Search Results
The IPCC AR5 guidance note on consistent treatment of uncertainties: A common approach across the working groups
Evaluation and communication of the relative degree of certainty in assessment findings are key cross-cutting issues for the three Working Groups of the Intergovernmental Panel on Climate Change. A goal for the Fifth Assessment Report, which is currently under development, is the application of a common framework with associated calibrated uncertainty language that can be used to characterize findings of the assessment process. A guidance note for authors of the Fifth Assessment Report has been developed that describes this common approach and language, building upon the guidance employed in past Assessment Reports. Here, we introduce the main features of this guidance note, with a focus on how it has been designed for use by author teams. We also provide perspectives on considerations and challenges relevant to the application of this guidance in the contribution of each Working Group to the Fifth Assessment Report. Despite the wide spectrum of disciplines encompassed by the three Working Groups, we expect that the framework of the new uncertainties guidance will enable consistent communication of the degree of certainty in their policy-relevant assessment findings.
Between Scylla and Charybdis: Delayed mitigation narrows the passage between large-scale CDR and high costs
There are major concerns about the sustainability of large-scale deployment of carbon dioxide removal (CDR) technologies. It is therefore an urgent question to what extent CDR will be needed to implement the long term ambition of the Paris Agreement. Here we show that ambitious near term mitigation significantly decreases CDR requirements to keep the Paris climate targets within reach. Following the nationally determined contributions (NDCs) until 2030 makes 2 °C unachievable without CDR. Reducing 2030 emissions by 20% below NDC levels alleviates the trade-off between high transitional challenges and high CDR deployment. Nevertheless, transitional challenges increase significantly if CDR is constrained to less than 5 Gt CO2 a−1 in any year. At least 8 Gt CO2 a−1 CDR are necessary in the long term to achieve 1.5 °C and more than 15 Gt CO2 a−1 to keep transitional challenges in bounds.
What is important for achieving 2 °C? UNFCCC and IPCC expert perceptions on obstacles and response options for climate change mitigation
Global mitigation efforts remain insufficient to limit the global temperature increase to well below 2 °C. While a growing academic literature analyzes this problem, perceptions of which obstacles inhibit goal attainment and which responses might be most effective seem to differ widely. This makes prioritization and agreement on the way forward difficult. To inform prioritization in global climate policy and research agendas, we present quantitative data on how 917 experts from the IPCC and the UNFCCC perceive the importance of different obstacles and response options for achieving 2 °C. On average, respondents consider opposition from special interest groups the most important obstacle and technological R&D the most important response. Our survey also finds that the majority of experts perceives a wide range of issues as important, supporting an agenda that is inclusive in terms of coverage. Average importance ratings differ between experts from the Global North and South, suggesting that balanced representation in global fora and regionally differentiated agendas are important. In particular, opposition from special interest groups is a top priority among experts from North America, Europe and Oceania. Investigating the drivers of individual importance ratings, we find little difference between experts from the IPCC and the UNFCCC, while expert's perceptions correlate with their academic training and their national scientific, regulatory, and financial contexts.
The strategic dimension of financing global public goods
One challenge in addressing transboundary problems such as climate change is the incentive to free-ride. Transfers from multilateral compensation funds are often used to counteract such incentives, albeit with varying success. We examine how such funds can change the incentive to free-ride in a global public-goods game. In our game, self-interested countries choose their own preferred course, deciding their voluntary public good provision, whether to join a fund that offers compensation for providing the public good and the volume of compensatory payments. We show that (i) total public-good provision is higher when those contributing are given more compensation; and (ii) non-participation in the fund can be punished if the remaining members decrease their public-good provision sufficiently. We then examine three specific fund designs. In the first, the compensation paid to each country is equal to the percentage of above-average total costs for public-goods provision. This design is best able to deter free-riding and can establish the social optimum as the equilibrium. In the second, the compensation paid to each country is a function of the marginal cost of their public-good provision. Here there are significant incentives to free-ride. In the third case, the monetary resources provided by the fund are fixed, a design frequently encountered in international funds. This design is the one least able to deter free-riding. © 2020 The Author(s)
Is atmospheric carbon dioxide removal a game changer for climate change mitigation?
The ability to directly remove carbon dioxide from the atmosphere allows the decoupling of emissions and emissions control in space and time. We ask the question whether this unique feature of carbon dioxide removal technologies fundamentally alters the dynamics of climate mitigation pathways. The analysis is performed in the coupled energy-economy-climate model ReMIND using the bioenergy with CCS route as an application of CDR technology. BECCS is arguably the least cost CDR option if biomass availability is not a strongly limiting factor. We compare mitigation pathways with and without BECCS to explore the impact of CDR technologies on the mitigation portfolio. Effects are most pronounced for stringent climate policies where BECCS is a key technology for the effectiveness of carbon pricing policies. The decoupling of emissions and emissions control allows prolonging the use of fossil fuels in sectors that are difficult to decarbonize, particularly in the transport sector. It also balances the distribution of mitigation costs across future generations. CDR is not a silver bullet technology. The largest part of emissions reductions continues to be provided by direct mitigation measures at the emissions source. The value of CDR lies in its flexibility to alleviate the most costly constraints on mitigating emissions.
Reports of coal's terminal decline may be exaggerated
We estimate the cumulative future emissions expected to be released by coal power plants that are currently under construction, announced, or planned. Even though coal consumption has recently declined and plans to build new coal-fired capacities have been shelved, constructing all these planned coal-fired power plants would endanger national and international climate targets. Plans to build new coal-fired power capacity would likely undermine the credibility of some countries' (Intended) Nationally Determined Contributions submitted to the UNFCCC. If all the coal-fired power plants that are currently planned were built, the carbon budget for reaching the 2 °C temperature target would nearly be depleted. Propositions about 'coal's terminal decline' may thereby be premature. The phase-out of coal requires dedicated and well-designed policies. We discuss the political economy of policy options that could avoid a continued build-up of coal-fired power plants.
Fossil-fueled development (SSP5): An energy and resource intensive scenario for the 21st century
This paper presents a set of energy and resource intensive scenarios based on the concept of Shared Socio-Economic Pathways (SSPs). The scenario family is characterized by rapid and fossil-fueled development with high socio-economic challenges to mitigation and low socio-economic challenges to adaptation (SSP5). A special focus is placed on the SSP5 marker scenario developed by the REMIND-MAgPIE integrated assessment modeling framework. The SSP5 baseline scenarios exhibit very high levels of fossil fuel use, up to a doubling of global food demand, and up to a tripling of energy demand and greenhouse gas emissions over the course of the century, marking the upper end of the scenario literature in several dimensions. These scenarios are currently the only SSP scenarios that result in a radiative forcing pathway as high as the highest Representative Concentration Pathway (RCP8.5). This paper further investigates the direct impact of mitigation policies on the SSP5 energy, land and emissions dynamics confirming high socio-economic challenges to mitigation in SSP5. Nonetheless, mitigation policies reaching climate forcing levels as low as in the lowest Representative Concentration Pathway (RCP2.6) are accessible in SSP5. The SSP5 scenarios presented in this paper aim to provide useful reference points for future climate change, climate impact, adaption and mitigation analysis, and broader questions of sustainable development.
Scientific assessments to facilitate deliberative policy learning
Putting the recently adopted global Sustainable Development Goals or the Paris Agreement on international climate policy into action will require careful policy choices. Appropriately informing decision-makers about longer-term, wicked policy issues remains a considerable challenge for the scientific community. Typically, these vital policy issues are highly uncertain, value-laden and disputed, and affect multiple temporal and spatial scales, governance levels, policy fields, and socioeconomic contexts simultaneously. In light of this, science-policy interfaces should help facilitate learning processes and open deliberation among all actors involved about potentially acceptable policy pathways. For this purpose, science-policy interfaces must strive to foster some enabling conditions: (1) “representation” in terms of engaging with diverse stakeholders (including experts) and acknowledging divergent viewpoints; (2) “empowerment” of underrepresented societal groups by co-developing and integrating policy scenarios that reflect their specific knowledge systems and worldviews; (3) “capacity building” regarding methods and skills for integration and synthesis, as well as through the provision of knowledge synthesis about the policy solution space; and (4) “spaces for deliberation”, facilitating direct interaction between different stakeholders, including governments and scientists. We argue that integrated, multi-stakeholder, scientific assessment processes—particularly the collaborative assessments of policy alternatives and their various implications—offer potential advantages in this regard, compared with alternatives for bridging scientific expertise and public policy. This article is part of a collection on scientific advice to governments.
Economic mitigation challenges: How further delay closes the door for achieving climate targets
While the international community aims to limit global warming to below 2 ° C to prevent dangerous climate change, little progress has been made towards a global climate agreement to implement the emissions reductions required to reach this target. We use an integrated energy–economy–climate modeling system to examine how a further delay of cooperative action and technology availability affect climate mitigation challenges. With comprehensive emissions reductions starting after 2015 and full technology availability we estimate that maximum 21st century warming may still be limited below 2 ° C with a likely probability and at moderate economic impacts. Achievable temperature targets rise by up to ~0.4 ° C if the implementation of comprehensive climate policies is delayed by another 15 years, chiefly because of transitional economic impacts. If carbon capture and storage (CCS) is unavailable, the lower limit of achievable targets rises by up to ~0.3 ° C. Our results show that progress in international climate negotiations within this decade is imperative to keep the 2 ° C target within reach.
Assessing human and environmental pressures of global land-use change 2000-2010
Global land is turning into an increasingly scarce resource. We here present a comprehensive assessment of co-occuring land-use change from 2000 until 2010, compiling existing spatially explicit data sources for different land uses, and building on a rich literature addressing specific land-use changes in all world regions. This review systematically categorizes patterns of land use, including regional urbanization and agricultural expansion but also globally telecoupled land-use change for all world regions. Managing land-use change patterns across the globe requires global governance. Here we present a comprehensive assessment of the extent and density of multiple drivers and impacts of land-use change. We combine and reanalyze spatially explicit data of global land-use change between 2000 and 2010 for population, livestock, cropland, terrestrial carbon and biodiversity. We find pervasive pressure on biodiversity but varying patterns of gross land-use changes across world regions. Our findings enable a classification of land-use patterns into three types. The 'consumers' type, displayed in Europe and North America, features high land footprints, reduced direct human pressures due to intensification of agriculture, and increased reliance on imports, enabling a partial recovery of terrestrial carbon and reducing pressure on biodiversity. In the 'producer' type, most clearly epitomized by Latin America, telecoupled land-use links drive biodiversity and carbon loss. In the 'mover' type, we find strong direct domestic pressures, but with a wide variety of outcomes, ranging from a concurrent expansion of population, livestock and croplands in Sub-Saharan Africa at the cost of natural habitats to strong pressure on cropland by urbanization in Eastern Asia. In addition, anthropogenic climate change has already left a distinct footprint on global land-use change. Our data- and literature-based assessment reveals region-specific opportunities for managing global land-use change. © 2019 The Author(s).