Global Warming:
The Mother of all Environmental Scares
by Geoff Hogbin

Over recent months there has been a spate of unusual weather events around the world – an extreme El Nino-related drought in much of South East Asia and New Guinea; serious flooding in China, Europe, Latin America and, more recently, in northern Australia; extremely cold weather in Northern Europe; severe ice-storms in Canada; severe tornadoes in the United States; and a hot summer accompanied by extensive, destructive bushfires last November here in Australia.

Graphic television reports of the consequences of weather-related disasters, combined with an avalanche of rhetoric leading up to the Kyoto Conference, have aroused widespread fears of global warming as a consequence of the build-up of greenhouse gases, primarily carbon dioxide (CO2), caused by capitalism’s voracious consumption of fossil fuel energy. Exploiting these anxieties, lobby groups and the media have put governments under strong pressures to cut consumption of fossil fuels with the objective of curbing greenhouse gas emissions.

However, contrary to much interest group and media rhetoric, the direct evidence of warming attributable to the accumulation of greenhouse gases is far from conclusive and the soundness of the highly publicised estimates of greenhouse effects which underlie calls to curb emissions is at least questionable. This is reflected in the following statement from a declaration signed late in 1995 by almost 100 scientists, many from leading universities and research institutions in North America and Europe, following an International Symposium on the Greenhouse controversy held in Leipzig, Germany:

As the debate unfolds, it has become increasingly clear that – contrary to conventional wisdom – there does not exist today a general scientific consensus about the importance of greenhouse warming from rising levels of carbon dioxide.

This is not to claim that climates will be unaffected by the build-up of greenhouse gases. Indeed, there are sound scientific reasons for believing that the build-up of greenhouse gases will cause some increase in global temperature. Moreover, burning fossil fuels is almost certainly not the only way in which human activities have changed climates. Centuries of land clearing, cropping, irrigation, animal husbandry and forestry must have changed surface temperatures and atmospheric composition over extensive areas. Heat stored in roads and buildings appears to increase the prevalence of storms in the vicinity of urban areas (urban ‘heat island’ effects). However, so far humans appear to have had little difficulty in adapting to such changes because they appear to have generally been small, slow and in many cases benign. Thus, the issue is not whether the build-up of greenhouse gases will cause climates to change – it will. What is uncertain, but central to determining what, if any, action should be taken (and when it should be taken), is the nature of those changes and, crucially, how big they can be expected to be.

This article summarises basic information about the relationship between the build-up of greenhouse gases and climate change, which bears on the important issue of how governments should respond to the threat of global warming.

Fundamental propositions

The temperature of the earth’s surface is kept warmer than it would otherwise be by a natural ‘blanket’ of greenhouse gases. This is known as the greenhouse effect. The enhanced greenhouse effect refers to additional warming caused by the build-up of atmospheric greenhouse gases resulting from human activities.

Just as the volume of water in a reservoir will continue to build up (i.e. the water level will continue to rise) as long as the rate of water inflow exceeds the outflow, so the quantities of greenhouse gases in the atmosphere will continue to build up as long as the amounts emitted exceed the amounts removed from the atmosphere either naturally (e.g. take-up by native plant communities and oceans) or through human activities (e.g. crop production, forestry). Although implementation of constraints on CO2 emissions, such as those agreed to by industrialised countries at the Kyoto conference, would reduce emissions by perhaps 5 or 10 per cent relative to what they would otherwise have been, quantities of CO2 emitted into the atmosphere per year will still exceed quantities absorbed by a very wide margin.

Consequently, even if the Kyoto constraints are implemented the build-up of greenhouse gases in the atmosphere will continue, albeit with CO2 accumluating somewhat more slowly than otherwise.

This qualifier is important. Even if the Kyoto constraints are implemented by industrialised countries, absolute rates of greenhouse gas emissions will almost certainly continue to rise over time because cuts achieved by developed countries are likely to be swamped by increases in emissions from developing countries (including the populous nations China, India, Indonesia, Pakistan, Brazil and Mexico), where per capita emissions can be expected to increase steadily as their economies grow. Put another way, the Kyoto constraints, if implemented and adhered to, will merely delay (and delay by only a few years) the time taken for the concentration of greenhouse gases to rise to, say, double pre-industrial levels. They would therefore merely delay any change in climate that would occur in the absence of measures to curb greenhouse gas emissions.

Halting the build-up of greenhouse gases (i.e. stabilising their atmospheric concentrations at current levels) to prevent climates from changing would require far more severe reductions in emissions. In the case of CO2, for example, reductions of 60 to 80 per cent below current levels across all countries – developed and developing – would be required to prevent further atmospheric build-up, rather than the 5 to 10 per cent reduction, confined to industrialised countries, that the Kyoto constraints aim to achieve. Put simply, stabilising atmospheric greenhouse gas concentrations at current levels is not a realistic option because the required emission cuts are well beyond the bounds of political feasibility. Consequently, we should expect greenhouse gases to continue to build up in the atmosphere for the foreseeable future, even if emissions are restricted (although somewhat more slowly than under a ‘business as usual’ scenario). We cannot escape the need to adapt to whatever climate change this might cause.

The global warming hypothesis

Some basic information about the facts and science of greenhouse warming is needed to form perspectives on the likely size of enhanced greenhouse effects on climates and how difficult it might be to adapt to them.

Gases such as water vapour and CO2, which are naturally present in the atmosphere, reduce heat loss from the earth by reducing terrestrial infra-red radiation. This ‘blanketing’ effect or ‘greenhouse effect’ keeps the world about 33°C warmer than it would otherwise be. Significantly, water vapour contributes about 98 per cent of the greenhouse effect. Other gases, primarily CO2, contribute the remaining (approximately) 2 per cent.

There is general agreement that the carbon dioxide (CO2) content of the atmosphere has risen by about 30 per cent since pre-industrial times, from about 275 parts per million by volume (ppmv) before AD 1800 to 355 ppmv today. It is certain that most of this increase, if not all, has been caused by worldwide deforestation and increased burning of fossil fuels (coal and oil) for electricity generation, transportation and other human activities. The equivalent of about half of all the CO2 added to the atmosphere by human activity has subsequently been removed by absorption into ‘CO2 sinks,’ principally oceans and growing plants.

Carbon dioxide is a stable, colourless, odourless and intrinsically harmless gas. It is essential for plant life – plants combine water absorbed through their roots with atmospheric CO2 extracted through their leaves to photosynthesise sugars, which are the basis for plant growth. There is conclusive experimental evidence that CO2 enrichment of the atmosphere stimulates plant growth. Interestingly, this has led some scientists to conjecture that some of the general increase in crop yields experienced over recent decades around the world may be attributable to the build-up of atmospheric CO2. Animals exhale CO2 as a waste product of metabolism. CO2 is used to produce carbonated drinks and for a host of industrial purposes.

There is much uncertainty about future rates of accumulation of CO2. Part of the reason is that it is difficult to predict future consumption of fossil fuels reliably, because it will depend on unknowable factors such as future prices of oil and coal, future rates of economic growth and, importantly, success in developing substitutes for fossil fuels. Another part of the reason is that the natural processes which determine rates of CO2 removal from the atmosphere, and the ways in which human activities influence them (e.g. crop fertilisation, forest regrowth, high-yielding crops, paper recycling), are not well understood.

There have also been atmospheric build-ups of other man-made (anthropogenic) greenhouse gases including sulphur dioxide (SO2), methane (CH4) and nitrous oxide (NO). However, certain other anthropogenic gases are believed to have had a net cooling effect. For example, degradation of atmospheric ozone (a greenhouse gas) by chemical reaction with anthropogenic CFCs (chlorofluorocarbon compounds) is believed to have had a cooling effect. Anthropogenic emissions of aerosol particles, notably sulphate aerosols formed from coal and oil combustion, tend to cool the earth’s surface by shielding it from solar radiation. Again, the strengths of these effects are uncertain.

Just as increasing the thickness of a blanket keeps a bed warmer, other things held constant, so the increase in concentration of greenhouse gases in the atmosphere can be expected to cause some global warming. However, as noted above, water vapour accounts for 98 per cent of the ‘thickness’ of the greenhouse gas blanket. Accordingly, logic suggests that even if the concentrations of CO2 and all other greenhouse gases apart from water vapour were to double, the effect on the overall ‘thickness’ of the blanket would be relatively small and consequently the increase in global temperature would also be small.

However, there are scientific reasons for believing that the primary warming effect of the build-up of CO2 may be amplified by various natural mechanisms to produce ultimately much stronger global warming effects. For example, by increasing rates of evaporation from ocean and land surfaces the direct heating effect might cause an increase in the amount of water vapour in the atmosphere, thereby adding further to the ‘thickness’ of the greenhouse gas blanket. Clearly, there may be further ‘flow-on’ effects. An increase in humidity might cause a change in the amount of cloud cover. On the one hand, more cloud during the day might have a net cooling effect because of increased reflection of incoming solar radiation, while on the other, more cloud at night would tend to produce warming by reducing heat radiation from the earth.

Temperature changes might cause further flow-on effects by, for example, changing patterns of air circulation, manifested as changes in strengths and directions of surface and upper atmospheric winds or changes in convection currents. Similarly, global temperature changes may change ocean surface and convection currents to produce further effects on levels of humidity and circulation. Since temperature changes are not expected to be uniform over the earth’s surface, patterns of air pressure can be expected to change, which in turn may produce changes in prevailing winds, with flow-on effects on evaporation, precipitation, etc.

There are numerous uncertainties about the nature and power of these postulated amplification mechanisms and ways in which they might interact to form climates. Accordingly, there is great uncertainty about both the nature and size of effects of the build-up of greenhouse gases on temperatures and climates.

Has the earth warmed?

One might expect that these uncertainties could be resolved simply by observing the relationship between the earth’s temperature and the CO2 content of the atmosphere over the last century or so that greenhouse gases have been accumulating. However, detecting and measuring the extent of greenhouse warming, if it has occurred, has proved to be extremely difficult. As a practical matter it is difficult to measure ‘the’ temperature of the earth’s surface and therefore to ascertain by how much it has changed.

There are various reasons for this. Determining the earth’s temperature for a given year entails producing a single number which accurately reflects temperature variations from day time to night time, from day to day, from season to season and from place to place at various altitudes over all parts of the globe, including land and ocean. Some places may experience warmer than average summers or winters at the same time as others are having cooler than average weather. Still others may have a hot summer and a cool winter. Recording stations are not distributed systematically over the earth’s surface. Whereas oceans cover about 75 per cent of the earth’s surface, the great majority of recording stations with suitably long records are located on land – mostly in a relatively few industrialised countries.

Moreover, while land temperatures are measured by the temperature of air about a metre above the earth’s surface, ocean temperatures are measured by the temperature of water, and these air and water temperatures must somehow be amalgamated to give a single number. Unfortunately, there is no way of knowing how closely any global temperature calculated from the available temperature recordings for a given year corresponds to the ‘true’ average surface temperature for that year.

Since it is not possible to ascertain the precision of any given annual measurement of global temperature, attempts to estimate changes in annual global temperatures over time are also fraught with uncertainties. Measured annual global temperatures exhibit apparently random year-to-year variations (averaging about ± 0·2°C) around the mean, which further complicates detection of trends.

These and other difficulties notwithstanding, several series of annual estimates of global surface temperatures have been produced. One such series, produced by Jones (East Anglia University) and Parker (United Kingdom Meteorological Office), is a key data source for the IPCC’s most recent major report on global warming and climate change, Climate Change 1995.1 This report was the basis for the targets for restricting emissions of CO2 recommended by the IPCC for adoption at the Kyoto conference. The Jones/Parker (JP) global surface temperature series indicates that between 1860 to 1996 (almost one and a half centuries) the global surface temperature has risen by about 0·6°C and, in particular, that there has been an increase of about 0·3°C since the late ’70s. Largely on the basis of these increases, the JP series (and other similar series) are frequently cited as evidence of global warming attributable to the build-up of greenhouse gases.

However, because of uncertainties about the reliability of the global temperature and natural variability in the temperature data the evidence is far from conclusive – either that global warming has occurred, or, if it has, that it has been caused by the build-up of greenhouse gases. Rather than exhibiting a persistent upward global temperature trend to match the steadily accelerating build-up of atmospheric greenhouse gases, the series is erratic. There was a persistent upward trend of about 0·6°C from about 1910 to the early 1940s, but this was followed by more than three decades of stable or downward trend lasting through to the late 1970s, during which there was strong build-up of greenhouse gases. There has, however, been a persistent upward trend of about 0·3°C over the last three decades, which has been stronger in the northern hemisphere than the southern hemisphere.

A further reason why the evidence from global temperature series is not conclusive is that there are doubts about whether it has been adequately ‘corrected’ for measurement anomalies (e.g. heat island effects, changes in ocean temperature recording techniques, etc.). Whereas temperatures at urban recording sites generally show upward trends, there is little sign of warming at many recording sites known to be remote from urban areas. While this is not necessarily inconsistent with global warming, it does raise questions about the reliability of the JP corrections for measurement anomalies.

For example, a study by Hughes and Balling compared regional temperatures for South Africa calculated by Jones for the period 1960 to 1990 with actual temperature recordings for South Africa over the same time interval (Hughes and Balling 1996). Whereas the Jones data exhibited rapid warming of approximately 0·3°C per decade for the region (or almost 1°C over the three decades), temperatures at 19 non-urban recording sites in the same regions were shown to have increased only by approximately 0·1°C per decade, and this increase was not statistically significant. Most of the increase in average temperatures at urban recording sites was attributable to increases in daily minimum temperatures (normally night temperatures), which is consistent with what is known about urban heat island temperature effects. This led the authors of the study to conclude that ‘half or more’ of the warming exhibited by the Jones data for South Africa ‘may be related to urban growth, and not to any widespread regional temperature increase.’

Satellite temperature measurements cast further doubt on the extent to which changes in calculated surface temperatures, such as the JP series, ‘track’ changes in true global temperatures. Theoretically the global lower troposphere temperature (surface to about 7km) should change in unison with surface temperatures. But whereas surface-based temperature data show a warming of about 0·3°C from the late 1970s to the present, satellite-based measurements of the lower troposphere temperature show no evidence of warming over this time in the northern hemisphere, and a slight cooling in the southern hemisphere.

While there is no objective way of deciding which set of data more closely tracks changes in actual surface temperatures, the satellite data, although not free of problems, have appealing features. Extensive checks show that satellite-measured temperatures correspond closely to weather-balloon-measured temperatures. Satellite-measured temperatures should not be subject to measurement anomalies because they are recorded with a single ‘thermometer’ and are taken systematically from all parts of the globe. In addition, detection of global warming should be easiest in the troposphere because, theoretically, this part of the atmosphere should experience the greatest greenhouse warming. The lack of correspondence between patterns computed from surface recordings and patterns computed from satellite and balloon-based temperature data is therefore puzzling.2 Curiously, the satellite data has been entirely ignored by the authors of Climate Change 1995.

Natural causes of global temperature change

Even if one accepts that global temperatures have increased over the last century, there are reasons for believing that some of the warming, perhaps most, may have been caused by factors other than the build-up of greenhouse gases. For example, as noted above, whereas most of the build-up of atmospheric CO2 has occurred in the second half of this century, most of the warming exhibited by the JP data occurred in the first half of the century. As Sallie Baliunas of Stanford University’s Hoover Institution has noted, ‘Increased greenhouse gases cannot be the cause of a temperature rise that occurred before the gases were added to the atmosphere’ (Baliunas 1996).

At least part of the apparent 0·6°C global warming over the last century or so may well have been caused by natural phenomena of the kinds responsible for well-recognised periods of warming and cooling in the past. For example, in relatively recent history a warmer period from about AD 1000 to AD 1350 (during which Vikings colonised Greenland) was followed by about four centuries of cooler temperatures. In the 19th century, Charles Dickens wrote of winter snow and frozen landscapes in the vicinity of London and skating on the Thames was a common pastime, indicative of a climate substantially different from today’s. While the cause of extended periods of changed global temperatures such as this are not well understood, it is virtually certain that they were caused by natural phenomena, including perhaps variations in solar radiation and variations in the earth’s orbit around the sun. If the earth has warmed over recent decades, then it may simply be a continuation of the warming which started early in the 19th century as the earth emerged from a little ice-age believed to have started around the 14th century.

Global Climate Change Models

What then is the basis for the IPCC’s prediction that the build-up of greenhouse gases will cause the earth to warm by between 1·5°C and 4·5°C over the next 50 years, with a ‘best estimate’ of 2·5°C?

The IPCC’s predictions are based entirely on computations from extremely complex computer models, developed over the last 25 years or so with the objective of simulating the determination of climates around the world. These Global Climate Models (GCMs) aim to calculate temperature and climate changes based on estimated changes in the balance between inflows of solar energy and outflows of energy radiated from earth. They comprise myriad mathematical equations and are essentially an amalgamation of numerous hypotheses – some tested, some not – about factors which influence the earth’s energy balance (including levels of greenhouse gases, clouds, convection currents, global air circulation patterns, ocean currents, polar ice-caps, etc.) and ways in which they interact. About 30 GCMs have been constructed, almost half by US climate research institutions, with others in Western Europe, Russia, East Asia, Canada and Australia (CSIRO, Melbourne).

As noted above, given that atmospheric CO2 contributes only about 2 per cent of the total greenhouse effect it seems implausible that even a doubling of atmospheric CO2 would by itself have a substantial direct effect on global temperatures. Thus the most significant design feature of GCMs is that they embody hypotheses or conjectures about various processes which the model-builders believe amplify the direct (or primary) warming effect of the build-up of atmospheric CO2 to produce an enhanced greenhouse effect. The nature and strengths of these amplification mechanisms are, however, controversial – in many cases closer to conjecture than scientifically verified theories.

GCMs have been continually modified and ‘re-calibrated’ in attempts to make their predictions conform more closely with past observations. For example, the early GCMs produced estimates of global temperatures that turned out to be implausibly high when compared with changes in computed global temperatures. To solve this problem a cooling effect, postulated to be caused by a build-up of anthropogenic sulphate aerosols, was built into the models to scale back predicted temperature increases. However, this has introduced further controversies because the cooling effects required to align model predictions with observations are considered by some scientists to be implausibly large.

Moreover, given that there is little mixing of air across the equator, the failure to observe greater warming in the northern hemisphere (where most of the sulphate emissions occur) than in the southern hemisphere (where sulphate emissions are low) seems also to be inconsistent with the sulphate cooling hypothesis. No doubt conjecture is integral to science, and modifying and recalibrating GCMs to produce desired ‘predictions’ is not necessarily an unscientific procedure. Nonetheless, if hindsight is required to ‘predict’ the past, how successful are the models likely to be in predicting the future?

GCMs have been shown to be unreliable in other ways. For example, whereas the models predict that day and night temperatures should rise together, observations show that almost all of the rise in computed global temperatures over time is a consequence of increases in measured night temperatures. Amplification of the primary warming in the models requires cloud cover to decline over time. However, all measurements show that cloud cover has increased over time. The models predict that from 1940 to the present, polar regions should have warmed by between 1°C and 3°C. However, with the exception of Alaska, which has warmed (apparently because of a change in air circulation), thermometer measurements show that the Arctic as a whole has cooled.

While such discrepancies may not invalidate GCMs, they further undermine confidence in their predictive power. There is an abundance of other examples of discrepancies between results generated by GCMs and real world observations. Yet, claims by the IPCC and others that a build-up of greenhouse gases will cause dangerous global warming, and the resultant campaign to restrict future consumption of fossil fuels, are underpinned almost entirely by GCM predictions.

Many reputable climatologists and other informed people are critical of the extent to which the results generated by GCMs have been presented to the public as scientific ‘predictions’ for the purposes of influencing policies. Brian Tucker, former head of the CSIRO’s Division of Atmospheric Research, has described them as ‘inadequate theory’ pressed prematurely into service. In an overall assessment of claims of dangerous global warming, Patrick J. Michaels of the University of Virginia, concludes:

How should governments respond?

Given the uncertainty about the consequences of the build-up in greenhouse gases, how should governments respond to the threat of global warming?

Cutting greenhouse gas emissions will not be costless. Freeing up resources to construct more energy-efficient machines and buildings and alternative sources of energy (wind power, solar power) will necessarily reduce the resources available for producing goods and services that benefit households directly, including items such as health care, education, aged care facilities and support, and so on. Curtailing energy consumption will oblige people to change their lifestyles by, for example, reducing use of motor vehicles and airlines for recreational and social travel. Thus the costs imposed by emission cuts will be manifested ultimately as reduced availability and higher prices of consumer goods and services, and forced shifts to less-preferred lifestyles.

These costs are unlikely to be distributed evenly. Employment and remuneration in industries which produce substitutes for existing energy-intensive products can be expected to increase, perhaps even adding to total employment. However, there is no question that any benefits people might derive from reduced rates of climate change will be (to some extent) offset and quite possibly outweighed by reduced availability of goods and services. The size of the costs will, of course, increase with the severity of restrictions on emissions.

If it turns out that GCM ‘predictions’ that a build-up of greenhouse gases would cause substantial warming (say 2°C to 4°C by 2100) and catastrophic climate change are correct, then the costs associated with cutting emissions may prove to be justified. On the other hand, if the effects on climate turn out to be small, then people will be unnecessarily harmed by emission cuts.

Invoking the ‘precautionary principle’ – the precept that if there is a threat of serious or irreversible environmental damage, action to prevent such damage should not be postponed because of lack of complete scientific certainty – many scientists and media commentators insist that even if knowledge of the effects the build-up of greenhouse gases is incomplete, measures to curb greenhouse gas emissions should be implemented expeditiously to reduce future warming.

However, the best available information suggests that even on pessimistic assumptions about the intensity of greenhouse warming, future temperatures will be affected little by delaying the implementation of limited measures such as those agreed to by the Kyoto conference. For example, leading proponents of the global warming thesis estimate that delaying until 2020 the starting time for a cut of 9 billion tonnes of CO2 emissions per year (roughly the reduction the Kyoto constraints would achieve) would increase the temperature in the year 2100 by a mere 0·2°C (Wigley et. al. 1996). And if the warming effect of greenhouse gases turns out to be less powerful than these researchers expect, then the impact of delaying the cuts would be even smaller.

Clearly, the benefits to be expected from such a small possible temperature reduction are relatively small and very uncertain. Against this, the costs of imposing Kyoto-type constraints are likely to be relatively high and far more certain. If Kyoto-type constraints are implemented, but greenhouse warming proves not to be a serious problem, then societies will have unnecessarily incurred costs, including reduced economic welfare and loss of life. Because the precautionary principle disregards an important risk – the risk of losses caused by the precautions – it is inappropriate as a guide for policy.

The case for delay is buttressed by another consideration. The cost of coping with global warming can be expected to fall over time. For example, the costs of producing energy from sources other than fossil fuels can be expected to fall with improvements in technology. The energy efficiency of machines and buildings can also be expected to improve. Accordingly, it is likely to be less costly to achieve, say, an atmospheric CO2 concentration of 400ppmv by 2030 if relatively larger reductions are made starting in 2010 than if we begin making relatively small reductions now.

In summary, the benefits of delay appear to be substantial. By, say, 2010 we should have more precise and reliable estimates of the strength of the greenhouse effect and its impact on climates, better alternatives to fossil fuels for producing energy, and a better understanding of ways of coping with whatever changes might be produced by the inevitable build-up of greenhouse gases.

Conclusion

Global warming is an important issue for all countries, but especially for Australia. Because of the size of the country, our remote location from trading partners, and our resource endowment, we are heavy users of fossil fuels for personal and commercial transport. Coal is our most important export and large quantities of fossil fuels are used to produce many other energy-intensive mineral, agricultural and manufactured exports. The way in which governments – our own as well as governments around the world – respond to the build-up of greenhouse gases will be an important determinant of future living standards in Australia.

However, as outlined above, the science of global warming is fraught with uncertainty and it is therefore not clear how serious the problem of anthropogenic climate change is likely to be. The claims of the IPCC notwithstanding, there simply is no consensus amongst scientists that dangerous global warming will occur.

The common tendency to interpret extreme weather events as portents of impending doom is antithetical to a rational approach to the threat of dangerous climate change. The laws of probability are such that periodic extreme weather events are inevitable. Melbourne had a very hot November day last year, but there was an even hotter day early this century. In September 1666 a most atypical hot, dry east wind fanned the Great Fire of London. At the time, this episode was interpreted by many as divine retribution for the excesses at the Court of Charles II. Although such an interpretation would be given little credence today, global warming fears appear to be coloured by perceptions of the modern world’s appetite for fossil fuels as a culpable extravagance.

References

Baliunas, Sallie 1996, ‘The Cold Facts on Global Warming,’ Earth Day ’96, Internet.

Hughes, Warwick S. and Robert C. Balling 1996, ‘Urban Influences on South African Temperature Trends,’ International Journal of Climatology 16: 935-940.

Michaels, Patrick J. 1997, ‘The search for an explanation of the apparant lack of dramatic and damaging global warming,’ (mimeo) paper delivered at Countdown to Kyoto conference, Australian APEC Centre, Canberra.

Wigley, T.M.L., R. Richels and J.A. Edmonds, 1996, Nature 379: 240-243.

Endnotes
1 The International Panel on Climate Change (IPCC) was set up in the late 1980s jointly by the United Nations Environment Program and the World Meteorological Organisation partly as a result of the report of the World Commission on Environment and Development (the Brundtland Commission), which had promoted the threat of greenhouse warming as a major public issue. The aim was to provide governments with authoritative scientific information and opinion on climate change. The IPCC orchestrates scientific investigations of greenhouse effects and global warming and has produced a series of major reports based on these investigations, including Climate Change 1995.

2 The main limitation of satellite recordings, of course, is that they did not begin until 1979.

Geoff Hogbin is a Sydney-based economist with broad interests in economic and social regulation.

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