WhiteCAP_Plan_01SEPT..

NCE WhiteCAP Climate Projections
Summary of Projected Climate Changes for the Whitehorse Region
The effects of climate change are apparent in the Yukon. These effects represent very early
evidence of the changes that climate change will have on Yukon, which are anticipated to
escalate as the climate continues to warm. To assess how climate change may affect the
Whitehorse area, 65 maps projecting future climate conditions were generated for use in the
development of the Whitehorse Adaptation Plan. These maps project a warmer Whitehorse which
experiences increased precipitation.
The intention of the projections is to illustrate a conservative range of anticipated changes to our
local climate over time. The projections are based on two time cuts (2030 and 2050) and two
standard IPCC scenarios (B1 and A1B), presented in the Special Report on Emissions
Scenarios 1 . These scenarios anticipate how various drivers (demographic development, socioeconomic
development and technological change) may influence greenhouse gas emissions
(GHGs). The B1 scenario projects moderate to low increases in CO2 over the next century. The
A1B scenario anticipates medium to high increases in CO2 by 2100. These two scenarios were
selected to provide the greatest range in possible shifts in temperature and precipitation by 2050.
Projected climate changes to the Whitehorse area were generated by the Scenarios Network for
Alaska Planning 2 (SNAP). SNAP is located at the University of Alaska-Fairbanks. The projections
are based on the use of General Circulation Models (GCMs), which are complex models that
anticipate how future climate may be influenced by GHGs. Because of the many variables that
determine global climate and the varying ways of constructing a GCM, different GCMs perform
differently, and are likely to have differing accuracy for any one region of the globe..
SNAP has selected five GCMs as the basis for projecting climate change based on the work of
Walsh et al 3 , which evaluated the performance of GCMs in northerly regions by comparing model
back-casts to historical climate date. 15 GCMs were compared to ERA-40 (the European Centre
for Medium-Range Weather Forecasts Re-Analysis) – one of the most consistent and accurate
representations of temperature and precipitation. Of the fifteen evaluated models, the models
ECHAM5 (Germany), CM2.1 (US), MIROC3.2 (Japan), HADCM3 (UK) and CGCM3.1 (Canada)
were found to perform best over Alaska and Yukon.
The GCMs were then regionally downscaled using data available from the Parameter-elevation
on Independent Slopes Model (PRISM). GCMs typically have a large-scale output with grid
squares between 1° and 5° in latitude or longitude (~300km 2 ). Once correlated to the GCM
output, PRISM allows for a resolution of 2km 2 and accounts for regional topography.
It should be noted that although SNAP models have been shown to provide valid data regarding
climate trends over time, uncertainty is inherent in this type of projections. These model outputs
incorporate the same degree of year-to-year variability found in real weather patterns, but cannot
anticipate the timing of highs and lows.
Temperature
Projected mean annual temperature (MAT) and seasonal temperatures for the Whitehorse area
were estimated for 2030 and 2050 using mean values from the five selected GCMs. These maps
are provided below. The projections provide an estimate of anticipated increases in temperature
compared to baselines established for the 1961-1990 climate normal. Annual and seasonal
baseline and projected temperatures are provided in Table 1.
1 http://www.ipcc.ch/pdf/special-reports/spm/sres-en.pdf
2 www.snap.auf.edu
3 Walsh, J.E., Chapman, W.L., Romanovsky, V., Christensen, J.H., Stendel, M. 2008. Global
Climate Model Performance over Alaska and Greenland. Journal of Climate, 21: 6156-6174.
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