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Background on Impacts, Emission Pathways, Mitigation Options and Costs The 2°C target Information Reference Document S UB 1 Information Reference Document Prepared and adopted by EU Climate Change Expert Group ‘EG Science’ th Final Version, Version 9.1, 9 July 2008, 16:15 With contributions to earlier drafts from: Terry Barker, Outi Bergall, Svante Bodin, Martin Cassel-Gintz, Steve Cornelius, Eric De Brabante, Ursula Fuentes, Hans-Martin Füssel, Marc Gillet, Benno Hain, William Hare, Ger Klaasen, Brigitte Knopf, Katrine Krogh Andersen, Gunnar Luderer, Ben Matthews, Frank McGovern, Malte Meinshausen (Ed.), Pauline Midgley, Klaus Radunsky, Jože Rakovec, Stefan Rösner, Tom van Ierland, David Warrilow, Martin Weiss. 2 Summary This paper outlines the scientific background for the EU climate protection target - the 2oC limit - established by the EU Governments in 1996 and reaffirmed since then by the Environment Council 2003, and European Council, 2005, 2007. The paper also identifies how this target may be achieved through global action. The Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR4) indicates that the global mean temperature increase 1 provides an important common metric for analysis of many climate change impacts associated with global warming. In highly vulnerable areas, such as parts of Africa, Asia and small island states in the Pacific and the Caribbean, serious regional impacts are already occurring. Significant global impacts on ecosystems and water resources are likely at global temperature rises of between 1 and 2°C, and the risks of net negative impacts on global food production occur at temperature increases upwards from 2-2.5°C, compared to pre-industrial levels. Analysis of current atmospheric greenhouse gas (GHG) concentrations indicates that only a narrow window of opportunity exists to ensure that these serious negative effects can be avoided. Within the next 10 to 15 years, global GHG emissions need to be shifted to a pathway consistent with the 2°C target. This can be achieved with technologies that already exist or are being developed, provided the appropriate incentives are given. However, the necessary departure of emissions from the present business-as-usual trends implies, on a global scale, immediate and substantial investment in these low-carbon technologies. The IPCC AR4 indicates that, up to 2050, substantial global emission reductions by at least 50% below 1990 levels are needed with additional global emission reductions beyond 2050 towards a zero carbon economy by the end of the century. Recent work on mitigation costs indicates that meeting the 2°C target could be achieved with GDP losses of at most 2.5% by 2050 (reducing annual growth by at most 0.05%/year), and with lower costs for earlier years. When taking into account co-benefits in terms of air pollution reduction, net costs could be significantly lower. The costs of actions to mitigate climate change are small when compared to the relative costs of impacts due to inaction. 1 A global mean temperature rise implies higher warming over land than over oceans, with the tropical regions warming least and the northern polar region warming the most. 3 Key Messages 4 • Negative effects of climate change are already observed at the current global mean temperature increase of 0.8°C above preindustrial levels. • Global mean temperature increases of up to 2°C (relative to preindustrial levels) are likely to allow adaptation to climate change for many human systems at globally acceptable economic, social and environmental costs. However, the ability of many natural ecosystems to adapt to rapid climate change is limited and may be exceeded before a 2°C temperature increase is reached. • A global mean temperature increase greater than 2°C will result in increasingly costly adaptation and considerable impacts that exceed the adaptive capacity of many systems and an increasing and unacceptably high risk of large scale irreversible effects. • In order to have a 50% chance of keeping the global mean temperature rise below 2°C relative to pre-industrial levels, atmospheric GHG concentrations must stabilise below 450ppm CO2 equivalence. Stabilisation below 400ppm will increase the probability to roughly 66% to 90%. • Current atmospheric GHG concentrations and trends in GHG emissions mean that these concentration levels may be exceeded. The 2°C target can still be achieved if this overshoot of concentrations is only temporary and reversed quickly. Thus, to avoid a warming in excess of 2°C, global GHG emissions should peak by 2020 at the latest and then be more than halved by 2050 relative to 1990. • Deep emission reductions can be achieved by employing a broad range of currently available technologies and technologies that are expected to be commercialised in coming decades. • Deployment requires clear, consistent and effective policies and incentives. • Action needs to be taken very urgently as inertia in both the climate and socio-economic systems means that mitigation actions and low-carbon investment decisions are needed now in order to avoid lock in of carbon-intensive technologies. • The costs of climate change impacts are directly related to their magnitude which increases with global temperature and may be between 5 and 20% of GDP or even higher in the long-term. • The costs of actions to mitigate climate change are small when compared to the relative costs of impacts due to inaction. • Some of the costs of impacts can be reduced through investment in adaptation. • According to recent studies, mitigation needed to meet the 2°C target is projected to cost at most 2.5% of global GDP in 2050 (reducing annual growth by at most 0.05%/year) if policies are designed in a cost-effective way. These costs are reduced significantly when co-benefits (i.e. reduction in air pollution health damage, air pollution control costs and energy security) are included. • Such mitigation, via a portfolio of coordinated policies including a long-term carbon price and the recycling of tax/auction revenues to promote low-carbon technologies and to improve market efficiencies, could even lead to global GDP gains (above those due to avoided climate impacts). 5 Table of Contents SUMMARY 3 KEY MESSAGES 4 TABLE OF CONTENTS 6 IMPACTS AND VULNERABILITIES 12 EMISSION PATHWAYS 26 MITIGATION OPTIONS 38 ECONOMICS OF CLIMATE CHANGE 44 CONCLUSIONS 51 APPENDIX 1 (REFERENCES) 52 APPENDIX 2 54 6 7 The ultimate objective of the UN Framework Convention on Climate Change (UNFCCC) as stated in Article 2 is to stabilise atmospheric greenhouse gas (GHG) concentrations at a level that would prevent dangerous 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 EU considers that this objective would be achieved by limiting GHG concentrations to levels that would keep the increase of global mean temperature below 2oC relative to pre-industrial temperatures 2 . This view is based on the assessment of the impacts and risks expected to occur, or to which the world would be committed as the global mean temperature approaches 2oC above pre-industrial temperatures, as well as those that are expected to occur if the global temperature increases beyond this level. The EU’s global temperature target of 2°C above pre-industrial was first established in 1996 during preparations for the Kyoto negotiations, and has been reaffirmed subsequently in various Environment Council and European Council conclusions. This limit was deduced in 1996 from the evidence available at the time, mostly from impacts studies that were assessed in the Second Assessment Report of the Intergovernmental Panel on Climate Change (IPCC SAR, 1996a,b,c). However, such studies tended to look only at the impact of doubling CO2 from preindustrial levels to 550ppm. A further consideration in setting a limit was the concern that rates of change needed to be limited to less than 0.1°C per decade in order to allow ecosystems time to adapt. Since then, the information provided in the IPCC’s Third Assessment Report (IPCC TAR, 2001a,b,c,d), and developments in the scientific literature and in peer reviewed publications such as “Avoiding Dangerous Climate Change” (Schellnhuber et al., 2005) supported and advanced the scientific basis for the assessment of impacts and risks that underpin the adoption of the 2oC target and confirms our view that 2oC is an appropriate target. The IPCC’s Fourth Assessment Report (hereafter: IPCC AR4), the Stern Review Report on the Economics of Climate Change (Stern, 2006) and the European Commission communication “Limiting Global Climate Change to 2 degree Celsius” (European Commission, 2007a) provide further and improved scientific, technical and socio-economic analyses. The comprehensive analyses and new findings in these reports are the main sources for the information contained in this paper. 2 8 Pre-industrial being defined as 1850-1899 average global mean surface temperatures. The 2oC limit cannot be considered to be entirely ’safe’, as severe impacts are likely to occur increasingly as the global mean temperature rise approaches 2°C above pre-industrial levels. Changes in extremes such as heat waves, droughts and extreme precipitation events will largely shape future climate impacts. In particular, significant impacts are expected for species, ecosystems and water resources, low latitude agriculture, and small island states. The latter will be increasingly impacted by the direct and indirect effects of sea-level rise. Impacts are already being observed which are consistent with or which can be attributed to warming to date. This document provides an overview of the EU’s assessment of the climate change impacts underpinning the 2°C target (Chapter 2 “Impacts & Vulnerabilities”) and the implications for global emissions (Chapter 3 “Emission Pathways”). Achievement of the 2°C target implies ambitious global GHG emissions reductions and a rapid reversal of current trends of rising emissions. The wide technology portfolio available for reducing emissions is presented (Chapter 4 “Mitigation Options”). The necessary deep cuts in global emissions will likely have to draw on the widest possible range of reduction options. Finally, the most recent literature on the economics of mitigation are summarised (Chapter 5 “Economics of Climate Change”), highlighting once more that the costs of inaction are likely to far outweigh the costs of climate change mitigation. 9 10 • Negative effects of climate change are already observed at the current global mean temperature increase of 0.8°C above pre-industrial levels. • Global mean temperature increases of up to 2°C (relative to pre-industrial levels) are likely to allow adaptation to climate change for many human systems at globally acceptable economic, social and environmental costs. However, the ability of many natural ecosystems to adapt to rapid climate change is limited and may be exceeded before a 2°C temperature increase is reached. • A global mean temperature increase greater than 2°C will result in increasingly costly adaptation and considerable impacts that exceed the adaptive capacity of many systems and an increasing and unacceptably high risk of large scale irreversible effects. 11 Impacts and Vulnerabilities Anthropogenic emissions of greenhouse gases perturb the global climate system, resulting in an increase of global mean temperature, changes in weather and precipitation patterns and increased climate variability resulting in a higher frequency of extreme events. There is significant regional variation in climate change and its impacts. In general, warming will be stronger over land areas than over the oceans, and some continents and regions will be subject to larger changes than others. In many regions, current differences in the distribution of precipitation tend to be amplified, i.e. wet regions generally will become wetter and dry regions will become drier. In addition to the impacts mediated via the climate system, increased atmospheric CO2 concentration results in ocean acidification, which will have significant negative consequences for marine biology (WBGU, 2006). Global mean temperature is an important indicator for communication of the causes and consequences of climate change and provides a common metric for the assessment of impacts of global warming. However, the global average temperature does not capture the details of spatial variability and the large variety of effects that occur at regional and local levels. The global mean temperature has risen by approximately 0.8°C above pre-industrial levels 3 (IPCC AR4 WGI SPM). Unless otherwise stated, all temperatures given in this paper refer to changes of global mean temperature relative to pre-industrial levels. Many climate change related impacts, such as coral reef bleaching, glacier retreat and changes in the frequency of extreme weather events are already evident (IPCC AR4 WGII). These impacts are expected to intensify and become more widespread in the future. The intensity of climate change impacts will accelerate as temperatures increase (IPCC AR4 WGII) (see Fig. 2.1 and 2.2). Moreover, the uncertainty of climate change impacts increases substantially with increasing levels of global warming. 3 Here defined as temperature change since 1850-1899 (beginning of instrumental temperature records). At that time the anthropogenic influence was small compared to natural variation; th temperatures in the late 19 century are in good agreement (order of 0.1°C) with conditions before the onset of industrialisation in 1750. 12 Fig 2.1: Examples of global impacts in various sectors associated with different levels of climate change based on published studies. Boxes indicate the range of temperature levels to which the impact relates. Arrows indicate increasing impacts with increasing warming. Adaptation to climate change is not considered in this overview. The black dashed line indicates the EU objective of a 2°C temperature change relative to pre-industrial. Source and explanation of superscript references: please consult IPCC AR4 WGII, Fig. TS.3. 13 14 Fig 2.2 (previous page): Examples of global impacts in various world regions associated with different levels of climate change based on published studies. Boxes indicate the range of temperature levels to which the impact relates. Arrows indicate increasing impacts with increasing warming. Adaptation to climate change is not considered in this overview. The black dashed line indicates the EU objective of 2°C temperature change relative to pre-industrial. Source and explanation of superscript references: please consult IPCC AR4 WGII, Fig. TS.4. 2.1 Projected climate change: impacts in various sectors and reasons for concern The Fourth Assessment Report of the IPCC’s Working Group II (WGII), indicates that climate change will affect a wide variety of natural and anthropogenic systems in all regions (Fig 2.1 and 2.2). The IPCC AR4 strengthens and advances the risk assessments provided by the Third Assessment Report (IPCC TAR, 2001b). For a number of areas of concern, the assessed risks are higher in the AR4 compared to the TAR assessment, particularly at lower temperatures. If global warming is limited, many impacts of climate change can be addressed through effective adaptation. With increasing levels of climate change, however, there are fewer options for successful adaptation. There is very limited knowledge on the limits and costs of adaptation. Significant reductions in emissions to meet long-term mitigation goals substantially decrease the level of adaptation required. Ecosystems and species Increasing levels of climate change are associated with increasing pressure on ecosystems. Many ecosystems will not be able to adapt to the projected rates of change. Particularly vulnerable ecosystems include coral reefs, Arctic ecosystems, Alpine ecosystems and tropical forests, which are likely to be severely impacted at levels of global warming approaching 2°C. A global mean temperature increase exceeding 2-3°C would increase the risk of extinction for about 20-30% of species and have widespread adverse effects on biodiversity and ecosystems. Increases significantly above this range are projected to lead to significant extinctions of species and, at just above this level, widespread mortality for coral reefs. Global losses are irreversible; therefore the impacts on biodiversity are of key relevance. There is a still poorly understood risk that temperature increases above 2-3°C could cause major and irreversible damage to the Amazonian rainforest and its biodiversity and, as a consequence, exert a strong positive feedback on the climate system by turning Amazonia into a large carbon source. 15 Polar regions The world’s polar regions are particularly vulnerable to climate change. Decreasing snow and ice cover in the northern hemisphere has reduced the reflection of sunlight back to space, amplifying climate change effects in northern high latitude regions (IPCC AR4 WGI). A mean global temperature increase of 3°C by the end of the 21st century corresponds to an increase in annual mean temperature of 5-7°C in the central Arctic Ocean (IPCC AR4 WGI, Ch. 11.8.1). Winter Arctic temperature increases are projected to be four times higher than the global mean increase. The extent and depth of Arctic sea ice in the summer time is presently observed to be reducing rapidly, with 2007 producing record losses. Some of the IPCC AR4 generation of climate models projected summer ice to disappear almost completely by the end of the 21st century if the global temperature increases beyond 3°C (IPCC AR4 WGI, Box 10.1, Ch. 10.3.3.1). The likelihood of abrupt changes in Arctic sea ice increases significantly with increasing anthropogenic GHG emissions (IPCC AR4 WGI, Ch. 10.3.3). Observed sea ice losses significantly exceed the rate of ice loss projected by the coupled ocean atmosphere models (AOGCMs) participating in the IPCC AR4 assessment for the period 1953-2006 and there is increasing concern that summer sea ice may be substantially eliminated well before the end of the 21st century (Stroeve et al. 2007). The loss of Arctic sea ice is likely to strongly perturb atmospheric and oceanic circulation patterns, to threaten the existence of sea icedependent ecosystems and species, and to change the marine food chain as well as the living space of about two hundred thousand indigenous people. Based on the projected loss of sea ice in the AR4, the polar bear (Ursus maritimus) has been assessed as facing a high risk of extinction with warming of 2.8°C above pre-industrial (range 2.53.0°C) (IPCC AR4 WGII, Box 4.3, Table 4.1). Earlier loss of ice at lower temperatures would lower this temperature threshold. Water Already at current levels of global warming, significant changes in water resources are evident, and impacts in the water sector will become increasingly severe as both precipitation and evaporation will continue to be altered as a consequence of climate change. The numbers of additional people at risk of water stress are projected to increase substantially with increasing temperature from 0.4-1.1 billion for 1-1.5°C warming above pre-industrial levels to 1.1-3.2 billion for ca 3-4°C warming. Areas affected by drought will probably increase, and flood risk will increase due to the higher likelihood of extreme precipitation events (IPCC AR4 WGII, Box TS.5). Regions already suffering from water scarcity, such as southern Africa, north-eastern Brazil, southern and eastern Australia, the Mediterranean basin, and western USA, are projected to experience further reductions in water availability (IPCC AR4 WGII, Ch. 3). Sea level rise will lead to salinisation of groundwater, affecting water supplies in coastal regions. 16 More than one sixth of the world’s population live in snowmelt- and glacier-fed river basins and depend on these systems for water resources. These basins are subject to increased river runoff during the peak spring and summer melt time, causing structural damage and flooding. Whilst water flows increase at first with glacial melting, as glacier mass declines, melt and runoff will substantially decrease. This will result in substantially increased water stress in such regions, e.g. the Ganges basin which is home to about half a billion people. The timing of this decrease depends on the individual region and on the rate of warming and varies from one decade (Andes) to many decades (Himalaya). High mountainous/Alpine regions High altitude, mountainous and Alpine regions are undergoing major changes. Most mountain glaciers are receding rapidly. Many small glaciers are projected to disappear during the 21st century, while large glaciers will suffer a substantial reduction in volume. The duration and depth of snow cover is projected to change with global warming. As outlined above, changes in glaciers and snow cover will have a strong impact on the water sector in many regions. Melting permafrost due to rising temperatures will destabilise mountain walls and increase rock fall. Endemic Alpine biota are highly vulnerable to climate change, and their adaptive capacity is limited. There is a disproportionately high risk of extinction in various mountain ecosystems. Agriculture and food security Risks to food production and security are projected to differ greatly by region. Above a global temperature rise of 1.5 to 2°C there is an increasing risk of a decline in global food production. Even below this level, at lower latitudes, especially in the seasonally dry tropics, agriculture will be negatively affected by climate change with negative impacts on the yield of major cereal crops. Food security and agricultural incomes are likely to be under threat in many regions of Africa, Asia and Latin America. In mid- to high latitude regions, increases in local temperature of 1-3ºC are projected to lead to small increases in yield which are reversed for higher temperatures (IPCC AR4 WGII, Ch. 5.4, 5.6). Health Human health will be strongly affected by climate change. Severe heat stress has already caused loss of life in Europe (cf. Section 2.2) and other regions of the world. Even a moderate temperature increase well below 2°C is likely to result in negative impacts in the health sector such as increased burden from malnutrition, increased incidence of diarrhoeal diseases and many vector-, food-, and water-borne infectious diseases. In particular, it will lead to a net increase in the geographic range of malaria and dengue fever. At higher levels of global warming, the negative impacts in the health sector are projected to become more 17 severe. Adverse health impacts will be greatest in low-income countries (IPCC AR4 WGII, Ch.13.4.1). Extreme events Increases in global mean temperatures will result in significant changes in the intensity, frequency and location of extreme events such as heat waves, flooding, wildfire and tropical cyclones, even below 2°C rises in temperature. Greater warming is projected to further substantially increase the risk, frequency and intensity of many extreme events. Extended heat waves are projected to become more intense and frequent, adversely affecting human health, natural ecosystems, agriculture, and the power industry (IPCC AR4 WGII, Ch. 12.6.1). Heat and drought will also strongly increase the risk and severity of wildfires. Tropical cyclone intensity (peak wind speeds and precipitation) is projected to increase with increasing tropical sea surface temperatures, and hence with increasing levels of global warming (IPCC AR4 WGI, Ch. 3.8.3 and Box 3.5; WBGU, 2006, Ch. 3.1.2). Above a global warming of 2-3°C, a greater increase in winter rainfall in combination with a loss of winter snow storage will increase flooding in many regions. High levels of global warming also imply a strongly increased risk of dam bursts in glacial mountain lakes. Coastal zones, small islands, sea-level rise In the long term, an increase in sea level rise is likely to be one of the most severe and important consequences of global warming. The IPCC AR4 report projects a sea-level rise of 0.18–0.59 m until 2100. This range does not account for possible rapid changes in ice sheet flow due to processes not presently included in the ice sheet models that were used in the AR4 assessment, which would result in significant additional sea level rise. Semi-empirical projections of sea level rise based on observed rates of temperature and sea level change over recent decades indicate that there is a risk that the IPCC AR4 sea level estimates are biased on the low side. These projections give a sea level rise of 0.4-1.4 m by 2100 (Rahmstorf, 2007). Even if the global temperature is stabilised, sea level would continue to rise for many centuries to millennia due to the enormous thermal inertia of the oceans and the slow melting of major ice sheets. Higher levels of global warming will result in a larger rise in sea level. Sustained global warming greater than 1.5-2.5°C is a threshold beyond which there is likely to be a commitment to at least partial deglaciation of the Greenland ice sheet, and possibly of the West Antarctic ice sheet, causing sea level rise of 4-6 m over centuries to millennia. For global warming of 3°C, WBGU (2006, Ch. 3.1.1.4 and Table 3.1-1) projects the global sea level to rise by as much as 2.5-5.1 m by 2300. Coastal zones are home to about one fifth of the world’s population and population growth rates in these areas are very high. Sea level rise, possibly in combination with changing atmospheric circulation patterns, 18 will increase the risk of storm surges. Sea level rise also increases coastal erosion and has impacts on groundwater levels and ecosystems in coastal zones. Small islands are especially vulnerable to an increase in sea level. Distribution of impacts The impacts of climate change are not evenly distributed across regions and sectors. At global warming levels below 2°C, a few sectors in certain regions might benefit from climate change (e.g., agriculture and tourism in high latitude regions), while in most other regions and sectors effects are likely to be negative, and sometimes even severely so. For many countries, a 2°C warming limit may not be wholly safe. Generally, less developed areas are at greatest risk due to both higher sensitivity (e.g., small islands) and lower adaptive capacity (IPCC AR4 WGII, Ch. 19.3.7). Climate change is identified as a major obstacle to poverty reduction objectives and achievement of the Millennium Development Goals (IPCC AR4 WGII, 2007; Stern, 2006). In developed countries, the poorest also tend to be the most vulnerable to climate change (Stern, 2006). Climate change tends to increase differences in economic wealth both between regions of the world and within individual countries. Given that industrialised countries are responsible for a large amount of the GHG emissions and that emissions are strongly related to consumption, this raises issues of international and social equity. As temperature increases in excess of 3°C, there will be net negative impacts in developed countries and also even more severe net negative impacts in many developing countries (IPCC AR4 WGII, Ch. 19.3.7). Security and migration Climate change could, within a few decades, become a major threat to international security (WBGU, 2008). Climate change will add an additional burden to already existing pressures in relation to food security and water availability in many unstable regions, particularly in the developing world. Moreover, climate change is likely to increase storm and flood disasters. The population in already politically unstable states with poorly performing governments and institutions will be most affected, since climate change will overwhelm local capacities to adapt (WBGU, 2008). Climate change is likely to induce additional migration both within national borders and internationally. Europe and North America are likely to have to face substantially increasing migratory pressure, and this migration will likely become an additional source of destabilisation on national, regional and international scales. Economic impacts Many economic sectors and activities will be adversely affected by climate change (Stern, 2006). Current studies estimate that, for a global mean temperature of up to 2 to 3°C above pre-industrial levels, positive market impacts (such as increasing crop yields in higher latitude regions) 19 almost balance the negative market impacts of climate change, giving rise to aggregate impacts of plus or minus a few percent of global gross domestic product. However, positive impacts are not likely to be evenly distributed and most people, particularly in developing countries, would be negatively affected (IPCC AR4 WGII, Ch. 19.3.7). With further increases in global temperature, the net damages are likely to increase at a disproportionate rate (Stern, 2006). Cost estimates increase if nonmarket impacts are considered (Stern, 2006; IPCC AR4 WGII, Ch. 19.3.7). A more detailed discussion on the costs of climate change is provided in Section 5. 2.2 Projected effects for Europe The European Environment Agency (EEA), IPCC and other regional and national analyses have provided extensive analyses on the impacts of climate change for Europe (EEA, 2004; IPCC AR4 WGII, Ch. 12). The magnitude of impacts is expected to increase as global temperatures rise. Europe, however, may have the capacity to substantially reduce the adverse impacts outlined here by undertaking adaptation measures (European Commission, 2007b). Heat waves In 2003, large parts of Europe were affected by an extended heat wave. This resulted in about 35,000 heat-related excess deaths (IPCC AR4 WGII, Ch. 12.6.1). A similar but less intense heat wave occurred in the summer of 2006. Increased evaporation and lack of precipitation during these heat wave events threatened water resources, causing adverse impacts in many economic sectors. Crop losses, heat-stress on livestock and widespread forest fires resulted in losses in the agriculture and forestry sectors. Extremely low river flow rates resulted in disruption of inland navigation. In combination with high water temperatures, the low water levels in rivers also forced a reduction of electricity generation in thermal power plants which utilise water cooling. The frequency of such extremely dry summer conditions will increase at a disproportionate rate (IPCC AR4 WGII, Ch. 12.6.1). Such heat wave events will become much more severe and frequent even with a 2°C temperature increase. The conditions experienced in 2003 could become the norm for the latter part of the 21st century under a non-mitigation scenario (IPCC AR4 WGII, Ch. 12.6.1). Water sector Many climate change impacts are related to the water cycle. Climate change is projected to result in a significant perturbation of precipitation patterns in Europe, with the sharpest decreases projected for summer precipitation in southern Europe. In contrary, northern Europe is likely to experience a substantial increase in winter precipitation (IPCC AR4 WGII, Ch. 12.3.1.1). Whereas the models agree well on the spatial and seasonal patterns of precipitation change, large uncertainty remains 20 about its magnitude. For large parts of the Mediterranean, a decrease in summer precipitation of up to 30-45% (in some parts up to 70%) is projected for the end of the 21st century for a scenario corresponding to a global warming of 3-3.5°C. For Scandinavia, an increase in winter precipitation of 15-30% is projected (IPCC AR4 WGII, 12.3.1.1). Such a precipitation change would exacerbate existing water stress in southern and south-eastern Europe and increase the frequency of drought. In these regions, agriculture already relies heavily on irrigation, and irrigation requirements are thus projected to increase. Changing precipitation patterns and larger climate variability are likely to increase the risk of floods in northern, central and eastern Europe (IPCC AR4 WGII, Ch. 12.4.1). An increase in the frequency of intense short-duration precipitation events will likely increase the risk of flash-floods in most of Europe. Coastal zones Europe has many low-lying coastal areas, many of which are densely populated and therefore vulnerable to sea level rise. The coastal strips of the North Sea running through eastern England, Belgium, the Netherlands, north-western Germany and Denmark as well as the Po delta in northern Italy are Europe’s most threatened coasts (WBGU, 2006). Regional influences may result in sea level rise in Europe exceeding the global mean increase by 50% (IPCC AR4 WGII). Maintaining the 2°C target is important for limiting the risk of destabilisation of polar ice sheets, which would contribute substantially to long-term sea level rise (cf. Section 2.3). Mountain regions Mountain regions are amongst the most vulnerable natural systems in Europe and climate change adds to other environmental stresses. Glaciers in the Alps are retreating at a rapid pace; for each degree of local warming, the snow line moves upward by about 150 m (EEA, 2004). Thawing of Alpine permafrost causes destabilisation of mountain walls and increases the frequency of rock falls. Fragile Alpine ecosystems are forced to move uphill and will eventually disappear. Recent findings indicate that impacts on biodiversity will be disproportionately severe in the European mountain regions, where the species loss by 2080 is projected to be as high as 60% for a high emissions scenario (IPCC AR4 WGII, Ch. 4.4.7). Climate change may also severely affect the tourism sector in mountain regions. In the Austrian Alps, for instance, an increase of 1°C may lead to some 70 fewer skiing days per year, depending on altitude (IPCC AR4 WGII, 12.4.9). Economic impacts Currently, research activities are being undertaken to quantify the economic impacts of climate change in various sectors such as coastal systems, energy demand, human health, agriculture, tourism and floods. The 2003 heat wave resulted in damages of 13 billion € in the agriculture 21 and forestry sectors alone (Stern, 2006 Box II5.4), mostly due to losses in crop yield, heat-stress on livestock and forest fires. Projections estimate a more than 10-fold increase in annual flood losses in Europe by the end of the century for a global warming of 3-4°C, some of which, however, are driven by economic growth and an increase in physical assets. Adaptation measures such as strengthening of flood management have the potential to significantly limit losses (Stern, 2006, II5.4). 2.3 Positive feedbacks, instabilities, irreversible changes and tipping points In assessing the level at which anthropogenic interference with the climate system must be considered “dangerous”, a particular focus should be given to instabilities, positive feedbacks and irreversible changes in the climate system – in risk management language, low probability, high impact events or processes. Once a certain level of warming has been reached, self-amplifying processes may result in a transition of the climate system to another state. Thresholds for such processes are called “tipping points” in the climate system (IPCC AR4 2007, Box 10.1; Lindsay and Zhang, 2005; Hansen et al., 2007, Lenton et al., 2008). They include especially the irreversible melting of the Greenland ice sheet, the risk of disintegration of the marine based West Antarctic ice sheet, a weakening or even complete shutdown of the Atlantic Meridional Overturning Circulation (MOC), often termed the thermohaline circulation (THC), and climate change-induced release of greenhouse gases from the land biosphere. All these processes have the potential to trigger large-scale changes, some of them irreversible on the timescales of centuries to millennia, with dramatic impacts. Polar ice sheets The amplified warming of the atmosphere at high latitudes and ocean warming threaten the Greenland Ice Sheet (GIS) and the West Antarctica Ice Sheet (WAIS). These account for water masses equivalent to approximately 7m and 5m of global sea level rise, respectively. Due to their thickness and the great thermal inertia, complete melting would not occur abruptly, but would likely take many centuries to complete. Rapid decay of these ice sheets, or even partial disintegration, leading to multimetre sea level rise over centuries to millennia is likely if warming is large enough and sustained for long enough. A multi-metre sea level rise would be a key impact due to the large magnitude of the consequences, its irreversibility and the likelihood that it would exceed the adaptive capacity of many regions (IPCC AR4 WGII, Ch. 6 and 19.3.5.2). 22 Above about 2°C warming 4 , there would be, with medium confidence, a commitment to widespread to near-total deglaciation of the Greenland ice sheet leading to 2-7m sea level rise over centuries to millennia (IPCC AR4 WGII, Ch. 19.3.5]. For the West Antarctic Ice sheet 5 , scientific confidence is lower; however it could be anticipated with low to medium confidence that for warming of over 2°C there would be a commitment to partial deglaciation with 1.5-5 m sea level rise over centuries to millennia (IPCC AR4 WGII, Ch. 19.3.5]. Even a warming of 2°C may commit us to a sea level rise from melting ice sheets, and this risk greatly increases for greater warming. Atlantic Meridional Overturning Circulation (MOC) The MOC is an important mechanism for the global redistribution of heat. It is largely responsible for the mild climate in the North Atlantic basin. According to IPCC AR4, a complete shutdown of the MOC is considered to be very unlikely to occur during the 21st century. The likelihood of large-scale MOC responses increases with the extent and rate of warming. In a risk context, it is to be noted that the likelihood in the 21st century (<10%) may still be significant given the high consequences of an abrupt shutdown: these include adverse effects on food production and terrestrial vegetation, changes in fisheries and effects on oceanic CO2 uptake and oceanic oxygen concentrations, an increased warming of southern hemisphere high latitudes and tropical drying. Adaptation to the impacts of a shutdown of the MOC is very likely to be difficult if the impacts occur abruptly (IPCC AR4 WGII, Ch. 19.3.5.3). Rapid ice loss from the Greenland ice sheet or rapid addition of freshwater fluxes from the Arctic flowing rivers would increase the risk. Coupled climate models project a decrease in the MOC of up to 50% or more by the end of the 21st century due to warming of the surface waters and increased precipitation in the North Atlantic (IPCC AR4 WGI, Ch. 10.3.4). Slowing down of the MOC decreases warming in Europe caused by the anthropogenic greenhouse effect, a process which is already embedded in the present generation of coupled ocean atmosphere models (AOGCMs). Land biosphere Currently, the global land biosphere acts as a net sink for CO2. Projected climate change is likely to add CO2 to the atmosphere and to increase the fraction of anthropogenic emissions that stay airborne, producing an additional warming of 0.1 to 1.5°C, which is already included in the AR4 temperature range (1.1-6.4°C). However, additional releases of CO2 and methane (CH4) are possible from permafrost, peat lands, wetlands, and 4 The model based threshold of global average warming for the onset a net loss of ice from Greenland is in the range of 1.9 to 4.6°C above pre-industrial levels (IPCC AR4 WGI, Ch. 10.7.4.2). 5 The Antarctic ice sheet as whole contains sufficient ice to raise sea level by 57m (IPCC AR4 WGI, Ch. 4.1). The potential for ice loss for the East Antarctic Ice Sheet is not discussed here due to scientific uncertainties although it is noted that some parts of the EAIS are presently losing ice to the oceans (Shepherd and Wingham, 2007) 23 large stores of marine hydrates at high latitudes (IPCC AR4 WGII, Ch. 4.4.6, and 15.4.2). These feedbacks are generally expected to increase with climate change. Some models indicate a risk that the land biosphere turns into a net source of CO2 by the 2050s. In these models this is mostly due to climate-driven decline of vegetation in South America and the loss of soil carbon due to increased respiration. A number of models also project an increase in biogenic methane emissions from wetlands and permafrost associated with a warming climate. Methane is the second most important contributor to the anthropogenic greenhouse effect. Several studies indicate that a warming of 2°C would result in ca. 20% growth in methane emissions from wetlands (IPCC AR4 WGI, Ch. 7.4.1.2), and the emissions are likely to further increase at higher temperatures. Furthermore, methane stored in the form of methane hydrates on the seafloor and in permafrost soils could become increasingly unstable with rising temperatures. Even though a catastrophic, sudden release of large amounts of methane is considered unlikely to happen on short to medium time scales, ongoing chronic release of methane as a result of anthropogenic warming could result in a substantial increase in its atmospheric concentration, thus further amplifying climate change (IPCC AR4 WGI, Ch. 7.4.1.2). 24 • In order to have a 50% chance of keeping the global mean temperature rise below 2°C relative to preindustrial levels, atmospheric GHG concentrations must stabilise below 450ppm CO2 equivalence. Stabilisation below 400ppm will increase the probability to roughly 66% to 90%. • Current atmospheric GHG concentrations and trends in GHG emissions mean that these concentration levels may be exceeded. The 2°C target can still be achieved if this overshoot of concentrations is only temporary and reversed quickly. Thus, to avoid a warming in excess of 2°C, global GHG emissions should peak by 2020 at the latest and then be more than halved by 2050 relative to 1990. 25 Emission pathways The implications of the EU 2°C target for future GHG emissions are outlined here. If no action is taken to reduce GHG emissions, global mean surface temperatures are projected to continue to increase, and will rise by more than 2°C above pre-industrial levels as early as the middle of this century. The IPCC AR4 indicates that, by the end of this century, global temperatures may increase to 2.3°C (“likely” range between 1.6°C and 3.4°C) for the lower and 4.5°C (2.9°C to 6.9°C) for the higher non-mitigation emission scenarios (see Figure 3.1 below and IPCC AR4 WGI, Tab.SPM3). Fig 3.1: Projections of global mean surface temperatures for three SRES non-mitigation scenarios as presented by IPCC AR4 and the “Year 2000 constant concentration” experiment. Without mitigation of emissions, the 2°C target (red dashed line) will be exceeded towards the middle of the century. “Likely” ranges in average 2090-2099 warming for the six SRES marker scenarios are shown on the right. Source: Adapted from IPCC AR4 WGI, SPM-5. 26 3.1 Concentration stabilisation levels for keeping below 2°C The complexity of the climate system does not allow the temperature response to GHG emissions to be estimated with absolute certainty. The IPCC AR4 provides temperature ranges associated with different GHG stabilisation levels (expressed in CO2 equivalent - CO2eq). For example, the IPCC estimates that doubling the atmospheric GHG concentration relative to pre-industrial levels (i.e. to about 550ppm CO2eq), is likely 6 to increase the global temperature by at least 2°C and up to 4.5°C above pre-industrial temperatures. The best guess is that this doubling of concentrations will cause a global temperature increase of 3°C. This analysis also implies that, at a concentration of 550ppm, CO2eq the probability of keeping the temperature increase below 2°C is 5-17% (see Figure 3.2). In order to meet the 2°C target with at least a 50% probability, atmospheric CO2eq concentration would need to be stabilised at approximately 440ppm or lower. Stabilisation at 400ppm CO2eq or lower would raise the probability of keeping the temperature increase below 2°C to above 66% (see Figure 3.2). 6 In the IPCC AR4, “likely” implies a 66-90% chance of occurrencel. 27 Fig 3.2: The probability of exceeding a 2°C warming at various stabilisation levels is shown. At stabilisation levels around 400ppm or below, global mean temperatures are likely to stay below 2°C, and there is a 50% probability of exceeding a 2°C temperature increase at levels of around 450ppm CO2eq. The target is unlikely or very unlikely to be achieved at stabilisation levels above approximately 500ppm CO2 eq. This figure combines analyses of climate sensitivity reported in IPCC AR4 WGI. The best estimate of climate sensitivity (the global temperature increase at 550ppm) is 3°C and the “likely” range is between 2 and 4.5°C. In addition, current (2005) CO2eq concentration levels are indicated for GHGs only and the net combined anthropogenic radiative forcing agents (top left, see text for further explanation) (IPCC AR4 WGI Tab.2.12). Source: Adapted from IPCC WGII Fig. 19.1. 28 3.2 How to achieve low GHG stabilisation levels: Peaking of concentrations a medium-term necessity. Current atmospheric GHG concentrations and emission trends indicate that meeting the EU climate protection target is very challenging. The current atmospheric concentrations of long-lived greenhouse gases i.e. CO2, CH4, N2O and halocarbons, are equivalent to about 450ppm CO2eq. However in addition to the warming effect of these GHGs, manmade aerosols have a cooling effect and black carbon a further warming effect. Although these vary considerably by region, their net global effect, together with the greenhouse gases, gives a warming effect equivalent to a best-estimate of about 375ppm CO2eq (IPCC AR4 WGI, Tab.2.12) (see Figure 3.2). Note that future aerosol emissions, and their regional net cooling effects on the climate, are assumed to decrease with increased effectiveness of air pollution control policies around the world. Because of the inertia of the climate system, the equilibrium temperature associated with higher GHG concentrations will not be reached if these concentrations are reduced rapidly enough to a lower stabilisation level, e.g. if the atmospheric GHG concentrations peak at 475 or 500ppm CO2 equivalence, and are then further reduced to a lower level (see Figure 3.3). In order to ensure a high degree of probability of staying below 2°C, urgent action is required to reduce global GHG emissions so that atmospheric concentrations will peak in the near future and return to a lower stabilisation level (see IPCC AR4 WGI, FAQ10.3). 29 Fig 3.3: Schematic overview of historic total CO2 emissions (grey), concentrations (blue) and global mean temperatures (black/red) and illustrative time-series for a future evolution highlighting the inertia of the climate system and the different peaking years. If global emissions peak in the near term, CO2eq concentrations could peak around the middle of the century before approaching long-term stabilisation levels consistent with a 2°C target. Owing to the inertia of the climate system, the peak in concentrations is not necessarily reflected in the global mean temperature 7 . 7 See Appendix 2 for the assumptions underlying this illustrative figure. 30 3.3 Global emissions have to peak by 2015-2020, and to decline rapidly until 2050 and beyond Translating the concentration requirements into emission pathways is subject to considerable uncertainties, primarily due to uncertainties in the carbon cycle. The IPCC WGIII analysed a large set of mitigation scenarios available in the literature and categorised them according to their maximum 21st century concentrations. The analysed set of lower mitigation scenarios (category I, see Table 3.1) implies that GHG concentrations will have to peak at or below 500ppm CO2eq (3.14W/m2). This provides a 50% or better chance of achieving the EU 2°C target, as long as the concentrations are further reduced after they peak. According to IPCC WGIII, the emission profiles for these scenarios require near-term infrastructure investments and early decarbonisation of the energy system, with global GHG emissions starting to decline before 2015 or 2020 (see Table 3.1 below). Scenarios in which the GHG concentrations peak later would require larger annual emissions reduction rates thereafter in order to keep within the 2°C limit. Global emissions need to be reduced by at least 50% of 1990 levels by 2050 (i.e. from around 40 GtCO2eq/year to ca. 20 GtCO2eq/year). There is, however, a considerable range within the IPCC scenario classes. Future emission pathways that aim at (at least) halving global emissions by 2050, as proposed in the Bali Action Plan, differ slightly depending on which reference year is chosen. Depending on the reference year and the emission pathway leading to the 2050 emission levels, the aim of halving global emissions by 2050 reflects a 50% or better probability of staying below 2°C (see Figure 3.4). For a current (2005) reference year, emissions would have to be reduced by about 60% in order to comply with a 50% reduction using a base year of 1990, since global emissions increased by approximately 20% between 1990 and 2005. 31 Table 3.1 – Stabilisation scenario classes and their 21st century characteristics adapted from IPCC AR4 WGIII, SPM 5 and Fig.3.18. Emission scenarios within category I and the lower end of II are consistent with a 2°C target, if the probabilities of staying below 2°C shall be 50% or higher 8 . Year in which emissions decrease below 2000 levels Cumulative CO2 emissions 20002100 Change in global emissions in 2050 (% of 1990 emissions) 9 IPCC Category CO2 conc. CO2eq conc. Peaking year for CO2 emissions WGIII Source SPM.5 SPM.5 SPM.5 Fig. 3.19 Fig.3.18 SPM.5 ppm ppm Year Year GtCO2 % I 350-400 445-490 2000-2015 2000-2030 800-1500 -83.5 to -40 II 400-440 490-535 2000-2020 2000-2040 1000-1800 -56 to -23 8 Note that the CO2eq concentrations listed in Table 3.1 are not directly comparable to the CO2eq stabilisation levels shown in Figure 3.2. Some of the scenarios envisaged stabilisation at st 21 century maximum concentrations, not a peak and subsequent decline to lower CO2 stabilisation levels. Thus, the CO2eq concentrations levels were rather comparable to peak concentrations levels with ultimate stabilisation levels only being determined by post-2050 emission levels. 9 Here the reference year is adjusted to 1990 in accordance with the Kyoto Protocol – taking into account an approximate 10% increase of global GHG emissions from 1990 to 2000. 32 Fig 3.4: Global GHG emissions under non-mitigation and mitigation scenarios. Shown in red are non-mitigation SRES scenarios. The blue lines indicate two mitigation pathways as presented in the Stern Review (Stern, 2006) and the European Commission (2007a) communication – leading to peaking concentrations at roughly 500ppm CO2eq concentrations and a subsequent 450ppm CO2eq stabilisation. The long-term goals for halving emissions by 2050, as agreed for serious consideration by G8 in Heiligendamm in 2007, are indicated by the yellow stars with reference years being 1990 (bottom), 2000 (middle) or 2007 emission levels (top star) 10 . The shaded bands denote series of different emission pathways ultimately stabilising at 450ppm CO2eq (orange) and 400ppm CO2eq (green) – with the latter being likely to stay below 2°C 11 . For comparison, global emissions according to the EDGAR database (as in IPCC AR4 WGIII, Fig. SPM.1) are shown for the years 1990, 2000, and 2004 (red circles). Note that current fossil CO2 emission estimates are estimated as being at the upper end of the SRES range, with additional differences to the EDGAR data points stemming from different land use-related emission estimates 12 . 10 Reference emission levels for Kyoto-basket greenhouse gas emissions are here derived from the median across all IPCC SRES scenarios. Actual emissions can differ and might be higher in recent years. 11 The series of emission pathways were created using the EQW method (Meinshausen, 2006) and the FAIR-SiMCaP method (den Elzen & Meinshausen, 2006) for the respective stabilisation levels – using default carbon cycle settings and various assumptions in regard to the shape of the emission pathway. Individual gas emissions for all scenarios are weighted by their respective Global Warming Potentials as applied under the UNFCCC and the Kyoto Protocol. 12 See IPCC AR4 WGIII, page 4, footnote 9 33 3.4 From global to regional emission pathways Emission pathways for different groups of countries are based on assumptions of global effort sharing. There is usually an assumption that emissions from developing countries will continue to grow, and that developed countries implement emissions reductions that will provide room for such growth and still result in an overall decrease in emissions. To illustrate what this might mean, Figure 3.5 shows a global emission pathway that halves global emissions by 50% by 2050. For simplicity and illustrative purposes, equal per-capita emissions by 2050 are assumed, which leads to an 85% emission reduction by 2050 in developed countries’ emissions relative to 1990 levels. 13 . Emissions from developing countries are then computed from the global and developed country emission profiles. This shows that, for both sets of countries, emissions need to stabilise and then be reduced in order to achieve the 2°C target (see Figure 3.5). 13 This assumes median population projections according to: Population Division of the Department of Economic and Social Affairs of the United Nations Secretariat (UN, 2007). 34 Fig 3.5: Greenhouse gas emissions under an indicative emission pathway that is consistent with meeting the 2°C target with a medium likelihood. Global emissions (black line) are assumed to be halved by 2050. Developed country emissions are assumed to decrease by 30% by 2020 and by 85% by 2050 relative to 1990. Developing country emissions are assumed to increase up to 2020 with following reductions determined by the prescribed global emission levels. The 2050 emission shares of developed and developing countries are illustrative only and represent an assumption of equal per-capita emissions by 2050. (Source: Adapted from UNDP, 2007) 35 36 • Deep reductions in GHG emissions are necessary in order to limit the global mean temperature rise to 2°C above pre-industrial temperatures. • Deep emission reductions can be achieved by employing a broad range of currently available technologies and technologies that are expected to be commercialised in coming decades. • Deployment requires clear, consistent and effective policies and incentives. • Action needs to be taken very urgently as inertia in the climate and socio-economic systems means that mitigation actions and low-carbon investment decisions are needed now in order to avoid lock in of carbonintensive technologies. 37 Mitigation Options The IPCC AR4, the Stern Review and the IEA Energy Technology Perspectives (IEA, 2008) have highlighted the urgent need for deep cuts in greenhouse gas emissions in order to stabilise atmospheric concentrations at a level that will avoid dangerous climate change. Significant GHG abatement potential exists across countries and sectors; the adoption of a broad portfolio of policies and technologies is required to realise this potential. However, this requires clear policy signals. Decisions on large investments in energy and transport infrastructure over the next few years will have a long-term impact on global emissions levels because of the long lifetimes of capital stock. The choice for our future is not between growth and non-growth – it is between high-carbon growth and low-carbon growth. A large shift in investment patterns is needed as the technology choices we make will play an important role in achieving the necessary deep cuts in GHG emissions. In order to achieve the necessary deep cuts in GHG emissions, policies are required to support the development and deployment of a range of low-carbon and high-efficiency technologies on an urgent timescale. Existing and soon-to-be-commercialised technology can provide feasible mitigation options. The cost of some options is currently high; however it is expected that costs will decrease with the scale of production, experience and with investments in research, development and demonstration (RD&D). IPCC AR4 suggests that mitigation opportunities with net negative costs have the potential to reduce emissions by around 6 GtCO2eq/yr in 2030 (for reference, emissions were 43 GtCO2eq/yr in 2000). Realising these opportunities requires the removal of implementation and behavioural barriers. Changes in lifestyle and behaviour patterns can contribute to climate change mitigation across all sectors. Management practices can also have a positive role. 4.1 A broad portfolio is needed A broad portfolio of technologies can be expected to play a role in managing the risk of climate change. This is because of the scale of reductions that are required, the large variation in national circumstances and sectoral differences. The uncertainty about performance of individual options needs to be included in this assessment as it is not possible to identify ex ante winners and losers. Results from low stabilisation studies in line with the 2°C target indicate that a broad portfolio of options is 38 needed and no one “silver bullet” or “quick fix” technology exists. Technology options across a range of sectors are listed in Table 4.1. Figure 4.1 gives an example of the options that could reduce global CO2 emissions in line with a medium likelihood of staying below the 2°C target. On top of energy savings, fossil fuel switches (to natural gas), renewable energy, increased nuclear power and carbon capture and sequestration could be part of the mix. Non-CO2 GHGs need to be reduced as well. Preliminary results of the EU’s ADAM project suggest that the portfolios depend on the model and on the assumptions made about the availability and costs of the various technologies. Clearly, leaving some of the options out, for example, without CCS or with a restricted supply of renewable energy (e.g. biomass), mitigation costs would tend to be higher. 45 Energy savings 40 avoided emissions 35 Gt CO2 30 25 Fossil fuel switch Renewable energies 20 Nuclear energy 15 Carbon sequestration 10 5 0 2000 Emission of reduction case 2010 2020 2030 2040 2050 Fig 4.1: An example portfolio of options needed for deep reductions of fossil CO2 emissions. Source: IPTS, (Russ et al., 2007) Key technologies and options include various renewable technologies, supply and end-use efficiency, CCS, including biomass in combination with CCS, hydrogen fuel cells and advanced biofuels. In addition, the assumed development of afforestation and deforestation varies between the various studies. Stopping (net) deforestation is assumed in some studies whereas others indicate that increased (forest) sink enhancement can be part of a cost-effective portfolio to meet stabilisation targets. 39 Sector Table 4.1: Key mitigation technologies and practices by sector (Source: IPCC WGIII) Key mitigation technologies and Key mitigation technologies and practices practices projected to be commercialised currently commercially available before 2030 Energy supply Improved supply and distribution efficiency; fuel switching from coal to gas; nuclear power; renewable heat and power (hydropower, solar, wind, geothermal and bioenergy); combined heat and power; early applications of Carbon Capture and Storage (CCS, e.g. storage of removed CO2 from natural gas). CCS for gas, biomass and coal-fired electricity generating facilities; advanced nuclear power; advanced renewable energy, including tidal and waves energy, concentrating solar and solar PV. Transport More fuel efficient vehicles; hybrid vehicles; cleaner diesel vehicles; biofuels; modal shifts from road transport to rail and public transport systems; non-motorised transport (cycling, walking); landuse and transport planning. Second generation biofuels; higher efficiency aircraft; advanced electric and hybrid vehicles with more powerful and reliable batteries. Buildings Efficient lighting and daylighting; more efficient electrical appliances and heating and cooling devices; improved cook stoves, improved insulation; passive and active solar design for heating and cooling; alternative refrigeration fluids, recovery and recycle of fluorinated gases. Integrated design of commercial buildings including technologies such as intelligent meters that provide feedback and control; solar PV integrated in buildings. Industry More efficient end-use electrical equipment; heat and power recovery; material recycling and substitution; control of non-CO2 gas emissions; and a wide array of process-specific technologies. Advanced energy efficiency; CCS for cement, ammonia, and iron manufacture; inert electrodes for aluminium manufacture. Agriculture Improved crop and grazing land management to increase soil carbon storage; restoration of cultivated peaty soils and degraded lands; improved rice cultivation techniques and livestock and manure management to reduce CH4 emissions; improved nitrogen fertiliser application techniques to reduce N2O emissions; dedicated energy crops to replace fossil fuel use; improved energy efficiency. Improvements of crop yields. Forestry/forests Afforestation; reforestation; forest management; reduced deforestation; harvested wood product management; use of forestry products for bioenergy to replace fossil fuel use. Tree species improvement to increase biomass productivity and carbon sequestration. Improved remote sensing technologies for analysis of vegetation/ soil carbon sequestration potential and mapping land use change. Waste management Landfill methane recovery; waste incineration with energy recovery; composting of organic waste; controlled waste water treatment; recycling and waste minimisation. Biocovers and biofilters to optimise CH4 oxidation. 40 4.2 The long-term impact of near-term decisions Investment decisions on energy and transport that will be taken over the next few years will have a huge long-term impact on emissions pathways – poor decisions could lock the energy system into a fuel mix and emissions trajectory that may be difficult and costly to change. However, new energy infrastructure investments in developing countries, capital turnover and upgrades to existing energy infrastructure in industrialised countries create opportunities to achieve significant GHG emission reductions compared to baseline scenarios. The IPCC AR4 WGIII estimates that a large shift in investment patterns in energy infrastructure will be needed by 2030 to achieve a sustainable emissions pathway. The net additional investment required ranges from negligible to 5-10% (of 20 trillion US$). 4.3 Investment, cost and RD&D The pace and cost of any response to climate change depends critically on the cost, performance and availability of technologies that can lower future GHG emissions. Currently, many low-carbon technologies are costly in comparison with the fossil-fuel alternatives. However, technological costs fall with increased production, scale of use and experience. Investments in and world-wide deployment of low-GHG emission technologies as well as technology improvements through public and private RD&D are required to achieve stabilisation targets as well as cost reduction. The lower the stabilisation levels, the greater is the need for more efficient RD&D efforts and investment in new technologies during the next few decades. This requires that barriers to development, deployment and diffusion of technologies are effectively addressed. Policy frameworks that set the right incentives and remove other barriers (e.g. market structure, institutional framework, subsidies) as well as focussed R&D programmes are essential to overcome the technical and cost barriers facing many new energy technologies. 41 Box 4.1 Legislative Action in the EU The European contribution to the global effort required to achieve the 2°C target and to avoid dangerous climate change is the climate change and energy package adopted by the European Commission on 10th January 2007 and endorsed by the European Heads of State and Government (European Council) on 8-9th March 2007. The European Council endorsed the following elements: Developed countries reduce their GHG emissions by 30% GHG by 2020, compared to 1990 levels, as part of a comprehensive global agreement; Until a global post-2012 agreement is concluded, EU decided on a firm independent commitment to achieve at least a 20% reduction of GHG emissions by 2020 compared to 1990. By 2050 global GHG emissions must be reduced by at least 50% compared to 1990, which means reductions in developed countries of 6080% compared to 1990 levels. Detailed legislative proposals have been adopted by the European Commission on 23rd January 2008 which were welcomed by the Environment Council on 3rd March 2008. Agreement and adoption of these proposals as a coherent package is foreseen within the current legislative term, at the latest early in 2009. For further information, see: http://ec.europa.eu/environment/climat/future_action.htm 42 • The costs of climate change impacts are directly related to their magnitude which increases with global temperature and may be between 5 and 20% of GDP or even higher in the long-term. • The costs of actions to mitigate climate change are small when compared to the relative costs of impacts due to inaction. • Some of the costs of impacts can be reduced through investment in adaptation. • According to recent studies, mitigation needed to meet the 2°C target is projected to cost at most 2.5% of global GDP in 2050 (reducing annual growth by at most 0.05%/year) if policies are designed in a cost-effective way. These costs are reduced significantly when cobenefits (i.e. reduction in air pollution health damage, air pollution control costs and energy security) are included. • Such mitigation, via a portfolio of co-ordinated policies including a long-term carbon price and the recycling of tax/auction revenues to promote low-carbon technologies and to improve market efficiencies, could even lead to global GDP gains (above those due to avoided climate impacts). 43 Economics of Climate Change 5.1 Analytical approaches Standard cost benefit analysis attempts to provide an assessment of the costs of mitigating greenhouse gases and of the benefits that result from reducing climate change. However, the widespread environmental, social and economic impacts of climate change, especially those that are irreversible, cannot be fully included in standard cost benefit analysis (IPCC AR4 WGIII]. Therefore more appropriate analytical methodologies are required. The EU climate objective is based on a broader risk assessment and avoidance of large-scale irreversible climate impacts. This integrated approach, which provides an alternative to cost-benefit analysis, is considered to provide a more suitable basis for decision-making on climate change issues. The Stern Report has also identified methodologies that take account of the long time horizons that are typical for climate change. They also take account of equity issues by differentiating the economic impacts in relation to different levels of regional development. 5.2 Adaptation lowers costs of climate change Adaptation can decrease costs substantially (IPCC AR4 WGII). For example, the PESETA project (Projection of Economic impacts of climate change in Sectors of the European Union based on bottom-up analysis) 14 estimated that effective adaptation could reduce the total cost of the impacts of sea-level rise on the EU by approximately 65% in 2020 and up to 83% by 2080. These estimates include the costs of adaptation investments. 5.3 Mitigation costs Mitigation costs have been assessed using bottom-up and top-down modelling. Bottom-up models estimate mitigation potential based on detailed sector-by-sector analysis of economically accessible technology options and behavioural responses. The top-down models are macroeconomic models that consider the economy-wide potential of mitigation options. The IPCC AR4 indicates that these approaches provide similar estimates of aggregate mitigation potentials based on carbon price levels. 14 See http://peseta.jrc.ec.europa.eu/ for further information. 44 However, the sector-based estimates show substantial cost differences between sectors. Bottom-up models suggest that mitigation potential can be achieved at no cost or net benefits/saving in many sectors. This “no regret” potential amounts to 6 GtCO2eq per year by 2030, or roughly 10% of nonmitigation baseline emissions. However, investment or removal of barriers (e.g. through policy measures) is required to achieve these savings. The IPCC AR4 analysis suggests that mitigation pathways consistent with stabilisation of atmospheric GHG levels at 550ppm CO2eq, can be achieved with carbon prices up to 40 €/tCO2 by 2030. Trajectories consistent with a 450ppm CO2eq stabilisation level will require higher carbon prices, up to 80 €/tCO2eq by 2030. In order to put these carbon prices in perspective of the recent rise in oil prices, Table 5.1 highlights the implied increments on energy prices. Table 5.1: How does a carbon price of €30, €50 or €80 per tonne of carbon dioxide affect energy prices? The table indicates the direct price effect for different fossil fuel energy carriers, for a range of carbon prices. Marginal increase of energy price Electricity Carbon price Crude Oil €30/tCO2eq +€15/barrel €50/tCO2eq +€25/barrel €80/tCO2eq +€40/barrel Gasoline +€0.07/litre (+€0.30/gallon) +€0.12/litre (+€0.50/gallon) +€0.19/litre (+€0.80/gallon) From coal fired plant From gas fired plant +€0.03/kWh +€0.009/kWh +€0.05/kWh +€0.015/kWh +€0.08/kWh +€0.024/kWh 15 Adapted from IPCC WGIII Outreach Presentation . Note: No indirect price effects due to change in demand are considered. IPCC analysis (AR4 WGIII SPM) indicates that achievement of emission scenarios consistent with the EU 2°C target are projected to reduce global GDP by 3% at most by 2030 and by 5.5% at most by 2050, compared to current growth projections. This high-cost estimate is based on a single study with relatively high baseline emissions that misses options to reduce emissions in the transport sector. On the other hand, recent, provisional results by EU’s ADAM research project 16 indicate that 15 16 Available at www.mnp.nl/ipcc/pages_media/FAR4docs/ IPCC_WGIII_basicpresentation.ppt See www.adamproject.eu for more information 45 stabilising levels at 450ppm CO2eq would reduce global GDP by 2.0 to 2.2% in 2050 (see Table 5.2, row 1). This implies reductions in annual GDP growth rates of around 0.05%. The exact costs would depend on a number of issues: the extent to which optimal policies are implemented, the availability of technology options and the impact of induced technological change, how revenues from taxes and/or CO2 permits are recycled, assumptions on afforestation and deforestation and the full (life-cycle) impacts of (increased) biomass use. A portfolio of coordinated policies including a long-term carbon price, and the recycling of tax/auction revenues to promote low-carbon technologies and to improve market efficiencies, could potentially lead to global GDP gains. Detailed energy models (POLES and TIMER) indicate that the mitigation costs of meeting a 450ppm CO2eq target would be around 0.2 to 0.8% of global GDP in 2050. A broad portfolio of options (including energy efficiency improvements, renewables (i.e. biomass) and CCS) will need to be employed to limit the costs. Table 5.2: Costs of stabilising greenhouse gas concentrations 17 Stabilisation levels (ppm CO2eq) Median GDP reduction Range of GDP reduction Reduction of average growth rates 2030 2050 2030 2050 2030 2050 450 (ADAM) not available. 2.1 0.7 to 1.7 2.0 to 2.2 not available <0.05 445-535 (AR4) not available 18 . not available <3. <5.5 <0.12 0.12 535-590 (AR4) 0.6 1.3 0.2 to 2.5 slightly negative to-4 <0.1 <0.1 590-710 (AR4) 0.2 0.5 -0.6 to 1.2 -1 to 2 <0.06 <0.05 Source: IPCC AR4 SPM and ADAM project (preliminary results E3MG, MERGE and REMIND) The European Commission analysis estimates higher mitigation costs for 2030, i.e. equivalent to a reduction of global GDP by 4.6 % (or a reduction in annual GDP growth rate by 0.19%), implying that global GDP in 2030 would only be 196% and not 201% of that in 1990. This is linked to an assumption of a more restrictive global carbon market and the absence of a well functioning carbon market before 2012. A gradual development of the carbon market is foreseen to occur only thereafter. 17 It should be noted that all of the above analysis assumed projections of fossil fuel prices which are much lower than the current level. 18 Although IPCC did not provide a median value, the wide range of estimates is shown in Fig. 3.25 in Chapter 3 of IPCC AR4 WGIII. 46 The Stern Review indicates a lower cost, of about 1% of GDP by 2050 for trajectories consistent with a 500-550ppm CO2eq. The cost estimates from sectoral analysis range from -1.5% (i.e. net gains) to 3.5% of GDP for different scenarios. These are sensitive to assumptions on technology development and the costs of fossil fuels (Stern, Table 9.3). IIASA estimates suggest global GDP losses of less than 0.5 to 4% in 2100 to stabilise CO2eq. concentrations at around 450ppm CO2eq (Riahi et al., 2007). The Stern Review also estimates that inaction on mitigation will result in costs equivalent to losing at least 5% of global GDP in 2200, not including wider market and non-market impacts. This could rise to 20% of GDP or more, if non-market impacts are included. Effective mitigation requires a significant shift in investment decisions towards mitigation technologies. The European Commission estimates that approximately 0.5% of annual global GDP will need to be invested in or re-directed towards mitigation measures up to 2030.The Stern Review suggests that this gross investment should be of the order of 1% of GDP by 2050. 5.4 Co-benefits Co-benefits are the ancillary benefits that occur when measures to mitigate GHG emissions are undertaken. Co-benefits are mostly not included in modelling exercises to determine the GHG mitigation costs. Co-benefits include reduced air pollution impacts and decreased dependency on energy imports. The IPCC AR4 WGIII concluded that health co-benefits can be substantial and that these may offset a significant fraction of mitigation costs. Other co-benefits include increased energy security and reduced damage to agriculture, materials and ecosystems from improved air quality and related deposition of nutrifying and acidifying compounds. Co-benefits depend substantially on the source sector and region in which the mitigation option is implemented and the technology used. For example, the replacement of low-quality biomass energy by modern renewable energy for cooking and heating in developing countries has a particularly high potential to cut both greenhouse gas emissions and adverse health effects from pollution. Improving energy efficiency also results in particularly high co-benefits. The European Commission’s impact assessment for the Climate and Energy Package indicated that reducing GHG emissions by 20% in 2020 reduces sulphur dioxide, nitrogen oxides and PM2.5 emissions by 10 to 15% compared to baseline emissions in 2020. This would reduce air pollution control costs by 8 to 11 billion €/year. That implies that around 10% of the costs for controlling GHG emissions would be saved by reduced air pollution control costs. In addition, negative impacts on 47 human health (mortality) would be reduced. The reduction in health damage costs (benefits) was estimated at 12 to 29 billion €. In addition, damage to materials, crops and ecosystems would be reduced. Taken together, reductions in air pollution costs and health damage costs in the EU would offset up to 50 to 75% of the additional costs for controlling GHGs. In addition, the European Commission has also identified improved energy security as a co-benefit. Reducing EU GHG emissions by 36% by 2030 would decrease oil and gas imports by 2030 by a fifth compared to baseline. This would allow for investment in other areas including wider investment in global sustainable development. Lack of a secure or reliable energy supply is a major limiting factor for economic growth in most newly industrialised countries. Mitigation options such as renewable energy or energy efficiency therefore often yield benefits for the economy and the environment. 48 49 50 Conclusions Global warming of 2ºC above pre-industrial levels cannot be considered safe. Considerable climate change impacts are already felt today and will have to be faced in the future – even below 2°C. Beyond this level, climate change impacts will increase substantially in scale and severity, including threats to unique ecosystems, risks of multi-metre long-term sea level rise, and both more frequent droughts and floods across the globe. If no action is taken, we may exceed 2ºC already by the middle of this century. To avoid this, global emissions need to peak before 20152020 and to be at least halved by 2050 relative to 1990 levels. These emission reductions pose a huge challenge. However, the loss of life, ecosystems and a planet as we know it, would weigh greater than the efforts needed to reduce emissions. Even in monetary terms, the cost of inaction is greater than the cost of action. Damage costs could be in the range of between 5 and 20% of global GDP in the absence of action on either mitigation or adaptation. On the other hand, avoiding most damages by following low emission pathways is achievable – both with existing technologies and enhanced innovation. Mitigation needed to meet the 2°C target is projected to cost at most 2.5% of global GDP in 2050 (reducing annual growth by at most 0.05%/year), provided that the right policies and incentives are put in place now. Co-benefits of mitigation, such as reduced air pollution and energy security, would be substantial. In summary: Acting on climate change ambitiously and swiftly is the only rational insurance strategy against the risks of irreversible climate change damages. This is why the EU believes that the 2 ºC limit can and should guide global efforts to address climate change. 51 Appendix 1 (References) For more information on European climate policy, please consult http://ec.europa.eu/environment/climat/future_action.htm EEA (2004). Impacts of Europe's changing climate. EEA report 2/2004. Copenhagen, EEA.http://reports.eea.europa.eu/climate_report_2_2004/en den Elzen, M. G. J. and M. Meinshausen (2006). Multi-Gas Emission Pathways for Meeting the EU 2°C Climate Target. Avoiding Dangerous Climate Change. J. S. Schellnhuber, W. Cramer, N. Nakicenovic, T. M. L. Wigley and G. Yohe. Cambridge, Cambridge University Press. European Commission (2007a). Communication from the Commission to the Council, the European Parliament, the European Economic and Social Committee and the Committee of the Regions - Limiting global climate change to 2 degrees Celsius - The way ahead for 2020 and beyond. Brussels, Belgium.http://eurlex.europa.eu/LexUriServ/LexUriServ.do?uri=CELEX:52007DC0002:EN:NOT European Commission (2007b). Adapting to climate change in Europe – options for EU action {SEC(2007) 849}; Green Paper from the Commission to the Council, the European Parliament, the European Economic and Social Committee and the Committee of the Regions. Brussels, Belgium, EU Comission.http://eurlex.europa.eu/LexUriServ/LexUriServ.do?uri=CELEX:52007DC0354:EN:NOT Hansen, J., M. Sato, R. Ruedy, P. Kharecha, A. Lacis, R. Miller, L. Nazarenko, K. Lo, G. A. Schmidt, G. Russell, I. Aleinov, S. Bauer, E. Baum, B. Cairns, V. Canuto, M. Chandler, Y. Cheng, A. Cohen, A. Del Genio, G. Faluvegi, E. Fleming, A. Friend, T. Hall, C. Jackman, J. Jonas, M. Kelley, N. Y. Kiang, D. Koch, G. Labow, J. Lerner, S. Menon, T. Novakov, V. Oinas, J. Perlwitz, J. Perlwitz, D. Rind, A. Romanou, R. Schmunk, D. Shindell, P. Stone, S. Sun, D. Streets, N. Tausnev, D. Thresher, N. Unger, M. Yao and S. Zhang (2007). "Dangerous human-made interference with climate: a GISS modelE study." Atmospheric Chemistry and Physics 7(9): 2287-2312. IEA (2008). Energy Technology Perspectives 2008. Paris, International Energy Agency. IPCC SAR (1996a). Climate Change 1995: Economic and Social Dimensions of Climate Change, Contribution of Working Group III to the Second Assessment of the Intergovernmental Panel on Climate Change. Cambridge, UK, Cambridge University Press. IPCC SAR (1996b). Climate Change 1995: Impacts, Adaptations and Mitigation of Climate Change: Scientific-Technical Analyses. Contribution of WGII to the Second Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge, UK, Cambridge University Press. IPCC SAR (1996c). Climate Change 1995: The Science of Climate Change. Contribution of WGI to the Second Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge, UK, Cambridge University Press. IPCC TAR (2001a). Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental 52 Panel on Climate Change. Cambridge, United Kingdom and New York, NY, USA, Cambridge University Press. IPCC TAR (2001b). Climate Change 2001: Impacts, Adaptation, and Vulnerability. Cambridge, UK, Cambridge University Press. IPCC TAR (2001c). Climate Change 2001: Mitigation: Contribution of Working Group III to the third assessment report of the Intergovernmental Panel on Climate Change. Cambridge, UK, Cambridge University Press. IPCC TAR (2001d). Climate Change 2001: Synthesis Report. Cambridge, UK, Cambridge University Press. Lenton, T. M., H. Held, E. Kriegler, J. W. Hall, W. Lucht, S. Rahmstorf and H. J. Schellnhuber (2008). "Tipping elements in the Earth's climate system." Proceedings of the National Academy of Sciences of the United States of America 105(6): 1786-1793. Lindsay, R. W. and J. Zhang (2005). "Thinning Arctic Sea ice: Have we passed a tipping point?" Bulletin of the American Meteorological Society 86(3): 325-326. Meinshausen, M. (2006). What does a 2°C target mean for greenhouse gas concentrations? - A brief analysis based on multi-gas emission pathways and several climate sensitivity uncertainty estimates. Avoiding Dangerous Climate Change. J. S. Schellnhuber, W. Cramer, N. Nakicenovic, T. M. L. Wigley and G. Yohe. Cambridge, Cambridge University Press. Rahmstorf, S. (2007). "A semi-empirical approach to projecting future sea-level rise." Science 315(5810): 368-370. Riahi, K., A. Gruebler and N. Nakicenovic (2007). "Scenarios of long-term socioeconomic and environmental development under climate stabilization." Technological Forecasting and Social Change (Special Issue: Greenhouse Gases - Integrated Assessment) 74(7): 887-935. Russ, P., T. Wiesenthal, D. van Regemorter and J. C. Ciscar (2007). Global Climate Policy Scenarios for 2030 and beyond – Analysis of Greenhouse Gas Emission Reduction Pathway Scenarios with the POLES and GEM-E3 models. Seville, European Commission Joint Research Centre.ftp://ftp.jrc.es/pub/EURdoc/eur23032en.pdf Schellnhuber, J. S., W. Cramer, N. Nakicenovic, T. M. L. Wigley and G. Yohe, Eds. (2006). Avoiding Dangerous Climate Change. Cambridge, Cambridge University Press. Shepherd, A. and D. Wingham (2007). "Recent sea-level contributions of the Antarctic and Greenland ice sheets." Science 315(5818): 1529-1532. Stern, N. (2006). The Economics of Climate Change - The Stern Review. Cambridge, UK, Cambridge University Press. Stroeve, J., M. M. Holland, W. Meier, T. Scambos and M. Serreze (2007). "Arctic sea ice decline: Faster than forecast." Geophysical Research Letters 34(9): -. UN. (2007). "World Population Prospects: The 2006 Revision Population Database." from http://esa.un.org/unpp. UNDP (2007). Human Development Report 2007/2008: Fighting climate change: Human solidarity in a divided world. New York, USA, Palgrave Macmillan. WBGU (2006). The Future Oceans – Warming Up, Rising High, Turning Sour. Berlin, Germany. WBGU (2008). World in Transition - Climate Change as a Security Risk. London, Earthscan. 53 Appendix 2 Assumptions underlying the illustrative Figure 3.3 The following section briefly highlights the assumptions, data sources and models employed for deriving the illustrative Figure 3.3. Note that this figure is intended to be an approximate illustration of the relative points in time when peaking in emissions is followed by a peak in concentration and stabilisation in temperatures. The absolute levels shown are of very limited significance as this schematic diagram neither takes into account any uncertainties, nor necessarily shows “bestestimate” evolutions. For transparency, the underlying assumptions are listed here. Emissions: The “Kyoto-basket” GHG emissions represent the sum of all greenhouse gases controlled under the Kyoto Protocol, weighted by their respective 1996 IPCC Global Warming Potential for 100 years in line with the UNFCCC inventory guidelines. The historic CO2 emissions shown are total emissions, i.e. the sum of fossil, industrial and land use CO2 inventories. Historic fossil CO2 emissions follow the CDIAC compendium data by G. Marland, T. A. Boden, and R. J. Andres as available on http://cdiac.ornl.gov/trends/emis/em_cont.htm. Historic land use CO2 emissions are taken from Houghton and Hackler, as available on CDIAC at http://cdiac.ornl.gov/trends/landuse/houghton/houghton.html. Future emissions until 2100 of greenhouse gases, tropospheric ozone precursors and aerosols follow a harmonised version of an IMAGE scenario (~500ppm CO2eq peaking / ~450ppm CO2eq stabilisation, see van Vuuren et al., Climatic Change 81, 119 (2007)). Beyond 2100, CO2 emissions were linearly reduced to zero in 2400 and non-CO2 emissions were kept constant. Concentrations: The CO2 equivalent concentrations express the net anthropogenic forcing effect, as if the forcing was only caused by elevated CO2 concentrations. Historic concentrations for CO2, CH4, N2O and other long-lived greenhouse gases are prescribed. Future concentrations are modelled using emissions as an input for a simple atmospheric chemistry and carbon cycle model (MAGICC) in line with the IPCC AR4. Specifically, a medium range carbon cycle model was emulated (BernCC) in order to represent the medium range of the carbon cycle intercomparison project C4MIP results (P. Friedlingstein et al., Journal of Climate 19, 3337 (July, 2006)). The CO2 equivalent concentrations represent the complete net anthropogenic forcing effect on the atmosphere (including long-lived greenhouse gases, tropospheric ozone, 54 land use albedo, direct and indirect aerosol effects, black carbon on snow, etc.) according to IPCC AR4 best estimates (see IPCC AR4 WGI, Table 2.12). Note that the indirect aerosol effect (a forcing with substantial uncertainty ranges) has been modelled based on SOx, black carbon, organic carbon and nitrate emissions, matching the IPCC AR4 best estimate for the 2005 forcing (-0.7W/m2). Temperature: The temperature evolution is calculated using an updated version of the simple climate model (MAGICC, see e.g. T.M.L. Wigley, S.C.B. Raper, Science 293, 451 (Jul 20, 2001)). MAGICC has been used as a simple climate model in the IPCC AR4 (see e.g. WGI Fig 10.26). The climate model parameter settings were adjusted to emulate the UKMO-HadCM3 AOGCM, although the climate sensitivity has been reduced from 3.2°C to 3°C in order to represent the “best-estimate” IPCC value. Hence, the temperature following this 500ppm CO2eq peaking and 450ppm CO2eq stabilisation scenario is roughly stabilising at 2°C. With higher than 3°C climate sensitivities, temperatures would exceed 2°C under this particular illustrative emission scenario. 55