IPCC Climate Change Data: GFDL99 B2a Model: 2020 Radiation

The experiments with the GFDL model used here were performed using the coupled ocean-atmosphere model described in Manabe et al. (1991) and Stouffer et al., (1994) and references therein. The model has interactive clouds and seasonally varying solar insolation. The atmospheric component has nine finite difference (sigma) levels in the vertical. This version of the model was run at a rhomboidal resolution of 15 waves (R15) yielding an equivalent resolution of about 4.5 degrees latitude by 7.5 degrees longitude. The model has global geography consistent with its computational resolution and seasonal (but not diurnal) variation of insolation. The ocean model is based on that of Byan and Lewis (1979) with a spacing between gridpoints of 4.5 degrees latitude and 3.7 degrees longitude. It has 12 unevenly spaced levels in the vertical dimension. To reduce model drift, the fluxes of heat and water are adjusted by amounts which vary seasonally and geographically, but do not change from one year to another. The model also includes a dynamic sea-ice model (Bryan, 1969) which allows the system additional degrees of freedom. The 1000-year unforced simulation used here is described in Manabe and Stouffer (1996). The drift in global-mean temperature during this unforced simulation is very small at about -0.023 degrees C per century. The two GFDL-R15 climate change experiments used here use the IS92a scenario of estimated past and future greenhouse gas (GGa1) and combined greenhouse gas and sulphate aerosol (GSa1) forcing for the period 1765-2065 (Haywood et al., 1997). For the GGa1 experiment only the 100-year segment from 1958-2057 are available through the IPCC DDC. The radiative effects of all greenhouse gases is represented in terms of an equivalent CO2 concentration, and the direct radiative sulphate aerosol forcing is parameterised in terms of specified spatially dependent surface albedo changes (following Mitchell et al., 1995). Results from these climate change experiments are discussed in Haywood et al. (1997). The model's climate sensitivity is about 3.7 degrees C. Like B1, the B2 world is one of increased concern for environmental and social sustainability, but the character of this world differs substantially. Education and welfare programs are widely pursued leading to reductions in mortality and, to a lesser extent, fertility. The population reaches about 10 billion people by 2100, consistent with both the United Nations and IIASA median projections. Income per capita grows at an intermediary rate to reach about US$12,000 by 2050. By 2100 the global economy might expand to reach some US$250 trillion. International income differences decrease, although not as rapidly as in scenarios of higher global convergence (A1, B1). Local inequity is reduced considerably through the development of stronger community support networks. Generally high educational levels promote both development and environmental protection. Indeed, environmental protection is one of the few remaining truly international priorities. However, strategies to address global environmental challenges are less successful than in B1, as governments have difficulty designing and implementing agreements that combine environmental protection with mutual economic benefits. The B2 storyline presents a particularly favorable climate for community initiative and social innovation, especially in view of high educational levels. Technological frontiers are pushed less than in A1 and B1 and innovations are also regionally more heterogeneous. Globally, investment in R and D continues its current declining trend, and mechanisms for international diffusion of technology and know-how remain weaker than in scenarios A1 and B1 (but higher than in scenario A2). Some regions with rapid economic development and limited natural resources place particular emphasis on technology development and bilateral co-operation. Technical change is therefore uneven. The energy intensity of GDP declines at about one percent per year, in line with the average historical experience of the last two centuries. Land-use management becomes better integrated at the local level in the B2 world. Urban and transport infrastructure is a particular focus of community innovation, contributing to a low level of car dependence and less urban sprawl. An emphasis on food self-reliance contributes to a shift in dietary patterns towards local products, with reduced meat consumption in countries with high population densities. Energy systems differ from region to region, depending on the availability of natural resources. The need to use energy and other resources more efficiently spurs the development of less carbon-intensive technology in some regions. Environment policy cooperation at the regional level leads to success in the management of some transboundary environmental problems, such as acidification due to SO2, especially to sustain regional self-reliance in agricultural production. Regional cooperation also results in lower emissions of NOx and VOCs, reducing the incidence of elevated tropospheric ozone levels. Although globally the energy system remains predominantly hydrocarbon-based to 2100, there is a gradual transition away from the current share of fossil resources in world energy supply, with a corresponding reduction in carbon intensity.本研究采用的GFDL模型（Geophysical Fluid Dynamics Laboratory Model）实验，基于Manabe等人（1991）与Stouffer等人（1994）及其引用文献中描述的耦合海气模式（coupled ocean-atmosphere model）开展。该模式集成了交互式云参数化方案与随季节变化的太阳辐射照度（solar insolation）。其大气分量在垂直方向上设置了9层有限差分（σ）垂直层级（finite difference (sigma) levels）。此版本模型采用菱形截断15波（R15）分辨率（rhomboidal resolution of 15 waves (R15)），等效分辨率约为纬度4.5度、经度7.5度。模式的全球地理分布与其计算分辨率匹配，且包含季节尺度（而非昼夜尺度）的辐射照度变化。海洋模式基于Byan与Lewis（1979）的方案，网格点间距为纬度4.5度、经度3.7度，垂直方向设有12层非均匀分布的层级。为减缓模式漂移，研究人员对热通量与水通量进行了随季节和区域变化的调整，但该调整不随年份改变。模式还集成了Bryan（1969）提出的动态海冰模式（sea-ice model），为系统增添了额外的自由度。本研究使用的1000年无强迫模拟实验，详见Manabe与Stouffer（1996）。该无强迫模拟中，全球平均温度的漂移极小，仅约为每百年-0.023摄氏度。 本研究使用的两项GFDL-R15气候变化实验，采用了IS92a情景（scenario），该情景针对1765-2065年时段，估算了过往及未来温室气体（greenhouse gas，GGa1）强迫与温室气体-硫酸盐气溶胶（sulphate aerosol，GSa1）混合强迫的辐射影响（Haywood等人，1997）。其中GGa1实验仅1958-2057年这100年时段的数据可通过政府间气候变化专门委员会数据分发中心（IPCC DDC, Intergovernmental Panel on Climate Change Data Distribution Center）获取。所有温室气体的辐射效应均以等效二氧化碳浓度（equivalent CO2 concentration）表征，直接辐射硫酸盐气溶胶强迫则通过指定的空间分布地表反照率变化（surface albedo changes）进行参数化（遵循Mitchell等人，1995的方法）。上述气候变化实验的结果已在Haywood等人（1997）的研究中讨论。该模式的气候敏感度（climate sensitivity）约为3.7摄氏度。 与B1情景类似，B2情景的世界同样更加关注环境与社会可持续性，但二者的核心特征存在显著差异。B2情景下，各国广泛推行教育与福利项目，推动了死亡率下降，并在一定程度上降低了生育率。到2100年，全球人口将达到约100亿，与联合国及国际应用系统分析研究所（IIASA）的中位数预测结果一致。人均收入以中等速率增长，到2050年将达到约12000美元。到2100年，全球经济总量或将达到约250万亿美元。国家间的收入差距有所缩小，但缩小速度慢于全球收敛性更高的A1、B1情景。通过构建更完善的社区支持网络，本地的不平等程度得到显著缓解。 普遍较高的教育水平同时推动了经济发展与环境保护。事实上，环境保护是当前少数真正具有全球共识的优先议题之一。然而，由于各国政府难以设计并实施兼顾环境保护与共同经济收益的国际协议，应对全球环境挑战的战略成效不及B1情景。B2情景的叙事线为社区倡议与社会创新提供了尤为有利的环境，尤其是在教育水平较高的背景下。技术前沿的推进速度慢于A1与B1情景，且创新在区域层面更具异质性。全球范围内，研发（R&D, Research and Development）投入延续了当前的下降趋势，技术与专业知识的国际扩散机制也弱于A1、B1情景（但强于A2情景）。部分经济快速发展但自然资源有限的地区，尤其重视技术研发与双边合作，因此技术进步存在区域不均衡性。国内生产总值（GDP, Gross Domestic Product）的能源强度以每年约1%的速率下降，与过去两个世纪的历史平均水平相符。 在B2情景的世界中，土地利用管理在地方层面得到了更好的整合。城市与交通基础设施是社区创新的重点领域，这推动了较低的汽车依赖度与更平缓的城市扩张。强调粮食自给自足促使饮食结构向本地产品转变，在人口密度较高的国家，肉类消费量有所下降。不同地区的能源系统存在差异，这取决于自然资源的禀赋情况。更高效地利用能源与其他资源的需求，推动了部分地区开发低碳排放技术。区域层面的环境政策合作，在部分跨界环境问题的治理中取得了成效，例如二氧化硫（SO2）导致的酸化问题，这尤其有助于维持区域农业生产的自给能力。区域合作还降低了氮氧化物（NOx）与挥发性有机化合物（VOCs）的排放量，减少了对流层臭氧（tropospheric ozone）浓度升高的发生概率。尽管到2100年，全球能源系统仍以碳氢化合物燃料（hydrocarbon-based fuel）为主，但世界能源供应中化石资源（fossil resources）的占比正逐步降低，相应的碳排放强度也随之下降。