IPCC Climate Change Data: GFDL99 A2a Model: 2050 Precipitation

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 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.