How Will the Risks for Climate Changes Limit the Use of Fossil Fuels?by Professor Emeritus Bert Bolin Lecture held at a seminar in the Academy on March 16, 2000.
A Human-induced Climate Change is on the WayAnalyses of available global meteorological data through 1998 shows clearly that a global climate change is under way. There is also increasing evidence that most of the change during the last 50 years is caused by human emissions of greenhouse gases and aerosols into the atmosphere, but the sensitivity of the climate system to such emissions has not yet been well established, but the increase of the global mean temperature is likely to be in the range 1.5 - 4.5°C, if the carbon dioxide concentrations would double. [1] It is, however, also important to recognise that because of the inertia of the climate system and some cooling due to aerosols, only 50 - 70 per cent of the changes, that are expected as a result of the greenhouse emissions emitted so far, have as yet been realised. A considerable part of the expected changes are indeed hidden. This inertia of the system also implies, that a future change of the climate, induced as a result of human activities, would decline only slowly, even if emissions were suddenly stopped. This inertia is primarily due to the rather slow response of the global circulation of carbon to external disturbances and the great heat capacity of the world oceans. However, society does not either change quickly. A sudden decrease of the greenhouse gas emissions is not possible. The complex infrastructure of modern society and the inertia of social institutions and values also imply that changes cannot not brought about quickly. To replace the present global energy supply system, to almost 80 per cent is based on fossil fuels, by a non-carbon dioxide emitting system, will necessarily take time. In addition, mitigation efforts will hardly be more fully implemented and accordingly have an effect on the course of events, until a decade has gone by. It is worth noting that it is thirteen years, since a first resolution was passed in the United Nations General Assembly in 1987 on environment and development, on which occasion the need to address the issue of human-induced climate change was also recognised for the first time. Mitigation has not yet reduced the rate of increase of carbon dioxide in the atmosphere noticeably. Nor is it likely that the agreements reached in Kyoto by 2010 will have a detectable effect of increase during the first decade of the 21st century, even if the Protocol were fully implemented. [2] Although a future human induced global climate change is recognised by almost all governments of the world, there is still considerable reluctance to take steps that mean a clear change of the present trend of increasing greenhouse gas emissions to the atmosphere. The Framework Concentration on Climate Change (FCCC) that was signed in 1992 in Rio formulates the ultimate goal of the Convention to be a stabilisation of greenhouse gas concentrations: The ultimate objective of this Convention and any legal instruments that the Conference of Parties (CoP) may adopt is to achieve, in accordance with relevant provisions of the Convention, stabilization of green-house 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 time-frame 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. The Convention further recommends that developed countries by the year 2000 would not exceed their emissions in 1990. The Convention entered into force in 1994 and the first binding commitments were agreed in 1997 in Kyoto in Japan. The Kyoto Protocol has, however, not been ratified yet, but the forthcoming sixth session of the Conference of the Parties (in The Hague in November 2000) hopefully will reach agreements that will lead to ratification in the course of 2001 or at the latest in 2002.
Table 1 deals with human-induced emissions of carbon dioxide (in Gt C yr-1) due to fossil fuel combustion and cement production as observed 1990 and 1998, and projected for 2010 based on the commitments for developed countries as prescribed by the Kyoto Protocol, and increasing emissions by 1.5 per cent and 4.5 per cent yr-1 for Countries in Economic Transition and developing countries respectively. Sources and Sinks of Atmospheric Greenhouse GasesCarbon DioxideThe changes of the emissions of carbon dioxide from 1990 until 1998 and projected changes by 2010 are shown in table 1. [3] It has been assumed that Countries in Economic Transition will increase their emissions by 1.5 per cent per year and Non-Annex I countries (i.e. developing countries) by 4.5 per cent per year, the latter implying a continued increase at the rate during the 1990s, while Annex-1 countries (developed countries) will decrease their emissions by 5 per cent since 1990 as prescribed in the Kyoto Protocol. These numbers should be considered as a possible but not unlikely, scenario. Emissions also occur because of deforestation and changing land use, particularly in developing countries, the net amount of which has been estimated to 1.7 ± 0.8 Gt yr-1 during the last two decades. It seems now to be declining slowly. [4] It is to be noted that in 2010 the Non-Annex-1 countries are at that time not yet expected to emit more carbon dioxide into the atmosphere than Annex-1 countries, even though their population, probably about 5.4 billion, is likely to be about four times the expected population in Annex-1 countries. A transition towards more equity amongst the countries of the world with regard to their energy use is progressing rather slowly. It is also possible to determine reasonably well the carbon balance of the atmosphere during the last about twenty years, cf table 2.
Based on IPCC, 2000; Houghton, 1999, 2000. The flows between reservoirs are given in Gt yr-1. Although the uncertainly of these estimates still is quite large, it seems plausible that the terrestrial systems have been a small net sink during the last decades of the 20th century, in spite of the fact that deforestation and changing land-use are causing emissions of about 1.7 Gt C yr-1. During this time the emissions as a result of human activities amounted to about 7.6 Gt yr-1 , of which about 78 per cent was due to fossil fuel burning and about 18 per cent to deforestation and changing land use. About 43 per cent of these emissions have stayed in the atmosphere, while the remainder has found its way into the oceans and the terrestrial ecosystems in roughly about equal amounts. Thus, the natural response of the carbon cycle to the human-induced disturbances quite effectively counteracts these. Naturally, one asks the questions: Will this situation remain or change in the future? Might it be possible to enhance the uptake by the terrestrial systems and in this way slow down the pace of the increase? This latter is at present being seriously considered by the Parties of the Convention and will be discussed below. Other Greenhouse GasesAt present the increase of atmospheric carbon dioxide accounts for about 60 per cent of the total enhanced radioactive forcing due to increasing greenhouse gas concentrations. Other contributions stem from enhanced concentrations of methane (about 22 per cent), nitrous oxide (about 5 per cent) and halocarbons (about 13 per cent). [5] More recent analyses show that the role of the halocarbons probably is less important, and also that aerosols should be considered. Although the greenhouse forcing thereby is reduced somewhat, the overall picture is not markedly changed. The atmospheric carbon dioxide concentrations has so far increased by about 31 per cent (from a pre-industrial concentration of about 280 to 367 ppmv in 1998). The total forcing due to all enhanced greenhouse gases is at present equivalent to a carbon dioxide concentration of about 425 ppmv, i.e. an increase of the pre-industrial concentration by about 50 per cent. Stabilisation of Atmospheric Greenhouse Gas ConcentrationsIt is obviously of prime interest to determine the required reductions of future greenhouse gas emissions, if a stabilisation of their concentrations would be aimed for. Carbon DioxideGood understanding of the circulation of carbon in nature is requires to determine emission scenarios that lead to stabilisation of atmospheric carbon dioxide concentrations. Figure 1 shows the outcome of such increase computations for a set of alternative stabilisation levels. [6] Such projections are, however, critically dependent on the future roles of the oceans and the terrestrial systems as sinks for human-induced emissions. This should be subject for some detailed considerations.
Figure 1. Alternative emission profiles of carbon dioxide to achieve stabilisation of atmospheric concentrations at 1000, 750, 650, 550 and 450 ppm. For each such level two pathways are shown and others could be chosen. They all, however, lie within a rather narrow band determined by the constraints imposed by the characteristic features of the global carbon cycle. An estimate of the recent uptake by the terrestrial systems was given in table 2. This is the result of a number of complex processes. Photosynthesis annually binds about 60 Gt carbon by the formation of organic tissues, but during preindustrial times this uptake was almost completely balanced by the return flow to the atmosphere resulting from the decomposition of dead organic matter. The enhanced atmospheric concentration of carbon dioxide has now led to more efficient diffusion of carbon dioxide through the stomata in the leaves during photosynthesis, often called 'the carbon dioxide fertilisation effect', whereby the net primary production of the terrestrial ecosystems has been enhanced. Photosynthesis is also stimulated by fertilisation of the soils by deposition of nitrogen compounds that partly stem from air pollution. In addition, forests in middle and high northern latitudes have also become a net sink as a result of greatly improved forest management. These are probably the prime reasons why terrestrial ecosystems at present serve as a net sink for carbon dioxide. To what extent will this be the case also in the future? It seems plausible that carbon dioxide fertilisation will continue to increase slowly during the next few decades as atmospheric concentrations increase, but later at a declining rate because of a saturation effect. A warmer climate will also enhance photosynthesis in vegetation at middle an high latitudes if water is available, and thus increase the total amount of carbon. This will, however, hardly be the case in the tropics. Bacterial decomposition of organic matter, on the other hand, will be enhanced in a warmer climate at both high and low latitudes. It is therefore possible that the terrestrial systems will serve as a slowly increasing sink for some time to come as it has done in the past, but we don't know if and for how long the airborne fraction of the human-induced emissions will remain at about 43 per cent in the future. The Kyoto Protocol has taken note of the fact that the terrestrial system serves as a sink and discussions are intense as to how its role might be taken advantage of and what specific measures might be considered. The IPCC was asked to analyse this issue in some detail and has recently presented its report. [7] The sixth session of the Convention will decide on rules and procedures for the appropriate paragraphs in the Protocol. It is, however, difficult to do so in a manner that is correct and fair and thus might be acceptable to the Parties to the Convention. In a long term perspective, the contributions from such mitigation might temporarily slow down the rate of increase in the atmosphere, but a stabilisation cannot be achieved in this manner. Emission profiles that will lead to stabilisation at the alternative carbon dioxide concentration levels of 450, 550, 650, 750 and 1000 ppmv have been deduced. [8] The improved understanding of the carbon cycle might lead to some modifications of these profiles, but it is not likely that the basic difficulties encountered would be very different. Two alternative paths are shown for each stabilisation level and others may be chosen, but for a given level the accumulation of the emitted amounts for the different path ways are about the same. Somewhat larger total emissions might be allowed. As was indicated before, however, the future capacity of the oceans and the terrestrial systems to serve as a sink cannot be projected very well. Aiming at stabilising at 550 ppmv would require that the emissions in 1998, about 8.3 Gt C year-1, as a result of fossil fuel burning (6.6 Gt C year-1) and deforestation (1.7 Gt C year-1) would be permitted to increase by 20 - 40 per cent during the next half century, and then to decrease to well below present levels towards the end of the century. The next decade will reveal much better how sensitive the climate system might be to rising concentrations of greenhouse gases in the atmosphere. It is possible that a concentration of 500 ppmv should rather be aimed for, which would impose considerably tougher restrictions on the future use of fossil fuels. The most cost-effective approach for mitigating climate change would be to start early and in order to change gradually from a primarily fossil fuel based global energy supply system to one based on non-carbon dioxide emitting sub-systems. Waiting still another decade to get going, might imply that more drastic measures would have to be taken later with the need for renovation or even early retirement of recently built facilities for the use of fossil fuels. On the other hand, technical development might in the mean time reduce costs. As IPCC say: "The challenge is not to find the best policy for the next hundred years, but to select a prudent strategy and to adjust it over time in the light of new information". [9] Stabilisation of Other Greenhouse Gas Concentrations in the AtmosphereThe atmospheric concentration of methane has increased by about 140 per cent since the middle of the 19th century. The residence time for a methane molecule in the atmosphere is merely about ten years and this implies that stabilisation at the present concentration can be achieved within a decade or two by decreasing emissions by about 10 per cent. The prime source for enhanced methane concentrations is husbandry and rice cultivation. In view of the increasing demand for food for a growing world population it does not seem likely that this source of emissions can easily be reduced. Leakage from coal mines and from the exploitation of gas and oil fields also result in considerable emissions. The slow down of the rate of increase of atmospheric concentrations during the last decade might at least to some extent be a result of reducing this leakage. The enhancement of the emissions of nitrous oxid and the increase of atmospheric concentrations so far by 12 - 15 per cent is primarily the result of the use of nitrogen fertilisation in agriculture and forestry, but is also produced in modest amounts in combustion processes. Nitrous oxide is destroyed by photo-chemical reactions, which, however, are slow. Its residence time in the atmosphere is therefore about 150 years. Because of the slow turn-over of fixed nitrogen in the terrestrial ecosystems, present emissions are still a response to the increasing use of fertilisers during the last half century or more and it will take time until it will be possible to reduce human-induced emissions. Neither is it therefore likely that atmospheric concentrations can be stabilised before 2100. Most other greenhouse gases, such as those that have been included in the Kyoto Protocol, also have long or very long residence times in the atmosphere. Their atmospheric concentrations cannot either be easily stabilised, but the measures taken to drastically reduce the use of CFC-gases also slows down the rate of climate change, but not very much so. Developed and Developing CountriesThere are very major difference between developed and developing countries with regard to their use of energy and emissions of carbon dioxide. A little more than 20 per cent of the world population live in Annex-1 countries, and their average emissions per capita is about 2.9 ton C year-1. Average emissions by Non-Annex-1 countries, on the other hand, is only 0.5 - 0.6 ton C yr-1. There are also large differences amongst nations. For example, the per capita emissions by USA, Sweden and China are about 5.5, 1.7 and 0.7 ton C year-1 respectively. These differences obviously provide a very strong argument for developing countries to demand that the developed world takes the lead in reducing their use of fossil fuels. This circumstance is a prime reason why the Kyoto protocol include specific targets for reductions of emissions by developed countries by 2010, while there are no formal quantitative restrictions imposed on developing countries. As can be concluded from our discussion and table 1, it is not likely that this difference between developed and developing countries will have been reduced much by 2010. While the figure for developed countries might have decreased slightly to about 2.8 tons of C per capita year-1, developing countries would probably not yet have increased much above 0.7 ton C per capita year-1, partly because of a still ongoing population increase of more than 1.5 per cent year-1. It should also be recalled that the present global average of the per capita emissions of carbon from fossil fuels burning are about 1.1 ton C year-1, if also including emissions as a result of land use and changing land use, most of which the global value is rather about 1.3 tons C per capita. It is then of interest to project the changes of the global carbon emissions per capita, based on the emission profiles for the stabilisation at alternative levels as given in figure 1 and the projected growth of world population, figure 2. The dashed curves show the limitations of the emissions, to stabilise at 750, 650, 550 and 450 ppm. Focussing again on the 550 ppm-curve, we note that the global per capita emissions must not much exceed the present value (~1.1 tons year-1) during the next half of the 21st century, see This implies that developing countries would never on average have the opportunity to base their energy supply for economic development on fossil fuels to the extent that has been the case for the industrialised world, even if energy would be used much more efficiently in the future. Even a marked reduction of the use of fossil fuels by developed countries to nil would not suffice. This is the result of the limitations imposed by Nature on its exploitation for human purposes as well as the continuing population increase in developing countries.
The main difficulty encountered when trying to replace the fossil fuels by renewable energy sources is of course the increasing costs for energy. Few other sources for prime energy can as yet compete. It will therefore obviously be necessary to use economic policy instruments in order to achieve a switch over to non-carbon emitting energy sources. The use of taxes or tradable emission permits are presently being considered. For obvious reasons this is not seen favourably upon by oil- and gas-producing countries. OPEC might therefore strive for rising their export prices to increase profits and in that way also contribute to reducing the use of fossil fuels, rather than letting the importing countries regulate the use of fossil fuels internally. Their fossil fuel resources and reserves would also last longer. This would require a powerful cartel, that for obvious reasons would be resisted by other countries. One may wonder if the present volatile oil market to some extent might be the result of such considerations and efforts. The present total proven reserves of conventional oil and natural gas contains approximately 250 Gt C, which is about equal to the total emissions from burning fossil fuels so far including the use of coal. This total amount can and probably will be used in spite of the restrictions imposed by the mitigation of a climate change, provided there would not be a rapid increase of the use of coal during this century.
Finally a few comments about the use of fossil fuels today. The schematic diagram in figure 3 shows the annual flow of energy and its use in the world society during the early 1990s (in EJ) and the associated annual emissions of carbon dioxide (in G). One notices that about one third of the emissions are associated with the conversion of primary to secondary energy, which is above all the result of producing electricity in power plants fuelled by coal, oil and natural gas. Few of these are built for co-generation of electricity and heat. This would obviously be an important opportunity for using primary energy more efficiently than today.
Losses are also encountered, when transferring electricity over long distances. Technological innovations to minimise these losses would of course contribute to making, for example, energy produced from solar radiation available far away from the source. This might imply a possibility to import electricity from sunny North Africa into the southern and central parts of Europe.
In spite of the increasing efficiency of energy end-use during the 20th century much more can still be done, not the least in the process industry. Nevertheless, the emerging newly industrialised countries will have increasing demands for energy, even if the more efficient use of energy as developed in industrial countries would be taken advantage of. It is obviously necessary to bring in new sources for the supply of primary energy. Nuclear energy is being used increasingly in some few nation, but the prospect of a more wide-spread use of nuclear energy still seems slim, for both safety and political reasons.
The most rapidly expanding use of fossil fuels takes place in the transport sector, particularly so in developed countries. Increased mobility is high on the priority list, when economic development has lead to a reasonable standard of living and the basic needs with regard to housing, food and clothing have been met. The number of cars is increasing through-out the world and fuel for the transport sector is the most rapidly increasing use of fossil fuels in developed countries. Air traffic increases by about 5 per cent per year.
It is and will be a slow process to get to grips with the climate change issue. The effects of a climate change cannot yet be seen clearly. The recent catastrophes as a result of storms, floods and droughts cannot yet be interpreted as a consequence of a global warming, even though the increasing humidity in the atmosphere implies that more energy is available in the atmosphere, whenever a storm is form and starts to grow. Major changes in society do usually not come gradually, but rather as paradigm shifts or in the worst case as catastrophes. I believe that the rapidly increasing awareness about the threats that we are being exposed to will lead to sufficiently far-reaching measures being taken early and that a development towards sustainability will be possible.
Bolin, B.: "The Kyoto Negotiations on Climate Change: A Scientific Perspective", Science, 1998, vol. 279, p. 330-331.
Houghton, R.A.: "The Annual Net Flux of Carbon to the Atmosphere from Changes in Land Use 1859-1990", Tellus, 1999, vol. 51B, p. 298-313.
Houghton, R.A.; Skole, D.L.; Hackler, J.L.; Lawrence, K.T.; Chomentowski, W.H.: "Annual Fluxes of Carbon from Deforestation and Regrowth in Brazilian, Amazon", Nature, 2000, vol. 403, p. 301-304.
IPCC: Climate Change 1994, Radiative Forcing and Climate Change, and an Evaluation of the IPCC Emissions Scenarios, IPCC, 339 pp, Cambridge University Press, 1994.
IPCC: Climate Change 1995, Part I: The Science of Climate Change, 572 pp; Part II: Impacts, Adaptations and Mitigation of Climate Change, 878 pp; Part III: Economic and Social Dimensions of Climate Change, 448 pp, Cambridge University Press, 1996.
IPCC: Special Report on Land Use, Land-Use Change, and Forestry, Cambridge University Press, 2000.
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