Climate change impacts in Canada

Climate change impacts in Canada - what the IPCC 4th Assessment Report has found:

• Break up of the sea ice on western Hudson Bay occurs ~3 weeks earlier than in the early 1970s. Polar bears area coming ashore earlier with reduced fat reserves (a 15% decline in body condition), fasting for longer periods of time, and having reduced productivity. Estimates suggest that the Western Hudson Bay population has declined from 1200 bears in 1987 to fewer than 950 in 2004. Polar bears will face a high risk of extinction with warming of 2.8°C above pre-industrial [Box 4.3]. Nutritional stresses related to longer ice-free seasons in the Beaufort Sea may be inducing declining survival rates, smaller size, and cannibalism among polar bears [1.3.1.1].
• Decline for a substantial portion of northern forest, possibly related to warmer and longer summers, whereas tundra productivity is continuing to increase [1.3.6.1].
• Droughts: 29% decrease in annual maximum daily streamflow due to temperature rise and increased evaporation with no change in precipitation (1847- 1996) in the south [1.3.2.1]. Drought has been more frequent and intense in the western parts[14.2.1].
• Earlier spring snowmelt has led to longer growing seasons and drought, especially at higher elevations, where the increase in wildfire activity has been greatest. Warmer May-August temperatures of 0.8°C since 1970 are highly correlated with area burned. Burned area has exceeded 60,000 km2/yr three times since 1990, twice the long-term average. [Box 14.1]
• The vegetation growing season has increased an average of 2 days/decade since 1950, with most of the increase resulting from earlier spring (influence of greenhouse gases, sulphate aerosols, and natural external forcing) [14.2].
• 1 to 2 week earlier peak streamflow due to earlier warming-driven snowmelt 1936- 2000 [1.3.2.1]. Rising temperatures will diminish snowpack and increase evaporation, affecting seasonal availability of water  [14.2.1, 14.4.1, 14.4.6, Boxes 14.2, 14.3]
• 19% of studied shoreline in the Manitounuk Strait is retreating, in spite of land uplift, due to thawing of permafrost (1950-1995) [1.3.3.1]
• Increased thermokarst erosion at the Arctic Ocean & Beaufort Sea coasts due to climate warming (1970-2000 relative to 1954- 1970) [1.3.3.1].
• Bioclimatic taiga- tundra ecotone indicator 12 km/yr northward shift (due to increased temperature) [1.3.5.2].
• Trend detected in water temperature in the Fraser River in British Columbia for longer river sections reaching a temperature over 20°C, which is considered a threshold for degrading salmon habitat [3.2]
• Arctic and sub-arctic ecosystems (particularly ombrotrophic bog communities; a form of wetland) above permafrost were considered likely to be most vulnerable to climatic changes, since impacts may turn arctic regions from a net carbon sink to a net source [4.4.6].