A Method for Estimating the Cost of CO2 Mitigation through Afforestation

The Kyoto Protocol allows Annex I countries to use afforestation (theconversion of non-forest landto forest) to meet emissions reduction targets. We present a new method forestimating the cost of CO₂mitigation through afforestation based on econometric models of land use. Landuse models are developed from dataon observed land allocation decisions and quantify the relationship betweenthe share of land in forest and the netreturns to forestry, among other land use determinants. The econometricapproach measures the actual responsesby landowners to observed changes in net returns, in contrast to earlierstudies in which landowner responses aredictated by the researcher. Models are estimated for Maine, South Carolina,and Wisconsin. The estimated modelsare used to simulate subsidies for afforestation, which imply increases inforest area and net reductions inatmospheric CO₂ concentrations. Average cost measures – totalsubsidies divided by total carbon sequestered –are derived for afforestation programs with and without timber harvesting. Theuse of econometric land use modelsin integrated assessments of climate change is explored. We model the effectson land use patterns and the costsof CO₂ mitigation of changes in the net returns to agricultureinduced by climate change.     

CO2 Mitigation by Agriculture: An Overview

Agriculture currently contributes significantly to the increase of CO2 in the atmosphere, primarily through the conversion of native ecosystems to agricultural uses in the tropics. Yet there are major opportunities for mitigation of CO2 and other greenhouse gas emissions through changes in the use and management of agricultural lands. Agricultural mitigation options can be broadly divided into two categories: (I) strategies to maintain and increase stocks of organic C in soils (and biomass), and (ii) reductions in fossil C consumption, including reduced emissions by the agricultural sector itself and through agricultural production of biofuels to substitute for fossil fuels.Reducing the conversion of new land to agriculture in the tropics could substantially reduce CO2 emissions, but this option faces several difficult issues including population increase, land tenure and other socio-political factors in developing countries. The most significant opportunities for reducing tropical land conversions are in the humid tropics and in tropical wetlands. An important linkage is to improve the productivity and sustainability of existing agricultural lands in these regions.Globally, we estimate potential agricultural CO2 mitigation through soil C sequestration to be 0.4-0.9 Pg C y-1, through better management of existing agricultural soils, restoration of degraded lands, permanent "set-asides" of surplus agricultural lands in temperate developed countries and restoration of 10-20% of former wetlands now being used for agriculture. However, soils have a finite capacity to store additional C and therefore any increases in C stocks following changes in management would be largely realized within 50-100 years.Mitigation potential through reducing direct agricultural emissions is modest, 0.01-0.05 Pg C y-1. However, the potential to offset fossil C consumption through the use of biofuels produced by agriculture is substantial, 0.5-1.6 Pg C y-1, mainly through the production of dedicated biofuel crops with a smaller contribution (0.2-0.3 Pg C y-1) from crop residues.Many agricultural mitigation options represent "win-win" situations, in that there are important side benefits, in addition to CO2 mitigation, that could be achieved, e.g. improved soil fertility with higher soil organic matter, protection of lands poorly suited for permanent agriculture, cost saving for fossil fuel inputs and diversification of agricultural production (e.g. biofuels). However, the needs for global food production and farmer/societal acceptability suggest that mitigation technologies should conform to: (I) the enhancement of agricultural production levels in parts of the world where food production and population demand are in delicate balance and (ii) the accrual of additional benefits to the farmer (e.g., reduced labor, reduced or more efficient use of inputs) and society at large.     

Estimating a Lagrangian Length Scale Using Measurements of CO2 in a Plant Canopy

Analytical Lagrangian equations capable of predicting concentration profiles from known source distributions offer the opportunity to calculate source/sink distributions through inverted forms of these equations. Inverse analytical Lagrangian equations provide a practical means of estimating source profiles using concentration and turbulence measurements. Uncertainty concerning estimates of the essentially immeasurable Lagrangian length scale ( ${\mathcal{L}}$ ), a key input, impedes the operational practicality of this method. The present study evaluates ${\mathcal{L}}$ within a corn canopy by using field measurements to constrain an analytical Lagrangian equation. Measurements of net CO₂ flux, soil-to-atmosphere CO₂ flux, and in-canopy profiles of CO₂ concentration provided the information required to solve for ${\mathcal{L}}$ in a global optimization algorithm for 30-min time intervals. For days when the canopy was a strong CO₂ sink, the optimization frequently located ${\mathcal{L}}$ profiles that follow a convex shape. A constrained optimization then fit the profile shape to a smooth sigmoidal equation. Inputting the optimized ${\mathcal{L}}$ profiles in the forward and inverse Lagrangian equations leads to strong correlations between measured and calculated concentrations and fluxes. Coefficients of the sigmoidal equation were specific to each 30-min period and did not scale with any measured variable. Plausible looking ${\mathcal{L}}$ profiles were associated with negative bulk Richardson number values. Once the canopy senesced, a simple eddy diffusivity profile sufficed to relate concentrations and sources in the analytical Lagrangian equations.     

我国部门减排行动可测量、可报告、可核实现状分析

通过一系列的部门政策和措施的论述,证明了我国各部门减缓政策和措施已经通过国内系统得到了报告和核证,显示了“可测量,可报告和可核实”（MRV）的实际部门应用,同时指出部门方案具有不同的度量、报告制度和核证程序,以及不同的减排效果。这些部门减缓行动的MRV特点为国际MRV的构建提供了案例基础。     

Potential impact of vegetation feedback on European heat waves in a 2 x CO 2 climate

Inclusion of the effects of vegetation feedback in a global climate change simulation suggests that the vegetation–climate feedback works to alleviate partially the summer surface warming and the associated heat waves over Europe induced by the increase in atmospheric CO₂ concentrations. The projected warming of 4°C over most of Europe with static vegetation has been reduced by 1°C as the dynamic vegetation feedback effects are included.. Examination of the simulated surface energy fluxes suggests that additional greening in the presence of vegetation feedback effects enhances evapotranspiration and precipitation, thereby limiting the warming, particularly in the daily maximum temperature. The greening also tends to reduce the frequency and duration of heat waves. Results in this study strongly suggest that the inclusion of vegetation feedback within climate models is a crucial factor for improving the projection of warm season temperatures and heat waves over Europe.     

Potential CO2-induced climate effects on North American wheat-producing regions

The environmental requirements for growth of winter, spring, and fallsown spring wheats in North America are specified and compared to temperature results from the control run of the Goddard Institute for Space Studies general circulation model (GISS GCM) and observed precipitation in order to generate a simulated map of current wheat production regions. The simulation agrees substantially with the actual map of wheat-growing regions in North America. Results from a doubled CO₂ run of the climate model are then used to generate wheat regions under the new climatic conditions. In the simulation, areas of production increase in North America, particularly in Canada, due to increased growing degree units (GDU). Although wheat classifications may change, major wheat regions in the United States remain the same under simulated doubled CO₂ conditions. The wheat-growing region of Mexico is identified as vulnerable due to high temperature stress. Higher mean temperatures during wheat growth, particularly during the reproductive stages, may increase the need for earlier-maturing, more heat-tolerant cultivars throughout North, America. The soil moisture diagnostic of the climate model is used to analyze potential water availability in the major wheat region of the Southern Great Plains.     

湖北省潜在蒸散估算模型对比

利用湖北省74个气象站1961~2011年逐日气象资料,通过与FAO56-Penman-Monteith(FAO-PM)模型潜在蒸散估算结果对比,从月、季、年际变化及不同干湿状况条件比较了PriestleyTaylor、Hargreaves及Thornthwaite 3种简化的经验模型在湖北省的适用性。结果表明:3种简化模型与FAO-PM模型计算的逐月潜在蒸散均存在一定偏差,Thornthwaite模型偏差最大且冬夏季偏差反位相,Priestley-Taylor模型偏差最小,Hargreaves模型各月间的偏差最为稳定。3种简化模型与FAOPM模型估算结果具有良好的线性关系,且在各区域间相对稳定,但不同季节和干湿状况下各有差异,其中Hargreaves模型各季节间和不同干湿状况下与FAO-PM模型的关系均最为稳定。在年际变化上,Priestley-Taylor和Hargreaves模型与FAO-PM模型计算结果年际波动基本一致,Thornthwaite模型与FAO-PM模型计算结果尽管在量值上较为接近,但年际波动偏小;Priestley-Taylor和FAOPM模型年潜在蒸散趋势变化基本一致,Hargreaves模型年潜在蒸散趋势变化微弱,而Thornthwaite模型年潜在蒸散趋势变化与FAO-PM模型相反。建议在湖北省气象资料匮乏或不便应用的情况下,作物模拟模型及气候变化等研究中采用Priestley-Taylor估算模型,日常干旱监测及水资源规划中采用Hargreaves模型,干湿气候区划等工作中可采用Thornthwaite模型。同时,使用中应基于FAO-PM模型对经验模型进行适当订正,模型订正应建立在季节或月尺度。     

The Potential Response of Terrestrial Carbon Storage to Changes in Climate and Atmospheric CO2

We use a georeferenced model of ecosystem carbon dynamics to explore the sensitivity of global terrestrial carbon storage to changes in atmospheric CO₂ and climate. We model changes in ecosystem carbon density, but we do not model shifts in vegetation type. A model of annual NPP is coupled with a model of carbon allocation in vegetation and a model of decomposition and soil carbon dynamics. NPP is a function of climate and atmospheric CO₂ concentration. The CO₂ response is derived from a biochemical model of photosynthesis. With no change in climate, a doubling of atmospheric CO₂ from 280 ppm to 560 ppm enhances equilibrium global NPP by 16.9%; equilibrium global terrestrial ecosystem carbon (TEC) increases by 14.9%. Simulations with no change in atmospheric CO₂ concentration but changes in climate from five atmospheric general circulation models yield increases in global NPP of 10.0–14.8%. The changes in NPP are very nearly balanced by changes in decomposition, and the resulting changes in TEC range from an increase of 1.1% to a decrease of 1.1%. These results are similar to those from analyses using bioclimatic biome models that simulate shifts in ecosystem distribution but do not model changes in carbon density within vegetation types. With changes in both climate and a doubling of atmospheric CO₂, our model generates increases in NPP of 30.2–36.5%. The increases in NPP and litter inputs to the soil more than compensate for any climate stimulation of decomposition and lead to increases in global TEC of 15.4–18.2%.     

Sensitivity of the Carbon Storage of Potential Vegetation to Historical Climate Variability and CO2 in Continental China

The interest in the national levels of the terrestrial carbon sink and its spatial and temporal variability with the climate and CO2 concentrations has been increasing. How the climate and the increasing atmospheric CO2 concentrations in the last century affect the carbon storage in continental China was investigated in this study by using the Modified Sheffield Dynamic Global Vegetation Model (M-SDGVM). The estimates of the M-SDGVM indicated that during the past 100 years a combination of increasing CO2 with historical temperature and precipitation variability in continental China have caused the total vegetation carbon storage to increase by 2.04 Pg C, with 2.07 Pg C gained in the vegetation biomass but 0.03 Pg C lost from the organic soil carbon matter. The increasing CO2 concentration in the 20th century is primarily responsible for the increase of the total potential vegetation carbon. These factorial experiments show that temperature variability alone decreases the total carbon storage by 1.36 Pg C and precipitation variability alone causes a loss of 1.99 Pg C. The effect of the increasing CO2 concentration alone increased the total carbon storage in the potential vegetation of China by 3.22 Pg C over the past 100 years. With the changing of the climate, the CO2 fertilization on China's ecosystems is the result of the enhanced net biome production (NBP), which is caused by a greater stimulation of the gross primary production (GPP) than the total soil-vegetation respiration. Our study also shows notable interannual and decadal variations in the net carbon exchange between the atmosphere and terrestrial ecosystems in China due to the historical climate variability.     

Estimating the consequences of CO2-induced climatic change on north american grain agriculture using general circulation model information

A procedure to estimate the potential climatic effects of a doubling of atmospheric carbon dioxide concentration on agricultural production is illustrated. The method combines use of atmospheric general circulation models (GCMs) and process-oriented crop models. Wheat and corn (maize) yields in three important North American grain cropping regions are treated. Combined use of these two types of models can provide insights into the impacts of climate changes at the level of plant physiology, and potential means by which agricultural production practices may adapt to these changes.Specific agronomic predictions are found to depend critically on the details of the projected climate change. Uncertainties in the specification of the doubled-CO₂ climate by the GCM, particularly with respect to precipitation, dictate that agricultural predictions derived from them at this time must be regarded only as illustrative of the impact assessment method.     

Carbon Dioxide Fluxes and Potential Mitigation in Agriculture and Forestry of Tropical and Subtropical China

Tropical and subtropical areas comprise about 23% of the total land area (960 Mha) of China. Of this, about 40% is in forests, 20% is in cropland and another 20% is wasteland. Preliminary estimates of overall sources and sinks of carbon dioxide indicate that current agricultural activities probably constitute a net sink. We estimate that improved agricultural management and wasteland reclamation have the potential to sequester an additional 1.9 Tg CO2-C y-1 or more, largely through increasing productivity and C inputs to soils and conversion of wasteland to agricultural production. We estimate that current forestry activities in the region could sequester about 7 Tg CO2-C y-1. There is also a large potential for increased C sequestration and fossil fuel offsets by conversion of wasteland to fuel wood plantations, on the order of 30-70 Tg C y-1. A number of practices for increasing mitigation of CO2 emissions in the forestry and agricultural sectors are presented.     

"两岸温室气体减排政策及其经济问题分析"学术研讨会在京召开

2006年8月19日,由中国社会科学院城市发展与环境研究中心主办的“两岸温室气体减排政策及其经济问题分析”学术研讨会在北京召开。来自台湾地区的清华大学、台湾大学、台湾中原大学、台北大学、台湾中央大学、台湾综合研究院、台湾经济研究院、台湾绿色生产力基金的专家和来自大陆的中国社会科学院、中国科学院、清华     

建筑风荷载风压计算中的若干问题

根据最新“建筑荷载规范”修订本讨论了应用气象台站的风观测资料来计算建筑风荷载中的几个需要注意的问题，其中包括风速资料的坡度订正、高度订正、时次订正以及应用极值Ⅰ型分布函数来估算R年重现期的最大风速等问题。     

Siberian CO2 efflux in winter as a CO2 source and cause of seasonality in atmospheric CO2

Over three years, we found a consistent CO₂ efflux from forest tundra of the Russian North throughout the year, including a large (89 g C m^–2 yr^–1) efflux during winter. Our results provide one explanation for the observations that the highest atmospheric CO₂ concentration and greatest seasonal amplitude occur at high latitudes rather than over the mid-latitudes, where fossil fuel sources are large, and where high summer productivity offset by winter respiration should give large seasonal oscillations in atmospheric CO₂. Winter respiration probably contributed substantially to the boreal winter CO₂ efflux. Respiration is an exothermic process that produces enough heat to warm soils and promote further decomposition. We suggest that, as a result of this positive feedback, small changes in surface heat flux, associated with human activities in the North or with regional or global warming, could release large quantities of organic carbon that are presently stored in permafrost.     

中国新能源发电生命周期温室气体减排潜力比较和分析

从生命周期的角度分析,各类新能源发电技术的开发、建设、运行过程,也会带来一定的温室气体排放,这引发了人们对于新能源发电技术“低碳”属性的担忧。遵循生命周期评价方法,在对国内外大量资料文献进行收集整理的基础上,对中国传统火电和主要新能源发电技术的温室气体排放系数进行了对比分析;并根据国家发展规划目标,对新能源发电替代火电的温室气体减排潜力进行了估算。分析结果表明,即使考虑生命周期内的排放,新能源发电技术的温室气体排放系数仍远远低于火电,新能源发电技术替代火电的温室气体减排潜力巨大。     

Problems in Estimating Impacts of Future Climate Change on Midwestern Corn Yields

Recent studies of trends in Midwestern precipitation show marked increases over the last 50 years of the 20th Century, and most climate models project that future rainfall in the Corn Belt will be increased further. During five years, 1988–1991 and 1994, field tests were conducted on agricultural test plots in central Illinois, an area typical of the Corn Belt, to discern how corn yields reacted to varying levels of added rainfall (+10%, +25%, and +40%) during the growing season. The best treatment over the five years was a 40% rain increase, with an average yield increase of 9%. Its yield increase was up to 34% in a hot-dry year, but below that of natural rainfall in a wet year as were the yields of the other lesser increases. The average yield changes from the three treatments were not statistically significantly different. Major interannual yield differences were found in the yields for each rain treatment, reflecting how rain timing and temperatures also have major effects on yields. A 40% summer rain increase has little influence if natural rains do not occur in the high stress period of mid summer. The plots results show that only small average increases in corn yields occur from growing season rain additions in the 10% to 40% range, except in dry years. Weather-crop yield regression models incorporating the same rain increases predict greater yield increases than found in these field tests. This suggests that future yields projected for a wetter climate using yield-weather models may be over-estimated. The plot sample size is small but conditions sampled in the five years represented 43% of all past 97 growing seasons in central Illinois and extremely good and bad weather years, which resulted in large between-year yield differences. Hence, the experimental results provide useful information about how increased rainfall may affect future corn yields, especially since the sample included three of the five types of dry growing seasons found in the area's climate since 1900.     

Carbon Reduction Policies: A Regional Comparison of Their Contributions to CO2 Abatement in Six Carbon Trading Pilot Schemes in China

The contributions of carbon reduction policies were evaluated and compared for six carbon trading pilot schemes in China, in four municipalities(Beijing, Shanghai, Tianjin, and Chongqing) and two provinces(Guangdong and Hubei). The carbon emissions accounting method of the Intergovernmental Panel on Climate Change was used to calculate the actual CO2 and the support vector machine model was used to predict CO2. Chinese carbon reduction policies abated CO2 in the six carbon trading pilot schemes after the comprehensive policies came into force. However, the contribution of policies to CO2 abatement varied among regions, and the effect of carbon reduction policy on municipality pilot schemes was greater than on provincial pilot schemes. The largest contribution of carbon reduction policy to CO2 abatement was 28.3%, for the pilot carbon trading scheme in Beijing, and the smallest contribution was 3.7%, for that in Hubei. It is crucial to consider “carbon leakage” and a carbon trading linking program in order to evaluate the effects of carbon reduction policies.     

Potential emissions of CO2 and methane from proved reserves of fossil fuels: An alternative analysis

Scientists have argued that no more than 275 GtC (IPCC, 2013) of the world’s reserves of fossil fuels of 746 GtC can be produced in this century if the world is to restrict anthropogenic climate change to ≤2 °C. This has raised concerns about the risk of these reserves becoming “stranded assets” and creating a dangerous “carbon bubble” with serious impacts on global financial markets, leading in turn to discussions of appropriate investor and consumer actions. However, previous studies have not always clearly distinguished between reserves and resources, nor differentiated reserves held by investor-owned and state-owned companies with the capital, infrastructure, and capacity to develop them in the short term from those held by nation-states that may or may not have such capacity. This paper analyzes the potential emissions of CO₂ and methane from the proved reserves as reported by the world's largest producers of oil, natural gas, and coal. We focus on the seventy companies and eight government-run industries that produced 63% of the world’s fossil fuels from 1750 to 2010 (Heede, 2014), and have the technological and financial capacity to develop these reserves. While any reserve analysis is subject to uncertainty, we demonstrate that production of these reported reserves will result in emissions of 440 GtC of carbon dioxide, or 160% of the remaining 275 GtC carbon budget. Of the 440 GtC total, the 42 investor-owned oil, gas, and coal companies hold reserves with potential emissions of 44 GtC (16% of the remaining carbon budget, hereafter RCB), whereas the 28 state-owned entities possess reserves of 210 GtC (76% of the RCB). This analysis suggests that what may be needed to prevent dangerous anthropogenic interference (DAI) with the climate system differs when one considers the state-owned entities vs. the investor-owned entities. For the former, there is a profound risk involved simply in the prospect of their extracting their proved reserves. For the latter, the risk arises not so much from their relatively small proved reserves, but from their on-going exploration and development of new fossil fuel resources. For preventing DAI overall, effective action must include the state-owned companies, the investor-owned companies, and governments. However, given that the majority of the world's reserves are coal resources owned by governments with little capacity to extract them in the near term, we suggest that the more immediate urgency lies with the private sector, and that investor and consumer pressure should focus on phasing out these companies’ on-going exploration programs.     

Carbon Capture and Storage From Fossil Fuels and Biomass – Costs and Potential Role in Stabilizing the Atmosphere

The capture and storage of CO₂ from combustion of fossil fuels is gaining attraction as a means to deal with climate change. CO₂ emissions from biomass conversion processes can also be captured. If that is done, biomass energy with CO₂ capture and storage (BECS) would become a technology that removes CO₂ from the atmosphere and at the same time deliver CO₂-neutral energy carriers (heat, electricity or hydrogen) to society. Here we present estimates of the costs and conversion efficiency of electricity, hydrogen and heat generation from fossil fuels and biomass with CO₂ capture and storage. We then insert these technology characteristics into a global energy and transportation model (GET 5.0), and calculate costs of stabilizing atmospheric CO₂ concentration at 350 and 450 ppm. We find that carbon capture and storage technologies applied to fossil fuels have the potential to reduce the cost of meeting the 350 ppm stabilisation targets by 50% compared to a case where these technologies are not available and by 80% when BECS is allowed. For the 450 ppm scenario, the reduction in costs is 40 and 42%, respectively. Thus, the difference in costs between cases where BECS technologies are allowed and where they are not is marginal for the 450 ppm stabilization target. It is for very low stabilization targets that negative emissions become warranted, and this makes BECS more valuable than in cases with higher stabilization targets. Systematic and stochastic sensitivity analysis is performed. Finally, BECS opens up the possibility to remove CO₂ from the atmosphere. But this option should not be seen as an argument in favour of doing nothing about the climate problem now and then switching on this technology if climate change turns out to be a significant problem. It is not likely that BECS can be initiated sufficiently rapidly at a sufficient scale to follow this path to avoiding abrupt and serious climate changes if that would happen.