The bottom-up approach of the Nationally Determined Contributions (NDCs) in the Paris Agreement has led countries to self-determine their greenhouse gas (GHG) emission reduction targets. The planned ...‘ratcheting-up’ process, which aims to ensure that the NDCs comply with the overall goal of limiting global average temperature increase to well below 2 °C or even 1.5 °C, will most likely include some evaluation of ‘fairness’ of these reduction targets. In the literature, fairness has been discussed around equity principles, for which many different effort-sharing approaches have been proposed. In this research, we analysed how country-level emission targets and carbon budgets can be derived based on such criteria. We apply novel methods directly based on the global carbon budget, and, for comparison, more commonly used methods using GHG mitigation pathways. For both, we studied the following approaches: equal cumulative per capita emissions, contraction and convergence, grandfathering, greenhouse development rights and ability to pay. As the results critically depend on parameter settings, we used the wide authorship from a range of countries included in this paper to determine default settings and sensitivity analyses. Results show that effort-sharing approaches that (i) calculate required reduction targets in carbon budgets (relative to baseline budgets) and/or (ii) take into account historical emissions when determining carbon budgets can lead to (large) negative remaining carbon budgets for developed countries. This is the case for the equal cumulative per capita approach and especially the greenhouse development rights approach. Furthermore, for developed countries, all effort-sharing approaches except grandfathering lead to more stringent budgets than cost-optimal budgets, indicating that cost-optimal approaches do not lead to outcomes that can be regarded as fair according to most effort-sharing approaches.
Over 100 countries have set or are considering net-zero emissions or neutrality targets. However, most of the information on emissions neutrality (such as timing) is provided for the global level. ...Here, we look at national-level neutrality-years based on globally cost-effective 1.5 °C and 2 °C scenarios from integrated assessment models. These results indicate that domestic net zero greenhouse gas and CO
emissions in Brazil and the USA are reached a decade earlier than the global average, and in India and Indonesia later than global average. These results depend on choices like the accounting of land-use emissions. The results also show that carbon storage and afforestation capacity, income, share of non-CO
emissions, and transport sector emissions affect the variance in projected phase-out years across countries. We further compare these results to an alternative approach, using equity-based rules to establish target years. These results can inform policymakers on net-zero targets.
Climate benefits of changing diet Stehfest, Elke; Bouwman, Lex; van Vuuren, Detlef P ...
Climatic change,
07/2009, Letnik:
95, Številka:
1-2
Journal Article
Recenzirano
Climate change mitigation policies tend to focus on the energy sector, while the livestock sector receives surprisingly little attention, despite the fact that it accounts for 18% of the greenhouse ...gas emissions and for 80% of total anthropogenic land use. From a dietary perspective, new insights in the adverse health effects of beef and pork have lead to a revision of meat consumption recommendations. Here, we explored the potential impact of dietary changes on achieving ambitious climate stabilization levels. By using an integrated assessment model, we found a global food transition to less meat, or even a complete switch to plant-based protein food to have a dramatic effect on land use. Up to 2,700 Mha of pasture and 100 Mha of cropland could be abandoned, resulting in a large carbon uptake from regrowing vegetation. Additionally, methane and nitrous oxide emission would be reduced substantially. A global transition to a low meat-diet as recommended for health reasons would reduce the mitigation costs to achieve a 450 ppm CO₂-eq. stabilisation target by about 50% in 2050 compared to the reference case. Dietary changes could therefore not only create substantial benefits for human health and global land use, but can also play an important role in future climate change mitigation policies.
On the basis of the IPCC B2, A1b and B1 baseline scenarios, mitigation scenarios were developed that stabilize greenhouse gas concentrations at 650, 550 and 450 and - subject to specific assumptions ...- 400 ppm CO₂-eq. The analysis takes into account a large number of reduction options, such as reductions of non-CO₂ gases, carbon plantations and measures in the energy system. The study shows stabilization as low as 450 ppm CO₂-eq. to be technically feasible, even given relatively high baseline scenarios. To achieve these lower concentration levels, global emissions need to peak within the first two decades. The net present value of abatement costs for the B2 baseline scenario (a medium scenario) increases from 0.2% of cumulative GDP to 1.1% as the shift is made from 650 to 450 ppm. On the other hand, the probability of meeting a two-degree target increases from 0%-10% to 20%-70%. The mitigation scenarios lead to lower emissions of regional air pollutants but also to increased land use. The uncertainty in the cost estimates is at least in the order of 50%, with the most important uncertainties including land-use emissions, the potential for bio-energy and the contribution of energy efficiency. Furthermore, creating the right socio-economic and political conditions for mitigation is more important than any of the technical constraints.
In the context of recent discussions at the UN climate negotiations we compared several ways of calculating historical greenhouse gas (GHG) emissions, and assessed the effect of these different ...approaches on countries’ relative contributions to cumulative global emissions. Elements not covered before are: (i) including recent historical emissions (2000–2010), (ii) discounting historical emissions to account for technological progress; (iii) deducting emissions for ‘basic needs’; (iv) including projected emissions up to 2020, based on countries’ unconditional reduction proposals for 2020. Our analysis shows that countries’ contributions vary significantly based on the choices made in the calculation: e.g. the relative contribution of developed countries as a group can be as high as 80 % when excluding recent emissions, non-CO
2
GHGs, and land-use change and forestry CO
2
; or about 48 % when including all these emissions and discounting historical emissions for technological progress. Excluding non-CO
2
GHGs and land-use change and forestry CO
2
significantly changes relative historical contributions for many countries, altering countries’ relative contributions by multiplicative factors ranging from 0.15 to 1.5 compared to reference values (i.e. reference contribution calculations cover the period 1850-2010 and all GHG emissions). Excluding 2000–2010 emissions decreases the contributions of most emerging economies (factor of up to 0.8). Discounting historical emissions for technological progress reduces the relative contributions of some developed countries (factor of 0.8) and increases those of some developing countries (factor of 1.2–1.5). Deducting emissions for ‘basic needs’ results in smaller contributions for countries with low per capita emissions (factor of 0.3–0.5). Finally, including projected emissions up to 2020 further increases the relative contributions of emerging economies by a factor of 1.2, or 1.5 when discounting pre-2020 emissions for technological progress.
In June 2015, China announced its post-2020 reduction targets, its central element being the intention to peak CO2 emissions by 2030 or earlier. China has implemented several policies to reduce its ...greenhouse gas (GHG) emissions. This study provides emission projections for China up to 2030 given current policies and a selected set of enhanced policies, and compares the results with projected CO2 emission trajectories that are consistent with the announced target for 2030. The projections are based on existing scenarios and energy system and land use model calculations. We project that the 2030 CO2 emission level consistent with a peak in CO2 emissions by 2030 ranges from 11.3 to 11.8 GtCO2. The corresponding total GHG emission level ranges from 13.5 to 14.0 GtCO2e in 2030. Current policies are likely not to be sufficient to achieve the 2030 targets, as our projected total GHG emission level under current policies ranges from 14.7 to 15.4 GtCO2e by 2030. However, an illustrative set of enhancement policy measures, all of which are related to national priorities, leads to projected GHG emission levels from 13.1 to 13.7 GtCO2e by 2030 – and thus below the levels necessary for peaking CO2 emissions before 2030.
•China has announced its intention to peak CO2 emissions by 2030 or earlier.•The peak in greenhouse gas emissions would reach 35–40% above 2010 levels.•Current policies are likely not to be sufficient to meet the announced 2030 target.•The expected emission levels reach about 50% above 2010 levels.•Our selected enhancement policy measures lead to peaking CO2 emissions before 2030.
The RCP2.6 emission and concentration pathway is representative of the literature on mitigation scenarios aiming to limit the increase of global mean temperature to 2°C. These scenarios form the low ...end of the scenario literature in terms of emissions and radiative forcing. They often show negative emissions from energy use in the second half of the 21st century. The RCP2.6 scenario is shown to be technically feasible in the IMAGE integrated assessment modeling framework from a medium emission baseline scenario, assuming full participation of all countries. Cumulative emissions of greenhouse gases from 2010 to 2100 need to be reduced by 70% compared to a baseline scenario, requiring substantial changes in energy use and emissions of non-CO
2
gases. These measures (specifically the use of bio-energy and reforestation measures) also have clear consequences for global land use. Based on the RCP2.6 scenario, recommendations for further research on low emission scenarios have been formulated. These include the response of the climate system to a radiative forcing peak, the ability of society to achieve the required emission reduction rates given political and social inertia and the possibilities to further reduce emissions of non-CO
2
gases.
This paper analyses the impact of postponing global mitigation action on abatement costs and energy systems changes in China and India. It compares energy-system changes and mitigation costs from a ...global and two national energy-system models under two global emission pathways with medium likelihood of meeting the 2°C target: a least-cost pathway and a pathway that postpones ambitious mitigation action, starting from the Copenhagen Accord pledges. Both pathways have similar 2010–2050 cumulative greenhouse gas emissions. The analysis shows that postponing mitigation action increases the lock-in in less energy efficient technologies and results in much higher cumulative mitigation costs. The models agree that carbon capture and storage (CCS) and nuclear energy are important mitigation technologies, while the shares of biofuels and other renewables vary largely over the models. Differences between India and China with respect to the timing of emission reductions and the choice of mitigation measures relate to differences in projections of rapid economic change, capital stock turnover and technological development. Furthermore, depending on the way it is implemented, climate policy could increase indoor air pollution, but it is likely to provide synergies for energy security. These relations should be taken into account when designing national climate policies.
•We analyze long-term impacts of the international pledges for China and India.•We compare a least-cost pathway with a pathway starting from the Copenhagen pledges.•Postponing mitigation action implies much higher cumulative mitigation costs.•Postponing increases fossil fuel dependence and requires deeper long-term reductions.•Countries differ mainly due to different periods of rapid economic change.
One of the most fundamental questions surrounding the new Paris Agreement is whether countries' proposals to reduce GHG emissions after 2020 are equally ambitious, considering differences in ...circumstances between countries. We review a variety of approaches to assess the ambition of the GHG emission reduction proposals by countries. The approaches are applied illustratively to the mitigation part of the post-2020 climate proposals (nationally determined contributions, or NDCs) by China, the EU, and the US. The analysis reveals several clear trends, even though the results differ per individual assessment approach. We recommend that such a comprehensive ambition assessment framework, employing a large variety of approaches, is used in the future to capture a wide spectrum of perspectives on ambition.
POLICY RELEVANCE
Assessing the ambition of the national climate proposals is particularly important as the Paris Agreement asks for regular reviews of national contributions, keeping in mind that countries raise their ambition over time. Such an assessment will be an important part of the regular global stocktake that will take place every five years, starting with a 'light' version in 2018. However, comprehensive methods to assess the proposals are lacking. This article provides such a comprehensive assessment framework.
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