IPCC Climate Change Data: NIES99 B2a Model: 2020 Minimum Temperature

The model used here is a coupled ocean-atmosphere model that consists of the CCSR/NIES atmospheric GCM, the CCSR ocean GCM, a thermodynamic sea-ice model, and a river routing model (Abe-Ouchi et al., 1996). The spatial resolution is T21 spectral truncation (roughly 5.6 degrees latitude/longitude) and 20 vertical levels for the atmospheric part, and roughly 2.8 degrees horizontal grid and 17 vertical levels for the oceanic part. Flux adjustment for atmosphere-ocean heat and water exchange is applied to prevent a drift of the modelled climate. The atmospheric model adopts a radiation scheme based on the k-distribution, two-stream discrete ordinate method (DOM) (Nakajima and Tanaka, 1986). This scheme can deal with absorption, emission and scattering by gases, clouds and aerosol particles in a consistent manner. In the calculation of sulphate aerosol optical properties, the volumetric mode radius of the sulphate particle in dry environment is assumed to be 0.2 micron. The hygroscopic growth of the sulphate is considered by an empirical fit of d'Almeida et al. (1991). The vertical distribution of the sulphate aerosol is assumed to be constant in the lowest 2 km of the atmosphere. The concentrations of greenhouse gases are represented by equivalent-CO2. Three integrations are made for 200 model years (1890-2090). In the control experiment (CTL), the globally uniform concentration of greenhouse gases is kept constant at 345 ppmv CO2-equivalent and the concentration of sulphate is set to zero. In the experiment GG, the concentration of greenhouse gases is gradually increased, while that of sulphate is set to zero. In the experiments GS, the increase in anthropogenic sulphate as well as that in greenhouse gases is given and the aerosol scattering (the direct effect of aerosol) is explicitly represented in the way described above. The indirect effect of aerosol is not included in any experiment. The scenario of atmospheric concentrations of greenhouse gases and sulphate aerosols is given in accordance with Mitchell and Johns (1997). The increase in greenhouse gases is based on the historical record from 1890 to 1990 and is increased by 1 percent / yr (compound) after 1990. For sulphate aerosols, geographical distributions of sulphate loading for 1986 and 2050, which are estimated by a sulphur cycle model (Langer and Rodhe, 1991), are used as basic patterns. Based on global and annual mean sulphur emission rates, the 1986 pattern is scaled for years before 1990; the 2050 pattern is scaled for years after 2050; and the pattern is interpolated from the two basic ones for intermediate years to give the time series of the distribution. The sulphur emission rate in the future is based on the IPCC IS92a scenario. The sulphate concentration is offset in our run so that it starts from zero at 1890. The seasonal variation of sulphate concentration is ignored. Discussion on the results of the experiments will be found in Emori et al. (1999). Climate sensitivity of the CCSR/NIES model derived by equilibrium runs is estimated to be 3.5 degrees Celsius. Global-Mean Temperature, Precipitation and CO2 Changes (w.r.t. 1961-90) for the CCSR/NIES model. 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.本研究采用的模式为耦合海-气模式（coupled ocean-atmosphere model），由CCSR/NIES大气通用环流模式（General Circulation Model, GCM）、CCSR海洋通用环流模式、热力学海冰模式与河道径流模式组成（Abe-Ouchi等，1996）。大气部分采用T21谱截断（约5.6度经纬度分辨率）与20层垂直结构；海洋部分则配置约2.8度水平网格与17层垂直结构。为抑制模拟气候的漂移，需对海气间的热量与水汽交换施加通量调整（flux adjustment）。 大气模式采用基于k分布、二流离散纵标法（Discrete Ordinate Method, DOM）的辐射方案（Nakajima与Tanaka，1986），该方案可统一处理气体、云和气溶胶粒子的吸收、发射与散射过程。在硫酸盐气溶胶光学特性计算中，假设干环境下硫酸盐粒子的体积模态半径为0.2微米；硫酸盐的吸湿性增长采用d'Almeida等（1991）提出的经验拟合公式表征。研究假设硫酸盐气溶胶的垂直分布在大气低层2公里内保持恒定。温室气体浓度以等效二氧化碳（equivalent-CO2）形式表征。本研究共开展3组积分试验，积分时长为200个模式年（1890-2090）。 三组试验设置如下： 1. 控制试验（CTL）：全球均匀分布的温室气体浓度固定为345ppmv二氧化碳当量，硫酸盐浓度设为0； 2. GG试验：温室气体浓度逐步升高，硫酸盐浓度维持为0； 3. GS试验：同时考虑人为硫酸盐与温室气体的排放增长，气溶胶散射（气溶胶直接效应）按前文所述方式显式表征；所有试验均未考虑气溶胶间接效应。 温室气体与硫酸盐气溶胶的大气浓度情景参考Mitchell与Johns（1997）的研究设定。温室气体浓度增长基于1890-1990年的历史记录，1990年后以每年1%的复合增长率递增。对于硫酸盐气溶胶，采用硫循环模型（Langer与Rodhe，1991）估算得到的1986年与2050年硫酸盐载荷空间分布作为基准模态。基于全球年平均硫排放率，1990年前的年份采用1986年基准模态缩放，2050年后的年份采用2050年基准模态缩放，中间年份通过两个基准模态插值得到空间分布的时间序列。未来硫排放率基于政府间气候变化专门委员会（Intergovernmental Panel on Climate Change, IPCC）IS92a情景设定。本试验中硫酸盐浓度初始值在1890年设为0，且未考虑硫酸盐浓度的季节变化。 相关试验结果的分析讨论可参见Emori等（1999）的研究。通过平衡积分得到的CCSR/NIES模式气候敏感性约为3.5摄氏度。本数据集包含CCSR/NIES模式的全球平均温度、降水与二氧化碳变化结果（相对于1961-1990年基准期）。 与B1情景类似，B2情景同样以提升环境与社会可持续性为核心关切，但二者的世界格局存在显著差异。B2情景下，各国广泛推行教育与福利项目，推动死亡率下降，同时生育率小幅降低。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（International Institute for Applied Systems Analysis, 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，全球经济总量有望达到约250万亿美元。 国际间收入差距有所缩小，但收敛速度慢于全球融合度更高的A1、B1情景。通过构建更完善的社区支持网络，区域内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，环境保护仍是少数几项真正具有全球共识的优先事项之一。然而，由于各国政府难以设计并落实兼顾环境保护与互利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情景的叙事线尤其有利于社区倡议与社会创新，尤其是在教育水平普遍较高的背景下。技术前沿的推进速度慢于A1与B1情景，且创新活动的区域异质性更强。全球范围内，研发（Research and Development, R&D）投入持续保持当前的下降趋势，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，格外重视技术研发与双边合作，因此技术进步的区域分布并不均衡。 单位GDP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。B2情景下，土地利用管理在地方层面得到更有效的整合。城市与交通基础设施建设是社区创新的重点领域，有助于降低汽车依赖度并减少城市蔓延。强调粮食自给自足推动了饮食结构向本地产品转型，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因自然资源禀赋差异而各不相同。提升能源与其他资源利用效率的需求，推动部分地区开发低碳排放技术。区域层面的环境政策合作在治理部分跨界环境问题上取得成效，例如二氧化硫导致的酸雨，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）与挥发性有机物（VOCs）的排放量，减少了对流层臭氧浓度升高的发生概率。尽管到2100年全球能源系统仍以烃类燃料为主导，但世界能源供应中化石资源的占比正逐步降低，能源碳强度也随之下降。