Differentiating (historic) responsibilities for climate change

Following the conclusion of the official work of the Ad Hoc Group for the Modelling and Assessment of Contributions to Climate Change (MATCH), this article considers the politically more sensitive aspect of the Brazilian proposal, namely the issue of differentiating (historic) responsibility for, and not merely (causal) contribution to climate change. Its aim is (1) to highlight the fact that, while related, the two issues (‘contribution to’ and ‘responsibility for’) are fundamentally different and should not be confused, and (2) to propose a methodology for calculating shares of responsibility as opposed to the shares in causal contribution arrived at through the MATCH results. Two conceptions of responsibility (‘strict’ or ‘limited’) are applied in order to operationalize the notion of ‘respective capabilities’ given in Article 3.1 of the UNFCCC. The key message resulting from the calculations is that causal contribution—while an important indicator of (environmental) relevance to the problem—must not be confused with the moral responsibility for it. The rather large difference between the responsibilities at the two extremes of the scale under both conceptions gives pause for thought as to what sorts of burdens can justly be demanded in any application of the UNFCCC principle of common but differentiated responsibilities, whether in the context of the Brazilian proposal or beyond.     

Cumulative CO2 emissions: shifting international responsibilities for climate debt

In contrast to many discussions based on annual emissions, this article presents calculations and projections of cumulative contributions to the stock of atmospheric CO₂ by the major players, China, Europe, India, Japan and the USA, for the period 1900–2080. Although relative contributions to the climate problem are changing dramatically, notably due to the rapid industrialization of China, long-term responsibilities for enhanced global warming have not been transparently quantified in the literature. The analysis shows that if current trends continue, by the middle of this century China will overtake the USA as the major cumulative contributor to atmospheric concentrations of CO₂. This has enormous implications for the debate on the ethical responsibilities of the major greenhouse gas emitters. Effective climate policy will require both the recognition of shared responsibility and an unprecedented degree of cooperation.     

Towards bridging the gap between climate change projections and maize producers in South Africa

Theoretical and Applied Climatology - Multi-decadal regional projections of future climate change are introduced into a linear statistical model in order to produce an ensemble of austral...     

Resilience compromised: Producing vulnerability to climate and market among quinoa producers in Southwestern Bolivia

Climate change is already affecting rural communities along the high Andean plateau, but it is just one of many stresses that Andean people experience on a regular basis. This paper examines the experiences of quinoa farmers in Southwestern Bolivia as they faced the overlapping crises of protracted drought and market disruption in 2017. Drawing on political ecologies of resilience, this paper argues that the ability of rural people to cope with this double exposure was already compromised by ecological and social vulnerabilities produced through the development trajectories of the previous two decades. These development strategies generated three overlapping processes: 1) neoliberal entanglements involving specialization in quinoa production, marketization, and individualization of livelihoods in ways that undermined collective action; 2) new relationships of debt that tied households to monetized response paths and undermined flexibility; and 3) the degradation of soils through extensification, overproduction, and industrialization of quinoa production. This paper argues that while climate and market disruptions are not to be dismissed, we must historicize the double exposure to also ask how resilience and vulnerability to such challenges are generated in the first place.     

从科学和政策视角看碳预算对全球气候治理的作用

IPCC第五次评估报告进一步阐述和明确了全球平均地表温升与累积CO₂排放之间的近似线性关系。尽管在科学上仍存在一定的不确定性,国际社会对2℃温升目标及所对应的全球累积碳排放空间(即全球碳预算目标)已达成一定的科学认知和政治共识。但如何将碳预算从目标要求转变为各国决策和实际行动,仍是政策制定者们所面临的一个重要问题。在此背景下,提出建立一个有效的碳预算综合管理框架,努力避免人为温室气体排放导致气候系统危害,并利用其科学和政策的双重内涵,来推动谈判进程和加大行动力度,在新型气候治理模式下推动全球减排目标的实现。     

The benefits of climate change mitigation in integrated assessment models: the role of the carbon cycle and climate component

Integrated Assessment Models (IAMs) are an important tool to compare the costs and benefits of different climate policies. Recently, attention has been given to the effect of different discounting methods and damage estimates on the results of IAMs. One aspect to which little attention has been paid is how the representation of the climate system may affect the estimated benefits of mitigation action. In that respect, we analyse several well-known IAMs, including the newest versions of FUND, DICE and PAGE. Given the role of IAMs in integrating information from different disciplines, they should ideally represent both best estimates and the ranges of anticipated climate system and carbon cycle behaviour (as e.g. synthesised in the IPCC Assessment reports). We show that in the longer term, beyond 2100, most IAM parameterisations of the carbon cycle imply lower CO₂ concentrations compared to a model that captures IPCC AR4 knowledge more closely, e.g. the carbon-cycle climate model MAGICC6. With regard to the climate component, some IAMs lead to much lower benefits of mitigation than MAGICC6. The most important reason for the underestimation of the benefits of mitigation is the failure in capturing climate dynamics correctly, which implies this could be a potential development area to focus on.     

The role of carbon plantations in mitigating climate change: potentials and costs

A methodology is presented to construct supply curves and cost–supply curves for carbon plantations based on land-use scenarios from the Integrated Model to Assess the Global Environment (IMAGE 2). A sensitivity analysis for assessing which factors are most important in shaping these curves is also presented. In the IPCC SRES B2 Scenario, the carbon sequestration potential on abandoned agricultural land increases from 60 MtC/year in 2010 to 2,700 MtC/year in 2100 for prices up to 1,000 $/tC, assuming harvest when the mean annual increment decreases and assuming no environmental, economical or political barriers in the implementation-phase. Taking these barriers into consideration would reduce the potential by at least 60%. On the other hand, the potential will increase 55 to 75% if plantations on harvested timberland are considered. Taking into account land and establishment costs, the largest part of the potential up to 2025 can be supplied below 100 $/tC (In this article all dollar values are in US dollars of 1995, unless indicated otherwise.). Beyond 2050, more than 50% of the costs come to over 200 $/tC. Compared to other mitigation options, this is relative cheap. So a large part of the potential will likely be used in an overall mitigation strategy. However, since huge emission reductions are probably needed, the relative contribution of plantations will be low (around 3%). The largest source of uncertainty with respect to both potentials and costs is the growth rate of plantations compared to the natural vegetation.     

The contribution of forest carbon credit projects to addressing the climate change challenge

This article addresses the question of how forestry projects, given the recently improved standards for the accounting of carbon sequestration, can benefit from existing and emerging carbon markets in the world. For a long time, forestry projects have been set up for the purpose of generating carbon credits. They were surrounded by uncertainties about the permanence of carbon sequestration in trees, potential replacement of deforestation due to projects (leakage), and how and what to measure as sequestered carbon. Through experience with Joint Implementation (JI) and Clean Development Mechanism (CDM) forestry projects, albeit limited, and with forestry projects in voluntary carbon markets, considerable improvements have been made with accounting of carbon sequestration in forests, resulting in a more solid basis for carbon credit trading. The scope of selling these credits exists both in compliance markets, although currently with strong limitations, and in voluntary markets for offsetting emissions with carbon credits. Improved carbon accounting methods for forestry investments can also enhance the scope for forestry in the Nationally Determined Contributions (NDCs) that countries must prepare under the Paris Agreement.

POLICY RELEVANCE

This article identifies how forestry projects can contribute to climate change mitigation. Forestry projects have addressed a number of challenges, like reforestation, afforestation on degraded lands, and long-term sustainable forest management. An interesting new option for forestry carbon projects could be the NDCs under the Paris Agreement in December 2015. Initially, under CDM and JI, the number of forestry projects was far below that for renewable energy projects. With the adoption of the Paris Agreement, both developed and developing countries have agreed on NDCs for country-specific measures on climate change mitigation, and increased the need for investing in new measures. Over the years, considerable experience has been built up with forestry projects that fix CO₂ over a long-term period. Accounting rules are nowadays at a sufficient level for the large potential of forestry projects to deliver a reliable, additional contribution towards reducing or halting emissions from deforestation and forest degradation activities worldwide.     

The European and global potential of carbon dioxide sequestration in tackling climate change

Although, it has received relatively little attention as a potential method of combating climate change in comparison to energy reduction measures and development of carbon-free energy technologies, sequestration of carbon dioxide in geologic or biospheric sinks has enormous potential. This paper reviews the potential for sequestration using geological and ocean storage as a means of reducing carbon dioxide emissions.Considerable quantities of carbon dioxide separated from natural gas deposits and from hydrogen production from steam reforming of methane are already used in enhanced oil recovery and in extraction of coalbed methane, the carbon dioxide remaining sequestered at the end of the process. A number of barriers lie in the way of its implementation on a large scale. There are concerns about possible environmental effects of large-scale injection of carbon dioxide especially into the oceans. Available technologies, especially of separating and capturing the carbon dioxide from waste stream, have high costs at present, perhaps representing an additional 40–100% onto the costs of generating electricity. In most of the world there are no mechanisms to encourage firms to consider sequestration.Considerable R&D is required to bring down the costs of the process, to elucidate the environmental effects of storage and to ensure that carbon dioxide will not escape from stores in unacceptably short timescales. However, the potential of sequestration should not be underestimated as a contribution to global climate change mitigation measures.     

Transient climate response to changing carbon dioxide concentration

The time-dependent response of climate changes to changing atmospheric concentration of carbon dioxide is modeled using an energy balance atmospheric model coupled to a one-dimensional upwelling diffusion model of the deep ocean. Such a model introduces time delays so that the calculated globally-averaged temperature lags that which would be predicted by assuming radiative equilibrium. The climate model is coupled to a simple carbon cycle model and a ‘social’ model that simulates decreasing emission in response to increasing global temperatures. The thermal inertia of the system is such that temperatures continue to increase after carbon dioxide concentrations are decreasing. Consultant to BNL from New York University. Semester Student, Fall 1979, Alcorn State College. This research was performed under the auspices of the United States Department of Energy under Contract No. DE-AC02-76CH00016. By acceptance of this article, the publisher and/or recipient acknowledges the U.S. Government’s right to retain a nonexclusive, royalty-free license in and to any copyright covering this paper.     

Terrestrial biosphere carbon storage under alternative climate projections

This study investigates commonalities and differences in projected land biosphere carbon storage among climate change projections derived from one emission scenario by five different general circulation models (GCMs). Carbon storage is studied using a global biogeochemical process model of vegetation and soil that includes dynamic treatment of changes in vegetation composition, a recently enhanced version of the Lund-Potsdam-Jena Dynamic Global Vegetation Model (LPJ-DGVM). Uncertainty in future terrestrial carbon storage due to differences in the climate projections is large. Changes by the end of the century range from −106 to +201 PgC, thus, even the sign of the response whether source or sink, is uncertain. Three out of five climate projections produce a land carbon source by the year 2100, one is approximately neutral and one a sink. A regional breakdown shows some robust qualitative features. Large areas of the boreal forest are shown as a future CO₂ source, while a sink appears in the arctic. The sign of the response in tropical and sub-tropical ecosystems differs among models, due to the large variations in simulated precipitation patterns. The largest uncertainty is in the response of tropical rainforests of South America and Central Africa.     

A note on the historical industrial production of carbon dioxide

The historical record of CO₂ emissions from industrial activity is reexamined. The overall annual growth rate has been about 3.5% but with wide variations due to economic fluctuations. It is unlikely that the total CO₂ production would have been greatly different had the major wars of the Twentieth Century been avoided.     

Expert assessment of vulnerability of permafrost carbon to climate change

Approximately 1700 Pg of soil carbon (C) are stored in the northern circumpolar permafrost zone, more than twice as much C than in the atmosphere. The overall amount, rate, and form of C released to the atmosphere in a warmer world will influence the strength of the permafrost C feedback to climate change. We used a survey to quantify variability in the perception of the vulnerability of permafrost C to climate change. Experts were asked to provide quantitative estimates of permafrost change in response to four scenarios of warming. For the highest warming scenario (RCP 8.5), experts hypothesized that C release from permafrost zone soils could be 19–45 Pg C by 2040, 162–288 Pg C by 2100, and 381–616 Pg C by 2300 in CO₂ equivalent using 100-year CH₄ global warming potential (GWP). These values become 50 % larger using 20-year CH₄ GWP, with a third to a half of expected climate forcing coming from CH₄ even though CH₄ was only 2.3 % of the expected C release. Experts projected that two-thirds of this release could be avoided under the lowest warming scenario (RCP 2.6). These results highlight the potential risk from permafrost thaw and serve to frame a hypothesis about the magnitude of this feedback to climate change. However, the level of emissions proposed here are unlikely to overshadow the impact of fossil fuel burning, which will continue to be the main source of C emissions and climate forcing.     

The carbon dioxide/climate controversy: Some personal comments on two recent publications

The pervasive opinion on the relationship between the state of the climate and the increasing concentration of CO₂ is that a general global warming will occur with social, economical and environmental corollaries that may be adverse. However, there exist a number of dissenting arguments that call for a much smaller increase in global temperature or even an induced global cooling. Furthermore, the positive biological effects of a greater atmospheric CO₂ loading are emphasized.The difference of opinion is highlighted in two recent publications: CO ₂, Friend or Foe by Sherwood Idso and Carbon Dioxide: A Second Assessment by the National Academy of Science CO₂/Climate Review Committee. Using the two publications as focal points, some personal remarks are made regarding the controversy and the relative merits of the scientific arguments.     

Incorporating blue carbon sequestration benefits into sub-national climate policies

The emissions reduction pledges made by individual countries through the 2015 Paris Agreement represent the current global commitment to mitigate greenhouse gas emissions in the face of the enduring climate crisis. Natural lands carbon sequestration and storage are critical for successful pathways to global decarbonization (i.e., as a negative emissions technology). Coastal vegetated habitats maintain carbon sequestration rates exceeding forest sequestration rates on a per unit area basis by nearly two orders of magnitude. These blue carbon habitats and their associated carbon sequestration benefits are vulnerable to losses from land-use change and sea-level rise. Incorporation of blue carbon habitats in climate change policy is one strategy for both maintaining these habitats and conserving significant carbon sequestration capabilities. Previous policy assessments have found the potential for incorporation of coastal carbon sequestration in national-level policies, yet there has – to date – been little inclusion of blue carbon in the national-scale implementation of Paris commitments. Recently, sub-national jurisdictions have gained attention as models for pathways to decarbonization. However, few previous studies have examined sub-national level policy opportunities for operationalizing blue carbon into climate decision-making. California is uniquely poised to integrate benefits from blue carbon into its coastal planning and management and its suite of climate mitigation policies. Here, we evaluated legal authorities and policy contexts addressing sequestration specifically from blue carbon habitats. We synthesized the progressive action in California’s approaches to mitigate carbon emissions including statutory, regulatory, and non-regulatory opportunities to incorporate blue carbon ecosystem service information into state- and local-level management decisions. To illustrate how actionable blue carbon information can be produced for use in decision-making, we conducted a spatial analysis of blue carbon sequestration in several locations in California across multiple agencies and management contexts. We found that the average market values of carbon sequestration services in 2100 ranged from $7,730 to $44,000 per hectare and that the social cost of carbon sequestration value was 1.3 to 2.7 times the market value. We also demonstrated that restoration of small areas with high sequestration rates can be comparable to the sequestration of existing marshes. Our results illustrate how accessible information about carbon sequestration in coastal habitats can be directly incorporated into existing policy frameworks at the sub-national scale. The incorporation of blue carbon sequestration benefits into sub-national climate policies can serve as a model for the development of future policy approaches for negative emissions technologies, with consequences for the success of the Paris Agreement and science-based decarbonization by mid-century.     

不同情景达到碳中和下中国区域气候变化的预估

利用第6次耦合模式比较计划(CMIP6)中的9个全球气候模式的模拟结果,通过CO₂浓度达峰时间确定SSP1-1.9和SSP1-2.6两种情景下的全球碳中和时间,预估了全球碳中和下中国区域气候较历史参考期(1995—2014年)的未来变化,分析不同时间达到碳中和下气候响应差异,并与未实现碳中和的SSP2-4.5情景下的气候变化对比。结果表明,SSP1-1.9和SSP1-2.6情景下全球达到碳中和的时间分别为2041年和2063年,相较于历史参考期,SSP1-1.9/SSP1-2.6下中国区域平均年气温上升1.22/1.58℃,平均年降水量增加7.1%/9.9%。SSP1-2.6(晚碳中和)较SSP1-1.9(早碳中和)情景下年均温增高约0.36℃,最大升温区位于西南及高原地区。对降水而言,晚碳中和较早碳中和全国平均年降水量增加约2.7%。全年及夏季降水量显著增加区主要在西北,新疆地区出现降水增加超过8%的大值区,冬季则集中于黄河中下游,增幅也超过8%。未碳中和的SSP2-4.5情景下中国区域的升温显著强于SSP1-2.6(碳中和)情景,年平均气温高约0.61℃,西北...     

Contributions of carbon cycle uncertainty to future climate projection spread

We have characterized the relative contributions to uncertainty in predictions of global warming amount by year 2100 in the C4MIP model ensemble ( Friedlingstein et al., 2006 ) due to both carbon cycle process uncertainty and uncertainty in the physical climate properties of the Earth system. We find carbon cycle uncertainty to be important. On average the spread in transient climate response is around 40% of that due to the more frequently debated uncertainties in equilibrium climate sensitivity and global heat capacity.
This result is derived by characterizing the influence of different parameters in a global climate-carbon cycle 'box' model that has been calibrated against the 11 General Circulation models (GCMs) and Earth system Models of Intermediate Complexity (EMICs) in the C4MIP ensemble; a collection of current state-of-the-art climate models that include an explicit representation of the global carbon cycle.