IPCC Climate Change Data: CSIRO B1a Model: 2080 Mean Temperature

The CSIRO Atmospheric Research Mark 2b climate model (Hirst et al., 1996, 1999) has recently been used for a number of more sophisticated climate change simulations. These start from 1880 to avoid the "cold start problem". This version of the CSIRO model includes the Gent-McWilliams mixing scheme in the ocean and shows greatly reduced climate drift relative to earlier versions (e.g. Dix and Hunt, 1998). The drift in global mean surface temperature in the new control run is about -0.02 degrees C/century. Note that the model uses flux correction. The model atmosphere has 9 levels in the vertical and horizontal resolution of spectral R21 (approximately 5.6 by 3.2 degrees). The ocean model has the same horizontal resolution with 21 levels. The equilibrium sensitivity to doubled CO2 of a mixed layer ocean version of the model is 4.3 degrees. This is at the high end of the range of model sensitivities (e.g. IPCC 1995, Table 6.3). In the basic greenhouse gas experiment the model combines the effect of all radiatively active trace gases into an "equivalent" CO2 concentration. Observed concentrations are used from 1880 to 1990 and the IS92a projections into the future. This gives close to a 1%/year compounding increase of equivalent CO2. Another model experiment includes the negative radiative forcing from atmospheric sulphate aerosol. The direct aerosol forcing is included via a perturbation of the surface albedo, similarly to the Hadley Centre experiments described by Mitchell et al (1995) and Mitchell and Johns (1997) . The sulphate concentrations are the same as used in the Hadley Centre experiments. However the chosen aerosol optical properties are different, giving a present day forcing due to anthropogenic sulphate of about -0.4 W/m^2. This can be compared to the 1880-1990 greenhouse gas forcing of about 2 W/m^2. The magnitude of the 20th century warming in the model including aerosol matches the observed reasonably well. However there are a number of forcings missing from the model, including solar variability, sulphate indirect effect and the effect of soot. The climate sensitivity of CSIRO-Mk2 is about 4.3 degrees C (Watterson et al.,1997). The central elements of the B1 future are a high level of environmental and social consciousness combined with a globally coherent approach to sustainable development. A strong welfare net prevents social exclusion on the basis of poverty. However, counter-currents may develop and in some places people may not conform to the main social and environmental intentions of the mainstream in this scenario family. Particular effort is devoted to increasing resource efficiency. Comprehensive incentive systems, combined with advances in international institutions, permit the rapid diffusion of cleaner technology. R and D to this end is also enhanced together with education and capacity building for clean and equitable development. Organizational measures are adopted to reduce material wastage, maximizing reuse and recycling. The combination of technical and organizational change yields high levels of material and energy saving as well as reductions in pollution. Labor productivity also improves as a byproduct of these efforts. Variants considered within the B1 family of scenarios include different rates of GDP growth and dematerialization (e.g., energy intensity declines). The demographic transition to low mortality and fertility occurs at the same rate as in A1 but for slightly different reasons, motivated partly by social and environmental concerns. Global population reaches nine billion by 2050 and declines to about seven billion by 2100. This is a world with high levels of economic activity and significant and deliberate progress toward international and national income equality. Global income per capita in 2050 averages US$13,000; somewhat lower than in A1. A higher proportion of this income is spent on services rather than on material goods, and on quality rather than quantity, because of less emphasis on material goods and also higher resource prices. The B1 storyline sees a relatively smooth transition to alternative energy systems as conventional oil resources decline. There is extensive use of conventional and unconventional gas as the cleanest fossil resource during the transition, but the major push is towards post fossil technologies driven in large part by environmental concerns. Given the high environmental consciousness and institutional effectiveness in the B1 storyline, environmental quality is high, as most potentially negative environmental aspects of rapid development are anticipated and dealt with effectively locally, nationally, and internationally. For example, transboundary air pollution (acid rain) is basically eliminated in the long-term. Land-use is carefully managed to counteract the impacts of activities potentially damaging to the environment. Cities are compact and designed for public and non-motorized transport, with suburban developments tightly controlled. Strong incentives for low-input, low-impact agriculture along with maintenance of large areas of wilderness contribute to high food prices with much lower levels of meat consumption than those in A1. These proactive local and regional environmental measures and policies also lead to relatively low GHG emissions even in the absence of explicit interventions directed at mitigating climate change.澳大利亚联邦科学与工业研究组织（CSIRO）大气研究部Mark 2b型气候模型（Hirst等，1996、1999）近期已被应用于多项更为精细的气候变化模拟实验。该系列模拟始于1880年，以规避“冷启动问题（cold start problem）”。此版本的CSIRO模型在海洋模块中集成了Gent-McWilliams混合方案，相较于早期版本（如Dix与Hunt，1998），其气候漂移现象得到显著抑制。新控制实验中，全球平均地表温度的漂移速率约为-0.02℃/世纪。需注意，该模型采用了通量校正（flux correction）技术。模型大气垂直方向共9层，光谱分辨率为R21（约5.6×3.2个经纬度度）；海洋模块与大气模块水平分辨率一致，垂直分层为21层。该模型的混合层海洋版本对CO₂倍增的平衡气候敏感度为4.3℃，处于各类模型敏感度区间的较高端（如IPCC（政府间气候变化专门委员会）1995年报告表6.3）。在基础温室气体模拟实验中，模型将所有具有辐射活性的痕量气体的效应整合为“等效（equivalent）”CO₂浓度。1880年至1990年采用观测浓度，1990年后采用IS92a情景的预测浓度，由此实现等效CO₂浓度以约1%的年复合增长率上升。另一组模型实验纳入了大气硫酸盐气溶胶带来的负辐射强迫。其直接气溶胶强迫通过地表反照率扰动实现，与Mitchell等人（1995）及Mitchell与Johns（1997）描述的哈德利中心（Hadley Centre）实验方法一致。硫酸盐气溶胶浓度取值与哈德利中心实验完全一致，但所选气溶胶光学特性存在差异，由此得到当前人为硫酸盐气溶胶的辐射强迫约为-0.4 W/m²。可将该值与1880年至1990年温室气体的辐射强迫（约2 W/m²）进行对比。纳入气溶胶强迫的模型模拟的20世纪变暖幅度与观测结果较为吻合。但该模型仍缺失部分强迫因子，包括太阳活动变化、硫酸盐气溶胶间接效应以及黑碳的影响。CSIRO-Mk2模型的气候敏感度约为4.3℃（Watterson等，1997）。B1未来情景的核心要素为高度的环境与社会意识，以及全球协同推进可持续发展的路径。完善的社会保障网络可防止因贫困引发的社会排斥。不过，该情景家族中仍可能出现逆流现象，部分地区的民众未必会遵循主流社会与环境的核心愿景。该情景致力于提升资源利用效率，通过全面的激励机制结合国际制度的进步，推动清洁技术的快速扩散。为此开展的研发工作、教育以及清洁公平发展的能力建设均得到强化。同时，采取组织化措施减少物料浪费，最大化物料复用与回收。技术与组织变革的结合可实现高水平的物料与能源节约，同时降低污染排放。劳动力生产率也会作为这些努力的副产品得到提升。B1情景家族内的变体包括不同的GDP增长率与去物质化（dematerialization）速率（如能源强度下降）。人口转型至低死亡率、低生育率的进程与A1情景速率一致，但驱动因素略有不同，部分源于社会与环境层面的考量。全球人口将于2050年达到90亿，2100年回落至约70亿。该情景下的世界经济活动规模可观，且在国际与国内收入平等方面取得了显著且审慎的进展。2050年全球人均收入平均为13000美元，略低于A1情景。由于对物质商品的关注度降低，加之资源价格走高，收入中用于服务而非物质商品的比例更高，且更注重品质而非数量。B1情景的叙事主线为：随着常规石油资源枯竭，世界将平稳过渡至替代能源体系。转型期内，常规与非常规天然气作为最清洁的化石能源被广泛使用，但推动向后化石燃料技术转型的主要动力源自环境关切。鉴于B1情景中高度的环境意识与制度效能，环境质量保持在较高水平，因为快速发展可能带来的各类潜在负面环境影响均可在地方、国家及国际层面得到有效预判与应对。例如，跨界空气污染（酸雨）在长期内基本得以消除。土地利用得到精心管理，以抵消各类可能破坏环境的人类活动的影响。城市布局紧凑，设计优先考虑公共交通与非机动交通，郊区开发受到严格管控。对低投入、低影响农业的强力激励，以及对大面积荒野区域的保护，推高了食品价格，同时肉类消费水平远低于A1情景。这些积极的地方与区域环境措施与政策，即便未出台专门针对气候变化减缓的干预手段，也可实现相对较低的温室气体（GHG, Greenhouse Gas）排放。