IPCC Climate Change Data: CSIRO A2a Model: 2080 Precipitation

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). For the A2 emissions scenario the main emphasis is on a strengthening of regional and local culture, with a return to family values in many regions. The A2 world consolidates into a series of roughly continental economic regions, emphasizing local cultural roots. In some regions, increased religious participation leads many to reject a materialist path and to focus attention on contributing to the local community. Elsewhere, the trend is towards increased investment in education and science and growth in economic productivity. Social and political structures diversify, with some regions moving towards stronger welfare systems and reduced income inequality, while others move towards "lean" government. Environmental concerns are relatively weak, although some attention is paid to bringing local pollution under control and maintaining local environmental amenities. The A2 world sees more international tensions and less cooperation than in A1 or B1. People, ideas and capital are less mobile so that technology diffuses slowly. International disparities in productivity, and hence income per capita, are maintained or increased. With the emphasis on family and community life, fertility rates decline only slowly, although they vary among regions. Hence, this scenario family has high population growth (to 15 billion by 2100) with comparatively low incomes per capita relative to the A1 and B1 worlds, at US$7,200 in 2050 and US$16,000 in 2100.Technological change is rapid in some regions and slow in others as industry adjusts to local resource endowments, culture, and education levels. Regions with abundant energy and mineral resources evolve more resource intensive economies, while those poor in resources place very high priority on minimizing import dependence through technological innovation to improve resource efficiency and make use of substitute inputs. The fuel mix in different regions is determined primarily by resource availability. And divisions among regions persist in terms of their mix of technologies, with high-income but resource-poor regions shifting toward advanced post fossil technologies (renewables in regions of large land availability, nuclear in densely populated, resource poor regions) and low-income resource-rich regions generally relying on older fossil technologies.With substantial food requirements, agricultural productivity is one of the main focus areas for innovation and RD efforts in this future. Initially high levels of soil erosion and water pollution are eventually eased through the local development of more sustainable high-yield agriculture.Although attention is given to potential local and regional environmental damage, it is not uniform across regions. For example, sulfur and particulate emissions are reduced in Asia due to impacts on human health and agricultural production but increase in Africa as a result of the intensified exploitation of coal and other mineral resources. The A2 world sees high energy and carbon intensity, and correspondingly high GHG emissions. Its CO2 emissions are the highest of all four scenario families. Data are available for the following periods: 1961-1990, 2010-2039; 2040-2069; and 2090-2099 Mean monthly and change fields.CSIRO大气研究Mark 2b型气候模式（Hirst等，1996、1999）近期被应用于多项更精细化的气候变化模拟试验，所有试验均以1880年为起始年份，以规避"冷启动问题"。该版本的CSIRO气候模式在海洋模块中引入了Gent-McWilliams混合方案，相较于早期版本（如Dix与Hunt，1998），其气候漂移现象已大幅减弱。新控制试验中全球平均地表温度的漂移速率约为-0.02℃/世纪。需注意，该模式采用了通量校正手段。模式大气垂直方向共9层，水平分辨率采用谱模式R21（约5.6°×3.2°）；海洋模块水平分辨率与大气一致，垂直方向共21层。该模式的混合层海洋版本对CO₂倍增的平衡气候敏感度为4.3℃，处于各类模式敏感度区间的上限（如政府间气候变化专门委员会（Intergovernmental Panel on Climate Change, 简称IPCC）1995年报告表6.3）。在基础温室气体试验中，模式将所有具有辐射活性的痕量气体的效应整合为"等效"CO₂浓度：1880年至1990年采用观测浓度，未来时段则采用IS92a情景的预测浓度，由此实现等效CO₂浓度以约1%/年的速率复合增长。另一项模式试验纳入了大气硫酸盐气溶胶产生的负辐射强迫：气溶胶直接强迫通过地表反照率扰动实现，其设置与Mitchell等（1995）及Mitchell与Johns（1997）描述的哈德利中心（Hadley Centre）试验一致。试验中采用的硫酸盐浓度与哈德利中心试验完全一致，但所选气溶胶光学特性存在差异，由此得到的当代人为硫酸盐辐射强迫约为-0.4 W/m²，可与1880-1990年温室气体辐射强迫（约2 W/m²）进行对比。纳入气溶胶强迫的模式对20世纪增温幅度的模拟结果与观测值吻合度较好，但该模式仍缺失部分辐射强迫因子，包括太阳活动变化、硫酸盐间接效应以及黑碳的气候效应。CSIRO-Mk2模式的气候敏感度约为4.3℃（Watterson等，1997）。 在A2排放情景中，核心导向为强化区域与本土文化，诸多地区回归家庭价值观念。A2情景下的世界将整合为若干大致以大陆为界的经济区域，凸显本土文化根源。部分地区中，宗教参与度的提升促使许多民众摒弃物质主义路径，转而聚焦于为本地社区贡献力量；而在其他地区，社会趋势则偏向于加大教育与科研投入，推动经济生产力增长。社会与政治结构呈现多元化发展：部分地区建立更完善的福利体系，降低收入不平等程度；而另一些地区则推行"精简型"政府治理模式。环境议题受关注度相对较低，尽管部分地区会着力管控本地污染并维护本土环境宜居性。相较于A1与B1情景，A2情景下的世界国际紧张局势更多、国际合作更少：人员、思想与资本的流动性更低，导致技术传播速度缓慢。各国间的生产力差距进而人均收入差距得以维持甚至扩大。由于情景核心强调家庭与社区生活，尽管各地区生育率存在差异，但整体下降速度缓慢。因此，该情景家族的人口增长较快（至2100年将达150亿），且相较于A1与B1情景，人均收入水平较低：2050年为7200美元，2100年为16000美元。 部分地区技术变革迅速，而另一些地区则进展缓慢，这是由于各地区产业需适配本地资源禀赋、文化与教育水平。能源与矿产资源丰富的地区将发展资源密集型经济；而资源匮乏的地区则将通过技术创新优先降低进口依赖，以提升资源利用效率并开发替代投入品。不同地区的能源结构主要由资源可获得性决定。各地区间的技术结构分化依然存在：高收入但资源匮乏的地区将转向先进的后化石能源技术（土地资源丰富地区发展可再生能源，人口密集且资源匮乏地区发展核电）；而低收入且资源丰富的地区则普遍依赖传统化石能源技术。由于粮食需求庞大，农业生产力成为该未来情景下创新与研发工作的核心方向之一。起初土壤侵蚀与水污染问题较为严重，但通过本地发展更可持续的高产农业，这些问题最终得到缓解。尽管社会对潜在的本地与区域环境破坏有所关注，但这种关注在各地区并不均衡。例如，由于硫氧化物与颗粒物排放会影响人类健康与农业生产，亚洲地区减少了此类排放；而非洲地区则因加大煤炭与其他矿产资源的开发力度，导致此类排放增加。A2情景下的世界能源与碳强度较高，相应的温室气体（Greenhouse Gas, 简称GHG）排放量也较大，其CO₂排放量在四类情景家族中位居最高。 数据集包含以下时段的数据：1961-1990年、2010-2039年、2040-2069年以及2090-2099年的逐月平均场与变化场。