IPCC Climate Change Data: CGCM1 B2a Model: 2050 Maximum Temperature

The first version of the Canadian Global Coupled Model,
CGCM1, and its control climate are described by Flato et al.
(1999). The atmospheric component of the model is essentially
GCMII described by McFarlane et al. (1992). It is a spectral
model with triangular truncation at wave number 32 (yielding a
surface grid resolution of roughly 3.7 degrees x3.7 degrees )
and 10 vertical levels. The ocean component is based on the GFDL
MOM1.1 code and has a resolution of approximately 1.8 degrees
x1.8 degrees and 29 vertical levels. The model uses heat and
water flux adjustments obtained from uncoupled ocean and
atmosphere model runs (of 10 years and 4000 years duration
respectively), followed by an `adaption' procedure in which the
flux adjustment fields are modified by a 14 year integration of
the coupled model. A multi-century control simulation with the
coupled model has been performed using the present-day CO2
concentration to evaluate the stability of the coupled model's
climate, and to compare the modelled climate and its variability
to that observed. An ensemble of four transient climate change
simulations has been performed and is described in Boer et al.
(1999a; b). Three of these simulations use an effective
greenhouse gas forcing change corresponding to that observed
from 1850 to the present, and a forcing change corresponding to
an increase of CO2 at a rate of 1% per year (compounded)
thereafter until year 2100. The direct forcing effect of
sulphate aerosols is also included by increasing the surface
albedo (as in Reader and Boer, 1999) based on loadings from the
sulphur cycle model of Langner and Rodhe (1991). The fourth
simulation considers the effect of greenhouse gas forcing only.
The change in climate predicted by a model clearly depends
directly on this specification of greenhouse gas (and aerosol)
forcing, and of course these are not well known. The
prescription described above is similar to the IPCC
"business as usual" scenario, and using a standard
scenario allows the results of this model to be compared to
those of other modelling groups around the world. Some initial
results from these simulations are presented below. The climate
sensitivity of CGCM1 is about 3.5 degrees C. From the IPCC website: The B2 world is one of increased
concern for environmental and social sustainability. 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& 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. Data are available for the following periods:
1961-1990, 2010-2039; 2040-2069; and 2090-2099 Mean monthly and
change fields.

弗拉托等（Flato et al., 1999）详细介绍了加拿大全球耦合模型的首个版本（CGCM1）及其控制气候态。该模式的大气分量本质上源自麦克法兰等（McFarlane et al., 1992）提出的GCMII模式，属于谱模式，采用波数32的三角形截断，其地表网格分辨率约为3.7°×3.7°，垂直方向共设10层。海洋分量则基于GFDL MOM1.1代码构建，分辨率约为1.8°×1.8°，垂直方向共29层。

该模式采用了来自非耦合海洋与大气模式积分（分别时长10年与4000年）的热通量与水通量调整方案，随后通过耦合模式14年的积分过程对通量调整场进行修正，即所谓的“适应”流程。研究团队采用当前二氧化碳浓度开展了多世纪时长的耦合模式控制模拟实验，用以评估耦合模式气候态的稳定性，并将模拟气候态及其变率与观测结果进行对比。

波尔等（Boer et al., 1999a; 1999b）对4组瞬变气候变化模拟集合实验进行了详细说明。其中3组模拟采用了与1850年至今实际观测一致的有效温室气体辐射强迫变化，后续则采用以年复合1%的速率增长的二氧化碳辐射强迫变化，直至2100年；同时基于朗格纳与罗德（Langner and Rodhe, 1991）提出的硫循环模型得到的硫酸盐气溶胶负荷，通过增加地表反照率（如Reader与Boer, 1999所述）纳入硫酸盐气溶胶的直接辐射强迫效应。第4组模拟仅考虑温室气体辐射强迫的影响。

模式预测的气候变化显然直接取决于温室气体（及气溶胶）辐射强迫的设定方案，而这类设定方案本身尚不具备充分的认知。上述设定方案与政府间气候变化专门委员会（IPCC）的"business as usual"情景相似，采用标准情景可便于将本模式的模拟结果与全球其他建模课题组的结果进行对标。下文将展示上述模拟实验的部分初步结果。CGCM1的气候敏感度约为3.5℃。

引自IPCC官网内容：B2情景下的全球社会更加关注环境与社会可持续性。各国广泛推行教育与福利项目，使得死亡率下降，生育率也出现一定程度的降低。到2100年，全球总人口将达到约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，全球经济规模有望达到约250万亿美元。

国际间收入差距有所缩小，但缩小速度慢于全球趋同程度更高的A1、B1情景。通过构建更完善的社区支持网络，当地的不平等状况得到显著改善。普遍较高的教育水平同时推动了经济发展与环境保护工作，事实上，环境保护仍是少数真正具有全球意义的优先议题之一。但应对全球环境挑战的战略实施效果逊于B1情景，原因在于各国政府难以设计并推行兼顾环境保护与互利经济收益的国际协议。

B2情景为社区自主行动与社会创新提供了尤为有利的环境，尤其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，且创新活动在区域分布上也更为分散不均。全球范围内，研发（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传播机制仍弱于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为重视技术研发与双边合作，因此技术进步的进程并不均衡。

单位GDP能耗以年均约1%的速率下降，与过去两个世纪的历史平均水平相符。在B2情景下，土地利用管理在地方层面的整合度有所提升。城市与交通基础设施建设是社区创新的重点方向，这有助于降低汽车依赖程度并减少城市无序扩张。对粮食自给的重视推动饮食结构向本地产品倾斜，人口密度较高的国家肉类消费量有所下降。

能源系统因区域而异，取决于当地的自然资源禀赋。提高能源与其他资源利用效率的需求，推动部分地区研发低碳排放技术。区域层面的环境政策合作有助于解决部分跨界环境问题，例如二氧化硫导致的酸雨，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，从而减少了对流层臭氧浓度超标事件的发生。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，碳排放强度也随之下降。

本次研究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场数据。