IPCC Climate Change Data: HADCM3 B2b Model: 2080 Maximum Temperature

The recent experiments performed at the Hadley Centre have
used the new Unified Model (Cullen, 1993). These experiments
represent a large step forward in the way climate change is
modelled by GCMs and raises new possibilities for scenario
construction. This experiment has overcome some of the major
difficulties that were associated with the previous generations
of equilibrium (circa IPCC 1990) and cold-start transient (circa
IPCC 1992) climate change experiments. HadCM2 has a spatial
resolution of 2.5 degrees x 3.75 degrees (latitude by longitude)
and the representation produces a grid box resolution of 96 x 73
grid cells. This produces a surface spatial resolution of about
417km x 278 km reducing to 295 x 278km at 45 degrees North and
South (comparable to a spectral resolution of T42). The
equilibrium climate sensitivity (DT2x) of HadCM2, that is the
global-mean temperature response to a doubling of effective CO2
concentration, is approximately 2.5 degrees C, although, this
quantity varies with the time-scale considered. This is somewhat
lower than most other GCMs (IPCC, 1992). In order to undertake a
'warm-start' experiment it is necessary to perturb the model
with a forcing from an early historical era, when the radiative
forcing was relatively small compared to the present. The Hadley
Centre started their experiments performed with HadCM2 with
forcing from the middle industrial era, about 1860 Mitchell et
al., 1995 and Johns et al., 1995. The greenhouse gas only
integrations, HadCM2GG, used the combined forcing of all the
greenhouse gases as an equivalent CO2 concentration. A further
series of integrations, HadCM2GS, used the combined equivalent
CO2 concentration plus the negative forcing from sulphate
aerosols. The HadCM2GG integrations simulated the change in
forcing of the climate system by greenhouse gases since the
early industrial period (taken by HadCM2 to be 1860). The
addition of the negative forcing effects of sulphate aerosols
represents the direct radiative forcing due to anthropogenic
sulphate aerosols by means of an increase in clear-sky surface
albedo proportional to the local sulphate loading (refer to
Mitchell et al., 1995 for details of this method). The indirect
effects of aerosols were not simulated. The modelled control
climate shows a negligible long term trend in surface air
temperature over the first 400 years. The trend is about +0.04
degrees C per century, which is comparable to other such
experiments. HadCM2CON represents an improvement over previous
generations of GCMs that have been used at the Hadley Centre
(Johns et al., 1995 and Airey et al., 1995). The experiments
performed have simulated the observed climate system using
estimated forcing perturbations since 1860. Johns et al., (1995)
and Mitchell et al., (1995) have established that HadCM2's
sensitivity is consistent with the real climate system. The
agreement between the observed global-mean temperature record
and that produced in these experiments is better for HadCM2GS
than for HadCM2GG. This implies that HadCM2Gs has captured the
observed signal of global-mean temperature changes better than
HadCM2GG for the recent 100-year record. The climate
sensitivity of HadCM2 is about 2.5 degrees C The central elements of the B1 future are a high level of
environmental and social consciousness combined with a globally
coherent approach to sustainable development. A strong welfare
net prevents social exclusion on the basis of poverty. However,
counter-currents may develop and in some places people may not
conform to the main social and environmental intentions of the
mainstream in this scenario family. Particular effort is devoted
to increasing resource efficiency. Comprehensive incentive
systems, combined with advances in international institutions,
permit the rapid diffusion of cleaner technology. R and D to
this end is also enhanced together with education and capacity
building for clean and equitable development. Organizational
measures are adopted to reduce material wastage, maximizing
reuse and recycling. The combination of technical and
organizational change yields high levels of material and energy
saving as well as reductions in pollution. Labor productivity
also improves as a byproduct of these efforts. Variants
considered within the B1 family of scenarios include different
rates of GDP growth and dematerialization (e.g., energy
intensity declines). The demographic transition to low mortality
and fertility occurs at the same rate as in A1 but for slightly
different reasons, motivated partly by social and environmental
concerns. Global population reaches nine billion by 2050 and
declines to about seven billion by 2100. This is a world with
high levels of economic activity and significant and deliberate
progress toward international and national income equality.
Global income per capita in 2050 averages US$13,000; somewhat
lower than in A1. A higher proportion of this income is spent on
services rather than on material goods, and on quality rather
than quantity, because of less emphasis on material goods and
also higher resource prices. The B1 storyline sees a relatively
smooth transition to alternative energy systems as conventional
oil resources decline. There is extensive use of conventional
and unconventional gas as the cleanest fossil resource during
the transition, but the major push is towards post fossil
technologies driven in large part by environmental concerns.
Given the high environmental consciousness and institutional
effectiveness in the B1 storyline, environmental quality is
high, as most potentially negative environmental aspects of
rapid development are anticipated and dealt with effectively
locally, nationally, and internationally. For example,
transboundary air pollution (acid rain) is basically eliminated
in the long-term. Land-use is carefully managed to counteract
the impacts of activities potentially damaging to the
environment. Cities are compact and designed for public and
non-motorized transport, with suburban developments tightly
controlled. Strong incentives for low-input, low-impact
agriculture along with maintenance of large areas of wilderness
contribute to high food prices with much lower levels of meat
consumption than those in A1. These proactive local and regional
environmental measures and policies also lead to relatively low
GHG emissions even in the absence of explicit interventions
directed at mitigating climate change.