Projected Change
This map shows the projected change in winter (December to February)
precipitation from the reference period 1961 to 1990 to the middle
(2040 to 2060) of the current century for Canadian land areas. 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. Precipitation changes are expressed as percentages
to indicate that a given change in precipitation amount is more
important in a region of low average precipitation than in a region
of high average precipitation.
In general, precipitation increases as the century progresses and
the climate warms. Projected precipitation changes are not evenly
distributed geographically nor seasonally. There are regions with
decreases of precipitation as well as those with increases. Precipitation
is projected to decrease slightly for some higher latitude regions.
The following animation
is created to show the projected change from year 1995 to 2070 in mean annual precipitations relative to 1961 to 1990 average.
Explanations
The hydrological cycle speeds up at least partially because the
warmer surface temperatures cause increased evaporation into the
atmosphere which then becomes available for precipitation. The marked
regions of both increasing and decreasing precipitation are associated
with shifts in the broad patterns of atmospheric circulation
under climate warming.
Data Source
The results are based on climate change simulations made with the
Coupled Global Climate Model (CGCM2)
developed at the Canadian Centre for Climate Modelling and Analysis
of Environment Canada. The projected changes in greenhouse
gases 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. For forestry
and other applications, the Canadian Forest Service of National
Resources Canada has derived the changes in climate based on the
simulation output with reference to the 1961 to 1990 normals, and
interpolated the data over Canada to finer resolution using a multi-step
methodology.
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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