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The current nationally determined contributions, pledged by the countries under the Paris Agreement, are far from limiting climate change to below 2 ∘C temperature increase by the end of the century. The necessary ratcheting up of climate policy is projected to come with a wide array of additional benefits, in particular a reduction of today's 4.5 million annual premature deaths due to poor air quality. This paper therefore addresses the question how climate policy and air pollution–related health impacts interplay until 2050 by developing a comprehensive global modeling framework along the cause and effect chain of air pollution–induced social costs. We find that ratcheting up climate policy to a 2 ∘ compliant pathway results in welfare benefits through reduced air pollution that are larger than mitigation costs, even with avoided climate change damages neglected. The regional analysis demonstrates that the 2 ∘C pathway is therefore, from a social cost perspective, a "no-regret option" in the global aggregate, but in particular for China and India due to high air quality benefits, and also for developed regions due to net negative mitigation costs. Energy and resource exporting regions, on the other hand, face higher mitigation cost than benefits. Our analysis further shows that the result of higher health benefits than mitigation costs is robust across various air pollution control scenarios. However, although climate mitigation results in substantial air pollution emission reductions overall, we find significant remaining emissions in the transport and industry sectors even in a 2 ∘C world. We therefore call for further research in how to optimally exploit climate policy and air pollution control, deriving climate change mitigation pathways that maximize co-benefits. [ABSTRACT FROM AUTHOR]

The IPCC Fourth Assessment Report, Working Group III, summarises in Box 13.7 the required emission reduction ranges in Annex I and non-Annex I countries as a group, to achieve greenhouse gas concentration stabilisation levels between 450 and 650 ppm CO2-eq. The box summarises the results of the IPCC authors’ analysis of the literature on the regional allocation of the emission reductions. The box states that Annex I countries as a group would need to reduce their emissions to below 1990 levels in 2020 by 25% to 40% for 450 ppm, 10% to 30% for 550 ppm and 0% to 25% for 650 ppm CO2-eq, even if emissions in developing countries deviate substantially from baseline for the low concentration target. In this paper, the IPCC authors of Box 13.7 provide background information and analyse whether new information, obtained after completion of the IPCC report, influences these ranges. The authors concluded that there is no argument for updating the ranges in Box 13.7. The allocation studies, which were published after the writing of the IPCC report, show reductions in line with the reduction ranges in the box. From the studies analysed, this paper specifies the “substantial deviation” or “deviation from baseline” in the box: emissions of non-Annex I countries as a group have to be below the baseline roughly between 15% to 30% for 450 ppm CO2-eq, 0% to 20% for 550 ppm CO2-eq and from 10% above to 10% below the baseline for 650 ppm CO2-eq, in 2020. These ranges apply to the whole group of non-Annex I countries and may differ substantially per country. The most important factor influencing these ranges above, for non-Annex I countries, and in the box, for Annex I countries, is new information on higher baseline emissions (e.g. that of Sheehan, Climatic Change, , this issue). Other factors are the assumed global emission level in 2020 and assumptions on land-use change and forestry emissions. The current, slow pace in climate policy and the steady increase in global emissions, make it almost unfeasible to reach relatively low global emission levels in 2020 needed to meet 450 ppm CO2-eq, as was first assumed feasible by some studies, 5 years ago. [ABSTRACT FROM AUTHOR]

In international climate policy discussions, one of the central issues for medium- to long run climate protection strategies is the uncertainty about the costs and the distributional effects of specific unilateral or multilateral emission reductions. This paper looks at the world-wide effects of climate protection strategies on the allocation of resources, on economic growth in different regions, and on the regional welfare effects. The analysis is based on a global recursively dynamic, multi-region, multi-sector computable general equilibrium model parameterized according to the ICLIPS (Integrated Assessment of Climate Protection Strategies) integrated assessment model. The simulations show that national climate policies will have important international repercussions. It is therefore important to consider international allocation effects in the analysis of national climate protection strategies. The welfare costs of greenhouse gas emission reductions rise more than proportionally with lower emission targets. The analysis of the carbon leakage rate indicates that most of the leakage rapidly disappears if emission reduction moves towards an efficient distribution of emission targets. [ABSTRACT FROM AUTHOR]

Today Africa is a small emitter, but it has a large and faster-than-average growing population and per capita income that could drive future energy demand and, if unconstrained, emissions. This paper uses a multi-model comparison to characterize the potential future energy development for Continental and Sub-Saharan Africa under different assumptions about population and income. Our results suggest that population and economic growth rates will strongly influence Africa's future energy use and emissions. We show that affluence is only one face of the medal and the range of future emissions is also contingent on technological and political factors. Higher energy intensity improvements occur when Africa grows faster. In contrast, climate intensity varies less with economic growth and it is mostly driven by climate policy. African emissions could account for between 5 % and 20 % of global emissions, with Sub-Saharan Africa contributing between 4 % and 10 % of world emissions in 2100. In all scenarios considered, affluence levels remain low until the middle of the century, suggesting that the population could remain dependent on traditional bioenergy to meet most residential energy needs. Although the share of electricity in final energy, electric capacity and electricity use per capita all rise with income, even by mid-century they do not reach levels observed in developed countries today. [ABSTRACT FROM AUTHOR]

Abstract 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. [ABSTRACT FROM AUTHOR]

This paper compares projections over the twenty-first century of SO, BC, and OC emissions from three technologically detailed, long-term integrated assessment models. The character of the projections and the response of emissions due to a comprehensive climate policy are discussed focusing on the sectoral level. In a continuation of historical experience, aerosol and precursor emissions are increasingly decoupled from carbon dioxide emissions over the twenty-first century due to a combination of emission controls and technology shifts over time. Implementation of a comprehensive climate policy further reduces emissions, although there is significant variation in this response by sector and by model: the response has many similarities between models for the energy transformation and transportation sectors, with more diversity in the response for the building and industrial sectors. Much of these differences can be traced to specific characteristics of reference case end-use and supply-side technology deployment and emissions control assumptions, which are detailed by sector. [ABSTRACT FROM AUTHOR]

This paper investigates the extent to which uncertainty on regional patterns of economic growth and fossil fuel availability impacts regional emission patterns, emission drivers, and regional mitigation potentials and strategies, through an analysis across five key world regions in different stages of their economic development (Africa, India, China, Europe and the USA) using a set of scenarios simulated with the REMIND model. Important differences are identified in emission trajectories of developed, emerging and developing regions, in both the baseline and the climate policy scenarios, due to differences in economic growth rates, energy and carbon intensity developments, and mitigation potentials. In the baseline, energy intensity developments vary strongly with economic growth assumptions, while fossil fuel availability has a particularly strong effect on carbon intensity developments which result in more region-specific sensitivity than do economic growth variations. On the other hand, the core findings associated to climate policy and regional mitigation strategies remain unaffected by this uncertainty. In all baseline scenarios China, the USA and India are the greatest emitters in terms of cumulated 21st century emissions, comprising almost 50 % of the global total. Differences in terms of per capita emissions between developed and developing countries persist under either baseline assumption, but are contracted under climate policy. Long-term per capita emissions remain above world average in China, India and Europe, reflecting their relatively smaller renewable resource potentials. The core regional technological implications of climate change mitigation are insensitive to economic growth and fossil fuel availability assumptions. [ABSTRACT FROM AUTHOR]

Climate policies must consider radiative forcing from Kyoto greenhouse gases, as well as other forcing constituents, such as aerosols and tropospheric ozone that result from air pollutants. Non-Kyoto forcing constituents contribute negative, as well as positive forcing, and overall increases in total forcing result in increases in global average temperature. Non-Kyoto forcing modeling is a relatively new component of climate management scenarios. This paper describes and assesses current non-Kyoto radiative forcing modeling within five integrated assessment models. The study finds negative forcing from aerosols masking (offsetting) approximately 25 % of positive forcing in the near-term in reference non-climate policy projections. However, masking is projected to decline rapidly to 5-10 % by 2100 with increasing Kyoto emissions and assumed reductions in air pollution-with the later declining to as much as 50 % and 80 % below today's levels by 2050 and 2100 respectively. Together they imply declining importance of non-Kyoto forcing over time. There are however significant uncertainties and large differences across models in projected non-Kyoto emissions and forcing. A look into the modeling reveals differences in base conditions, relationships between Kyoto and non-Kyoto emissions, pollution control assumptions, and other fundamental modeling. In addition, under climate policy scenarios, we find air pollution and resulting non-Kyoto forcing reduced to levels below those produced by air pollution policies alone-e.g., China sulfur emissions fall an additional 45-85 % by 2050. None of the models actively manage non-Kyoto forcing for climate implications. Nonetheless, non-Kyoto forcing may be influencing mitigation results, including allowable carbon dioxide emissions, and further evaluation is merited. [ABSTRACT FROM AUTHOR]

This paper synthesizes results of the multi-model Energy Modeling Forum 27 (EMF27) with a focus on climate policy scenarios. The study included two harmonized long-term climate targets of 450 ppm CO-e (enforced in 2100) and 550 pm CO-e (not-to-exceed) as well as two more fragmented policies based on national and regional emissions targets. Stabilizing atmospheric GHG concentrations at 450 and 550 ppm CO-e requires a dramatic reduction of carbon emissions compared to baseline levels. Mitigation pathways for the 450 CO-e target are largely overlapping with the 550 CO-e pathways in the first half of the century, and the lower level is achieved through rapid reductions in atmospheric concentrations in the second half of the century aided by negative anthropogenic carbon flows. A fragmented scenario designed to extrapolate current levels of ambition into the future falls short of the emissions reductions required under the harmonized targets. In a more aggressive scenario intended to capture a break from observed levels of stringency, emissions are still somewhat higher in the second half due to unabated emissions from non-participating countries, emphasizing that a phase-out of global emissions in the long term can only be reached with full global participation. A key finding is that a large range of energy-related CO emissions can be compatible with a given long-term target, depending on assumptions about carbon cycle response, non-CO and land use CO emissions abatement, partly explaining the spread in mitigation costs. [ABSTRACT FROM AUTHOR]

This paper presents a new accounting mechanism in the context of the UNFCCC issue on reducing emissions from deforestation in developing countries, including technical options for determining baselines of forest conversions. This proposal builds on the recent scientific achievements related to the estimation of tropical deforestation rates and to the assessment of 'intac' forest areas. The distinction between 'intact' and 'non intact' forests used here arises from experience with satellite-based deforestation measurements and allows accounting for carbon losses from forest degradation. The proposed accounting system would use forest area conversion rates as input data. An optimal technical solution to set baselines would be to use historical average figures during the time period from 1990 to 2005. The system introduces two different schemes to account for preserved carbon: one for countries with high forest conversion rates where the desired outcome would be a reduction in their rates, and another for countries with low rates. A 'global' baseline rate would be used to discriminate between these two country categories (high and low rates). For the hypothetical accounting period 2013-2017 and considering 72% of the total tropical forest domain for which data are available, the scenario of a 10% reduction of the high rates and of the preservation of low rates would result in approximately 1.6 billion tCO2 of avoided emissions. The resulting benefits of this reduction would be shared between those high-rate countries which reduced deforestation and those low-rate countries which did not increase their deforestation over an agreed threshold (e.g., half of "global" baseline rate). [ABSTRACT FROM AUTHOR]

The greenhouse gas emissions scenarios published by the IPCC in the Special Report on Emission Scenarios (SRES) continue to serve as a primary basis for assessing future climate change and possible response strategies. These scenarios were developed between 1996 and 1999 and sufficient time has now passed to make it worth examining their consistency with more recent data and projections. The comparison performed in this paper includes population, GDP, energy use, and emissions of CO2, non-CO2 gases and sulfur. We find the SRES scenarios to be largely consistent with historical data for the 1990-2000 period and with recent projections. Exceptions to this general observation include (1) in the long-term, relatively high population growth assumptions in some regions, particularly in the A2 scenario; (2) in the medium-term, relatively high economic growth assumptions in the LAM (Latin America, Africa and Middle East) region in the A1 scenario; (3) in the short-term, CO2 emissions projections in Al that are somewhat higher than the range of current scenarios; and (4) substantially higher sulfur emissions in some scenarios than in historical data and recent projections. In conclusion, given the relatively small inconsistencies for use as global scenarios there seems to be no immediate need for a large-scale IPCC-led update of the SRES scenarios that is solely based on the SRES scenario performance vis-a-vis data for the 1990-2000 period and/or more recent projections. Based on reported findings, individual research teams could make, and in some cases already have made, useful updates of the scenarios. [ABSTRACT FROM AUTHOR]

In this paper, we present a method to quantify the effectiveness of carbon mitigation options taking into account the `permanence' of the emissions reduction. While the issue of permanence is most commonly associated with a `leaky' carbon sequestration reservoir, we argue that this is an issue that applies to just about all carbon mitigation options. The appropriate formulation of this problem is to ask `what is the value of temporary storage?' Valuing temporary storage can be represented as a familiar economic problem, with explicitly stated assumptions about carbon prices and the discount rate. To illustrate the methodology, we calculate the sequestration effectiveness for injecting CO2 at various depths in the ocean. Analysis is performed for three limiting carbon price assumptions: constant carbon prices (assumes constant marginal damages), carbon prices rise at the discount rate (assumes efficient allocation of a cumulative emissions cap without a backstop technology), and carbon prices first rise at the discount rate but become constant after a given time (assumes introduction of a backstop technology). Our results show that the value of relatively deep ocean carbon sequestration can be nearly equivalent to permanent sequestration if marginal damages (i.e., carbon prices) remain constant or if there is a backstop technology that caps the abatement cost in the not too distant future. On the other hand, if climate damages are such as to require a fixed cumulative emissions limit and there is no backstop, then a storage option with even very slow leakage has limited value relative to a permanent storage option. [ABSTRACT FROM AUTHOR]

This paper presents an approach to estimating world-regional carbon mitigation cost functions for the years 2020, 2050, and 2100. The approach explicitly includes uncertainty surrounding such carbon reduction costs. It is based on the analysis of global energy-economy-environment scenarios described for the 21st century. We use one baseline scenario and variants thereof to estimate cumulative costs of carbon mitigation as a function of cumulative carbon emission reductions. For our baseline for estimating carbon mitigation cost curves, we use the so-called IIASA F scenario. The F scenario is a high-growth, high-emissions scenario designed specifically to be used as a reference against which to evaluate alternatives. Carbon emissions and energy systems costs in the F scenario are then compared with (reduced) emissions and (higher) costs (including macroeconomic adjustment costs) of alternative scenarios taken from the IIASA scenario database. As a kind of sensitivity analysis of our approach, we also present the results of a scenario involving assumptions on particularly rapid technological progress. [ABSTRACT FROM AUTHOR]

In integrated assessments of climate change, greenhouse-gas emissions and climate change impacts provide the linkages between the world economy and the climate system. Key climatic processes operate at the scales of centuries. This requires highly aggregated models for portraying the dynamics of the economic system. An extended Ramsey-type optimal growth model is presented as the appropriate tool to be integrated with a reduced-form climate model in the ICLIPS integrated assessment. The eleven-region model of the world economy involves exogenous population and endogenous investment dynamics with productivity progress based on a technological diffusion model. World regions are linked via intertemporal trade flows of the composite consumption/investment good, capital mobility, and emission permit trading. Coupled with the ICLIPS Climate Model, the Aggregated Economic Model can determine corridors of permitted long-term carbon emission paths or, as primarily discussed in this paper, specific cost-effective emission trajectories. The sensitivity of mitigation costs to externally specified climate change/impact constraints and to assumptions about non-CO2 greenhouse-gas emissions is also discussed. [ABSTRACT FROM AUTHOR]

We have compiled historical greenhouse gas emissions and their uncertainties on country and sector level and assessed their contribution to cumulative emissions and to global average temperature increase in the past and for a the future emission scenario. We find that uncertainty in historical contribution estimates differs between countries due to different shares of greenhouse gases and time development of emissions. Although historical emissions in the distant past are very uncertain, their influence on countries' or sectors' contributions to temperature increase is relatively small in most cases, because these results are dominated by recent (high) emissions. For relative contributions to cumulative emissions and temperature rise, the uncertainty introduced by unknown historical emissions is larger than the uncertainty introduced by the use of different climate models. The choice of different parameters in the calculation of relative contributions is most relevant for countries that are different from the world average in greenhouse gas mix and timing of emissions. The choice of the indicator (cumulative GWP weighted emissions or temperature increase) is very important for a few countries (altering contributions up to a factor of 2) and could be considered small for most countries (in the order of 10%). The choice of the year, from which to start accounting for emissions (e.g. 1750 or 1990), is important for many countries, up to a factor of 2.2 and on average of around 1.3. Including or excluding land-use change and forestry or non-CO gases changes relative contributions dramatically for a third of the countries (by a factor of 5 to a factor of 90). Industrialised countries started to increase CO emissions from energy use much earlier. Developing countries' emissions from land-use change and forestry as well as of CH and NO were substantial before their emissions from energy use. [ABSTRACT FROM AUTHOR]

The tolerable windows approach (TWA) allows the climate policy formulation process to be safeguarded in the following way. First, guardrails are defined in order to exclude intolerable climate change impacts, on the one hand, and unacceptable socioeconomic consequences of climate change mitigation measures, on the other. Second, a scientific analysis is conducted to investigate the features of those emission paths that are compatible with the guardrail constraints. The fundamental methodology of the TWA is best described in terms of the theory of differential inclusions. This emerging mathematical theory already provides numerical methods applicable as long as the underlying integrated assessment models are of limited complexity. In order to identify emissions corridors, we propose a novel calculation scheme applicable also for large-scale integrated assessment models. [ABSTRACT FROM AUTHOR]

The overlap in sources of greenhouse gas and local air pollutant emissions creates scope for policy measures to limit global warming and improve air quality simultaneously. In a first step, we derive estimates for the air pollution mortality-related component of the social cost of atmospheric release for 6 pollutants and 56 regions in the world. Combining these estimates with emission inventory data highlights that sector contributions to greenhouse gas emissions and air pollution health impacts differ widely across regions. Next, simulations of future emission pathways consistent with the 2 °C and 1.5 °C targets illustrate that strengthening climate policy ambition raises the total value of air quality co-benefits despite lower marginal co-benefits per tonne of greenhouse gas emissions abated. Finally, we use results from a multi-model ensemble to quantify and compare the value of health-related ambient air quality co-benefits of climate policy across sectors and regions. On the global level, overall air quality co-benefits range from $8 to $40 per tonne of greenhouse gases abated in 2030, with median across models and scenarios of $18/tCO2e. These results mask strong differentiation across regions and sectors, with median co-benefits from mitigation in the residential and service sectors in India exceeding $500/tCO2e. By taking a sector- and region-specific perspective, the results presented here reveal promising channels to improve human health outcomes and to ratchet up greenhouse gas reduction efforts to bridge the gap between countries' pledges and the global targets of the Paris Agreement. [ABSTRACT FROM AUTHOR]

A variety of decision makers need projections of future energy demand, CO2 emissions and similar factors that extend many decades into the future. The past performance of such projections has been systematically overconfident. Analysts have often used scenarios based on detailed story lines that spell out “plausible alternative futures” as a central tool for evaluating uncertainty. No probabilities are typically assigned to such scenarios. We argue that this practice is often ineffective. Rather than expanding people’s judgment about the range of uncertainty about the future, scenario-based analysis is more likely to lead to systematic overconfidence, to an underestimate of the range of possible future outcomes. We review relevant findings from the literature on human judgment under uncertainty and discuss their relevance to the task of making probabilistic projections. The more detail that one adds to the story line of a scenario, the more probable it will appear to most people, and the greater the difficulty they likely will have in imagining other, equally or more likely, ways in which the same outcome could be reached. We suggest that scenario based approaches make analysts particularly prone to such cognitive biases, and then outline a strategy by which improved projections, tailored to the needs of specific decision makers, might be developed. [ABSTRACT FROM AUTHOR]

Institutional investors have two important roles to play in encouraging companies to address the risks and take advantage of the opportunities presented by climate change. The first is through using their influence as shareholders to encourage companies to adopt more proactive approaches to managing the risks and opportunities presented by climate change. The second is through explicitly factoring climate change risks and opportunities into ‘mainstream’ investment analysis processes. While there is growing investor activity on the former, the integration of climate change into investment analysis remains confined to sectors where there are strong government incentives (e.g. for renewable energy) or where greenhouse gas emissions have a market price. This article reviews the evolution of UK institutional investor interest in climate change from 1990 to 2005, focusing in particular on the relative contributions of ‘soft’ policy measures such as information-disclosure and awareness raising, and ‘hard’ policy measures such as regulation and market-based instruments. The article concludes that, over this period, soft policy measures played an important role in encouraging investors to discuss climate change issues with companies, but had minimal influence on investment decisions. It was only with the introduction of hard policy measures that climate change started to be systematically factored into investment analysis. The article canvasses the implications of these findings for government efforts in the UK and elsewhere to encourage investors to play a more proactive role in the climate change debate. It also considers the role that institutional investors themselves can play in strengthening public policy measures to reduce greenhouse gas emissions. [ABSTRACT FROM AUTHOR]

Stabilization of atmospheric CO2 concentrations below a pre-industrial doubling (~550 ppm) is a commonly cited target in climate policy assessment. When the rate at which future emissions can fall is assumed to be fixed, the peak atmospheric concentration - or the stabilization "frontier" - is an increasing and convex function of the length of postponement. Here we find that a decline in emissions of 1% year-1 beginning today would place the frontier near 475 ppm and that when mitigation is postponed, options disappear (on average) at the rate of ~9 ppm year-1, meaning that delays of more than a decade will likely preclude stabilization below a doubling. When constraints on the future decline rate of emissions are relaxed, a particular atmospheric target can be realized in many ways, with scenarios that allow longer postponement of emissions reductions requiring greater increases in the intensity of future mitigation. However, the marginal rate of substitution between future mitigation and present delay becomes prohibitively large when the balance is shifted too far toward the future, meaning that some amount of postponement cannot be fully offset by simply increasing the intensity of future mitigation. Consequently, these results suggest that a practical transition path to a given stabilization target in the most commonly cited range can allow, at most, one or two decades of delay. [ABSTRACT FROM AUTHOR]

We investigate uncertainties about conventional petroleum resources and substitutes for conventional petroleum, focusing on the impact of these uncertainties on future greenhouse gas (GHG) emissions. We use examples from the IPCC Special Report on Emissions Scenarios as a baseline for comparison. The studied uncertainties include, (1) uncertainty in emissions factors for petroleum substitutes, (2) uncertainties resulting from poor knowledge of the amount of remaining conventional petroleum, and (3) uncertainties about the amount of production of petroleum substitutes from natural gas and coal feedstocks. We find that the potential effects of a transition to petroleum substitutes on GHG emissions are significant. A transition to low-quality and synthetic petroleum resources such as tar sands or coal-to-liquids synfuels could raise upstream GHG emissions by several gigatonnes of carbon (GtC) per year by mid-century unless mitigation steps are taken. [ABSTRACT FROM AUTHOR]

Countries can use both mitigation and adaptation strategies to protect their citizens from catastrophic risk posed by climate change (e.g., shift in the jet stream). A nation can mitigate by reducing CO2 emissions, which reduces the probability of a catastrophic event; it can adapt by altering the infrastructure so that damages can be reduced in the event a catastrophe is realized. Herein we add to the current literature by extending the endogenous risk framework into a dynamic framework permitting analysis of both mitigation and adaptation while allowing for the dynamic process of global climate change. Our results suggest adaptation to catastrophe is a small fraction of the national climate protection budget relative to mitigation when nations cooperate fully, when damages are both continuous and catastrophic, and when nations have a short planning horizon. Adaptation becomes more important relative to mitigation when nations are unlikely to cooperate, when damages are mainly catastrophic, or when the nation's planning horizon increases. [ABSTRACT FROM AUTHOR]

Evidence of increasing nitrogen levels in the Suwannee River Basin in North Florida demands a collaborative effort to find creative ways to reduce N pollution. This study explores the perspectives, perceptions, and attitudes of dairy farmers regarding adoption of climate forecasts as a potential way to mitigate the problem. These farmers are heavily scrutinized because of their nitrogen emissions. By contrasting scientists' pre-conceived attitudes about the usefulness of ENSO-based forecasts with dairy farmers' perceptions, gathered in a participatory and consensual manner, valuable lessons were learned. A deeper understanding of the day to day realities of dairy farming systems help researchers pinpoint management adaptations that are not only useful, but feasible, in light of improved seasonal climate forecasts. Furthermore, dairy farmers' perceptions regarding the use of seasonal climate information to mitigate the nitrate problem are critical for designing future dairy systems. [ABSTRACT FROM AUTHOR]

We estimate the domestic environmental and health benefits of exploiting China's energy-related CDM potential. Exploiting the CDM potential may save between 3,000 and 40,000 lives annually. Additional gains are estimated to reach upwards from 1 billion RMB annually. The key to these gains is the fact that actions and measures to reduce CO2 emissions also reduce emissions of TSP and SO2. In our estimate, exploiting the CDM-potential will cut SO2-emissions by between one-half and three million tons annually. To arrive at these conclusions we synthesize a significant body of recent research on co-benefits of climate abatement in China. [ABSTRACT FROM AUTHOR]

Today's climate policy is based on the assumption that the location of emissions reductions has no impact on the overall climate effect. However, this may not be the case since reductions of greenhouse gases generally will lead to changes in emissions of short-lived gases and aerosols. Abatement measures may be primarily targeted at reducing CO2, but may also simultaneously reduce emissions of NOx, CO, CH4 and SO2 and aerosols. Emissions of these species may cause significant additional radiative forcing. We have used a global 3-D chemical transport model and a radiative transfer model to study the impact on climate in terms of radiative forcing for a realistic change in location of the emissions from large-scale sources. Based on an assumed 10% reduction in CO2 emissions, reductions in the emissions of other species have been estimated. Climate impact for the SRES A1B scenario is compared to two reduction cases, with the main focus on a case with emission reductions between 2010 and 2030, but also a case with sustained emission reductions. The emission reductions are applied to four different regions (Europe, China, South Asia, and South America). In terms of integrated radiative forcing (over 100 yr), the total effect (including only the direct effect of aerosols) is always smaller than for CO2 alone. Large variations between the regions are found (53-86% of the CO2 effect). Inclusion of the indirect effects of sulphate aerosols reduces the net effect of measures towards zero. The global temperature responses, calculated with a simple energy balance model, show an initial additional warming of different magnitude between the regions followed by a more uniform reduction in the warming later. A major part of the regional differences can be attributed to differences related to aerosols, while ozone and changes in methane lifetime make relatively small contributions. Emission reductions in a different sector (e.g. transportation instead of large-scale sources) might change this conclusion since the NOx to SO2 ratio in the emissions is significantly higher for transportation than for large-scale sources. The total climate effect of abatement measures thus depends on (i) which gases and aerosols are affected by the measure, (ii) the lifetime of the measure implemented, (iii) time horizon over which the effects are considered, and (iv) the chemical, physical and meteorological conditions in the region. There are important policy implications of the results. Equal effects of a measure cannot be assumed if the measure is implemented in a different region and if several gases are affected. Thus, the design of emission reduction measures should be considered thoroughly before implementation. [ABSTRACT FROM AUTHOR]

The capture and storage of CO2 from combustion of fossil fuels is gaining attraction as a means to deal with climate change. CO2 emissions from hiomass conversion processes can also be captured. If that is done, biomass energy with CO2 capture and storage (BECS) would become a technology that removes CO2 from the atmosphere and at the same time deliver CO2-neutral energy carriers (heat, electricity or hydrogen) to society. Here we present estimates of the costs and conversion efficiency of electricity, hydrogen and heat generation from fossil fuels and biomass with CO2 capture and storage. We then insert these technology characteristics into a global energy and transportation model (GET 5.0), and calculate costs of stabilizing atmospheric CO2 concentration at 350 and 450 ppm. We find that carbon capture and storage technologies applied to fossil fuels have the potential to reduce the cost of meeting the 350 ppm stabilisation targets by 50% compared to a case where these technologies are not available and by 80% when BECS is allowed. For the 450 ppm scenario, the reduction in costs is 40 and 42%, respectively. Thus, the difference in costs between cases where BECS technologies are allowed and where they are not is marginal for the 450 ppm stabilization target. It is for very low stabilization targets that negative emissions become warranted, and this makes BECS more valuable than in cases with higher stabilization targets. Systematic and stochastic sensitivity analysis is performed. Finally, BECS opens up the possibility to remove CO2 from the atmosphere. But this option should not be seen as an argument in favour of doing nothing about the climate problem now and then switching on this technology if climate change turns out to be a significant problem. It is not likely that BECS can be initiated sufficiently rapidly at a sufficient scale to follow this path to avoiding abrupt and serious climate changes if that would happen. [ABSTRACT FROM AUTHOR]

We investigate the sensitivity of emissions corridors for the 21st century to various factors that are currently under debate in the climate change arena. Emissions corridors represent the range of admissible emissions futures that observe some predefined guardrails on the future development of the human-climate system. They are calculated on the conceptual and methodological basis of the tolerable windows approach. We assess the sensitivity of the corridors to the choice of time-resolved as well as intertemporally aggregated guardrails that exclude an intolerable amount of climate change on the one hand and unbearable mitigation burdens on the other. In addition, we investigate the influence of climate sensitivity on the corridors. [ABSTRACT FROM AUTHOR]

The anthropogenic era is generally thought to have begun 150 to 200 years ago, when the industrial revolution began producing CO2 and CH4 at rates sufficient to alter their compositions in the atmosphere. A different hypothesis is posed here: anthropogenic emissions of these gases first altered atmospheric concentrations thousands of years ago. This hypothesis is based on three arguments. (1) Cyclic variations in CO2 and CH4 driven by Earth-orbital changes during the last 350,000 years predict decreases throughout the Holocene, but the CO2 trend began an anomalous increase 8000 years ago, and the CH4 trend did so 5000 years ago. (2) Published explanations for these mid- to late-Holocene gas increases based on natural forcing can be rejected based on paleoclimatic evidence. (3) A wide array of archeological, cultural, historical and geologic evidence points to viable explanations tied to anthropogenic changes resulting from early agriculture in Eurasia, including the start of forest clearance by 8000 years ago and of rice irrigation by 5000 years ago. In recent millennia, the estimated warming caused by these early gas emissions reached a global-mean value of ~ 0.8 °C and roughly 2 °C at high latitudes, large enough to have stopped a glaciation of northeastern Canada predicted by two kinds of climatic models. CO2 oscillations of ~ 10 ppm in the last 1000 years are too large to be explained by external (solar-volcanic) forcing, but they can be explained by outbreaks of bubonic plague that caused historically documented farm abandonment in western Eurasia. Forest regrowth on abandoned farms sequestered enough carbon to account for the observed CO2 decreases. Plague-driven CO2 changes were also a significant causal factor in temperature changes during the Little Ice Age (1300–1900 AD). [ABSTRACT FROM AUTHOR]

Given the present commitment of the developed countries according to the Kyoto Protocol, most published scenarios demonstrate that global greenhouse gases concentrations would not be stabilized at any level. In order to stabilize these concentrations, a deeper global involvement is needed. Taking Israel as an example of a `recently-developed' country, we assess the role that such countries could play by assuming voluntary commitments in strengthening global involvement. This case as a model may encourage a global scheme for curbing carbon emissions, in which the more developed countries assume a stronger role and the less developed countries participate according to the principle of common but differentiated responsibility. The scheme builds on the inverse relation that exists between the per capita gross domestic product and the rate of increase of emissions due to economic growth. According to this theoretical scheme, the voluntary commitments assumed by the `recently-developed' countries encourage the more developed countries to deepen their involvement by assuming more stringent reductions of emissions at home and transferring technological and financial means to the less developed countries. The proposed scheme would enable non-Annex I countries, both `recently-developed' countries and less developed countries, to participate much earlier in the net mitigation of greenhouse gases. [ABSTRACT FROM AUTHOR]

The annual trace gas emissions from a West African rural region were calculated using direct observations of gas emissions and burning practices, and the findings compared to the guidelines published by the IPCC. This local-scale study was conducted around the village of Dalun in the Northern Region of Ghana, near the regional capital of Tamale. Two types of fires were found in the region – agricultural fires and wildfires. Agricultural fires are intentionally set in order to remove shrub and crop residues; wildfires are mostly ignited by herders to remove inedible grasses and to promote the growth of fresh grass. An agricultural fire is ignited with a fire front moving against the wind (backfire), whereas a wildfire moves with the wind (headfire). Gas emissions (CO2, CO and NO) were measured by burning eight experimental plots, simulating both headfires and backfires. A common method of evaluating burning conditions is to calculate modified combustion efficiency (MCE), which expresses the percentage of the trace gases released as CO2. Modified combustion efficiency was 95% in the wildfires burned as headfires, but only 90% in the backfires. The burned area in the study region was determined by classifying a SPOT HRV satellite image taken about two months into the dry season. Fires were classified as either old burned areas or new burned areas as determined by the gradient in moisture content in the vegetation from the onset of the dry season. Classified burned areas were subsequently divided into two classes depending on whether the location was in the cultivated area or in the rangeland area, this sub-classification thus indicating whether the fire had been burned as a backfire or headfire. Findings showed that the burned area was 48% of the total region, and that the ratio of lowland wildfires to agricultural fires was 3:1. The net trace gas release from the classified vegetation burnings were extrapolated to 26–46×108 g CO2, 78–302×106 g CO, 17–156×105 g CH4, 16–168×105 g NMHC and 11–72×103 NOx. Calculation of the emissions using proposed IPCC default values on burned area and average biomass resulted in a net emission 5 to 10 times higher than the measured emission values. It was found that the main reason for this discrepancy was not the emission factors used by the IPCC, but an exaggerated fuel load estimate. [ABSTRACT FROM AUTHOR]

The computational burden associated with applications of the Tolerable Windows Approach (TWA) considerably exceeds that of traditional integrated assessments of global climate change. As part of the ICLIPS (Integrated Assessment of Climate Protection Strategies) project, a computationally efficient climate model has been developed that can be included in integrated assessment models of any kind. The ICLIPS climate model (ICM) is implemented in GAMS. It is driven by anthropogenic emissions of CO2, CH4, N2O, halocarbons, SF6, and SO2. The output includes transient patterns of near-surface air temperature, total column-integrated cloud cover fraction, precipitation, humidity, and global mean sea-level rise. The carbon cycle module explicitly treats the nonlinear sea water carbon chemistry and the nonlinear CO2 fertilized biosphere uptake. Patterns of the impact-relevant climate variables are derived form empirical orthogonal function (EOF) analysis and scaled by the principal component of temperature change. The evolution of the latter is derived from a box-model-type differential analogue to its impulse response function convolution integral. We present a description of the ICM components and some results to demonstrate the model's applicability in the TWA setting. [ABSTRACT FROM AUTHOR]