Climate Change

Photo: alder buds © iStock.com/serg269
Alder buds

Climate trends for Canada, 1950 to 20075

Temperature

  • Average annual air temperature increased by 1.4ºC.
  • Strongest warming (>2ºC) was in the west and northwest.
  • No significant cooling trend occurred at any location in any season.
  • Largest temperature increases were in winter (>4ºC at 26 locations).
  • Warming was most prevalent in winter and spring, leading to widespread:
    • decrease in winter snowpack and earlier snowmelt;
    • earlier start to the growing season.
  • Summer warming trends were mainly over southwestern and southeastern Canada.
  • Smallest temperature change occurred in the fall.

Precipitation

  • Annual precipitation generally increased, most strongly in the northern half of Canada.
  • Precipitation increased over the Arctic in all seasons except summer.
  • Winter precipitation decreased in southwestern and southeastern Canada.
  • The fraction of precipitation falling as snow decreased in southern Canada.
Trends in mean annual temperature
Total change (ºC), 1950 to 2007
Map: trends in mean annual temperature. Click for graphic description (new window).
Long Description for Trends in mean annual temperature

This map of Canada shows trends in mean annual temperature at climate stations with long-term records. Trends are shown as total change from 1950 to 2007. Temperature change is categorized into four ranges of magnitude: first, increases greater than 3 degrees Celsius; second, increases or decreases from 1.5 to 3 degrees Celsius; third, increases or decreases from 0.5 to 1.5 degrees Celsius; and fourth, increases or decreases from 0 to 0.5 degrees Celsius. The symbols on the map also show which of the trends are statistically significant. Overall the map shows a mix of significant and non-significant warming trends of varying magnitudes over most of Canada, along with a few low-magnitude cooling trends, none of which is statistically significant. A description of temperature trends on this map is in the main text.

 
Source: Zhang et al., 20105

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Earlier springs lead to changes in timing of bird migration and nesting

The trend to earlier, warmer springs appears to be leading to earlier arrival at prairie nesting grounds for some waterfowl and earlier hatching for some seabirds.

Canada geese arrival dates, Delta Marsh

1939 to 2001
Graph: Canada geese arrival dates, Delta Marsh. Click for graphic description (new window). Photo: Geese © iStock.com/scol22.
Long Description for Canada geese arrival dates, Delta Marsh

This graph shows the date of the arrival of Canada geese at Delta Marsh, plotted as points for each spring from 1940 to 2001. The trend line shows a progressively earlier arrival date, moving from an average date of April 29th to an average date of March 15th. This means that Canada geese arrived at Delta Marsh an average of more than two weeks earlier in 2001 than in 1940.

 
Source: adapted from Murphy-Klassen et al., 20056

Timing of annual arrival at Delta Marsh, along the shore of Lake Manitoba, was strongly related to the average March temperature for about half of the 96 migratory bird species studied, including Canada geese. Spring arrival dates of most of these species shifted earlier at rates of 0.6 to 2.6 days for each 1°C rise in average March temperature.6

Hatching dates for tufted puffins, Triangle Island

1975 to 2002
Graph: hatching dates for tufted puffins, Triangle Island. Click for graphic description (new window). Photo: Tufted puffin © Kyle Morrison.
Long Description for Hatching dates for tufted puffins, Triangle Island

This graph shows the mean annual hatch date for tufted puffins from 1975 to 2002. An overall shift towards earlier hatch dates is evident. From 1975 to the early 1980s mean annual hatch dates ranged from July 25th to June 8th.  From the mid 1990s to 2002 the mean annual hatch date ranged from July 9 to approximately June 20th.

 
Source: adapted from Gjerdrum et al., 20037 and Gaston et al., 20098

Tufted puffins, rhinoceros auklets, and Cassin’s auklets at Triangle Island off the B.C. coast have shifted to an earlier breeding season in the past 30 years. The populations of these burrow-nesting seabirds declined from 1984 to 2004, likely due to changes in ocean conditions. The declines may be partly caused by a mismatch between timing of nest hatching and peak food availability, as has been confirmed for Cassin’s auklets.8

Moving north

There are many observations throughout the country of shifts in species ranges, generally northward. Many of these shifts are likely related to climate change. Some examples include:

  • The northern limit of the breeding range of landbirds that breed in southern Canada moved northward by an average of 2.4 km per year from 1964 to 2002 – for example, Swainson’s thrush has extended its range 141 km northward over this period.9
  • Declining sea ice in Arctic straits has led to killer whales expanding their range into Hudson Bay where they are now sighted every summer.10
  • Northward range shifts have been noted since the 1960s in the Northwest Territories for whitetailed deer, coyote, wood bison, cougar, magpies, and the winter tick parasite.11, 12
  • White-tailed deer have been expanding northward from B.C. to Yukon since 1974 and now range as far north as central Yukon.13 They have also been observed to be expanding northward in Saskatchewan, Quebec, and Ontario.14, 15
  • The Inuvialuit of Banks Island in the Arctic have noted new species of beetles and sand flies. Robins and barn swallows are also new to the region.16
  • Northward expansion of racoons into the Prairies during the 20th century may be linked to longer growing seasons along with increased agricultural production.17

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Photo: Alexandra Fiord, Ellesmere Island, Nunavut © Greg Henry
International Tundra Experiment (ITEX) site, showing open-topped greenhouses, Alexandra Fiord, Ellesmere Island, Nunavut

Warmer temperatures lead to changes in the tundra biome

Evidence from around the circumpolar Arctic indicates that tundra is changing.18, 19 Climate records show that the particular conditions of cold temperatures and low precipitation needed to support polar tundra, barrens, and ice and snow biomes declined about 20% in the past 25 years.20 This trend is linked with increases in primary productivity and increased biomass in tundra plant communities. This “greening” signal is particularly strong in the Canadian Western Arctic where there is evidence of shrub cover increasing in the forest-tundra and adjacent tundra. Studies based on satellite images from 1986 to 2005 along the treeline zone west of Hudson Bay show trends to increased shrubbiness, especially west of the Mackenzie Delta.21 In the delta, the combination of warming temperatures and increasing permafrost degradation is creating new growing conditions suitable for colonization by tall deciduous shrubs such as alder.21

Several sites in Canada conduct research and monitoring on changes in tundra through the International Tundra Experiment (ITEX). Analysis of vegetation plots from ITEX sites around the circumpolar Arctic shows that, although changes vary from region to region, increases in vegetation canopy height and dominance of shrubs are common findings.22 The ITEX program also includes passive warming experiments using small, open-topped greenhouses (see photograph) which increase plant-level air temperature by 1 to 3°C. Analysis of 11 ITEX warming experiments from around the Arctic indicates that future trends in tundra are likely to include increases in canopy height, changes in species composition and abundance, and reduction in species diversity.23

Increases in evergreen shrubs and mosses, Ellesmere Island, Nunavut

Index of the mass of different vegetation categories, 1995 to 2007
Map and graph: increases in evergreen shrubs and mosses, Ellesmere Island, Nunavut. Click for graphic description (new window).
Long Description for Increases in evergreen shrubs and mosses, Ellesmere Island, Nunavut

This stacked bar graph shows the increase in an index of the mass of different tundra vegetation categories in 1995, 2000, and 2007 on Ellesmere Island. Overall the total mass of vegetation increased significantly, as is described in the text below the graph. Mosses and evergreen shrubs, which together accounted for the majority of the tundra biomass, both increased in total mass between each study year. Lichens, flowering plants, grasses and sedges and deciduous shrubs all remained at approximately the same levels of biomass over the study period. An inset map shows the location of Ellesmere Island in the far north of the Arctic Ecozone+.

 
Source: adapted from Hudson and Henry, 200922

High Arctic tundra at the ITEX site on Ellesmere Island has become more productive, with biomass increasing by 50% over 13 years. This change was mainly due to an increase in growth of evergreen shrubs and moss. Because of the greater shrub growth, average canopy height increased, doubling from 17 to 34 cm between 2000 and 2007. Species diversity did not change.22

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