Global Triptych: a bottom-up approach for the differentiation of commitments under the Climate Convention

Abstract

In the coming years the international debate on commitments for the second commitment period under the Kyoto Protocol will intensify. In this study, the Global Triptych approach is put forward as an input for international decision-making concerning the differentiation of commitments by 2020. It is a sector- and technology-oriented approach, and we calculated quantitative emission limitation objectives and global emissions starting from bottomup information on long-term reduction opportunities. Central to the calculations were long-term sustainability targets for the year 2050, formulated for (1) energy efficiency in the energy-intensive industry, (2) greenhouse gas intensity of electricity production, and (3) per capita emissions in the domestic sectors. Calculated emission limitation objectives for 13 world regions ranged from about ?30% to more than +200%. The ranking of world regions in the differentiation turned out to be independent of the levels chosen for the long-term sustainability targets. The objectives seem sufficient to maintain the long-term possibility of stabilizing atmospheric greenhouse gas concentrations at about 550 ppm CO₂-eq, but will require severe emission reductions. These may be relaxed to a certain degree if stabilization at 650 ppm CO₂-eq is aimed for. We conclude that the bottom-up character of the approach made it possible to examine important basic principles of the Climate Convention, including equity, the needs and circumstances of developing countries, cost-effectiveness and sustainable development.     

A simple model for estimating methane concentration and lifetime variations

A simple methane model is presented in which lifetime changes are expressed as a function of CH₄ concentration and emissions of NO_x CO and NMHCs. The model parameters define the relative sensitivities of lifetime to these determining factors. The parameterized model is fitted to results from five more complex atmospheric chemistry models and to 1990 IPCC concentration projections. The IPCC data and four of the five models are well fitted, implying that the models have similar relative sensitivities. However, overall sensitivities of lifetime to changes in atmospheric composition vary widely from model to model. The parameterized model is used to estimate the history of past methane emissions, lifetime changes and OH variations, with estimates of uncertainties. The pre-industrial lifetime is estimated to be 15–34% lower than today. This implies that 23–55% of past concentration changes are due to lifetime changes. Pre-industrial emissions are found to be much higher (220–330 TgCH₄/y) than the best estimate of present natural emissions (155 TgCH₄/y). The change in emissions since pre-industrial times is estimated to lie in the range 160–260 TgCH₄/y, compared with the current best guess for anthropogenic emissions of 360 TgCH₄/y. These results imply either that current estimates of anthropogenic emissions are too high and/or that there have been large changes in natural emissions. 1992 IPCC emissions scenarios are used to give projections of future concentration and lifetime changes, together with their uncertainties. For any given emissions scenario, these uncertainties are large. In terms of future radiative forcing and global-mean temperature changes over 1990–2100 they correspond to uncertainties of at least ±0.2 Wm^–2 and ± 0.1° C, respectively.     

Managing atmospheric CO2

A coupled carbon cycle-climate model is used to compute global atmospheric CO₂ and temperature variation that would result from several future CO₂ emission scenarios. The model includes temperature and CO₂ feedbacks on the terrestrial biosphere, and temperature feedback on the oceanic uptake of CO₂. The scenarios used include cases in which fossil fuel CO₂ emissions are held constant at the 1986 value or increase by 1% yr^–1 until either 2000 or 2020, followed by a gradual transition to a rate of decrease of 1 or 2% yr^–1. The climatic effect of increases in non-CO₂ trace gases is included, and scenarios are considered in which these gases increase until 2075 or are stabilized once CO₂ emission reductions begin. Low and high deforestation scenarios are also considered. In all cases, results are computed for equilibrium climatic sensitivities to CO₂ doubling of 2.0 and 4.0 °C.Peak atmospheric CO₂ concentrations of 400–500 ppmv and global mean warming after 1980 of 0.6–3.2 °C occur, with maximum rates of global mean warming of 0.2–0.3 °C decade^–1. The peak CO₂ concentrations in these scenarios are significantly below that commonly regarded as unavoidable; further sensitivity analyses suggest that limiting atmospheric CO₂ to as little as 400 ppmv is a credible option.Two factors in the model are important in limiting atmospheric CO₂: (1) the airborne fraction falls rapidly once emissions begin to decrease, so that total emissions (fossil fuel + land use-induced) need initially fall to only about half their present value in order to stabilize atmospheric CO₂, and (2) changes in rates of deforestation have an immediate and proportional effect on gross emissions from the biosphere, whereas the CO₂ sink due to regrowth of forests responds more slowly, so that decreases in the rate of deforestation have a disproportionately large effect on net emission.If fossil fuel emissions were to decrease at 1–2% yr^–1 beginning early in the next century, emissions could decrease to the rate of CO₂ uptake by the predominantly oceanic sink within 50–100 yrs. Simulation results suggest that if subsequent emission reductions were tied to the rate of CO₂ uptake by natural CO₂ sinks, these reductions could proceed more slowly than initially while preventing further CO₂ increases, since the natural CO₂ sink strength decreases on time scales of one to several centuries. The model used here does not account for the possible effect on atmospheric CO₂ concentration of possible changes in oceanic circulation. Based on past rates of atmospheric CO₂ variation determined from polar ice cores, it appears that the largest plausible perturbation in ocean-air CO₂ flux due to changes of oceanic circulation is substantially smaller than the permitted fossil fuel CO₂ emissions under the above strategy, so tieing fossil fuel emissions to the total sink strength could provide adequate flexibility for responding to unexpected changes in oceanic CO₂ uptake caused by climatic warming-induced changes of oceanic circulation.     

Measurement of Carbon Dioxide Emissions Plumes from Prudhoe Bay, Alaska Oil Fields

Large carbon dioxide plumes with concentrations up to 45 ppm aboveambient levels were measured about 15 km downwind of the Prudhoe Bay, Alaskamajor oil production facilities, located at 70° N Lat. above the ArcticCircle. The measured emissions were 1.3 × 10³ metrictons (C) hour^-1 (11.4× 10⁶ metric tons(C) year^-1), six times greater than the combustion emissionsassumed by Jaffe and coworkers in J. Atmos. Chem. 20 (1995), 213–227,based on 1989 reported Prudhoe Bay oil facility fuel consumption data, andfour times greater than the total C emissions reported by the oil facilitiesfor the same months as the measurement time periods. Variations in theemissions were estimated by extrapolating the observed emissions at a singlealtitude for all tundra research transect flights conducted downwind of theoil fields. These 30 flights yielded an average emission rate of1.02 × 10³ metric tons (C) hour^-1 with astandard deviation of 0.33 × 10³. These quantity ofemissions are roughly equivalent to the carbon dioxide emissions of7–10 million hectares of arctic tussock tundra (Oechel and Vourlitis,Trends in Ecol. Evolution 9 (1994), 324–329).     

The emissions gap between the Copenhagen pledges and the 2 °C climate goal: Options for closing and risks that could widen the gap

As part of the Copenhagen Accord, Annex I Parties (industrialised countries) and non-Annex I Parties (developing countries) have submitted reduction proposals (pledges) and mitigation actions to the UNFCCC secretariat. Our calculations show that if the current reduction offers of Annex I and non-Annex I countries are fully implemented, global greenhouse gas emissions could amount to 48.6-49.7 GtCO₂eq by 2020. Recent literature suggests that the emission level should be between 42 and 46 GtCO₂eq by 2020 to maintain a “medium” chance (50-66%) of meeting the 2 °C target. The emission gap is therefore 2.6-7.7 GtCO₂eq. We have identified a combined set of options, which could result in an additional 2.8 GtCO₂eq emission reduction. This would lead to an emission level just within the range needed. The options include reducing deforestation and emissions from bunker fuels, excluding emissions allowance increases from land use and forestry rules, and taking into account the national climate plans of China and India. However, there are also important risks that could widen the emissions gap, like lower reductions from countries with only a conditional pledge and the use of Kyoto and/or trading of new surplus emission allowances.     

The Tolerable Windows Approach: Theoretical and Methodological Foundations

The tolerable windows (TW) approach is presented as a novel scheme for integrated assessment of climate change. The TW approach is based on the specification of a set of guardrails for climate evolution which refer to various climate-related attributes. These constraints, which define what we call tolerable windows, can be purely systemic in nature – like critical thresholds for the North Atlantic Deep Water formation – or of a normative type – like minimum standards for per-capita food production worldwide. Starting from this catalogue of knock-out criteria and using appropriate modeling techniques, those policy strategies which are compatible with all the constraints specified are sought to be identified. In addition to the discussion of the basic elements and the general theory of the TW approach, a modeling exercise is carried out, based on simple models and assumptions adopted from the German Advisory Council on Global Change (WBGU). The analysis shows that if the global mean temperature is restricted to 2°C beyond the preindustrial level, the cumulative emissions of CO2 are asymptotically limited to about 1550 Gt C. Yet the temporal distribution of these emissions is also determined by the climate and socio-economic constraints: using, for example, a maximal tolerable rate of temperature change of 0.2°C/dec and a smoothly varying emissions profile, we obtain the maximal cumulative emissions, amounting to 370 Gt C in 2050 and 585 Gt C in 2100.     

Permafrost Thaw Accelerates in Boreal Peatlands During Late-20th Century Climate Warming

Permafrost covers 25% of the land surface in the northern hemisphere, where mean annual ground temperature is less than 0°C. A 1.4–5.8 °C warming by 2100 will likely change the sign of mean annual air and ground temperatures over much of the zones of sporadic and discontinuous permafrost in the northern hemisphere, causing widespread permafrost thaw. In this study, I examined rates of discontinuous permafrost thaw in the boreal peatlands of northern Manitoba, Canada, using a combination of tree-ring analyses to document thaw rates from 1941–1991 and direct measurements of permanent benchmarks established in 1995 and resurveyed in 2002. I used instrumented records of mean annual and seasonal air temperatures, mean winter snow depth, and duration of continuous snow pack from climate stations across northern Manitoba to analyze temporal and spatial trends in these variables and their potential impacts on thaw. Permafrost thaw in central Canadian peatlands has accelerated significantly since 1950, concurrent with a significant, late-20th-century average climate warming of +1.32 °C in this region. There were strong seasonal differences in warming in northern Manitoba, with highest rates of warming during winter (+1.39 °C to +1.66 °C) and spring (+0.56 °C to +0.78 °C) at southern climate stations where permafrost thaw was most rapid. Projecting current warming trends to year 2100, I show that trends for north-central Canada are in good agreement with general circulation models, which suggest a 4–8 °C warming at high latitudes. This magnitude of warming will begin to eliminate most of the present range of sporadic and discontinuous permafrost in central Canada by 2100.     

Climate change: long-term targets and short-term commitments

International negotiations under the UN Framework Convention on Climate Change could take several different approaches to advance future mitigation commitments. Options range from trying to reach consensus on specific long-term atmospheric concentration targets (e.g. 550 ppmv) to simply ignoring this contentious issue and focusing instead on what can be done in the nearer term. This paper argues for a strategy that lies between these two extremes. Internationally agreed threshold levels for certain categories of impacts or of risks posed by climate change could be translated into acceptable levels of atmospheric concentrations. This could help to establish a range of upper limits for global emissions in the medium term that could set the ambition level for negotiations on expanded GHG mitigation commitments. The paper thus considers how physical and socio-economic indicators of climate change impacts might be used to guide the setting of such targets. In an effort to explore the feasibility and implications of low levels of stabilisation, it also quantifies an intermediate global emission target for 2020 that keeps open the option to stabilise at 450 ppmv CO₂ If new efforts to reduce emissions are not forthcoming (e.g. the Kyoto Protocol or similar mitigation efforts fail), there is a significant chance that the option of 450 ppmv CO₂ is out of reach as of 2020. Regardless of the preferred approach to shaping new international commitments on climate change, progress will require improved information on the avoided impacts climate change at different levels of mitigation and careful assessment of mitigation costs.     

Climate Change Impacts on the Potential Productivity of Corn and Winter Wheat in Their Primary United States Growing Regions

We calculate the impacts of climate effects inferred from three atmospheric general circulation models (GCMs) at three levels of climate change severity associated with change in global mean temperature (GMT) of 1.0, 2.5 and 5.0 °C and three levels of atmospheric CO2 concentration ([CO2]) – 365 (no CO2 fertilization effect), 560 and 750 ppm – on the potential production of dryland winter wheat (Triticum aestivum L.) and corn (Zea mays L.) for the primary (current) U.S. growing regions of each crop. This analysis is a subset of the Global Change Assessment Model (GCAM) which has the goal of integrating the linkages and feedbacks among human activities and resulting greenhouse gas emissions, changes in atmospheric composition and resulting climate change, and impacts on terrestrial systems. A set of representative farms was designed for each of the primary production regions studied and the Erosion Productivity Impact Calculator (EPIC) was used to simulate crop response to climate change. The GCMs applied were the Goddard Institute of Space Studies (GISS), the United Kingdom Meteorological Transient (UKTR) and the Australian Bureau of Meteorological Research Center (BMRC), each regionalized by means of a scenario generator (SCENGEN). The GISS scenarios have the least impact on corn and wheat production, reducing national potential production for corn by 6% and wheat by 7% at a GMT of 2.5 °C and no CO2 fertilization effect; the UKTR scenario had the most severe impact on wheat, reducing production by 18% under the same conditions; BMRC had the greatest negative impact on corn, reducing production by 20%. A GMT increase of 1.0°C marginally decreased corn and wheat production. Increasing GMT had a detrimental impact on both corn and wheat production, with wheat production suffering the greatest losses. Decreases for wheat production at GMT 5.0 and [CO2] = 365 ppm range from 36% for the GISS to 76% for the UKTR scenario. Increases in atmospheric [CO2] had a positive impact on both corn and wheat production. AT GMT 1.0, an increase in [CO2] to 560 ppm resulted in a net increase in corn and wheat production above baseline levels (from 18 to 29% for wheat and 2 to 5% for corn). Increases in [CO2] help to offset yield reductions at higher GMT levels; in most cases, however, these increases are not sufficient to return crop production to baseline levels.     

COMPARISON OF GLOBAL CLIMATE CHANGE SIMULATIONS FOR 2 × CO2-INDUCED WARMING

In this article we compile 108 national and international studies on global climate change, each projecting a quantitative impact on global surface-air temperature due to a doubling of the atmospheric CO₂ concentration. These predictions, documented between 1980 and 1995, are based primarily on climate-modeling research, including radiative-convective, energy-balance, and general circulation models. Collectively over the past 15 years, the average (mean) temperature change projection due to doubled CO₂ is +2.62°C, with a range of 0.16–8.7°C. General circulation models tend to estimate slightly higher values (2.98°C), compared with radiative-convective models (1.98°C) and energy-balance models (2.54°C). During the years 1980 through 1995, an increasing trend in predictions is noticed, although the mean temperature change prediction each year has remained fairly consistent near 2–3°C. These findings suggest that the estimated sensitivity of the climate system continues to remain comparable to the range calculated in earlier studies. However, tremendous advancements in the capacity of climate models continue to reveal important uncertainties in the dynamic nature of global atmospheric interactions. The predictions continue to validate the need for a global policy relating to human influence on global climate change.     

Spatial and temporal analysis of Middle Eastern temperature changes

The intense interest in the greenhouse effect has stimulated detailed studies of temperature records in North America, Europe, and Australia. In this investigation, the temperature records from the Middle East region (defined here as the land area extending from Morocco to Afghanistan) are investigated over the period 1950–1990. Results reveal a linear, statistically significant, temperature increase of 0.07°C per decade over the study area that may or may not be associated with the concurrent rise in equivalent carbon dioxide from approximately 350 ppm to 430 ppm. Seasonal analyses reveal that most of this increase has occurred in the spring season, moderate amounts of warming occurred in the summer and fall seasons, and virtually no warming has occurred in the winter months. An analysis of spatial controls on these temperature changes reveals a general cooling effect associated with the atmospheric sulfate levels and a warming effect associated with the degree of human-induced desertification. The results of this study may prove useful to policymakers in the Middle East who are confronted with many difficult decisions regarding highly interrelated global warming and energy issues.     

Options for differentiation of future commitments in climate policy: how to realise timely participation to meet stringent climate goals?

This paper aims at exploring options for differentiation of future commitments in global greenhouse gas emissions control, linked to climate targets. This is done on the basis of the EU target of a maximum global temperature increase of 2°C compared to pre-industrial levels. The Framework to Assess International Regimes for the differentiation of commitments (FAIR) is used to explore the implications of two possible climate regimes: (1) increasing participation (i.e. a gradual increase in the number of parties involved and their level of commitment according to participation and differentiation rules) and (2) ‘contraction and convergence’ (C&C) with universal participation and a convergence of per capita emission permits. It is found that in a regime of increasing participation, stabilising the CO₂ concentration at 450 ppmv by 2100 requires participation of major developing countries before 2050 in global emission control, irrespective of the participation and differentiation rules chosen. In the case of stringent climate targets, a convergence regime seems to provide more incentives for a timely participation of developing countries, and opportunities for an effective and efficient regime for controlling global emissions than increasing participation.     

Emission and flux of DMS from the Australian Antarctic and Subantarctic Oceans during the 1988/89 summer

DMS emissions and fluxes from the Australasian sector of the Antarctic and Subantarctic Oceans, bound by 46–68° S and 65.5–142.6° E, were determined from a limited number of samples (n=32) collected during three summer resupply voyages to Australian Antarctic continental research bases between November 1988 and January 1989 (a 92 day period). The maximum DMS emission from this sector of the Antarctic Ocean was in an area near the Antarctic Divergence (60–63° S) and the minimum DMS emission was from the Antarctic coastal and offshelf waters. The greatest emission of DMS from this sector of the Southern Ocean was from the Subantarctic waters. DMS flux from the Australasian Antarctic Ocean was 64.3×10⁶ (±115) mol d^–1 or 5.9 (±10.6)×10⁹ mol based on an emission of 10.9 (±19.5) µmol m^–2 d^–1 (n=26). The flux of DMS from the Australasian sector of the Subantarctic Ocean was probably twice the flux of DMS from the adjacent Antarctic Ocean.     

Comparative assessment of Japan's long-term carbon budget under different effort-sharing principles

This article assesses Japan's carbon budgets up to 2100 in the global efforts to achieve the 2?°C target under different effort-sharing approaches based on long-term GHG mitigation scenarios published in 13 studies. The article also presents exemplary emission trajectories for Japan to stay within the calculated budget.

The literature data allow for an in-depth analysis of four effort-sharing categories. For a 450?ppm CO₂e stabilization level, the remaining carbon budgets for 2014–2100 were negative for the effort-sharing category that emphasizes historical responsibility and capability. For the other three, including the reference ‘Cost-effectiveness’ category, which showed the highest budget range among all categories, the calculated remaining budgets (20th and 80th percentile ranges) would run out in 21–29 years if the current emission levels were to continue. A 550?ppm CO₂e stabilization level increases the budgets by 6–17 years-equivalent of the current emissions, depending on the effort-sharing category. Exemplary emissions trajectories staying within the calculated budgets were also analysed for ‘Equality’, ‘Staged’ and ‘Cost-effectiveness’ categories. For a 450?ppm CO₂e stabilization level, Japan's GHG emissions would need to phase out sometime between 2045 and 2080, and the emission reductions in 2030 would be at least 16–29% below 1990 levels even for the most lenient ‘Cost-effectiveness’ category, and 29–36% for the ‘Equality’ category. The start year for accelerated emissions reductions and the emissions convergence level in the long term have major impact on the emissions reduction rates that need to be achieved, particularly in the case of smaller budgets.

Policy relevance

In previous climate mitigation target formulation processes for 2020 and 2030 in Japan, neither equity principles nor long-term management of cumulative GHG emissions was at the centre of discussion. This article quantitatively assesses how much more GHGs Japan can emit by 2100 to achieve the 2?°C target in light of different effort-sharing approaches, and how Japan's GHG emissions can be managed up to 2100. The long-term implications of recent energy policy developments following the Fukushima nuclear disaster for the calculated carbon budgets are also discussed.     

Global distribution of natural freshwater wetlands and rice paddies,their net primary productivity,seasonality and possible methane emissions

A global data set on the geographic distribution and seasonality of freshwater wetlands and rice paddies has been compiled, comprising information at a spatial resolution of 2.5° by latitude and 5° by longitude. Global coverage of these wetlands total 5.7×10⁶ km² and 1.3×10⁶ km², respectively. Natural wetlands have been grouped into six categories following common terminology, i.e. bog, fen, swamp, marsh, floodplain, and shallow lake. Net primary productivity (NPP) of natural wetlands is estimated to be in the range of 4–9×10¹⁵ g dry matter per year. Rice paddies have an NPP of about 1.4×10¹⁵ g y^–1. Extrapolation of measured CH₄ emissions in individual ecosystems lead to global methane emission estimates of 40–160 Teragram (1 Tg=10¹² g) from natural wetlands and 60–140 Tg from rice paddies per year. The mean emission of 170–200 Tg may come in about equal proportions from natural wetlands and paddies. Major source regions are located in the subtropics between 20 and 30° N, the tropics between 0 and 10° S, and the temperate-boreal region between 50 and 70° N. Emissions are highly seasonal, maximizing during summer in both hemispheres. The wide range of possible CH₄ emissions shows the large uncertainties associated with the extrapolation of measured flux rates to global scale. More investigations into ecophysiological principals of methane emissions is warranted to arrive at better source estimates.     

Burden sharing and cohesion countries in European climate policy: the Portuguese example

Global climate change has emerged as a major policy issue in the last decade. The EU has fiercely advocated domestic action, but it is finding it hard to cope with its commitments. This is due to the stronger impact of interest groups on the national level when it comes to implementation. It is shown that Portugal and other cohesion countries may be incapable of complying with their commitments within the internal burden sharing agreement unless they manage to improve energy efficiencies. Fast growth in Portuguese emissions is expected in the face of a non-existent national plan and deteriorating energy efficiencies, unless additional measures and policies are implemented. Institutional and scientific deficiency supplemented by rapid economic development seem to be impeding the Portuguese policy goal. Moreover, the proposed formula to limit the use of flexible instruments places cohesion countries at a disadvantage. Several lessons for international and European environmental policy are taken from this case study. To reach the Kyoto target, the EU will have to develop credible mechanisms to enforce the targets of its Member States. If that is not feasible, it will have to revert to central acquisition of emission permits from abroad to make up internal shortfalls.     

Modelling of the long-range transport of peroxyacetylnitrate to Scandinavia

Model calculations and field measurements have shown that when air masses accumulate emissions of hydrocarbons and nitrogen oxides from sources in continental Europe and then move towards Scandinavia without any synoptic scale break-up of the atmospheric boundary layer (e.g. frontal passages), elevated PAN concentrations in southern Norway or Sweden in the range 1–5 ppb may be caused by long-range transport. The model calculations showed that over sea, the persistence of PAN was comparable to that of ozone in an ageing air mass when the temperatures were fairly low (5–10°C). At higher temperatures the thermal decomposition of PAN made the compound less persistent than ozone. Over land, the situation may be different since the ground removal is typically three times more efficient for ozone than for PAN.According to the model, the concentration of PAN did not change very much when an ageing air mass was exposed to moderate emissions of hydrocarbons, nitrogen oxides, or both. The concentration of PAN decreased less than the concentration of ozone when an ageing air mass was exposed to high emissions of nitrogen oxides.     

European climate in the late twenty-first century: regional simulations with two driving global models and two forcing scenarios

A basic analysis is presented for a series of regional climate change simulations that were conducted by the Swedish Rossby Centre and contribute to the PRUDENCE (Prediction of Regional scenarios and Uncertainties for Defining EuropeaN Climate change risks and Effects) project. For each of the two driving global models HadAM3H and ECHAM4/OPYC3, a 30-year control run and two 30-year scenario runs (based on the SRES A2 and B2 emission scenarios) were made with the regional model. In this way, four realizations of climate change from 1961–1990 to 2071–2100 were obtained. The simulated changes are larger for the A2 than the B2 scenario (although with few qualitative differences) and in most cases in the ECHAM4/OPYC3-driven (RE) than in the HadAM3H-driven (RH) regional simulations. In all the scenario runs, the warming in northern Europe is largest in winter or late autumn. In central and southern Europe, the warming peaks in summer when it locally reaches 10 °C in the RE-A2 simulation and 6–7 °C in the RH-A2 and RE-B2 simulations. The four simulations agree on a general increase in precipitation in northern Europe especially in winter and on a general decrease in precipitation in southern and central Europe in summer, but the magnitude and the geographical patterns of the change differ markedly between RH and RE. This reflects very different changes in the atmospheric circulation during the winter half-year, which also lead to quite different simulated changes in windiness. All four simulations show a large increase in the lowest minimum temperatures in northern, central and eastern Europe, most likely due to reduced snow cover. Extreme daily precipitation increases even in most of those areas where the mean annual precipitation decreases.     

Differentiating Future Commitments on the Basis of Countries’ Relative Historical Responsibility for Climate Change: Uncertainties in the ‘Brazilian Proposal’ in the Context of a Policy Implementation

During the negotiations on the Kyoto Protocol, Brazil proposed allocating the greenhouse gas emission reductions of Annex I Parties according to the relative effect of a country’s historical emissions on global temperature increase. This paper analyses the impact of scientific uncertainties and of different options in policy implementation (policy choices) on the contribution of countries’ historical emissions to indicators of historical responsibility for climate change. The influence of policy choices was found to be at least as large as the impact of the scientific uncertainties analysed here. Building on this, the paper then proceeds to explore the implications of applying the Brazilian Proposal as a climate regime for differentiation of future commitments on the global scale combined with an income threshold for participation of the non-Annex I regions. Under stringent climate targets, such a regime leads to high emission reductions for Annex I regions by 2050, in particular for Europe and Japan. The income threshold assumptions strongly affect the Annex I reductions, even more than the impact of another burden-sharing key. A variant of the Brazilian Proposal, allocating emission reductions on the basis of cumulative emissions since 1990, would lead to a more balanced distribution of emission reductions.     

CMIP6情景中主要温室气体和气溶胶排放强度的时空分布特征分析

基于不同共享社会经济路径（Shared Socioeconomic Pathways, SSPs）形成的8组最新的未来可能情景（SSPx-y情景）,被用于第六次耦合模式比较计划（CMIP6）,以据此来预估未来气候变化的可能幅度和趋势。本文主要对比分析了8组SSPx-y新情景中主要温室气体和气溶胶排放数据的基准年排放强度分布、未来排放强度的时空变化、以及在6个典型区域排放强度的逐年变化等特征。结果表明:二氧化碳（CO₂）、甲烷（CH₄）、黑碳（BC）、二氧化硫（SO₂）在基准年的排放强度高值区都位于东亚和南亚。相比于基准年,2100年CO₂和CH₄在高和低辐射强迫情景下表现出的排放强度变化有显著差异。此外,所有情景下2100年的BC和SO₂全球平均排放强度都弱于基准年的排放强度。在时间变化上,随着生物质能碳捕获与封存技术的不断进步,所有地区在4组不超过3.4 W/m2的低辐射强迫情景下,CO₂排放强度到2100年都呈现负值。其中,南美洲的负排放最强,2100年在SSP5-3.4情景下该地区的排放强度为－0.3 kg m－2 a－1。最后,对比东亚和南亚排放强度的逐年变化可以发现,在各情景所描述的未来发展过程中,东亚的减排行动的成效都要好于南亚。