IPCC Climate Change Data: CSIRO A1a Model: 2020 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). From the IPCC website: The A1 Family storyline is a case of
rapid and successful economic development, in which regional
averages of income per capita converge - current distinctions
between poor and rich countries eventually dissolve. In this
scenario family, demographic and economic trends are closely
linked, as affluence is correlated with long life and small
families (low mortality and low fertility). Global population
grows to some nine billion by 2050 and declines to about seven
billion by 2100. Average age increases, with the needs of
retired people met mainly through their accumulated savings in
private pension systems. The global economy expands at an
average annual rate of about three percent to 2100. This is
approximately the same as average global growth since 1850,
although the conditions that lead to a global economic in
productivity and per capita incomes are unparalleled in history.
Income per capita reaches about US$21,000 by 2050. While the
high average level of income per capita contributes to a great
improvement in the overall health and social conditions of the
majority of people, this world is not without its problems. In
particular, many communities could face some of the problems of
social exclusion encountered by the wealthiest countries in the
20th century and in many places income growth could come with
increased pressure on the global commons. Energy and mineral
resources are abundant in this scenario family because of rapid
technical progress, which both reduce the resources need to
produce a given level of output and increases the economically
recoverable reserves. Final energy intensity (energy use per
unit of GDP) decreases at an average annual rate of 1.3 percent.
With the rapid increase in income, dietary patterns shift
initially significantly towards increased consumption of meat
and dairy products, but may decrease subsequently with
increasing emphasis on health of an aging society. High incomes
also translate into high car ownership, sprawling
suburbanization and dense transport networks, nationally and
internationally. Land prices increase faster than income per
capita. These factors along with high wages result in a
considerable intensification of agriculture. Three scenario
groups are considered in A1 scenario family reflecting the
uncertainty in development of energy sources and conversion
technologies in this rapidly changing world. Near-term
investment decisions may introduce long-term irreversibilities
into the market, with lock-in to one technological configuration
or another. The A1B scenario group is based on a balanced mix of
energy sources and has an intermediate level of CO2 emissions,
but depending on the energy sources developed, emissions in the
variants cover a very wide range. In the fossil-fuel intensive
scenario group A1FI, emissions approach those of the A2
scenarios; conversely in scenario group A1T with low labor
productivity or of rapid progress in "post-fossil"
energy technologies, emissions are intermediate between those of
B1 and B2. These scenario variants have been introduced into
the A1 storyline because of its "high growth with high
tech" nature, where differences in alternative technology
developments translate into large differences in future GHG
emission levels Ecological resilience is assumed to be high in
this storyline. Environmental amenities are viewed in a
utilitarian way, based on their influence on the formal economy.
The concept of environmental quality might change in thisstoryline from"conservation" of nature to active
"management" - and marketing - of natural and
environmental services. Data are available for the following
periods: 1961-1990, 2010-2039; 2040-2069; and 2090-2099 Mean
monthly and change fields.