17 results found
Peters GP, Al Khourdajie A, Sognnaes I, et al., 2023, AR6 scenarios database: an assessment of current practices and future recommendations, npj Climate Action, Vol: 2
<jats:title>Abstract</jats:title><jats:p>Mitigation scenarios have become an important element of Intergovernmental Panel on Climate Change (IPCC) reports. We critically assess the curation of the IPCC mitigation scenarios database, with a focus on improving curation and utilisation. The existing method of curation favours particular models, and results may have limited statistical meaning. We draw lessons from experiences with the Coupled Model Intercomparison Project (CMIP) used by the IPCC Working Group I and II communities. We propose that the scientific community takes a more active role in curating the database around policy-relevant knowledge gaps, through an open and peer reviewed process of Model Intercomparison Projects (MIPs) supplemented with individual model studies. The database should be publicly accessible from the time of scenario submission, and actively involve a broad community in developing tools and analysing the database. These suggestions can broaden participation, increase transparency, and enhance the relevance of the database for users.</jats:p>
Smith CJ, Al Khourdajie A, Yang P, et al., 2023, Climate uncertainty impacts on optimal mitigation pathways and social cost of carbon, Environmental Research Letters, Vol: 18
Emissions pathways used in climate policy analysis are often derived from integrated assessment models. However, such emissions pathways do not typically include climate feedbacks on socioeconomic systems and by extension do not consider climate uncertainty in their construction. We use a well-known cost-benefit integrated assessment model, the Dynamic Integrated Climate-Economy (DICE) model, with its climate component replaced by the Finite-amplitude Impulse Response (FaIR) model (v2.1). The climate uncertainty in FaIR is sampled with an ensemble that is consistent with historically observed climate and Intergovernmental Panel on Climate Change (IPCC) assessed ranges of key climate variables such as equilibrium climate sensitivity (ECS). By varying discounting assumptions, three scenarios are produced: a pathway similar to the ‘optimal welfare’ scenario of DICE that has similar warming outcomes to current policies, and pathways that limit warming to ‘well-below’ 2 ∘ C and 1.5 ∘ C with a short-term overshoot, aiming to meet Paris Agreement long-term temperature goals. Climate uncertainty alone is responsible for a factor of five variation (5%-95% range) in the social cost of carbon (SCC) in the 1.5 ∘ C overshoot scenario, with the spread in SCC increasing in relative terms with increasing stringency of climate target. CO2 emissions trajectories resulting from the optimal level of emissions abatement in all pathways are also sensitive to climate uncertainty, with 2050 emissions ranging from −12 to +14 GtCO2 yr−1 in the 1.5 ∘ C scenario. ECS and the strength of present-day aerosol effective radiative forcing are strong determinants of SCC and mid-century CO2 emissions. This shows that narrowing climate uncertainty leads to more refined estimates for the social cost of carbon and provides more certainty about the optimal rate of emissions abatement. Including climate and climate uncertainty in integrated assessment model derived emis
Smith C, Al Khourdajie A, Yang P, et al., 2023, Climate uncertainty as an integral part of integrated assessment models
<jats:p>Cost-benefit integrated assessment models (IAMs) such as the Dynamic Integrated model of Climate and the Economy (DICE) are often used to assess the social cost of carbon (SCC), the marginal damage arising from each additional ton of emitted CO2. The climate component of such IAMs has recently come under increased scrutiny. Alongside ensuring that economists are getting climate dynamics correct, the uncertainty in the climate system should be embraced, as it greatly influences the appropriate SCC and CO2 emissions mitigation pathway.We use DICE, replacing its native climate module with the Finite-amplitude Impulse Response (FaIR) model (v2.1). FaIR is assessed to be fit-for-purpose for evaluating emissions projections from IAMs by the IPCC, and has an advantage over the native DICE module in that carbon cycle feedbacks are included. The FaIR emulator has been calibrated to CMIP6 models and constrained such that its projections are consistent with historical global mean temperature change, atmospheric CO2 concentration and ocean heat content, and IPCC Sixth Assessment Report assessed uncertainty ranges for equilibrium climate sensitivity (ECS), transient climate response and non-CO2 effective radiative forcing, constructing a 1000-member posterior ensemble from a 1.5 million member prior. Three ensembles are produced: a Nordhaus &#8220;socially optimal&#8221; ensemble with median 2100 warming of around 2.8&#176;C, somewhat consistent with current Nationally Determined Contributions; a 2&#176;C-consistent ensemble; and a 1.5&#176;C-consistent ensemble. We update the economic and climate baseline in DICE/FaIR to 2023 and use a 3-year model timestep. The three scenarios are constructed solely by modifying the discount rate.The influence of climate uncertainty is profound, having a factor of 5 uncertainty (5-95% range) in the social cost of carbon for a 1.5&#176;C consistent ensemble, and a factor of 3 uncerta
Al Khourdajie A, Skea J, Green R, 2023, Models, scenarios or ambition? A decomposition analysis of factors influencing future mitigation indicators.
<jats:p>&lt;p&gt;In this paper we apply a statistical decomposition analysis in order to understand the drivers behind key mitigation indicators in long-term mitigation scenarios. These scenarios are generated using integrated assessment models (IAMs) which crucially require input assumptions of alternative futures described by the Shared Socioeconomic Pathways (SSPs). Additionally, IAMs generate these scenarios in order to stabilise the carbon budget to a pre-defined constraint that aligns with certain peak warming level under some probability. Given this framework for generating scenarios, we therefore identify three factors: model, scenario and warming ambition, which collectively determine the future evolution of the chosen key mitigation indicators, or any other variable for that matter, in these scenarios. Using statistical decomposition analysis, particularly variance decomposition, in this paper we attribute the individual contribution of these three factors separately to shaping the evolution of the chosen indicators. Such analysis is key for developing a deeper understanding of which factors are the most important in influencing these mitigating indicators, what does that mean for policymakers and sectoral practitioners in terms of interpreting the findings of these indicators and scenarios, and importantly what are the implications for the scientific community in cases where the contribution of the individual factors reflect lack of consensus within the community on current markets conditions and driving forces of future projections. We apply our analysis to the SSPs database, and focus on decadal years only, i.e. 2020, 2030 and so on. We focus on primary energy, final energy, emissions and land use indicators.&lt;/p&gt;&lt;p&gt;Our initial analysis indicates that the primary energy generated by solar and wind is primarily influenced by the model factor, with a high level of residuals in the second hal
Kikstra JS, Nicholls ZRJ, Smith CJ, et al., 2022, The IPCC Sixth Assessment Report WGIII climate assessment of mitigation pathways: from emissions to global temperatures, GEOSCIENTIFIC MODEL DEVELOPMENT, Vol: 15, Pages: 9075-9109, ISSN: 1991-959X
Iturbide M, Fernandez J, Gutierrez JM, et al., 2022, Implementation of FAIR principles in the IPCC: the WGI AR6 Atlas repository, SCIENTIFIC DATA, Vol: 9
Kikstra JS, Nicholls ZRJ, Smith CJ, et al., 2022, Supplementary material to "The IPCC Sixth Assessment Report WGIII climate assessment of mitigation pathways: from emissions to global temperatures"
Kikstra JS, Nicholls ZRJ, Smith CJ, et al., 2022, The IPCC Sixth Assessment Report WGIII climate assessment of mitigation pathways: from emissions to global temperatures
<jats:p>Abstract. While the IPCC’s physical science report usually assesses a handful of future scenarios, the IPCC Sixth Assessment Working Group III report (AR6 WGIII) on climate mitigation assesses hundreds to thousands of future emissions scenarios. A key task is to assess the global-mean temperature outcomes of these scenarios in a consistent manner, given the challenge that the emission scenarios from different integrated assessment models come with different sectoral and gas-to-gas coverage and cannot all be assessed consistently by complex Earth System Models. In this work, we describe the “climate assessment” workflow and its methods, including infilling of missing emissions and emissions harmonisation as applied to 1,202 mitigation scenarios in AR6 WGIII. We evaluate the global-mean temperature projections and effective radiative forcing characteristics (ERF) of climate emulators FaIRv1.6.2, MAGICCv7.5.3, and CICERO-SCM, discuss overshoot severity of the mitigation pathways using overshoot degree years, and look at an interpretation of compatibility with the Paris Agreement. We find that the lowest class of emission scenarios that limit global warming to “1.5 °C (with a probability of greater than 50 %) with no or limited overshoot” includes 90 scenarios for MAGICCv7.5.3, and 196 for FaIRv1.6.2. For the MAGICCv7.5.3 results, “limited overshoot” typically implies exceedance of median temperature projections of up to about 0.1 °C for up to a few decades, before returning to below 1.5 °C by or before the year 2100. For more than half of the scenarios of this category that comply with three criteria for being “Paris-compatible”, including net-zero or net-negative greenhouse gas (GHG) emissions, are projected to see median temperatures decline by about 0.3–0.4 °C after peaking at 1.5–1.6 °C in 2035–2055. We compare the methods applied in AR6 with the methods used f
Lamb WF, Wiedmann T, Pongratz J, et al., 2022, A review of trends and drivers of greenhouse gas emissions by sector from 1990 to 2018, Environmental Research Letters, Vol: 17, ISSN: 1748-9326
McCollum DL, Al Khourdajie A, 2021, Little room for new fossil fuel development if global temperatures are to stay below 1.5 degrees C, Joule, Vol: 5, Pages: 2542-+, ISSN: 2542-4351
A new paper in Nature by Welsby et al. makes clear that pursuing efforts to limit global average temperature increase to 1.5°C above pre-industrial levels—the most frequently stated goal of the 2015 Paris Agreement—implies the vast majority of coal, crude oil, and natural gas must remain underground and undeveloped.
Skea J, Shukla P, Al Khourdajie A, et al., 2021, Intergovernmental Panel on Climate Change: transparency and integrated assessment modeling, Wiley Interdisciplinary Reviews: WIREs Climate Change, Vol: 12, ISSN: 1757-7780
Integrated assessment models (IAMs) connect trends in future socioeconomic and technological development with impacts on the environment, such as global climate change. They occupy a critical position at the global science-policy interface. IAMs and associated scenarios have come under intense scrutiny, with critiques addressing both methodological and substantive issues, such as land use, carbon dioxide removal and technology performance. Criticisms have also addressed the transparency of IAM methods and assumptions as well as the transparency of the Intergovernmental Panel on Climate Change (IPCC) assessment of IAMs. This paper, authored by the co-chairs of IPCC Working Group III and members of the Technical Support Unit, documents activities aiming to enhance the transparency of IAMs and their assessment. It includes a history of IPCC's approach to scenarios covering the formation of the Integrated Assessment Modeling Consortium (IAMC) in 2007 and the emergence of the approach by which IPCC facilitates the development of scenarios, but does not produce them itself. An IPCC Expert Meeting at the start of the current assessment cycle made transparency recommendations targeted at both the research community and IPCC. The community has taken steps to “open the black box” by moving toward open-source and web-publishing IAM documentation. IPCC has included an Annex to its next report focusing on scenarios and modeling methodologies. An open call for scenario data linked to the current IPCC report includes an expanded set of input and output variables. This paper ends with suggested criteria for measuring the success of these efforts to improve transparency.
Lamb WF, Wiedmann T, Pongratz J, et al., 2021, A review of trends and drivers of greenhouse gas emissions by sector from 1990 to 2018, Environmental Research Letters, Vol: 16, Pages: 1-31, ISSN: 1748-9326
Global greenhouse gas (GHG) emissions can be traced to five economic sectors: energy, industry, buildings, transport and AFOLU (agriculture, forestry and other land uses). In this topical review, we synthesise the literature to explain recent trends in global and regional emissions in each of these sectors. To contextualise our review, we present estimates of GHG emissions trends by sector from 1990 to 2018, describing the major sources of emissions growth, stability and decline across ten global regions. Overall, the literature and data emphasise that progress towards reducing GHG emissions has been limited. The prominent global pattern is a continuation of underlying drivers with few signs of emerging limits to demand, nor of a deep shift towards the delivery of low and zero carbon services across sectors. We observe a moderate decarbonisation of energy systems in Europe and North America, driven by fuel switching and the increasing penetration of renewables. By contrast, in rapidly industrialising regions, fossil-based energy systems have continuously expanded, only very recently slowing down in their growth. Strong demand for materials, floor area, energy services and travel have driven emissions growth in the industry, buildings and transport sectors, particularly in Eastern Asia, Southern Asia and South-East Asia. An expansion of agriculture into carbon-dense tropical forest areas has driven recent increases in AFOLU emissions in Latin America, South-East Asia and Africa. Identifying, understanding, and tackling the most persistent and climate-damaging trends across sectors is a fundamental concern for research and policy as humanity treads deeper into the Anthropocene.
Skea J, van Diemen R, Portugal-Pereira J, et al., 2021, Outlooks, explorations and normative scenarios: approaches to global energy futures compared, Technological Forecasting and Social Change, Vol: 168, ISSN: 0040-1625
This paper compares recent global energy scenarios developed by governments, international bodies, businesses and the scientific community. We divide the scenarios into three broad classes: outlooks which extrapolate current trends and anticipate policy developments; exploratory scenarios which may consider disruptions; and normative scenarios which derive energy system pathways consistent with a long-term goal. Many organisations are starting to blend outlooks, exploratory and normative approaches. The paper covers trends in primary energy demand to 2040, snapshots of the energy mix in 2040, drivers of demand, and the evolution of scenarios projections developed in recent years. We find sharp divergences between outlooks and normative scenarios compatible with the Paris Agreement on climate change. All published outlooks imply that the world is not on an energy pathway compatible with the Paris Agreement. We conclude with an assessment of emerging themes including: scenario benchmarking and group think; adaptation of scenarios to real world developments; and the plausibility of different types of scenarios. We propose that more dialogue between scenario developers from the scientific community and those working in governments and commercial organisations could be beneficial. Research focusing on the organisational processes through which scenarios are developed could usefully extend this work.
Stockhause M, Al Khourdajie A, Alegria A, et al., 2020, IPCC Sixth Assessment approaches towards FAIR data and an enhanced data reuse
Stockhause M, Al Khourdajie A, Alegria A, et al., 2020, IPCC Sixth Assessment approaches towards FAIR data and an enhanced data reuse
Al Khourdajie A, Finus M, 2020, Measures to enhance the effectiveness of international climate agreements: The case of border carbon adjustments, European Economic Review, Vol: 124, ISSN: 0014-2921
Actions on climate change which are not supported by all countries are not very effective. However, full participation in a global climate treaty with meaningful emission reductions is difficult to achieve. The non-excludability of the public good mitigation provides an incentive to abstain from global action. Moreover, carbon leakage renders it unattractive to join a treaty without full participation. We study whether and under which conditions border carbon adjustments (BCAs) can mitigate free-riding and reduce carbon leakage in a simple strategic trade model. We show that BCAs can lead to large stable climate agreements, including full participation, associated with large global welfare gains if treaties do not restrict membership (open membership), as this is typical for environmental agreements. We caution against restricting accession to treaties (exclusive membership), as this is typical for trade agreements, which may serve individual but not global interests.
Finus M, Al Khourdajie A, 2017, Strategic Environmental Policy, International Trade and Self-enforcing Agreements: The Role of Consumers' Taste for Variety, STRATEGIC BEHAVIOR AND THE ENVIRONMENT, Vol: 7, Pages: 317-350, ISSN: 1944-012X
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