Fixing a Critical Climate Accounting Error Searchinger, Timothy D.; Hamburg, Steven P.; Melillo, Jerry ...
Science (American Association for the Advancement of Science),
10/2009, Letnik:
326, Številka:
5952
Journal Article
Recenzirano
Rules for applying the Kyoto Protocol and national cap-and-trade laws contain a major, but fixable, carbon accounting flaw in assessing bioenergy.
The accounting now used for assessing compliance ...with carbon limits in the Kyoto Protocol and in climate legislation contains a far-reaching but fixable flaw that will severely undermine greenhouse gas reduction goals (
1
). It does not count CO
2
emitted from tailpipes and smokestacks when bioenergy is being used, but it also does not count changes in emissions from land use when biomass for energy is harvested or grown. This accounting erroneously treats all bioenergy as carbon neutral regardless of the source of the biomass, which may cause large differences in net emissions. For example, the clearing of long-established forests to burn wood or to grow energy crops is counted as a 100% reduction in energy emissions despite causing large releases of carbon.
The livestock sector is the largest source of anthropogenic methane emissions and is projected to increase in the future with the increased demand for livestock products. Here, we compare livestock ...methane emissions and emission intensities, defined by the amount of methane emitted per unit of animal proteins, estimated by different methodologies, and identify mitigation potentials in different regions of the world based on possible future projections. We show that emission intensity decreased for most livestock categories globally during 2000–2018, due to an increasing protein‐production efficiency, and the IPCC Tier 2 method should be used for capturing the temporal changes in the emission intensities. We further show that efforts on the demand‐side to promote balanced, healthy, and environmentally sustainable diets in most countries will not be sufficient to mitigate livestock methane emissions without parallel efforts to improve production efficiency. The latter efforts have much greater mitigating effects than demand‐side efforts, and hence should be prioritized in a few developing countries that contribute most of the mitigation potential.
Plain Language Summary
Livestock production represents a third of the global anthropogenic methane emissions nowadays, and the emissions are expected to keep increasing in the future. Using three sets of methodologies and emission factors from two versions of the IPCC guidelines (the 2006 and the 2019 refinement), we re‐assess global livestock methane emissions over the past two decades and project the emissions till 2050. We find a decreasing trend of methane emission intensity per kg of protein produced during the past two decades. We show that promoting balanced, healthy, and environmentally sustainable diets in most countries can mitigate future livestock methane emissions, but a larger mitigation potential is projected if the past trend in decreasing emission intensity (i.e., increasing production efficiency) can be continued. We further identify major countries that have the largest mitigation potential through increasing production efficiency.
Key Points
Emission intensity decreased for most livestock categories globally during 2000–2018, with an increasing protein‐production efficiency
The continuation of the past decreases in emission intensity provides a large potential to mitigate livestock emissions
Improving production efficiency has a much greater mitigating effect than demand‐side efforts, and should be prioritized in a few countries
Changes in agricultural land use have important implications for environmental services. Previous studies of agricultural land-use futures have been published indicating large uncertainty due to ...different model assumptions and methodologies. In this article we present a first comprehensive comparison of global agro-economic models that have harmonized drivers of population, GDP, and biophysical yields. The comparison allows us to ask two research questions: (1) How much cropland will be used under different socioeconomic and climate change scenarios? (2) How can differences in model results be explained? The comparison includes four partial and six general equilibrium models that differ in how they model land supply and amount of potentially available land.We analyze results of two different socioeconomic scenarios and three climate scenarios (one with constant climate). Most models (7 out of 10) project an increase of cropland of 10–25% by 2050 compared to 2005 (under constant climate), but one model projects a decrease. Pasture land expands in some models, which increase the treat on natural vegetation further. Across all models most of the cropland expansion takes place in South America and sub-Saharan Africa. In general, the strongest differences in model results are related to differences in the costs of land expansion, the endogenous productivity responses, and the assumptions about potential cropland.
As ongoing research efforts contribute to elucidating the consequences of climate change as well as adaptation and mitigation options, aligning the current research knowledge with stakeholder ...opinions and perceptions remains critical for adopting effective climate change policies. This paper utilizes an interactive survey to (1) address the aforementioned gap in studies involving three groups of stakeholders and opinion makers and (2) perform a comparative primary study of the climate change assumptions, risk perceptions, policy preferences, observations, and knowledge of Czech farmers, governmental policy-makers and researchers. This study shows that the stakeholder groups agree that the climate is clearly changing, attribute this change mostly to man-made causes and expect the negative effects to either prevail or be unevenly geographically distributed. The large majority of all three groups consider unmitigated climate change a major threat even by 2050 and agree that preparing in advance is the best sectoral strategy. Importantly, while investment in adaptation measures is considered the most efficient tool for accelerating the implementation of adaptation measures, the CAP and EU rules (as valid in 2016) are believed to hinder such measures. The results of this study have ramifications for the wider region of Central Europe.
Previous studies have projected a significant role for bioenergy in decarbonizing the global economy and helping realize international climate goals such as limiting global average warming to 2 ˚C or ...1.5 ˚C. However, with substantial variability in bioenergy results and significant concerns about potential environmental and social implications, greater transparency and dedicated assessment of the underlying modeling and results and more detailed understanding of the potential role of bioenergy are needed. Stanford University’s Energy Modeling Forum (EMF) initiated a 33rd study (EMF-33) to explore the viability of large-scale bioenergy as part of a comprehensive climate management strategy. This special issue presents the papers of the EMF-33 study—a multi-year inter-model comparison project designed to understand and assess global, long-run biomass supply and bioenergy deployment potentials and related uncertainties. Using a novel scenario design with independent biomass supply and bioenergy demand protocols, EMF-33 separately elucidates and explores the modeling of biomass feedstock supplies and bioenergy technologies and their deployment—revealing, comparing, and assessing the modeling that is suggesting that bioenergy could be a key climate containment strategy. This introduction provides an overview of the EMF-33 study design and the overview, thematic, and individual modeling team papers and types of insights that make up this special issue. By providing enhanced transparency and new detailed insights, we hope to inform policy dialogue about the potential role of bioenergy and facilitate new research.
The Agricultural Model Intercomparison and Improvement Project (AgMIP) has developed novel methods for Coordinated Global and Regional Assessments (CGRA) of agriculture and food security in a ...changing world. The present study aims to perform a proof of concept of the CGRA to demonstrate advantages and challenges of the proposed framework. This effort responds to the request by the UN Framework Convention on Climate Change (UNFCCC) for the implications of limiting global temperature increases to 1.5°C and 2.0°C above pre-industrial conditions. The protocols for the 1.5°C/2.0°C assessment establish explicit and testable linkages across disciplines and scales, connecting outputs and inputs from the Shared Socio-economic Pathways (SSPs), Representative Agricultural Pathways (RAPs), Half a degree Additional warming, Prognosis and Projected Impacts (HAPPI) and Coupled Model Intercomparison Project Phase 5 (CMIP5) ensemble scenarios, global gridded crop models, global agricultural economics models, site-based crop models and within-country regional economics models. The CGRA consistently links disciplines, models and scales in order to track the complex chain of climate impacts and identify key vulnerabilities, feedbacks and uncertainties in managing future risk. CGRA proof-of-concept results show that, at the global scale, there are mixed areas of positive and negative simulated wheat and maize yield changes, with declines in some bread basket regions, at both 1.5°C and 2.0°C. Declines are especially evident in simulations that do not take into account direct CO2 effects on crops. These projected global yield changes mostly resulted in increases in prices and areas of wheat and maize in two global economics models. Regional simulations for 1.5°C and 2.0°C using site-based crop models had mixed results depending on the region and the crop. In conjunction with price changes from the global economics models, productivity declines in the Punjab, Pakistan, resulted in an increase in vulnerable households and the poverty rate. This article is part of the theme issue ‘The Paris Agreement: understanding the physical and social challenges for a warming world of 1.5°C above pre-industrial levels’.
Background
In preparation for the 2015 international climate negotiations in Paris, Parties submitted Intended Nationally Determined Contributions (INDCs) to the United Nations Framework Convention ...on Climate Change (UNFCCC) expressing each countries’ respective post-2020 climate actions. In this paper we assess individual Parties’ expected reduction of emissions/removals from land use, land use change, and forest (LULUCF) sector for reaching their INDC target, and the aggregate global effect on the INDCs on the future development of emission and removals from the LULUCF sector. This has been done through analysis Parties’ official information concerning the role of LULUCF mitigation efforts for reaching INDC targets as presented in National Communications, Biennial Update Reports, and Additional file
1
.
Results
On the aggregate global level, the Parties themselves perceive that net LULUCF emissions will increase over time. Overall, the net LULUCF emissions are estimated to increase by 0.6 Gt CO
2
e year
−1
(range: 0.1–1.1) in 2020 and 1.3 Gt CO
2
e year
−1
(range: 0.7–2.1) in 2030, both compared to 2010 levels. On the other hand, the full implementation of the INDCs is estimated to lead to a reduction of net LULUCF emissions in 2030 compared to 2010 levels. It is estimated that if all conditional and unconditional INDCs are implemented, net LULUCF emissions would decrease by 0.5 Gt CO
2
e year
−1
(range: 0.2–0.8) by 2020 and 0.9 Gt CO
2
e year
−1
(range: 0.5–1.3) by 2030, both compared to 2010 levels. The largest absolute reductions of net LULUCF emissions (compared to 2010 levels) are expected from Indonesia and Brazil, followed by China and Ethiopia.
Conclusions
The results highlights that countries are expecting a significant contribution from the LULUCF sector to meet their INDC mitigation targets. At the global level, the LULUCF sector is expected to contribute to as much as 20% of the full mitigation potential of all the conditional and unconditional INDC targets. However, large uncertainties still surround how Parties estimate, project and account for emissions and removals from the LULUCF sector. While INDCs represent a new source of land-use information, further information and updates of the INDCs will be required to reduce uncertainty of the LULUCF projections.
The role of improving the enforcement of Brazil's Forest Code in reducing deforestation in the Amazon has been highlighted in many studies. However, in a context of strong political pressure for ...loosening environmental protections, the future impacts of a nationwide implementation of the Forest Code on both environment and agriculture remain poorly understood. Here, we present a spatially explicit assessment of Brazil's 2012 Forest Code through the year 2050; specifically, we use a partial equilibrium economic model that provides a globally consistent national modeling framework with detailed representation of the agricultural sector and spatially explicit land-use change. We test for the combined or isolated impacts of the different measures of the Forest Code, including deforestation control and obligatory forest restoration with or without environmental reserve quotas. Our results show that, if rigorously enforced, the Forest Code could prevent a net loss of 53.4 million hectares (Mha) of forest and native vegetation by 2050, 43.1 Mha (81%) of which are in the Amazon alone. The control of illegal deforestation promotes the largest environmental benefits, but the obligatory restoration of illegally deforested areas creates 12.9 Mha of new forested area. Environmental reserve quotas further protect 5.8 Mha of undisturbed natural vegetation. Compared to a scenario without the Forest Code, by 2050, cropland area is only reduced by 4% and the cattle herd by 8%. Our results show that compliance with the Forest Code requires an increase in cattle productivity of 56% over four decades, with a combination of a higher use of supplements and an adoption of semi-intensive pasture management. We estimate that the enforcement of the Forest Code could contribute up to 1.03 PgCO2e to the ambitious GHG emissions reduction target set by Brazil for 2030.
Agriculture is unique among economic sectors in the nature of impacts from climate change. The production activity that transforms inputs into agricultural outputs involves direct use of weather ...inputs (temperature, solar radiation available to the plant, and precipitation). Previous studies of the impacts of climate change on agriculture have reported substantial differences in outcomes such as prices, production, and trade arising from differences in model inputs and model specification. This article presents climate change results and underlying determinants from a model comparison exercise with 10 of the leading global economic models that include significant representation of agriculture. By harmonizing key drivers that include climate change effects, differences in model outcomes were reduced. The particular choice of climate change drivers for this comparison activity results in large and negative productivity effects. All models respond with higher prices. Producer behavior differs by model with some emphasizing area response and others yield response. Demand response is least important. The differences reflect both differences in model specification and perspectives on the future. The results from this study highlight the need to more fully compare the deep model parameters, to generate a call for a combination of econometric and validation studies to narrow the degree of uncertainty and variability in these parameters and to move to Monte Carlo type simulations to better map the contours of economic uncertainty.
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