IPCC Climate Change Data: GFDL99 A2a Model: 2080 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. 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.