IPCC Climate Change Data: GFDL99 A2a Model: 2050 Mean Temperature

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. 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 ncreased
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.

本研究使用的GFDL（地球流体动力学实验室，Geophysical Fluid Dynamics Laboratory）模型实验，基于Manabe等人（1991）与Stouffer等人（1994）及其参考文献中描述的耦合海气模式开展。该模式具备交互式云物理过程与随季节变化的太阳辐射。大气分量在垂直方向上设置9个有限差分（σ坐标）层级。本版本模式采用15波菱形截断（R15）的分辨率，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，且考虑季节（而非昼夜）尺度的太阳辐射变化。海洋模式基于Bryan与Lewis（1979）的框架，网格点间距为纬度4.5度、经度3.7度，垂直方向设12个非均匀分布的层级。为抑制模式漂移，对热通量与水通量进行季节与空间分布上的调整，但年际间保持不变。模式还包含动态海冰模式（Bryan, 1969），为系统引入额外的自由度。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，约为每百年-0.023℃。

本研究使用的两个GFDL-R15气候变化实验，采用IS92a情景，涵盖1765-2065年的预估历史与未来温室气体（GGa1）强迫、以及温室气体与硫酸盐气溶胶混合（GSa1）强迫（Haywood等人，1997）。其中GGa1实验仅可通过IPCC数据分发中心（IPCC DDC）获取1958-2057年的100年时段数据。所有温室气体的辐射效应以等效CO₂浓度表征，硫酸盐气溶胶的直接辐射强迫则通过指定的空间分布地表反照率变化进行参数化（遵循Mitchell等人，1995）。相关气候变化实验的结果详见Haywood等人（1997）。该模式的气候敏感度约为3.7℃。

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，强调本地文化根源。部分区域内，宗教参与度提升使得许多人摒弃物质主义路径，转而聚焦于为本地社区做贡献。在其他区域，趋势则是加大教育与研发（Research and Development，R&D）投入，推动经济生产率增长。社会与政治结构呈现多元化：部分区域建立更完善的福利体系、缩小收入不平等，而其他区域则转向“小政府”模式。环境关注度相对较低，尽管部分区域会着力管控本地污染、维护本地环境宜居性。A2情景下的国际紧张局势更多、合作程度低于A1或B1情景。人员、思想与资本的流动性更低，导致技术扩散速度缓慢。国际间的生产率差异，进而人均收入差异，得以维持甚至扩大。由于强调家庭与社区生活，生育率仅缓慢下降，但区域间存在差异。因此，该情景家族的人口增长较高（至2100年达到150亿），且相对于A1与B1情景，人均收入较低：2050年为7200美元，2100年为16000美元。部分区域的技术变革迅速，部分区域则较为缓慢，这是因为工业需适配本地的资源禀赋、文化与教育水平。能源与矿产资源丰富的区域会发展资源密集型经济，而资源匮乏的区域则将通过技术创新提升资源利用效率、开发替代投入品，以最大限度降低进口依赖度作为核心目标。不同区域的燃料结构主要由资源可得性决定。区域间的技术分化持续存在：高收入但资源匮乏的区域转向先进的后化石燃料技术（土地充足区域使用可再生能源，人口稠密、资源匮乏区域使用核能），而低收入且资源丰富的区域通常依赖老旧的化石燃料技术。由于存在大量粮食需求，农业生产率是本未来情景下创新与研发工作的核心领域之一。起初较为严重的土壤侵蚀与水污染问题，最终会通过本地发展可持续高产农业得到缓解。尽管会关注潜在的局地与区域环境损害，但这种关注在区域间并不均衡。例如，亚洲地区由于考虑到对人类健康与农业生产的影响，会减少硫与颗粒物排放，而非洲则因加大煤炭与其他矿产资源的开发力度，此类排放有所增加。A2情景下的世界能源与碳强度较高，相应的温室气体排放也较高，其CO₂排放量在四个情景家族中位居首位。

本数据集提供以下时段的数据：1961-1990年、2010-2039年、2040-2069年以及2090-2099年的月平均场与变化量场数据。