145 results found
Allen MR, Peters GP, Shine KP, et al., 2022, Indicate separate contributions of long-lived and short-lived greenhouse gases in emission targets, NPJ CLIMATE AND ATMOSPHERIC SCIENCE, Vol: 5, ISSN: 2397-3722
Fiedler S, Wyser K, Rogelj J, et al., 2021, Radiative effects of reduced aerosol emissions during the COVID-19 pandemic and the future recovery, Atmospheric Research, Vol: 264, Pages: 1-11, ISSN: 0169-8095
The pandemic in 2020 caused an abrupt change in the emission of anthropogenic aerosols and their precursors. We estimate the associated change in the aerosol radiative forcing at the top of the atmosphere and the surface. To that end, we perform new simulations with the CMIP6 global climate model EC-Earth3. The simulations use the here newly created data for the anthropogenic aerosol optical properties and an associated effect on clouds from the simple plumes parameterization (MACv2-SP), based on revised SO2 and NH3 emission scenarios. Our results highlight the small impact of the pandemic on the global aerosol radiative forcing in 2020 compared to the CMIP6 scenario SSP2-4.5 of the order of +0.04 Wm−2, which is small compared to the natural year-to-year variability in the radiation budget. Natural variability also limits the ability to detect a meaningful regional difference in the anthropogenic aerosol radiative effects. We identify the best chances to find a significant change in radiation at the surface during cloud-free conditions for regions that were strongly polluted in the past years. The post-pandemic recovery scenarios indicate a spread in the aerosol forcing of −0.68 to −0.38 Wm−2 for 2050 relative to the pre-industrial, which translates to a difference of +0.05 to −0.25 Wm−2 compared to the 2050 baseline from SSP2-4.5. This spread falls within the present-day uncertainty in aerosol radiative forcing and the CMIP6 spread in aerosol forcing at the end of the 21st century. We release the new MACv2-SP data for studies on the climate response to the pandemic and the recovery scenarios. Our 2050 forcing estimates suggest that sustained aerosol emission reductions during the post-pandemic recovery cause a stronger climate response than in 2020, i.e., there is a delayed influence of the pandemic on climate.
Gambhir A, George M, McJeon H, et al., 2021, Near-term transition and longer-term physical climate risks of greenhouse gas emissions pathways, NATURE CLIMATE CHANGE, Vol: 12, Pages: 88-+, ISSN: 1758-678X
MacDougall AH, Rogelj J, Withey P, 2021, Estimated climate impact of replacing agriculture as the primary food production system, ENVIRONMENTAL RESEARCH LETTERS, Vol: 16, ISSN: 1748-9326
Koberle AC, Vandyck T, Guivarch C, et al., 2021, The cost of mitigation revisited (Nov, 10.1038/s41558-021-01203-6, 2021), NATURE CLIMATE CHANGE, Vol: 12, Pages: 298-298, ISSN: 1758-678X
Riahi K, Bertram C, Huppmann D, et al., 2021, Cost and attainability of meeting stringent climate targets without overshoot, NATURE CLIMATE CHANGE, Vol: 11, Pages: 1063-+, ISSN: 1758-678X
Sognnaes I, Gambhir A, van de Ven D-J, et al., 2021, A multi-model analysis of long-term emissions and warming implications of current mitigation efforts, Nature Climate Change, Vol: 11, Pages: 1055-1062, ISSN: 1758-678X
Most of the integrated assessment modelling literature focuses on cost-effective pathways towards given temperature goals. Conversely, using seven diverse integrated assessment models, we project global energy CO2 emissions trajectories on the basis of near-term mitigation efforts and two assumptions on how these efforts continue post-2030. Despite finding a wide range of emissions by 2050, nearly all the scenarios have median warming of less than 3 °C in 2100. However, the most optimistic scenario is still insufficient to limit global warming to 2 °C. We furthermore highlight key modelling choices inherent to projecting where emissions are headed. First, emissions are more sensitive to the choice of integrated assessment model than to the assumed mitigation effort, highlighting the importance of heterogeneous model intercomparisons. Differences across models reflect diversity in baseline assumptions and impacts of near-term mitigation efforts. Second, the common practice of using economy-wide carbon prices to represent policy exaggerates carbon capture and storage use compared with explicitly modelling policies.
Estimates of economic implications of climate policy are important inputs into policy-making. Despite care to contextualize quantitative assessments of mitigation costs, one strong view outside academic climate economics is that achieving Paris Agreement goals implies sizable macroeconomic losses. Here, we argue that this notion results from unwarranted simplification or omission of the complexities of quantifying mitigation costs, which generates ambiguity in communication and interpretation. We synthesize key factors influencing mitigation cost estimates to guide interpretation of estimates, for example from the Intergovernmental Panel on Climate Change, and suggest ways to improve the underlying models. We propose alternatives for the scenario design framework, the framing of mitigation costs and the methods used to derive them, to better inform public debate and policy.
Ou Y, Iyer G, Clarke L, et al., 2021, Can updated climate pledges limit warming well below 2 degrees C? Increased ambition and implementation are essential, Science, Vol: 374, Pages: 693-695, ISSN: 0036-8075
Martin MA, Alcaraz Sendra O, Bastos A, et al., 2021, Ten new insights in climate science 2021: a horizon scan, Global Sustainability, Vol: 4, Pages: 1-20, ISSN: 2059-4798
A synthesis is made of 10 topics within climate research, where there have been significant advances since January 2020. The insights are based on input from an international open call with broad disciplinary scope. Findings include: (1) the options to still keep global warming below 1.5 °C; (2) the impact of non-CO2 factors in global warming; (3) a new dimension of fire extremes forced by climate change; (4) the increasing pressure on interconnected climate tipping elements; (5) the dimensions of climate justice; (6) political challenges impeding the effectiveness of carbon pricing; (7) demand-side solutions as vehicles of climate mitigation; (8) the potentials and caveats of nature-based solutions; (9) how building resilience of marine ecosystems is possible; and (10) that the costs of climate change mitigation policies can be more than justified by the benefits to the health of humans and nature.
Kikstra JS, Vinca A, Lovat F, et al., 2021, Climate mitigation scenarios with persistent COVID-19-related energy demand changes, NATURE ENERGY, Vol: 6, Pages: 1114-1123, ISSN: 2058-7546
Thiery W, Lange S, Rogelj J, et al., 2021, Intergenerational inequities in exposure to climate extremes Young generations are severely threatened by climate change, Science, Vol: 374, Pages: 158-160, ISSN: 0036-8075
Schultes A, Piontek F, Soergel B, et al., 2021, Economic damages from on-going climate change imply deeper near-term emission cuts, ENVIRONMENTAL RESEARCH LETTERS, Vol: 16, ISSN: 1748-9326
Hoehne N, Gidden MJ, den Elzen M, et al., 2021, Wave of net zero emission targets opens window to meeting the Paris Agreement, NATURE CLIMATE CHANGE, Vol: 11, Pages: 820-+, ISSN: 1758-678X
Hoepner AGF, Rogelj J, 2021, Emissions estimations should embed a precautionary principle, NATURE CLIMATE CHANGE, Vol: 11, Pages: 638-640, ISSN: 1758-678X
Gibson M, Slade R, Pereira JP, et al., 2021, Comparing mechanisms of food choice in an agent-based model of milk consumption and substitution in the UK, JASSS-THE JOURNAL OF ARTIFICIAL SOCIETIES AND SOCIAL SIMULATION, Vol: 24, ISSN: 1460-7425
Substitution of food products will be key to realising widespread adoption of sustainable diets. We present an agent-based model of decision-making and influences on food choice, and apply it to historically observed trends of British whole and skimmed (including semi) milk consumption from 1974 to 2005. We aim to give a plausible representation of milk choice substitution, and test different mechanisms of choice consideration. Agents are consumers that perceive information regarding the two milk choices, and hold values that inform their position on the health and environmental impact of those choices. Habit, social influence and post-decision evaluation are modelled. Representative survey data on human values and long-running public concerns empirically inform the model. An experiment was run to compare two model variants by how they perform in reproducing these trends. This was measured by recording mean weekly milk consumption per person. The variants differed in how agents became disposed to consider alternative milk choices. One followed a threshold approach, the other was probability based. All other model aspects remained unchanged. An optimisation exercise via an evolutionary algorithm was used to calibrate the model variants independently to observed data. Following calibration, uncertainty and global variance-based temporal sensitivity analysis were conducted. Both model variants were able to reproduce the general pattern of historical milk consumption, however, the probability-based approach gave a closer fit to the observed data, but over a wider range of uncertainty. This responds to, and further highlights, the need for research that looks at, and compares, different models of human decision-making in agent-based and simulation models. This study is the first to present an agent-based modelling of food choice substitution in the context of British milk consumption. It can serve as a valuable pre-curser to the modelling of dietary shift and sustainable
Lamboll RD, Jones CD, Skeie RB, et al., 2021, Modifying emissions scenario projections to account for the effects of COVID-19: protocol for CovidMIP, GEOSCIENTIFIC MODEL DEVELOPMENT, Vol: 14, Pages: 3683-3695, ISSN: 1991-959X
Nikas A, Elia A, Boitier B, et al., 2021, Where is the EU headed given its current climate policy? A stakeholder-driven model inter-comparison., Science of the Total Environment, Vol: 793, Pages: 148549-148549, ISSN: 0048-9697
Recent calls to do climate policy research with, rather than for, stakeholders have been answered in non-modelling science. Notwithstanding progress in modelling literature, however, very little of the scenario space traces back to what stakeholders are ultimately concerned about. With a suite of eleven integrated assessment, energy system and sectoral models, we carry out a model inter-comparison for the EU, the scenario logic and research questions of which have been formulated based on stakeholders' concerns. The output of this process is a scenario framework exploring where the region is headed rather than how to achieve its goals, extrapolating its current policy efforts into the future. We find that Europe is currently on track to overperforming its pre-2020 40% target yet far from its newest ambition of 55% emissions cuts by 2030, as well as looking at a 1.0-2.35 GtCO2 emissions range in 2050. Aside from the importance of transport electrification, deployment levels of carbon capture and storage are found intertwined with deeper emissions cuts and with hydrogen diffusion, with most hydrogen produced post-2040 being blue. Finally, the multi-model exercise has highlighted benefits from deeper decarbonisation in terms of energy security and jobs, and moderate to high renewables-dominated investment needs.
Nicholls Z, Meinshausen M, Lewis J, et al., 2021, Reduced Complexity Model Intercomparison Project Phase 2: Synthesizing Earth System Knowledge for Probabilistic Climate Projections, EARTHS FUTURE, Vol: 9
Rogelj J, Schleussner C-F, 2021, Reply to Comment on 'Unintentional unfairness when applying new greenhouse gas emissions metrics at country level', ENVIRONMENTAL RESEARCH LETTERS, Vol: 16, ISSN: 1748-9326
Grassi G, Stehfest E, Rogelj J, et al., 2021, Critical adjustment of land mitigation pathways for assessing countries’ climate progress, Nature Climate Change, Vol: 11, Pages: 425-434, ISSN: 1758-678X
Mitigation pathways by Integrated Assessment Models (IAMs) describe future emissions that keep global warming below specific temperature limits and are compared with countries’ collective greenhouse gas (GHG) emission reduction pledges. This is needed to assess mitigation progress and inform emission targets under the Paris Agreement. Currently, however, a mismatch of ~5.5 GtCO2 yr−1 exists between the global land-use fluxes estimated with IAMs and from countries’ GHG inventories. Here we present a ‘Rosetta stone’ adjustment to translate IAMs’ land-use mitigation pathways to estimates more comparable with GHG inventories. This does not change the original decarbonization pathways, but reallocates part of the land sink to be consistent with GHG inventories. Adjusted cumulative emissions over the period until net zero for 1.5 or 2 °C limits are reduced by 120–192 GtCO2 relative to the original IAM pathways. These differences should be taken into account to ensure an accurate assessment of progress towards the Paris Agreement.
Jones CD, Hickman JE, Rumbold ST, et al., 2021, The Climate Response to Emissions Reductions Due to COVID-19: Initial Results From CovidMIP, GEOPHYSICAL RESEARCH LETTERS, Vol: 48, ISSN: 0094-8276
Rogelj J, Geden O, Cowie A, et al., 2021, Net-zero emissions targets are vague: three ways to fix, Nature, Vol: 591, Pages: 365-368, ISSN: 0028-0836
Kikstra J, Vinca A, Lovat F, et al., 2021, COVID-19 impacts on energy demand can help reduce long-term mitigation challenge
<jats:title>Abstract</jats:title> <jats:p>The COVID-19 pandemic caused radical temporary breaks with past energy use trends. However, how a post-pandemic recovery will impact the longer-term energy transition is unclear. Here, we present a set of global COVID-19 shock-and-recovery scenarios that systematically explore the demand-side effect on final energy and GHG emissions. Our pathways project final energy demand reductions of 12 to 40 EJ/yr by 2025 and cumulative CO2 emissions reductions by 2030 of 28 to 53 GtCO2, depending on the depth and duration of the economic downturn and demand-side changes. Recovering from the pandemic with low energy demand practices - embedded in new patterns of travel, work, consumption, and production – reduces climate mitigation challenges. A low energy demand recovery reduces carbon prices for a 1.5°C consistent pathway by 19%, lowers energy supply investments until 2030 by 2.1 trillion USD, and lessens pressure on the upscaling of renewable energy technologies.</jats:p>
Matthews HD, Tokarska KB, Rogelj J, et al., 2021, An integrated approach to quantifying uncertainties in the remaining carbon budget, Communications Earth & Environment, Vol: 2, Pages: 1-11, ISSN: 2662-4435
The remaining carbon budget quantifies the future CO2 emissions to limit global warming below a desired level. Carbon budgets are subject to uncertainty in the Transient Climate Response to Cumulative CO2 Emissions (TCRE), as well as to non-CO2 climate influences. Here we estimate the TCRE using observational constraints, and integrate the geophysical and socioeconomic uncertainties affecting the distribution of the remaining carbon budget. We estimate a median TCRE of 0.44 °C and 5–95% range of 0.32–0.62 °C per 1000 GtCO2 emitted. Considering only geophysical uncertainties, our median estimate of the 1.5 °C remaining carbon budget is 440 GtCO2 from 2020 onwards, with a range of 230–670 GtCO2, (for a 67–33% chance of not exceeding the target). Additional socioeconomic uncertainty related to human decisions regarding future non-CO2 emissions scenarios can further shift the median 1.5 °C remaining carbon budget by ±170 GtCO2.
Riahi K, Bertram C, Huppmann D, et al., 2021, Long-term economic benefits of stabilizing warming without overshoot – the ENGAGE model intercomparison
<jats:title>Abstract</jats:title> <jats:p>Global emissions scenarios play a critical role in the assessment of strategies to mitigate climate change and their related societal transformations. The current generation of scenarios, however, are criticized because they rely heavily on net negative CO2 emissions (NNCE) that result from allowing temperature limits to be temporarily exceeded. In this study we present a new set of emissions scenarios that exclude NNCE. We show that such scenarios require a more rapid near-term transformation with significant long-term gains for the economy (even without considering the benefits of avoided climate impacts). Scenarios that avoid temperature overshoot and NNCE are thus not only economically more attractive over the long term, they also involve lower climate risks. Our study further identifies possible alternative configurations of net-zero CO2 emissions systems and the distinct roles of different sectors and regions in order to balance emissions sources and sinks.</jats:p>
Matthews HD, Tokarska KB, Nicholls ZRJ, et al., 2020, Opportunities and challenges in using remaining carbon budgets to guide climate policy, NATURE GEOSCIENCE, Vol: 13, Pages: 769-779, ISSN: 1752-0894
Gibson MF, Rao ND, Slade RB, et al., 2020, The role of energy in mitigating grain storage losses in India and the impact for nutrition, Resources, Conservation and Recycling, Vol: 163, ISSN: 0921-3449
Globally, India's population is amongst the most severely impacted by nutrient deficiency, yet millions of tonnes of food are lost along the supply chain before reaching consumers. Across food groups, grains represent the largest share of daily calories and overall losses by mass in India. This study quantifies energy input to minimise storage losses across India, responsible for up to a quarter of grain losses. In doing so, we explore links between three Sustainable Development Goals-SDG2, SDG7, and SDG12-, and provide insight for development of joined up agriculture and health policy in the country. Focusing on rice, wheat, maize, bajra, and sorghum, we quantify one route to reduce losses in supply chains, by modelling the energy input to maintain favourable climatic conditions in modern silo storage. We quantify key nutrients (calories, protein, zinc, iron, vitamin A) contained within these losses, and calculate roughly how much deficiency in these dietary components could be reduced if grain losses were eliminated. Our modelling indicates that maize has the highest energy input intensity for storage, at 110 (18) kWh per tonne of grain (kWh/t), and wheat the lowest, at 72 (14) kWh/t. This energy cost represents 8%-16% of the energy input required in grain production. We estimate if grain losses across the supply chain were saved and targeted to India's nutritionally deficient population, average protein deficiency could reduce by 46±4%, calorie by 27±2%, zinc by 26±2% and iron by 11±1%.
Lamboll RD, Nicholls ZRJ, Kikstra JS, et al., 2020, Silicone v1.0.0: an open-source Python package for inferring missing emissions data for climate change research, GEOSCIENTIFIC MODEL DEVELOPMENT, Vol: 13, Pages: 5259-5275, ISSN: 1991-959X
Graven H, Keeling RF, Rogelj J, 2020, Changes to carbon isotopes in atmospheric CO2 over the industrial era and into the future, Global Biogeochemical Cycles: an international journal of global change, Vol: 34, Pages: 1-21, ISSN: 0886-6236
In this “Grand Challenges” paper, we review how the carbon isotopic composition of atmospheric CO2 has changed since the Industrial Revolution due to human activities and their influence on the natural carbon cycle, and we provide new estimates of possible future changes for a range of scenarios. Emissions of CO2 from fossil fuel combustion and land use change reduce the ratio of 13C/12C in atmospheric CO2 (δ13CO2). This is because 12C is preferentially assimilated during photosynthesis and δ13C in plant-derived carbon in terrestrial ecosystems and fossil fuels is lower than atmospheric δ13CO2. Emissions of CO2 from fossil fuel combustion also reduce the ratio of 14C/C in atmospheric CO2 (Δ14CO2) because 14C is absent in million-year-old fossil fuels, which have been stored for much longer than the radioactive decay time of 14C. Atmospheric Δ14CO2 rapidly increased in the 1950s to 1960s because of 14C produced during nuclear bomb testing. The resulting trends in δ13C and Δ14C in atmospheric CO2 are influenced not only by these human emissions but also by natural carbon exchanges that mix carbon between the atmosphere and ocean and terrestrial ecosystems. This mixing caused Δ14CO2 to return toward preindustrial levels in the first few decades after the spike from nuclear testing. More recently, as the bomb 14C excess is now mostly well mixed with the decadally overturning carbon reservoirs, fossil fuel emissions have become the main factor driving further decreases in atmospheric Δ14CO2. For δ13CO2, in addition to exchanges between reservoirs, the extent to which 12C is preferentially assimilated during photosynthesis appears to have increased, slowing down the recent δ13CO2 trend slightly. A new compilation of ice core and flask δ13CO2 observations indicates that the decline in δ13CO2 since the preindustrial period is less than some prior estimates, which may have incorporated
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