Publications
186 results found
Vinca A, Kikstra JS, Lovat F, et al., 2021, Impacts of COVID-19 induced energy demand changes on emissions and mitigation challenges 
<jats:p>&lt;p&gt;The COVID-19 pandemic is causing radical temporary breaks with past energy use and GHG emissions trends. However, how a post-pandemic recovery will impact longer-term transformations to a low-carbon society is unclear. Here, we present different global COVID-19 shock-and-recovery scenarios that systematically explore economic uncertainty and the demand-side effect on emissions. We consider changes in the residential, industry and transport energy sub-sectors under diverging cases that might lead to a more carbon intensive and individualistic way of consumption, or to a policy-advised new future that supports the emission reduction opportunities seen during the pandemic. The resulting impact on cumulative CO2 emissions over the coming decade can range from 28 to 53 GtCO2 reduction depending on the depth and duration of the economic downturn and the extent and persistence of demand-side changes. Recovering from the pandemic with low energy demand practices - embedded in new patterns of travel, work, consumption, and production &amp;#8211; reduces climate mitigation challenges in the long run. We show that a low energy demand recovery reduces carbon prices for a 1.5&amp;#176;C consistent pathway by 19%, saves energy supply investments until 2030 by 2.1 trillion USD, and lessens pressure on the upscaling of renewable energy technologies.&amp;#160;&amp;#160;&lt;/p&gt;</jats:p>
Schleussner C-F, Lejeune Q, Ciais P, et al., 2021, Overshooting warming targets &#8211; temperature reversibility and implications for impacts, adaptation needs and near-term mitigation
<jats:p>&lt;p&gt;Limiting global mean temperature increase to politically agreed temperature limits such as the 1.5&amp;#176;C threshold in the Paris Agreement becomes increasingly challenging. This has given rise to a class of overshoot emissions pathways in the mitigation literature that limit warming to such thresholds only after allowing for a temporary overshoot. However, substantial biogeophysical uncertainties remain regarding the large-scale deployment of Carbon Dioxide Removal technologies required to potentially reverse global warming. Additionally, beyond global mean temperature very little is known about the benefits of declining temperatures on impacts and adaptation needs. Here we will provide an overview of the current state of understanding regarding the reversibility of global warming, as well as impacts and adaptation needs under overshoot pathways.&lt;/p&gt;&lt;p&gt;We highlight the characteristics of the overshoot scenarios from the literature, and especially those that are compatible with identified sustainability limits for Carbon Dioxide Removal deployment. We will compare those characteristics with uncertainties arising from the Earth System&amp;#8217;s response which may complicate the efforts to achieve a decrease in Global Mean Temperature after peak warming is reached. This part will include latest results of the permafrost carbon feedback under stylized overshoot scenarios. Eventually, we will summarise the state-of-the-art knowledge and present new results regarding the impacts of overshoot scenarios for non-linear and time-lagged responses such as sea-level rise, permafrost and glaciers. This will allow for a preliminary assessment of the impact and adaptation benefits of early mitigation compatible with a no or low overshoot pathways.&lt;/p&gt;</jats:p>
Rogelj J, Reisinger A, Cowie A, et al., 2021, Towards high-quality net-zero targets
<jats:p>&lt;p&gt;With the adoption of the Paris Agreement in 2015 the world has decided that warming should be kept well below 2&amp;#176;C while pursuing a limit of 1.5&amp;#176;C above preindustrial levels. The Paris Agreement also sets a net emissions reduction goal: in the second half of the century, the balance of global anthropogenic greenhouse gas emissions and removals should become net zero. Since 2018, in response to the publication of the IPCC Special Report on Global Warming of 1.5&amp;#176;C, a flurry of net zero target announcements has ensued. Many countries, cities, regions, companies, or other organisations have come forward with targets to reach net zero, or become carbon or climate neutral. These labels describe a wide variety of targets, and rarely detailed. Lack of transparency renders it impossible to understand their ultimate contribution towards the global goal. Here we present a set of key criteria that high-quality net zero targets should address. These nine criteria cover emissions, removals, timing, fairness and a long-term vision. Unless net zero targets provide clarity on these nine criteria, we may not know until it is too late whether the collective promise of net zero targets is adequate to meet the global goal of the Paris Agreement.&lt;/p&gt;</jats:p>
Nauels A, Schleussner C-F, Rogelj J, 2021, Greenhouse gas metrics for net zero targets in science and policy
<jats:p>&lt;p&gt;The treatment of non-CO&lt;sub&gt;2&lt;/sub&gt; greenhouse gases is central for scientific assessments of effective climate change mitigation and climate policy. Radiative forcing of a unit of emitted short-lived gases decays quickly; on the order of a decade for methane, as opposed to centuries for CO&lt;sub&gt;2&lt;/sub&gt;. Metric selection for comparing the climate effect of these emissions with CO&lt;sub&gt;2&lt;/sub&gt; thereby comes with choices regarding short- vs. long-term priorities to achieve mitigation. The global nature of the well-mixed atmosphere also has implications for the transferability of concepts such as global warming potentials from the global to the national scale.&lt;/p&gt;&lt;p&gt;Here we present the implications of metric choice on global emissions balance and net zero, with a particular emphasis on the consistency with the wider context of the Paris Agreement, both on the global as well as the national level. Stylized scenarios show that interpreting the Paris Agreement emissions goals with metrics different from the IPCC AR5 can lead to inconsistencies with the Agreement&amp;#8217;s temperature goal. Furthermore, we illustrate that introducing metrics that depend on historical emissions in a national context raises profound questions of equity and fairness, thereby questioning the applicability of non-constant global warming potentials at any but the global level. We provide suggestions to adequately approach these issues in the context of the Paris Agreement and national policy making.&lt;/p&gt;</jats:p>
Thiery W, Lange S, Rogelj J, et al., 2021, The kids aren't alright
<jats:p>&lt;p&gt;People are being affected by climate change around the globe today at around 1&amp;#176;C of warming above pre-industrial levels. Current policies towards climate mitigation would result in about twice as much warming over the next 80 years, roughly the lifetime of a today's newborn. Here we quantify the stronger climate change burden that will fall on younger generations by introducing a novel analysis framework that expresses impacts as a function of how they are experienced along the course of a person's life. Combining projections of population, temperature, and 15 impact models encompassing droughts, heatwaves, tropical cyclones, crop failure, floods, and wildfires, we show that, under current climate pledges, newborns in 2020 are projected to experience 2-13 times more extreme events during their life than a person born in 1960, with substantial variations across regions. Limiting warming to 1.5&amp;#176;C consistently reduces that burden, while still leaving younger generations with unavoidable impacts that are unmatched by the impacts experienced by older generations. Our results provide a quantified scientific basis to understand the position from which younger generations challenge the present shortfall of adequate climate action.&lt;/p&gt;</jats:p>
MacDougall AH, Rogelj J, Withey P, 2021, Estimated climate impact of the end of agriculture as the primary food production system
<jats:p>&lt;p&gt;Global agriculture is the second largest contributor to anthropogenic climate change after the burning of fossil fuels. However the potential to mitigate the agricultural contribution is limited by the imperative to supply food for the global population. Advances in microbial biomass cultivation technology have recently opened a pathway to growing substantial amounts of food for humans or livestock, by fuelling microbial growth with hydrogen produced from electrolysis powered by renewable energy. This method of food production would use a small fraction of the land presently used for agriculture. Here we investigate the potential climate change impacts of the end of agriculture as the primary human food production system. We find that microbial biomass cultivation technology has both the potential to exacerbate climate change by outcompeting economic decarbonization for renewable energy and the potential to mitigate climate change if deployed following economic decarbonization. A duality which originates from the contrast between the reversibility of agricultural driven climate change and the irreversibility of fossil-fuel CO&lt;sub&gt;2&lt;/sub&gt; driven climate change. The range of reduced warming from the replacement of agriculture ranges from -0.22 [-0.29 to -0.04]&lt;sup&gt;o&lt;/sup&gt;C for Shared Socioeconomic Pathway (SSP) 1-1.9 to -0.85 [-0.99 to -0.39]&lt;sup&gt;o&lt;/sup&gt;C for SSP4-6.0. For limited temperature target overshoot scenarios, replacement of agriculture could thus eliminate or reduce the need for active atmospheric CO&lt;sub&gt;2&lt;/sub&gt; removal to achieve the necessary peak and decline in global warming. Given current societal barriers to switching to a microbial-based diet, deep near-term emissions reductions in CO&lt;sub&gt;2&lt;/sub&gt;
Fiedler S, Wyser K, Joeri R, et al., 2021, Implication of the reduction in anthropogenic aerosols due to the COVID-19 pandemic and the future recovery scenarios for radiative forcing
<jats:p>&lt;p&gt;The COVID-19 pandemic has led to unprecedented reductions in socio-economic activities. Associated decreases in anthropogenic aerosol emissions are not represented in the original CMIP6 emission scenarios. Here we estimate the implications of the pandemic for the aerosol forcing in 2020 and quantify the spread in aerosol forcing associated with the differences in the post-pandemic recovery pathways. To this end, we use new emission scenarios taking the COVID-19 crisis into account and projecting different socio-economic developments until 2050 with fossil-fuel based and green pathways (Forster et al., 2020). We use the new emission data to generate input for the anthropogenic aerosol parameterization MACv2-SP for CMIP6 models. In this presentation, we first show the results for the anthropogenic aerosol optical depth and associated effects on clouds from the new MACv2-SP data for 2020 to 2050 (Fiedler et al., in review). We then use the MACv2-SP data to provide estimates of the effective radiative effects of the anthropogenic aerosols for 2020 and 2050. Our forcing estimates are based on new atmosphere-only simulations with the CMIP6 model EC-Earth3. The model uses MACv2-SP to represent aerosol-radiation and aerosol-cloud interactions including aerosol effects on cloud lifetime. For each anthropogenic aerosol pattern, we run EC-Earth3 simulations for fifty years to substantially reduce the impact of model-internal variability on the forcing estimate. Our results highlight: (1) a change of +0.04 Wm&lt;sup&gt;-2&lt;/sup&gt; in the global mean effective radiative forcing of anthropogenic aerosols for 2020 due to the pandemic, which is small compared to the magnitude of internal variability, (2) a spread of -0.38 to -0.68 Wm&lt;sup&gt;-2&lt;/sup&gt; for the effective radiative forcing associated with anthropogenic aerosols in 2050 depending on the recovery scenario in
Lamboll R, Forster P, Jones C, et al., 2021, Modifying emissions data and projections to incorporate the effects of lockdown in climate modelling
<jats:p>&lt;p&gt;Lockdowns to avoid the spread of COVID-19 have created an unprecedented reduction in human emissions, however emissions estimates are typically only available after one or more years, making it hard to incorporate these reductions into emissions projections. In this talk we will outline how mobility data and power usage can nowcast country-and-sector emissions of various gases. In this way we show that the short-term impact of lockdown on emissions data is not expected to be significant for long-term temperature trends.&lt;/p&gt;&lt;p&gt;We will also outline how different recovery pathways can be made using basic longer-term emissions projections and how to construct detailed scenarios for non-CO2 emissions, using assumptions about the effects of lockdown on nationally determined contributions and a new software package called Silicone that can infill missing greenhouse gas emissions. Silicone allows the consistent incorporation of tradeoffs between emission species as modelled by IAMs, and as expressed in available greenhouse gas emission scenarios, to be applied to the proposed pathways. We will then show how to make these projections into the more detailed, gridded, CMIP-6 compatible emissions estimates that are required to run General Circulation Models (GCM).&lt;/p&gt;</jats:p>
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>
Rogelj J, Schleussner C-F, 2021, Reply to Comment on: ‘Unintentional unfairness when applying new greenhouse gas emissions metrics at country level’
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>
Lamboll RD, Jones CD, Skeie RB, et al., 2020, Modifying emission scenario projections to account for the effects ofCOVID-19: protocol for Covid-MIP
<jats:p>Abstract. Lockdowns to avoid the spread of COVID-19 have created an unprecedented reduction in human emissions. While the country-level scale of emissions changes can be estimated in near-real-time, the more detailed, gridded emissions estimates that are required to run General Circulation Models (GCM) of the climate will take longer to collect. In this paper we use recorded and projected country-and-sector activity levels to modify gridded predictions from the MESSAGE-GLOBIOM SSP2-4.5 scenario. We provide updated projections for concentrations of greenhouse gases, emissions fields for aerosols and precursors, and the ozone and optical properties that result from this. The codebase to perform similar modifications to other scenarios is also provided. We outline the means by which these results may be used in a model intercomparison project (CovidMIP) to investigate the impact of national lockdown measures on climate. This includes three strands: an assessment of short-term effects (5-year period), of longer-term effects (30 years) and an investigation into the separate effects of changes in emissions of greenhouse gases and aerosols. This last strand supports possible attribution of observed changes in the climate system, hence these simulations will also form part of the Detection and Attribution Model Intercomparison Project (DAMIP). </jats:p>
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%.
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
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- Citations: 45
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
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- Citations: 13
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
Nicholls ZRJ, Meinshausen M, Lewis J, et al., 2020, Reduced Complexity Model Intercomparison Project Phase 1: introduction and evaluation of global-mean temperature response, GEOSCIENTIFIC MODEL DEVELOPMENT, Vol: 13, Pages: 5175-5190, ISSN: 1991-959X
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- Citations: 48
Andrijevic M, Schleussner C-F, Gidden MJ, et al., 2020, COVID-19 recovery funds dwarf clean energy investment needs., Science, Vol: 370, Pages: 298-300, ISSN: 1095-9203
Tokarska KB, Arora VK, Gillett NP, et al., 2020, Uncertainty in carbon budget estimates due to internal climate variability, Environmental Research Letters, Vol: 15, Pages: 1-12, ISSN: 1748-9326
Remaining carbon budget specifies the cap on global cumulative CO2 emissions from the present-day onwards that would be in line with limiting global warming to a specific maximum level. In the context of the Paris Agreement, global warming is usually interpreted as the externally-forced response to anthropogenic activities and emissions, but it excludes the natural fluctuations of the climate system known as internal variability. A remaining carbon budget can be calculated from an estimate of the anthropogenic warming to date, and either (i) the ratio of CO2-induced warming to cumulative emissions, known as the Transient Climate Response to Emissions (TCRE), in addition to information on the temperature response to the future evolution of non-CO2 emissions; or (ii) climate model scenario simulations that reach a given temperature threshold. Here we quantify the impact of internal variability on the carbon budgets consistent with the Paris Agreement derived using either approach, and on the TCRE diagnosed from individual models. Our results show that internal variability contributes approximately ±0.09 °C to the overall uncertainty range of the human-induced warming to-date, leading to a spread in the remaining carbon budgets as large as ±50 PgC, when using approach (i). Differences in diagnosed TCRE due to internal variability in individual models can be as large as ±0.1 °C/1000 PgC (5%–95% range). Alternatively, spread in the remaining carbon budgets calculated from (ii) using future concentration-driven simulations of large ensembles of CMIP6 and CMIP5 models is estimated at ±30 PgC and ±40 PgC (5%–95% range). These results are important for model evaluation and imply that caution is needed when interpreting small remaining budgets in policy discussions. We do not question the validity of a carbon budget approach in determining mitigation requirements. However, due to intrinsic uncertainty arising from interna
Andrijevic M, Schleussner C-F, Gidden MJ, et al., 2020, climate-analytics/covid_recovery: Data and analysis scripts
This is the (final) version of the code for Andrijevic et al. 2020, "COVID-19 recovery funds dwarf clean energy investment needs"Built on v1.0 with a bit of spring cleaning
Smith SJ, Chateau J, Dorheim K, et al., 2020, Impact of methane and black carbon mitigation on forcing and temperature: a multi-model scenario analysis, Climatic Change, Vol: 163, Pages: 1427-1442, ISSN: 0165-0009
The relatively short atmospheric lifetimes of methane (CH4) and black carbon (BC) have focused attention on the potential for reducing anthropogenic climate change by reducing Short-Lived Climate Forcer (SLCF) emissions. This paper examines radiative forcing and global mean temperature results from the Energy Modeling Forum (EMF)-30 multi-model suite of scenarios addressing CH4 and BC mitigation, the two major short-lived climate forcers. Central estimates of temperature reductions in 2040 from an idealized scenario focused on reductions in methane and black carbon emissions ranged from 0.18–0.26 °C across the nine participating models. Reductions in methane emissions drive 60% or more of these temperature reductions by 2040, although the methane impact also depends on auxiliary reductions that depend on the economic structure of the model. Climate model parameter uncertainty has a large impact on results, with SLCF reductions resulting in as much as 0.3–0.7 °C by 2040. We find that the substantial overlap between a SLCF-focused policy and a stringent and comprehensive climate policy that reduces greenhouse gas emissions means that additional SLCF emission reductions result in, at most, a small additional benefit of ~ 0.1 °C in the 2030–2040 time frame.
Fofrich R, Tong D, Calvin K, et al., 2020, Early retirement of power plants in climate mitigation scenarios, Environmental Research Letters, Vol: 15, Pages: 1-12, ISSN: 1748-9326
International efforts to avoid dangerous climate change aim for large and rapid reductions of fossil fuel CO2 emissions worldwide, including nearly complete decarbonization of the electric power sector. However, achieving such rapid reductions may depend on early retirement of coal- and natural gas-fired power plants. Here, we analyze future fossil fuel electricity demand in 171 energy-emissions scenarios from Integrated Assessment Models (IAMs), evaluating the implicit retirements and/or reduced operation of generating infrastructure. Although IAMs calculate retirements endogenously, the structure and methods of each model differ; we use a standard approach to infer retirements in outputs from all six major IAMs and—unlike the IAMs themselves—we begin with the age distribution and region-specific operating capacities of the existing power fleet. We find that coal-fired power plants in scenarios consistent with international climate targets (i.e. keeping global warming well-below 2 °C or 1.5 °C) retire one to three decades earlier than historically has been the case. If plants are built to meet projected fossil electricity demand and instead allowed to operate at the level and over the lifetimes they have historically, the roughly 200 Gt CO2 of additional emissions this century would be incompatible with keeping global warming well-below 2 °C. Thus, ambitious climate mitigation scenarios entail drastic, and perhaps un-appreciated, changes in the operating and/or retirement schedules of power infrastructure.
Forster PM, Forster HI, Evans MJ, et al., 2020, Current and future global climate impacts resulting from COVID-19 (vol 82, pg 613, 2020), Nature Climate Change, Vol: 10, Pages: 971-971, ISSN: 1758-678X
Forster PM, Forster HI, Evans MJ, et al., 2020, Current and future global climate impacts resulting from COVID-19, Nature Climate Change, Vol: 10, Pages: 913-919, ISSN: 1758-678X
The global response to the COVID-19 pandemic has led to a sudden reduction of both GHG emissions and air pollutants. Here, using national mobility data, we estimate global emission reductions for ten species during the period February to June 2020. We estimate that global NOx emissions declined by as much as 30% in April, contributing a short-term cooling since the start of the year. This cooling trend is offset by ~20% reduction in global SO2 emissions that weakens the aerosol cooling effect, causing short-term warming. As a result, we estimate that the direct effect of the pandemic-driven response will be negligible, with a cooling of around 0.01 ± 0.005 °C by 2030 compared to a baseline scenario that follows current national policies. In contrast, with an economic recovery tilted towards green stimulus and reductions in fossil fuel investments, it is possible to avoid future warming of 0.3 °C by 2050.
MacDougall AH, Frölicher TL, Jones CD, et al., 2020, Is there warming in the pipeline? A multi-model analysis of the zero emissions commitment from CO2, Biogeosciences, Vol: 17, Pages: 2987-3016, ISSN: 1726-4170
The Zero Emissions Commitment (ZEC) is the change in global mean temperature expected to occur following the cessation of net CO2 emissions and as such is a critical parameter for calculating the remaining carbon budget. The Zero Emissions Commitment Model Intercomparison Project (ZECMIP) was established to gain a better understanding of the potential magnitude and sign of ZEC, in addition to the processes that underlie this metric. A total of 18 Earth system models of both full and intermediate complexity participated in ZECMIP. All models conducted an experiment where atmospheric CO2 concentration increases exponentially until 1000 PgC has been emitted. Thereafter emissions are set to zero and models are configured to allow free evolution of atmospheric CO2 concentration. Many models conducted additional second-priority simulations with different cumulative emission totals and an alternative idealized emissions pathway with a gradual transition to zero emissions. The inter-model range of ZEC 50 years after emissions cease for the 1000 PgC experiment is −0.36 to 0.29 ∘C, with a model ensemble mean of −0.07 ∘C, median of −0.05 ∘C, and standard deviation of 0.19 ∘C. Models exhibit a wide variety of behaviours after emissions cease, with some models continuing to warm for decades to millennia and others cooling substantially. Analysis shows that both the carbon uptake by the ocean and the terrestrial biosphere are important for counteracting the warming effect from the reduction in ocean heat uptake in the decades after emissions cease. This warming effect is difficult to constrain due to high uncertainty in the efficacy of ocean heat uptake. Overall, the most likely value of ZEC on multi-decadal timescales is close to zero, consistent with previous model experiments and simple theory.
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
<jats:p>Abstract. Integrated assessment models (IAMs) project future anthropogenic emissions for input into climate models. However, the full list of climate-relevant emissions is lengthy and most IAMs do not model all of them. Here we present silicone, an open-source Python package which infers anthropogenic emissions of missing species based on other known emissions. For example, it can infer nitrous oxide emissions in one scenario based on carbon dioxide emissions from that scenario plus the relationship between nitrous oxide and carbon dioxide emissions in other scenarios. This broadens the range of IAMs available for exploring projections of future climate change. Silicone forms part of the open-source pipeline for assessments of the climate implications of IAMs by the IAM consortium (IAMC). A variety of infilling options are outlined and their suitability for different cases are discussed. The code and notebooks explaining details of the package and how to use it are available from the GitHub repository, https://github.com/GranthamImperial/silicone. There is an additional repository showing uses of the code to complement existing research at https://github.com/GranthamImperial/silicone_examples. </jats:p>
Pfleiderer P, Schleussner C-F, Mengel M, et al., 2020, global mean temperature indicators linked to warming levels avoiding climate risks (vol 13, 064015, 2018), Environmental Research Letters, Vol: 15, Pages: 1-1, ISSN: 1748-9326
Rogelj J, Forster PM, Kriegler E, et al., 2020, Estimating and tracking the remaining carbon budget for stringent climate targets (vol 571, pg 335, 2019), Nature, Vol: 580, ISSN: 0028-0836
Correction to: Nature https://doi.org/10.1038/s41586-019-1368-z Published online 17 July 2019
Duan H, Rogelj J, Veysey J, et al., 2020, Modeling deep decarbonization: Robust energy policy and climate action, Applied Energy, Vol: 262, Pages: 1-3, ISSN: 0306-2619
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