past 420,000 years are unprecedented and that the present concentration has probably not been exceeded during the past 15 million years.

The third message is that most research since the Second Assessment Report of the IPCC in 1995 strengthens the conclusion that… the balance of evidence suggests a discernible human influence on global climate… . Furthermore, it now appears that, on the basis of more rigorous and comprehensive statistical techniques, human activity may account for a substantial fraction of the observed global temperature increase during the 20th century. [34]

2.36 Professor Zillman also cautioned that these strengthening conclusions were tempered by other uncertainties:

The reliability of these conclusions, however, continues to be limited by uncertainties in the observation record and in the estimates of the internal natural variability of the climate system of the radiative forcing - that is the effects of the greenhouse gases - and of general climate system response to external influences such as volcanoes and fluctuations in the energy coming from the sun and so on. [35]

2.37 In evidence to the Committee, Dr Geoff Jenkins of the United Kingdom's Hadley Centre for Climate Prediction and Research, explained the recent findings of the Centre's latest climate change model, HADCM3. He argued that this model has achieved a better representation of climate and climate change than previous models through a better resolution of the ocean and the coupling of ocean, atmospheric and land surface measurements, and has largely confirmed the IPCC's Second Assessment Report climate predictions:

We believe that the prediction in the future is pretty much as we would have expected, based on past climate change over the past 150 years. So the predictions in the future are maybe slightly too high, but not very much too high, and the uncertainty range of 5 per cent to 95 per cent… is not one million miles away from the IPCC figures of 1.5 to 4.5. So we do believe we have shown… that both the central prediction and range of predictions are pretty much as IPCC would have it. [36]

2.38 The Committee also heard evidence from the Chairman of the IPCC, Dr Robert Watson. Although the IPCC has not yet publicly released the results from its Third Assessment Report, which is currently under peer review, Dr Watson advised the Committee in general terms that the most recent modelling largely reinforces its previous findings and those of other modelling agencies such as the Hadley Centre:

In the Second Assessment Report we came up with a range of plausible [increases] in global mean surface temperature of one to 3.5ºC. If you use these more recent emission scenarios, which have yet to be approved, we are probably going to see a slightly larger range. If you take both the range of the socioeconomic conditions with the range of climate sensitivity, I would imagine we are going to see a range of something like 1ºC to 5ºC. [37]

2.39 Dr Robert Watson then outlined to the Committee the main consequences of increasing global temperatures over the next 100 years for issues such as water resources, agriculture, coral reefs, forests, human health and human settlements. Many of his statements in relation to these issues mirrored those listed earlier in this chapter, from the IPCC's Second Assessment Report. In summary, he told the Committee that:

• water resources will be significantly affected. Arid and semi arid areas of the world, especially in the northern parts of Africa, the southern parts of Africa, areas in Latin America, the Middle East and the southern Mediterranean will become considerably drier. These areas, which suffer from drought today, will also be more adversely affected by drought in the future;
• water stressed or water scarce areas, which currently occupy less than 10 per cent of the world today, will probably increase to 50 per cent by 2050;
• globally, agriculture may not be significantly affected due to the effects of carbon dioxide fertilisation in some parts of the world. However, regionally there could be significant changes in agricultural productivity with significant decreases in Africa, the Middle East and Latin America, areas where water resources will become more scarce;
• a sustained increase in temperature of 2ºC to 4ºC could lead to a significant adverse effect on coral reefs around the world;
• one-third of all forest tree species will no longer be viable in a world with double pre-industrial CO2 levels;
• there will be increases in vector-borne diseases, especially malaria and dengue fever. Water borne diseases such as cholera will also become more prevalent, as too will heat stress mortality; and
• tens of millions of people could be displaced, especially from small island states and deltaic systems in Egypt, Bangladesh and China. [38]

2.40 In particular, Dr Watson stressed that developing countries would be particularly vulnerable to climate change:

Overall, if one were to try and summarise the impact of likely climate change, one would say that developing countries are much more vulnerable than developed countries, largely because they do not have the technical, economic and institutional capacity to deal with climate change and to adapt to climate change. The poor in these countries are the most vulnerable. [39]

2.41 Both Dr Jenkins and Dr Watson told the Committee that considerable evidence now exists which supports the contention that human activities are in part responsible for increases in global temperatures over the latter half of the 20th century:

• Dr Jenkins:

  On the attribution question… the more work we do - not just ourselves but other people as well - the more the pointers are in the direction of a substantial proportion of the temperature rise over the last 50 years being attributable to human activities. [40]

• Dr Watson:

It is quite clear that human activities are increasing the atmospheric burden of greenhouse gases, in particular carbon dioxide, primarily from the combustion of fossil fuels, coal, oil, and gas and through land use change - [and] primarily at the moment [through] deforestation in the tropics. [41]

2.42 These conclusions are also shared by Australian climate scientist Professor David Karoly, Convening Lead Author of the IPCC Third Assessment Report chapter `Detection of climate change and attribution causes'. Professor Karoly told the Committee:

In the Second Assessment Report there was a conclusion that was reached that stated that the balance of evidence suggested discernible human influence on global climate. The evidence collected since that time… strengthens the evidence that there has been a discernible human influence on climate. The attempts to try to quantify that human influence on climate suggest that a substantial fraction of the global temperature change over the last century is most likely attributable or due to human activity. We cannot say exactly how much, but [it is] a substantial fraction. [42]

2.43 Recently, the robustness of climate change models, such as the Hadley Centre's HADCM3, have been improved by incorporating important climate change feedback mechanisms such as the sulphur cycle - the oxidation of sulphur dioxide into aerosol particles and the subsequent cooling effect on the atmosphere, and the carbon cycle - the effects of climate change on the natural carbon cycle.

2.44 In the case of the latter, Dr Jenkins told the Committee that a `reasonably high positive feedback' will result from the carbon cycle which will accentuate global warming over the course of the 21st century. As temperatures rise the amount of carbon stored in soils increases, which in turn creates more emissions as soil temperatures increase and release carbon back into the atmosphere. [43]

2.45 In his evidence to the Committee, Professor Karoly also discussed the effects of feedbacks on climate system. He warned the Committee that carbon cycle feedbacks actually cause accelerated emissions of carbon because of the loss of plants in forests and other factors, making it even harder to achieve stabilisation of emissions. He went on to explain that:

If those feedbacks are taken into account, we are in an even worse situation if the climate warms. If there are changes in the natural carbon cycle which produce natural reductions in carbon uptake, we are even worse [off] than that, and we have to come down to even lower human emissions. I think that we have to think of an analogy. We have a tap, which are the carbon emissions that are still running. Unless we effectively turn that tap off, the bucket, which is the atmospheric carbon concentrations, will keep on increasing. So unless that tap is really turned off to just a trickle, the bucket is going to keep on going up and up and up. To stabilise carbon dioxide concentrations requires very substantial reductions in how much that tap is turned on. [44]

2.46 The Hadley Centre's climate change modelling supports the mid-range sea-level rise predictions made by the IPCC's 1996 assessment: half a metre over the next 100 years. In addition, Dr Jenkins confirmed the IPCC's earlier conclusion that sea-level rise would continue beyond 2100, even if emissions were stabilised. In a recent Hadley Centre climate change model experiment, the effects of global warming on sea-level rise were simulated over a 70 year period. Greenhouse gases were allowed to increase at the rate of 1 per cent per year. After 70 years these gases were then stabilised at about double pre-industrial concentrations (about 550 ppmv) and the model was allowed to run for a further 800 years:

We found that due to this penetration of the warming that starts at the top and penetrates deeper and deeper into the ocean, that the expansion of the ocean carries on for the whole of this period for many hundreds of years afterwards, and the melting of land ice carries on for maybe two or three centuries until basically all the land ice has gone. So the actual sea level rise over that few hundred year period carries on and on almost as if the climate change stabilisation after 70 years had not occurred at all. So you end up with sea level rises of maybe 10 times the original sea level rise even though climate change has been stabilised. We think that points to a very long commitment over a very long period with sea level rise that has to be borne in mind. [45]

2.47 The Committee received similar evidence on the effects of climate change on sea-level rise over the next few centuries from Dr Watson of the IPCC:

… even if we stabilise atmospheric concentrations of greenhouse gases which then maybe 50 years later we would stabilise the earth's climate, sea-level would continue to rise for many, many centuries… .[Sea-level rise] would be somewhere between one-half and one-and-a-half metres over the next 200 or 300 years… . [46]

2.48 Dr Jenkins went on to inform the Committee that the implications of sea-level rise for small island nations and other states could be very significant, even if the increase is relatively small:

Some island states and other countries such as India and Bangladesh, where even a relatively small rise in sea level combined with storm surges that you get when depressions, storms and cyclones go through, can produce quite a big change in the frequency of currents, given the high water levels. Because of the frequency of occurrence of high water and the high water itself - it is a logarithmic one - you do not have to change sea level much to get quite a large increase in the frequency of the occurrence of storm surges in some areas. [47]

Regional Climate Change: Australasia

2.49 According to Australian climate scientist Dr Barrie Pittock, Australia is the most vulnerable OECD country to the impacts of climate change because of its low latitudes and naturally occurring high temperatures which are already above optimum levels. In addition, Australia is relatively arid, particularly in the more populated parts of southern Australia and although the tropical north in the monsoon season has a surplus of water, the rest of Australia, with the exception of Tasmania, often suffers from drought:

The suggestion is that the sort of stresses we have now will get much worse as a result of climate change. That has to be weighed in to our policy thinking. It is not an altruistic thing that we are talking about. It is something which is in our own interests. [48]

2.50 Dr Pittock's conclusions were echoed in evidence to the Committee by German climate scientist and coordinating lead officer for the IPCC's synthesis chapter on global vulnerability for the Third Assessment Report, Professor Dr Hans-Joachim Schellnhuber. Professor Schellnhuber told the Committee that Australia may be among the most vulnerable regions due to the isolated evolution of its ecosystems, to aridity and in part due to its immense coastline. The natural consequence of this was that:

… it seems reasonable [for Australia] to support emissions reductions… but also to prepare for adapting to the unavoidable climatic change. Adaptation policy and risk management seem to be a major challenge for your country. [49]

Earlier regional impact studies

2.51 In 1997 the IPCC reported on its collation of regional level projections for Australasia and other regions of the world. In addition, the potential impacts on our region have been the focus of research efforts by the CSIRO.

2.52 In presenting their estimates, as part of an assessment of the potential impacts of global warming on a number of discrete global regions, the IPCC qualified their analysis by saying that regional level predictions were: `necessarily qualitative… because the available studies have not employed a common set of climate scenarios and methods, and because of uncertainties regarding the sensitivities and adaptability of natural and social systems'. [50]

2.53 The IPCC said that `some of the [Australasian] region's ecosystems appear to be very vulnerable to climate change, at least in the long term, because alterations to soils, plants and ecosystems are very likely, and there may be increases in fire occurrence and insect outbreaks'. Possible impacts of climate change on the region include:

• a `highly likely' reduction of species diversity, despite some adaptation potential;
• the exacerbation of existing problems of land degradation, weed and pest infestation;
• changes to river flows, flood frequencies and nutrient and sediment outputs particularly in drier areas;
• increased bleaching and death of coral due to higher sea temperatures;
• damage to coastal ecosystems and communities, especially indigenous communities, through sea-level rise, flooding and weather changes;
• vulnerability to falls in the availability of water, especially in drought prone areas;
• more frequent rainfall events which, while filling dams and replenishing groundwater, could worsen flooding, landslides and erosion;
• reduced snowpack, a shorter ski season, and further shrinkage of New Zealand's glaciers;
• a long term trend to increased agricultural vulnerability as initial growth gains are eroded by rainfall and soil changes, especially with irrigated crops and range pastoralism, and economic effects through changed prices of agricultural imports;
• longer maturity times for forests, increasing the financial risks involved in plantations; and
• other climate-related impacts on air quality, drainage, waste disposal, mining, insurance and tourism, which will interact with other human and economic factors. [51]

2.54 The IPCC's predictions about the impact of global warming on coral reefs were supported by analysis published in 1998 by Professor Ove Hoegh-Guldberg of the Coral Reef Research Institute at the University of Sydney. It stated that coral reefs were close to their upper thermal limits, due to an increase of 1ºC in sea temperatures since 1900, and that 1998 saw some of the worst bleaching and coral death yet recorded in many reefs around the world. The report built four simulations from global climate models which predict that `the thermal tolerances of reef-building corals are likely to be exceeded within the next few decades'. Bleaching events like those in 1998 could become commonplace within 20 years and are likely to occur annually within 50 years. The southern and central parts of the Great Barrier Reef could be vulnerable to increased bleaching within the next 20 to 40 years, and northern parts of the reef in 60 years. [52]

2.55 In evidence to the Committee, Professor Hoegh-Guldberg and Dr Peter Doherty from the Australian Institute of Marine Science (AIMS), said that 1998 saw the warmest sea temperatures on record, both globally and in Australian waters. Professor Hoegh-Guldberg said that there had been six mass bleaching events since 1979, events which were largely unknown before that year and were caused by `higher than normal temperature signals in the ocean'. During 1998, coral reefs in the Maldives, Okinawa and Palau were wiped out by bleaching. Areas of the Great Barrier Reef were also affected and, while some managed to recover within 18 months, two reefs north of Townsville sustained irreversible damage. Dr Doherty said that they `were subjected to some of the hottest water for the longest periods, had the most complete bleaching, and there was substantial death of the coral subsequently'. [53]

2.56 Dr Hoegh-Guldberg emphasised the economic and environmental importance of the reefs, both for stabilising coastal ecosystems and tourism:

… there is a possibility that the expected increase in mass bleaching and mortality may lead to the collapse of coral dominated ecosystems. If that happens you have to look at what coral reefs are to people in the world. One hundred million depend directly on coral reefs. In Australia, there are key fisheries - we have million-dollar industries; we have got billion-dollar tourism; and, of course, if we look at the state of Queensland, entire coastlines are stabilised by coral reefs. [54]

2.57 In November 1996 the CSIRO published a summary of its own research on the regional impact of global warming. In doing so, it used the assumptions underpinning the IPCC's 1996 Assessment Report and combined them with regional climate change models. Regional scenarios were then matched with the IPCC's range of possible changes (IS92a-f). The changes they discussed included:

• regional temperature increases;
• changes in precipitation;
• tropical cyclones; and
• soil moisture and runoff. [55]

2.58 Regional sea-level changes are the subject of continuing research, and no special estimates were included in the 1996 paper. Temperature changes were plotted for three broad regions (the coast north of 25ºS, the coast south of 25ºS, and inland), and for high to low change scenarios. [56]

2.59 Inland temperatures were predicted to rise from between 0.4ºC and 1.4ºC by 2030, and from 0.7ºC to 3.8ºC by 2070. On the northern coast, increases range from 0.3ºC to 1ºC by 2030 and 0.6ºC to 2.7ºC by 2070. On the southern coasts, increases range from 0.3ºC to 1.3ºC by 2030 and 0.6ºC to 3.4ºC by 2070. These figures can be compared with the IPCC's global mean estimates of between 1ºC to 3.5ºC temperature increase by 2100. [57]

2.60 Precipitation changes were modelled using both `coupled' (atmosphere plus ocean circulation temperature) and `slab' (atmosphere plus surface ocean temperature only) models. It is believed that fully coupled models produce more reliable results, but results from slab models have also been developed because of uncertainties about coupled models and because, in the Australian region, the two models sometimes produce very different results. [58] Future rainfall patterns could also be affected by difficult-to-model local changes in ocean circulation, in large-scale atmospheric circulation (due to high sulphate aerosols in Asia) and changes in El Nino-Southern Oscillation (ENSO) behaviour. Rainfall changes were projected for winter across three broad regions and, in summer, for two broad regions. [59]

Figure 2.1

CSIRO Scenarios of precipitation change for the Australian region based on `coupled' models

Figures not available in Htm Version

Winter Summer

2.61 In both models, areas that had very low rainfall in winter, in the north and centre of Australia, would remain dry. Coupled models predicted the following changes:

• In winter, the area comprising most of the south and east, but not the Queensland coast, would see falls of between zero and 8 per cent by 2030 and zero and 20 per cent by 2070. The Queensland coast, parts of Tasmania and seas to the south of Australia would see a range from a fall of 4 per cent to an 8 per cent increase by 2030, and a fall of 10 per cent to an increase of 10 per cent by 2070. Northeast Tasmania and the Southern Ocean would see increases of between zero and 8 per cent by 2030 and zero and 20 per cent by 2070.
• In summer, south, central and northern Australia (excluding the southwest of Western Australia and including Tasmania) would see falls of between zero and 8 per cent by 2030 and of zero to 20 per cent by 2070. In the eastern states south of Cairns, there would be a range of –4 to +4 per cent by 2030 and –10 to +10 per cent by 2070. [60]

2.62 Using slab models, the predicted changes were:

• In winter, in the band from Shark Bay in Western Australia around to Cairns and the Victorian coast, falls of between zero and 4 per cent by 2030, and of between zero and 10 per cent by 2070. Southwest Western Australia, the northern part of the Southern Ocean and southern Victoria could experience a changes of –2 to +2 per cent by 2030 and –5 to +5 per cent by 2070. In the Southern Ocean and Tasmania there could be increases of between zero and 4 per cent by 2030 and zero and 10 per cent by 2070.
• In summer, the western half of the continent would see increases from 2 to 12 per cent by 2030 and from 4 to 30 per cent by 2070. The eastern half would see increases of between zero and 8 per cent by 2030 and zero to 20 per cent by 2070. [61]

Figure 2.2

CSIRO Scenarios for precipitation change for the Australian region based on `slab' models

Figures not available in Htm Version

Winter Summer

2.63 The CSIRO also commented that where models simulated an increase in average rainfall, this would be accompanied by an increase in intensity, leading to heavier and more frequent rain. Where falls in rainfall were simulated this tendency was less marked or absent. [62]

2.64 Notwithstanding the manifest uncertainties regarding exact predictions between models and in some regions, in general the models predict large changes in rainfall in a relatively short period. The CSIRO also states that `significantly larger or smaller changes would apply at the local scale, particularly in locations where topography still controls weather patterns'. [63] Should precipitation changes approach the extreme end of these predictions, substantial changes to Australian climate, agriculture, flooding patterns, vegetation and biodiversity could be expected.

2.65 The CSIRO stated that tropical cyclones were difficult to model and continued to be a research priority. Present indications were that their region of origin would be unchanged, that there may be some increase in intensity, that their paths may change and that their location and frequency were also affected by ENSO patterns. [64]

2.66 Soil moisture and runoff are particularly important for agriculture and biodiversity. They are sensitive to changes in temperature (increasing evaporation) and changes in rainfall. The CSIRO stated that uncertainties remain about quantifying the exact hydrological response for a given climate change scenario. [65]

(Chapter 2 - Part b)

Footnotes

[1] Intergovernmental Panel on Climate Change, IPCC Second Assessment Synthesis of Scientific-Technical Information Relevant to Interpreting Article 2 of the UN Framework Convention on Climate Change, clause 2.4.

[2] Australian Greenhouse Office, The National Greenhouse Strategy: Strategic Framework for Advancing Australia's Greenhouse Response, 1998, p 1.

[3] Dr Chris Mitchell, `Greenhouse and the Science of uncertainty', ABC Online, http://www.abc.net.au/ science/earth/climate/uncertain.htm, 1997.

[4] The Global Warming Potentials (GWPs) are: HFC-23 11,700, HFC-134a 1,300, Perfluoromethane 6,500, Perfluoroethane 9,200, Perfluoropropane 7,000 and Sulphur Hexaflouride SF6 23,900. Australian Greenhouse Office, Synthetic Gas Use in Non-Montreal Protocol Industries, April 2000, p 3.

[5] IPCC Working Group 1, Summary for Policymakers: The Science of Climate Change, http://www.ipcc.ch/pub/sarsum1.htm (01/09/00).

[6] Intergovernmental Panel on Climate Change, IPCC Second Assessment Synthesis of Scientific-Technical Information Relevant to Interpreting Article 2 of the UN Framework Convention on Climate Change, clause 4.15.

[7] Australian Greenhouse Office, The National Greenhouse Strategy: Strategic Framework for Advancing Australia's Greenhouse Response, 1998, p 85.

[8] Michael Grubb, The Kyoto Protocol: A Guide and Assessment, The Royal Institute of International Affairs, London, 1999, pp 3-4.

[9] Intergovernmental Panel on Climate Change, IPCC Second Assessment Synthesis of Scientific-Technical Information Relevant to Interpreting Article 2 of the UN Framework Convention on Climate Change, clause 1.4.

[10] Commonwealth Bureau of Meteorology, Submission 207, p 2492.

[11] Intergovernmental Panel on Climate Change, IPCC Second Assessment Synthesis of Scientific-Technical Information Relevant to Interpreting Article 2 of the UN Framework Convention on Climate Change, clause 1.1.

[12] Intergovernmental Panel on Climate Change, IPCC Second Assessment Synthesis of Scientific-Technical Information Relevant to Interpreting Article 2 of the UN Framework Convention on Climate Change, clause 1.6.

[13] Commonwealth Bureau of Meteorology, Submission 207, p 2492.

[14] Michael Grubb, The Kyoto Protocol: A Guide and Assessment, The Royal Institute of International Affairs, London, 1999, p 6.

[15] Intergovernmental Panel on Climate Change, IPCC Second Assessment Synthesis of Scientific-Technical Information Relevant to Interpreting Article 2 of the UN Framework Convention on Climate Change.

[16] Intergovernmental Panel on Climate Change, IPCC Second Assessment Synthesis of Scientific-Technical Information Relevant to Interpreting Article 2 of the UN Framework Convention on Climate Change, clause 2.2.

[17] Intergovernmental Panel on Climate Change, IPCC Second Assessment Synthesis of Scientific-Technical Information Relevant to Interpreting Article 2 of the UN Framework Convention on Climate Change, clause 2.4.

[18] Intergovernmental Panel on Climate Change, IPCC Second Assessment Synthesis of Scientific-Technical Information Relevant to Interpreting Article 2 of the UN Framework Convention on Climate Change, clause 2.2.

[19] Intergovernmental Panel on Climate Change, IPCC Second Assessment Synthesis of Scientific-Technical Information Relevant to Interpreting Article 2 of the UN Framework Convention on Climate Change, clause 2.5.

[20] CSIRO, Submission 206, p 2463.

[21] Intergovernmental Panel on Climate Change, IPCC Second Assessment Synthesis of Scientific-Technical Information Relevant to Interpreting Article 2 of the UN Framework Convention on Climate Change, clause 2.6.

[22] Source: IPCC Working Group 11, Summary for Policymakers: Scientific Technical Analyses of Impacts, Adaptations and Mitigation of Climate Change, section 1.

[23] Intergovernmental Panel on Climate Change, IPCC Second Assessment Synthesis of Scientific-Technical Information Relevant to Interpreting Article 2 of the UN Framework Convention on Climate Change, clause 2.7.

[24] Intergovernmental Panel on Climate Change, IPCC Second Assessment Synthesis of Scientific-Technical Information Relevant to Interpreting Article 2 of the UN Framework Convention on Climate Change, clause 2.8.

[25] Intergovernmental Panel on Climate Change, IPCC Second Assessment Synthesis of Scientific-Technical Information Relevant to Interpreting Article 2 of the UN Framework Convention on Climate Change, clauses 2.10-2.12.

[26] Intergovernmental Panel on Climate Change, IPCC Second Assessment Synthesis of Scientific-Technical Information Relevant to Interpreting Article 2 of the UN Framework Convention on Climate Change, clauses 3.6-3.10.

[27] Intergovernmental Panel on Climate Change, IPCC Second Assessment Synthesis of Scientific-Technical Information Relevant to Interpreting Article 2 of the UN Framework Convention on Climate Change, clause 3.13.

[28] Intergovernmental Panel on Climate Change, IPCC Second Assessment Synthesis of Scientific-Technical Information Relevant to Interpreting Article 2 of the UN Framework Convention on Climate Change, clause 3.13.

[29] Intergovernmental Panel on Climate Change, IPCC Second Assessment Synthesis of Scientific-Technical Information Relevant to Interpreting Article 2 of the UN Framework Convention on Climate Change, clause 3.14.

[30] Intergovernmental Panel on Climate Change, IPCC Second Assessment Synthesis of Scientific-Technical Information Relevant to Interpreting Article 2 of the UN Framework Convention on Climate Change, clause 3.14.

[31] Intergovernmental Panel on Climate Change, IPCC Second Assessment Synthesis of Scientific-Technical Information Relevant to Interpreting Article 2 of the UN Framework Convention on Climate Change, clauses 3.14-3.16.

[32] Professor David Karoly, Submission 204, p 2.

[33] Professor David Karoly, Submission 204, p 2.

[34] Proof Committee Hansard, Melbourne, 20 March 2000, p 129.

[35] Proof Committee Hansard, Melbourne, 20 March 2000, p 129.

[36] Official Committee Hansard, Canberra, 9 March 2000, p 22.

[37] Official Committee Hansard, Canberra, 9 March 2000, p 35.

[38] Official Committee Hansard, Canberra, 9 March 2000, p 35.

[39] Official Committee Hansard, Canberra, 9 March 2000, p 35.

[40] Official Committee Hansard, Canberra, 9 March 2000, p 22.

[41] Official Committee Hansard, Canberra, 9 March 2000, p 34.

[42] Official Committee Hansard, Canberra, 9 March 2000, p 40.

[43] Official Committee Hansard, Canberra, 9 March 2000, p 23.

[44] Official Committee Hansard, Canberra, 9 March 2000, p 43.

[45] Official Committee Hansard, Canberra, 9 March 2000, p 24.

[46] Official Committee Hansard, Canberra, 9 March 2000, p 38.

[47] Official Committee Hansard, Canberra, 9 March 2000, p 26.

[48] Dr Barrie Pittock, Proof Committee Hansard, Canberra, 22 June 2000, p 736.

[49] Professor Dr Hans-Joachim Schellnhuber, Proof Committee Hansard, Canberra, 22 June 2000, p 733.

[50] Robert Watson, Marufu Zinyowera, Richard Moss, David Dokken ed. The Regional Impacts of Climate change: An Assessment of Vulnerability, Summary for Policymakers, Intergovernmental Panel on Climate Change, 1997, p 2.

[51] Robert Watson, Marufu Zinyowera, Richard Moss, David Dokken ed., The Regional Impacts of Climate change: An Assessment of Vulnerability, Summary for Policymakers, Intergovernmental Panel on Climate Change, 1997, pp 9-10.

[52] Professor Ove Hoegh-Guldberg, Climate Change, Coral Bleaching and the Future of the World's Coral Reefs, Coral Reef Research Institute, Sydney, 1998.

[53] Proof Committee Hansard, Brisbane, 26 May 2000, pp 642-29.

[54] Proof Committee Hansard, Brisbane, 26 May 2000, p 643.

[55] Climate Impact Group, Climate Change Scenarios for the Australian Region, CSIRO Division of Atmospheric Research, Melbourne, 1996.

[56] Climate Impact Group, Climate Change Scenarios for the Australian Region, CSIRO Division of Atmospheric Research, Melbourne, 1996, p 2.

[57] Climate Impact Group, Climate Change Scenarios for the Australian Region, CSIRO Division of Atmospheric Research, Melbourne, 1996, p 3.

[58] The CSIRO states that, over Australia, coupled models tend to produce summer rainfall decreases and slab models summer rainfall increases. They also show that rainfall changes differ between the models because the coupled models include a strong delay in warming in the higher latitudes of the southern hemisphere. However, there is considerable uncertainty about the ocean processes which lead to this result. There are also conflicts between coupled model simulations and observed 20th Century trends in some aspects of warming in the southern hemisphere, although there are some doubts whether this is greenhouse related. Climate Impact Group, Climate Change Scenarios for the Australian Region, CSIRO Division of Atmospheric Research, Melbourne, 1996, p 4.

[59] Climate Impact Group, Climate Change Scenarios for the Australian Region, CSIRO Division of Atmospheric Research, Melbourne, 1996, pp 3-4.

[60] Climate Impact Group, Climate Change Scenarios for the Australian Region, CSIRO Division of Atmospheric Research, Melbourne, 1996, pp 3-4.

[61] Climate Impact Group, Climate Change Scenarios for the Australian Region, CSIRO Division of Atmospheric Research, Melbourne, 1996, pp 3-4.

[62] Climate Impact Group, Climate Change Scenarios for the Australian Region, CSIRO Division of Atmospheric Research, Melbourne, 1996, p 5.

[63] Climate Impact Group, Climate Change Scenarios for the Australian Region, CSIRO Division of Atmospheric Research, Melbourne, 1996, p 5.

[64] Climate Impact Group, Climate Change Scenarios for the Australian Region, CSIRO Division of Atmospheric Research, Melbourne, 1996, p 5.

[65] Climate Impact Group, Climate Change Scenarios for the Australian Region, CSIRO Division of Atmospheric Research, Melbourne, 1996, p 6.

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