Projected Change
This map shows the global distribution of projected changes in
December to February (Northern Hemisphere winter, Southern Hemisphere
summer) mean temperatures from the reference period 1975 to 1995
to the end (2080 to 2100) of the current century. These changes
are the response simulated in the Canadian Centre for Climate Modelling
and Analysis (CCCma) global climate model to projected increases in atmospheric greenhouse
gas concentrations and sulfate aerosol loadings associated with
human activity.
There is typically more warming over land than over oceans, at
higher latitudes than at lower latitudes, and in winter compared
to summer. This pattern is seen in Northern Hemisphere winter where,
according to this projection, the Arctic would experience the greatest
warming followed by other areas in northern Canada and central and
northern Asia. The Southern Hemisphere shows less marked warming,
generally, and especially in its summer period.
Explanations
Temperatures generally increase as the century progresses as a
consequence of the projected increase in greenhouse
gases concentrations in the atmosphere. Broadly speaking, the
land warms more than the oceans because of the ability of the oceans
to store more heat. Warming is larger at higher latitudes at least
partially because of the strong feedback effect of ice and snow
which reflect sunlight: as the system warms the amount of ice and
snow decreases and more sunlight is absorbed which acts to warm
the surface. In winter, the cold temperatures over the ice-covered
ocean in the current climate are replaced by warmer temperatures
over the open, or partially open, ocean.
There is a range of other less prominent features of the simulated
warming such as the tendency for more warming in the northern compared
to the southern hemispheres and the existence of regions of retarded
warming, or even slight cooling, in certain ocean regions such as
that between Canada and Greenland. This latter feature depends on
changes in deep ocean mixing which act to sequester heat in the
ocean.
Data Source
The results are based on climate change simulations made with the
Coupled Global Climate Model (CGCM1)
developed at the Canadian Centre for Climate Modelling and Analysis
of Environment Canada. The projected changes in greenhouse
gas concentrations and aerosol loadings are based on the IS92a scenario
developed in conjunction with the Intergovernmental Panel on Climate
Change to portray one of several possible futures. The output
of the model is produced on a grid of 3.75 degrees in latitude
and longitude. This represents a grid square of approximately 400
kilometres by 300 kilometres at Canadian latitudes.
The digital data for this map can be downloaded
here.
Caution in Interpreting the Map
The aim of global climate models is to simulate past, current,
and future large-scale climate based on the physical principles
governing the climate system. The Canadian Centre for Climate Modelling
and Analysis model is reasonably successful in reproducing
the current climate and the climate change observed over the past
century. Nevertheless, future climate scenario results must be treated
with caution and this is especially the case when results are viewed
at smaller local scales. Regional
climate models are one approach to "downscaling" the
large-scale results from global climate models to more local scales.
These models are under active development in Canada and elsewhere.
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