Researched and written by Bill Hare
Climate Policy Director, Greenpeace International
Greenpeace International
Greenpeace International
Keizersgracht 176
1016 DW Amsterdam
The Netherlands
Phone: +31 20 5236222
Fax: +31 20 5236200
The Carbon Logic
Researched and written by Bill Hare
Climate Policy Director, Greenpeace International
Greenpeace International
Greenpeace International
Keizersgracht 176
1016 DW Amsterdam
The Netherlands
Phone: +31 20 5236222
Fax: +31 20 5236200
Preventing dangerous climate change will involve limiting both the rate and magnitude of climate change over the next century to levels that natural and human systems can tolerate without significant damage. This report shows the implications for overall fossil fuel use, in the form of a `carbon budget', over the next century if the global community is to prevent dangerous climate change.
It is demonstrated that it is only possible to burn a small fraction of the total oil, coal and gas that has already been discovered, if such dangerous changes are to be avoided. Even the reserves of fossil fuels that are considered economic to recover now, with no advances in technology, are far greater than the total allowable `carbon budget'.
This conclusion is shown to be robust to a wide range of assumptions about how sensitive the climate is to human interference, and the levels of change that might be considered unacceptable or dangerous.
Comparison of the `carbon budget' with projections of possible future energy sources nevertheless suggests that such a target is both technically and economically feasible.
W.L. Hare
Climate Policy Director
This paper calculates a carbon budget for a given set of ecological constraints on climate change over the next century. The carbon budget concept has the capacity to shed significant light on the implications of current fossil fuel policy for long term climate policy objectives. It can also provide some novel insight into the debate over whether or not the world is facing an oil shortage, by comparing an allowed carbon budget against estimates of available oil.
In the international policy context the idea of carbon budget makes clear the choices that developed and developing countries face in the current round of climate negotiations. The more fossil fuel that developed countries use now (i.e. the slower they reduce emissions) the less may be left over for developing countries if climate goals are to be met.
Each year the world releases approximately 6 billion tonnes of carbon (gigatonnes or GtC) in the form of carbon dioxide (CO2) from the burning of fossil fuels - coal, oil and gas. These emissions have increased at around 2% per year over the past several decades. CO2 is the major greenhouse gas and its significance is likely to grow over the next century. Fossil fuel use was responsible for nearly 60% of greenhouse gas emissions in 1990.
In the absence of action to reduce CO2 emissions, around 1,500 GtC are likely to be emitted over the next century. Deforestation may contribute 30-95 GtC of this, with the rest being from the use of coal, oil and gas. Over the next century human activities are likely to add some 4-10 times more fossil carbon to the atmosphere than has been added since the industrial era began.
In broad terms, reserves of oil, gas and coal identified as "economically recoverable" total over 1,000 GtC. Economically recoverable "reserves" are expanding due to oil, coal and gas exploration and technical development. The "resource base" that could be ultimately brought into reserves is well over 4,000 GtC.
Estimates of economically recoverable reserves of fossil fuels range from 829 GtC to 1,501 GtC. Coal predominates in the reserve estimates, totalling 638-1,034 GtC. Conventional oil and gas reserves are much smaller by comparison, but still total 182-205 GtC. Unconventional reserves of oil and gas, which are likely to be economically recoverable, total a further 133-262 GtC.
At present, if one compares fossil fuel reserve estimates with future CO2 emission scenarios in the absence of climate policies to the year 2100 then only at the upper end of these estimates are there `enough' economically recoverable reserves of fossil fuels. This does not tell the full story however as there are over 4,000 GtC of fossil fuel resources, which with ongoing technical advances are likely, over time, to become economically recoverable.
It seems clear that if productivity gains in the fossil fuel industry continue at historical rates in the future, there is unlikely to be a shortage of fossil fuels - coal, oil or gas - over the next century. The analysis in this report shows that environmental considerations will have to limit the use of fossil fuels well before technical scarcity becomes a limiting factor.
The more investment that occurs in the exploration and technical development of resources ( or of marginal reserves) the more of these will be converted to reserves (i.e. classified as economically recoverable). Investment in further exploration and development of oil, for example, will be conditioned by market expectations of the future demand. If markets expect increasing demand in the future then investments are likely to be made in "expanding" the reserves available. If, as is concluded in this report known, economically reserves of fossil fuels already exceed ecological limits then such investments by the market would be unnecessary and unwise.
One of the policy implications of this situation is that governments need to act urgently to curtail market expectations of increasing use of fossil fuels. Government encouragement of fossil fuel use through direct and indirect subsidies and the issuing of exploration licenses will only lead to more exploration and development of fossil fuel reserves. Failure by governments to act now to curtail market expectations of future fossil fuel demand can only impose higher political and economic costs on future generations' attempts to constrain the amounts of fossil fuels exploited in order to protect the climate system.
The 1992 UN Framework Convention on Climate Change makes staying within ecological limits its central objective. Its ultimate objective is to stabilize greenhouse gas concentrations at a level that would prevent dangerous human interference with the climate. And further, it requires that this be done fast enough so that ecosystems can adapt naturally to climate change and food production is not threatened.
In 1990 a United Nations Advisory Group on Greenhouse Gases recommended global targets for the maximum rates and total amounts of temperature and sea-level rise as a consequence of the emissions of greenhouse gases. In other words, what level of change nature can tolerate, or "ecological limits". Temperature increases above 1.0oC above pre-industrial levels could bring about rapid and unpredictable changes to ecosystems, leading to large damages. In addition, the rate of increase of global mean temperature was found to be a major determinant of damage. A rate of increase above 0.1oC/decade could lead to major ecosystem damage as well as an increasing risk of climate instabilities.
A sea-level rise of 20 centimetres (cm) above 1990 levels was found to be a threshold of significant damage. Further, it was found that whilst a 50 cm sea-level rise limit above 1990 levels may possibly prevent the complete destruction of many island nations it would lead to large increases in the damage caused by storms.
The findings of the Intergovernmental Panel on Climate Change (IPCC) and other scientific developments over the past seven years have tended to reinforce the validity of the global targets for climate change described by the UN Advisory Group on Greenhouse Gases.
An equivalent doubling of CO2 over pre-industrial levels, which could occur between 2030 and 2040, is likely to cause dangerous climate changes.[1] The projected damages include significant loss of human life from the direct and indirect effects of climate change, a loss of biodiversity and, under highly optimistic assumptions, a further 60-350 million more people placed at risk of hunger, predominantly in developing countries. For a 50 cm increase in sea-level, which is projected over the next century, there could be a dramatic increase in the number of people at risk of flooding, loss of small island countries and significant impacts on rice production in Asia.
In the very long term (i.e. several centuries) an equivalent doubling of CO2 is estimated to raise sea-level by over a metre and probably increase the global mean temperature by around 3.5oC (using the estimate for climate sensitivity to greenhouse gases adopted in this report).
For increases in greenhouse gas concentrations lower than doubling large damages are still predicted. One study has shown that stabilizing CO2 at 450 ppmv would lead to a temperature increase of 1.7oC above pre-industrial levels and a sea-level rise of 29 cm by 2100. About one quarter of natural vegetation would be threatened and there is likely to be significant impacts on agricultural production in many regions.
Major changes in the earth's forests are projected for only a 1oC increase in global mean temperature, leading to very large changes and the possible disappearance of entire forest types.
It has been shown that many of the projected impacts of future emissions are only avoidable if action is taken early. A "safe emissions corridor" analysis has shown that large emissions reductions are needed to avoid ecologically dangerous climate changes.
The rapidity of the current increase in greenhouse gas concentrations could lead to major climate instabilities. A permanent shut down of the ocean thermohaline circulation (of which the Gulf stream is a part) has been projected as possibility. A weakening (or shutdown) of the thermohaline circulation would lead to CO2 concentrations increasing faster than expected and would lead to some very significant regional climate changes.
Projected climate change, if not controlled, could lead to some major feedbacks (i.e. amplifications of changes) which would make it difficult if not impossible to prevent dangerous climate change. Large amounts of carbon, relative to human emissions, may be released into the atmosphere from forests in response to changing climate. The response of the oceans could also have a big impact on future CO2 concentrations, leading to atmospheric CO2 concentration being higher than the IPCC has estimated.
Overall the likely effect of feedbacks from the terrestrial biosphere (e.g. forests) and oceans over the next century may be to amplify human induced climate change and reduce the amount of fossil carbon (and hence the carbon budget) that can be emitted for any given set of climate targets.
Since 1990 the IPCC has adopted a `best-estimate' of the warming that would occur if CO2 concentration is doubled and the climate allowed to stabilize (i.e. the climate sensitivity) of 2.5oC, with a range of 1.5-4.5oC. Scientific evidence is increasingly pointing towards a higher sensitivity than the IPCC `best-estimate'.
A climate sensitivity in the range of 3-4oC appears to better fit observations than 2.5oC when the combined effects of greenhouse gas concentration increases, sulphur aerosols and solar irradiance changes are taken into account. The most advanced climate models reviewed in the IPCC Second Assessment Report have climate sensitivities in the range 2.1-4.6oC with the median of the models being around 3.7oC.
A higher climate sensitivity magnifies the risk created by an increase in greenhouse gas concentrations and also reduces the `carbon budget' for any given set of global climate targets.
From a precautionary policy perspective it would be prudent to base climate policy on a higher climate sensitivity than that adopted by the IPCC as its `best-estimate'. For this reason, throughout this work 3.5oC will be used as the central estimate for policy purposes.
Scientific uncertainties in relation to the explanation of sea-level rise observed over the past century have grown in the past decade rather than narrowed. The direction of these uncertainties is sufficient to raise serious concern that the risks of large, long term, irreversible sea-level rise as a consequence of the effects of greenhouse warming on the West Antarctic Ice Sheet, and to a lesser extent the Greenland Ice Sheet, have been underestimated.
Projected climate change over the next century will almost certainly breach the ecological limits described above if action is not taken to reduce emissions. In 1995 the Intergovernmental Panel on Climate Change (IPCC) found that global mean temperature has already risen 0.3-0.6oC above pre-industrial levels. Projected rates of increase of global temperature due to existing and forecast emissions are expected to be 0.2-0.3oC per decade over the next few decades. The rates of change over the next century are likely to exceed any in the last 10,000 years. In the absence of action to reduce emissions global temperature is likely to increase by about 2.4oC and sea-level by approximately 50 cm above 1990 levels by 2100, based on IPCC best-estimates of climate science. With the climate sensitivity adopted in this work the warming is likely to be more than 3.0 oC above the pre-industrial global mean temperature and sea-level rise 55-60 cm above 1990 levels.
These projected changes are well above the levels identified as likely to lead to significant ecosystem damage and are likely to lead to damages to food production in the most vulnerable parts of the world. There is also likely to be a significant loss of human life from the indirect health effects of climate change.
Given this situation Greenpeace believes that the overall goals for global climate protection should be to:
* Limit the long term committed increase of temperature to less than 1oC above pre-industrial global average temperature.
* Bring the rate of change to below 0.1oC per decade as fast as possible - i.e. within a few decades.
* Limit the long term sea-level rise to less than 20 cm above 1990 levels
* Limit the rate of sea-level rise to below a maximum of 20mm/decade
Greenpeace recognises that any attempt to quantify future climate change impacts is fraught with uncertainties. However, this cannot be used to justify inaction, but instead means that the precautionary principle must be urgently applied. The extent of human interference with the climate system means that potential catastrophic changes beyond those considered here are always possible and will become more likely the longer action is delayed.
A `carbon budget' - i.e. the total emissions to the atmosphere of carbon dioxide (taking into account the mix of greenhouse gases of which CO2 is most important) - can be calculated on the basis of the ecological targets. What actually happens to the climate can only be significantly affected by changes (i.e. major reductions) in emissions of greenhouse gases, both in total (for example taking "long term" as being up to 2100) and in terms of the "pathway" or trajectory that emissions take, e.g. how much is emitted sooner, or later. Calculating the `carbon budget' requires assumptions to be made about several factors including how sensitive the climate is to human interference, the role of other greenhouse gases and what level of damage is acceptable.
Taking the climate sensitivity to be 3.5oC, with a limit of a 1oC increase in global mean surface temperature above pre-industrial levels and assuming that other greenhouse gases contribute about one quarter of the effect of CO2 alone in the long term, the `carbon budget' over the next century can be estimated in terms of billions of tonnes of carbon ( GtC). With these assumptions, the `carbon budget' is:
* 145 GtC - With no action to stop current trends of deforestation (as forests release carbon when destroyed), with 80 GtC emitted from this source over the next century.
* 225 GtC - With major action to halt deforestation, stabilising the role of forests at current levels, which would involve a significant global reafforestation programme next century.
* 265 GtC - With major action to halt deforestation and a major global afforestation programme to sequester (take up) an extra 40 GtC.
There is an uncertainty of around 50% associated with these budgets deriving from uncertainties in the climate sensitivity, the role of other greenhouse gases, in the carbon cycle models and other factors.
It should be noted that limiting the long term temperature rise may mean getting back below a 1.0oC increase above pre-industrial levels as it may not be possible to avoid a rise of 1.0oC. Because of the lag between temperature rise in the air and the thermal expansion of the sea, it is still possible to avoid breaking the limit for sea-level rise if fast enough action is taken.
The central estimate of the `carbon budget' of 225 GtC is only about a quarter of existing reserves and is a very small fraction (5%) of the estimated resource base of oil, coal and gas.
The climate effects of this budget, based on the climate sensitivity adopted in this report, are such that the global mean temperature is calculated to peak at 1.4oC above pre-industrial levels and then decline reaching around an increase of 1.2oC by 2100. In the absence of climatic surprises the temperature would continue to decline slowly and fall below the long term limit of 1oC in the 22nd century. Sea-level would rise by about 20 cm by 2100 (based on IPCC best estimates of sea-level rise parameters).
See main body of report for description of assumptions. The climate sensitivity used throughout this report is 3.5oC.
Greenpeace advocates a precautionary approach to environmental protection. However, it is worth exploring the effect on the `carbon budget' of different assumptions about the sensitivity of the climate system, and different views on the limits that should be set to climate change.
The European Union has proposed that global temperatures should not be allowed to exceed a 2oC increase above pre-industrial levels. With a 3.5 oC climate sensitivity and with the deforestation assumption used in the central estimate this would require that total fossil fuel emissions be below 410 GtC over the next century. However, a
2 oC warming was identified by the Advisory Group on Greenhouse gases as an upper limit beyond which the risks of grave damage to ecosystems increases rapidly. Yet the carbon budget for this limit is less than 40% of known economically recoverable reserves of fossil fuels - oil, coal and gas is less than 10% of the resource base.
Avoiding an equivalent doubling of CO2 concentration, with the same assumption as above would require the total fossil fuel emissions over the next century to be less than 720 GtC. This is about 70% of economically recoverable reserves of oil, coal and gas and less than one fifth of the total fossil fuel resource base. Further, it is only one half of what the world is likely to burn in the absence of action on climate change in the next century. Allowing a doubling of CO2 would lead to major damages including significant loss of human life from the indirect and direct health effects of rapid climate change, increasing hunger and famine in several parts of the world and major damage to ecosystems. Furthermore, economic losses from climate impacts would increase from an increase in extreme weather events such as floods, droughts and forest fires.
If all the currently estimated fossil fuel reserves were burnt over the next century this could lead to a long term increase in global mean temperature of over 5oC above pre-industrial levels when the effects of other greenhouse gases are taken into account[2].
The central IPCC business as usual scenario for fossil fuel use over the next century projects the release of approximately 1,415 GtC into the atmosphere by 2100. This would lead to a global average increase of around 2.5-2.9oC above pre-industrial temperatures by 2100 (with 2.5 oC climate sensitivity). The longer term (equilibrium) increase in global mean temperature corresponding to the greenhouse gas concentrations in 2100 resulting from this scenario, would be over 4 oC or 5.6 oC with a 3.5oC climate sensitivity.
Even if more `optimistic' scenarios are used, the logic of an immediate start to a fossil fuel phase out remains. For example, to keep to the 1.0oC limit, a 225 GtC budget results from assuming a 3.5oC climate sensitivity. A 295 GtC budget results from assuming a 2.5oC climate sensitivity. This is still far less than fossil fuel reserves. The EU's global objective of keeping the global average increase in temperature below 2.0oC above pre-industrial levels implies a `carbon budget' of 410 GtC with a 3.5oC climate sensitivity and 585 GtC with a 2.5oC climate sensitivity.
The estimated carbon budgets are vastly exceeded by known fossil fuel reserves, and are even exceeded by known oil and gas reserves. A phase out of fossil fuels therefore logically follows.
An urgent start is required for several reasons:
* To meet ecological targets for rates of sea-level and temperature rise.
* At current rates of fossil fuel use a 225 GtC budget will be exceeded in about 30 years globally (2025).
* At historic rates of increase in fossil fuel emissions (about 2%/yr.) a 225 GtC budget would be exceeded by around 2020.
* Energy planning and infrastructure is long term and major change is required (switching to renewable energy and energy efficient technologies).
* Industrialised countries will be required to give a lead to other countries and begin a phase out sooner.
* Climate change may proceed faster as a result of "surprise" positive feedbacks not included in models. The longer action is delayed, the more likely climate catastrophes are to occur. these could include, for example, a shift in the ocean currents that presently warm Europe; a collapse of part of the Antarctic ice sheet causing a massive rise in sea-levels; a shift in the monsoon having major impacts on agriculture in Asia. Such catastrophes, once triggered, are effectively irreversible.
Some of the key implications for policy flowing from the limited `carbon budget' are:
* Coal use needs to be phased out as rapidly as possible as it has the highest carbon intensity of the conventional fossil fuels and the largest reserves. Only a small fraction of the economically recoverable reserves can ever be used.
* There should be no further exploration and/or technical development of unconventional oil and gas reserves. Estimated economically recoverable volumes of gas and oil in this category are sufficient alone to breach the `carbon budget'.
* There will need to be immediate and significant constraints placed on the technical development and exploration of known oil and gas reserves. Volumes in these reserves, particularly when taking into account the process of reserve appreciation following technical developments, are sufficient already to breach the `carbon budget'.
This is the carbon logic. The inescapable conclusion, and Greenpeace's immediate call for action is for national governments in industrialized countries to:
* Adopt legally binding obligations to reduce their CO2 emissions by 20% on 1990 levels by 2005 at the Third Conference of the parties of the Framework Convention on Climate Change in Kyoto in December 1997.
* Adopt national policies to substantially reduce emissions of CO2 and other greenhouse gases.
* Stop plans to allow the expansion of exploration for oil and gas reserves.
* Stop all technical and other developments that would facilitate the exploitation of unconventional oil and gas reserves.
* Begin the phase out of coal power stations and coal mining.
Further exploration and development of fossil fuel resources by industrial nations should be halted immediately, as it makes the problem worse and more difficult to solve and is a waste of money that should be invested in clean energy.
1.1.1.1.1.12.1 Acknowledgments
The author would like to acknowledge with thanks the comments and advice from several workers in the preparation of this paper. Dr. Helen Wallace provided extensive and constructive review comments at each stage. Dr. Dan Lashof made crucial suggestions at an early stage in this work and provided review comments on earlier drafts. Corine Veithen and Kalle Hesstvedt also provided helpful comments on review drafts. Heather Broadbent, Karen Brouwer and Angela Congedo helped with editing and production of the report.
1.1.1.1.1.12.1.1 Bill Hare, Amsterdam
September 1997
1.1.1.1.1.12.2 Fossil Fuels and Climate Protection - The Carbon Logic
[1] Equivalent doubling of CO2 means an increase of all the greenhouse gases - CO2, methane, nitrous oxides - to a concentration equivalent to a doubling of CO2 (about 560 ppmv). This would obviously mean a lower level of actual CO2
[2] Assuming the climate sensitivity is 3.5oC, the radiative forcing of other greenhouse gases adds 23% to that of CO2 alone and atmospheric concentrations of greenhouse gases remain constant at the level reached when this volume of carbon is emitted to the atmosphere. Setting the climate sensitivity to 2.5oC would reduce the long term warming to around 3.6oC with the same assumptions.